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AAPS PharmSciTech     Hybrid Journal   (4 followers)
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Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology     Hybrid Journal   (5 followers)
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DNA Barcodes     Open Access  
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Egyptian Journal of Biochemistry and Molecular Biology     Full-text available via subscription  
FEBS Letters     Hybrid Journal   (24 followers)
FEBS Open Bio     Open Access   (1 follower)

        1 2     

Insect Biochemistry and Molecular Biology    [5 followers]  Follow    
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
     ISSN (Print) 0965-1748
     Published by Elsevier Homepage  [2556 journals]   [SJR: 1.333]   [H-I: 69]
  • Functional analysis of the glycogen binding subunit CG9238/Gbs-70E of
           protein phosphatase 1 in Drosophila melanogaster
    • Abstract: Publication date: Available online 12 April 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Éva Kerekes , Endre Kókai , Ferenc Sándor Páldy , Viktor Dombrádi
      The product of the CG9238 gene that we termed glycogen binding subunit 70E (Gbs-70E) was characterized by biochemical and molecular genetics methods. The interaction between Gbs-70E and all catalytic subunits of protein phosphatase 1 (Pp1-87B, Pp1-9C, Pp1-96A and Pp1-13C) of Drosophila melanogaster was confirmed by pairwise yeast two-hybrid tests, co-immunoprecipitation and pull down experiments. The binding of Gbs-70E to glycogen was demonstrated by sedimentation analysis. With RT-PCR we found that the mRNAs coding for the longer Gbs-70E PB/PC protein was expressed in all developmental stages of the fruit flies while the mRNA for the shorter Gbs-70E PA was restricted to the eggs and the ovaries of the adult females. The development specific expression of the shorter splice variant was not conserved in different Drosophila species. The expression level of the gene was manipulated by P-element insertions and gene deletion to analyze the functions of the gene product. A small or moderate reduction in the gene expression resulted in no significant changes, however, a deletion mutant expressing very low level of the transcript lived shorter and exhibited reduced glycogen content in the imagos. In addition, the gene deletion decreased the fertility of the fruit flies. Our results prove that Gbs-70E functions as the glycogen binding subunit of protein phosphatase 1 that regulates glycogen content and plays a role in the development of eggs in D. melanogaster.
      Graphical abstract image

      PubDate: 2014-04-16T04:14:08Z
  • Bacterial origin of a diverse family of UDP-glycosyltransferase genes in
           the Tetranychus urticae genome
    • Abstract: Publication date: Available online 12 April 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Seung-Joon Ahn , Wannes Dermauw , Nicky Wybouw , David G. Heckel , Thomas Van Leeuwen
      UDP-glycosyltransferases (UGTs) catalyze the conjugation of a variety of small lipophilic molecules with uridine diphosphate (UDP) sugars, altering them into more water-soluble metabolites. Thereby, UGTs play an important role in the detoxification of xenobiotics and in the regulation of endobiotics. Recently, the genome sequence was reported for the two-spotted spider mite, Tetranychus urticae, a polyphagous herbivore damaging a number of agricultural crops. Although various gene families implicated in xenobiotic metabolism have been documented in T. urticae, UGTs so far have not. We identified 80 UGT genes in the T. urticae genome, the largest number of UGT genes in a metazoan species reported so far. Phylogenetic analysis revealed that lineage-specific gene expansions increased the diversity of the T. urticae UGT repertoire. Genomic distribution, intron-exon structure and structural motifs in the T. urticae UGTs were also described. In addition, expression profiling after host-plant shifts and in acaricide resistant lines supported an important role for UGT genes in xenobiotic metabolism. Expanded searches of UGTs in other arachnid species (Subphylum Chelicerata), including a spider, a scorpion, two ticks and two predatory mites, unexpectedly revealed the complete absence of UGT genes. However, a centipede (Subphylum Myriapoda) and a water flea and a crayfish (Subphylum Crustacea) contain UGT genes in their genomes similar to insect UGTs, suggesting that the UGT gene family might have been lost early in the Chelicerata lineage and subsequently re-gained in the tetranychid mites. Sequence similarity of T. urticae UGTs and bacterial UGTs and their phylogenetic reconstruction suggest that spider mites acquired UGT genes from bacteria by horizontal gene transfer. Our findings show a unique evolutionary history of the T. urticae UGT gene family among other arthropods and provide important clues to its functions in relation to detoxification and thereby host adaptation.
      Graphical abstract image

      PubDate: 2014-04-16T04:14:08Z
  • Postintegration stability of the silkworm piggyBac transposon
    • Abstract: Publication date: Available online 13 April 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Liang Jiang , Qiang Sun , Weiqiang Liu , Huizhen Guo , Zhengwen Peng , Yinghui Dang , Chunlin Huang , Ping Zhao , Qingyou Xia
      The piggyBac transposon is the most widely used vector for generating transgenic silkworms. The silkworm genome contains multiple piggyBac-like sequences that might influence the genetic stability of transgenic lines. To investigate the postintegration stability of piggyBac in silkworms, we used random insertion of the piggyBac [3×p3 EGFP afm] vector to generate a W chromosome-linked transgenic silkworm, named W-T. Results of Southern blot and inverse PCR revealed the insertion of a single copy in the W chromosome of W-T at a standard TTAA insertion site. Investigation of 11 successive generations showed that all W-T females were EGFP positive and all males were EGFP negative; PCR revealed that the insertion site was unchanged in W-T offspring. These results suggested that endogenous piggyBac-like elements did not affect the stability of piggyBac inserted into the silkworm genome.

      PubDate: 2014-04-16T04:14:08Z
  • Transcriptional Regulation of De Novo Biosynthesis of Cyanogenic
           Glucosides throughout the Life-Cycle of the Burnet Moth Zygaena
           filipendulae (Lepidoptera)
    • Abstract: Publication date: Available online 12 April 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Joel Fürstenberg-Hägg , Mika Zagrobelny , Carl Erik Olsen , Kirsten Jørgensen , Birger Lindberg Møller , Søren Bak
      The six-spotted burnet moth Zygaena filipendulae (Lepidoptera) utilize the two cyanogenic glucosides (CNglcs) linamarin and lotaustralin as deterrents against predators throughout the entire life cycle. CNglcs can be hydrolyzed and bioactivated by β-glucosidases, resulting in the release of toxic hydrogen cyanide. CNglcs are retained through metamorphosis, probably involved in mating communication, and transferred during mating from the male to the female as a nuptial gift. CNglcs can be biosynthesized de novo by Z. filipendulae larvae, but may also be sequestered from their food plant Lotus corniculatus (Fabaceae). These two strategies are tightly linked and adjusted according to the CNglc content and composition of the food plant in order to balance CNglc homeostasis in the larva. In this study, the amounts of CNglcs and transcript levels of the biosynthetic genes were monitored in all life-stages and tissues of Z. filipendulae. During pupation, transcription of the biosynthetic genes is turned off and the CNglc content slowly declines. In females but not males, transcription of the biosynthetic genes is re-activated at the end of pupation. Eggs and embryos do not biosynthesize CNglcs de novo, but are endowed with CNglcs following eclosion of the female. Similarly to larvae, de novo biosynthesis in female adults takes place in the integument from which CNglcs are then transported to other organs. This study demonstrates that Z. filipendulae has evolved the ability to adjust the production of CNglcs throughout its life-cycle for optimal utilization in defense and possibly other metabolic functions, while at the same time avoiding intoxication.
      Graphical abstract image

      PubDate: 2014-04-16T04:14:08Z
  • Host plant-specific remodeling of midgut physiology in the generalist
           insect herbivore Trichoplusia ni
    • Abstract: Publication date: Available online 12 April 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Marco Herde , Gregg A. Howe
      Species diversity in terrestrial ecosystems is influenced by plant defense compounds that alter the behavior, physiology, and host preference of insect herbivores. Although it is established that insects evolved the ability to detoxify specific allelochemicals, the mechanisms by which polyphagous insects cope with toxic compounds in diverse host plants are not well understood. Here, we used defended and non-defended plant genotypes to study how variation in chemical defense affects midgut responses of the lepidopteran herbivore Trichoplusia ni, which is a pest of a wide variety of native and cultivated plants. The genome-wide midgut transcriptional response of T. ni larvae to glucosinolate-based defenses in the crucifer Arabidopsis thaliana was characterized by strong induction of genes encoding Phase I and II detoxification enzymes. In contrast, the response of T. ni to proteinase inhibitors and other jasmonate-regulated defenses in tomato (Solanum lycopersicum) was dominated by changes in the expression of digestive enzymes and, strikingly, concomitant repression of transcripts encoding detoxification enzymes. Unbiased proteomic analyses of T. ni feces demonstrated that tomato defenses remodel the complement of digestive enzymes, which was associated with increased amounts of serine proteases and decreased lipase protein abundance upon encountering tomato defense chemistry. These collective results indicate that T. ni adjusts its gut physiology to the presence of host plant-specific chemical defenses, and further suggest that plants may exploit this digestive flexibility as a defensive strategy to suppress the production of enzymes that detoxify allelochemicals.
      Graphical abstract image

      PubDate: 2014-04-16T04:14:08Z
  • Wolbachia-Induced Paternal Defect in Drosophila is likely by Interaction
           with the Juvenile Hormone Pathway
    • Abstract: Publication date: Available online 8 April 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Chen Liu , Jia-Lin Wang , Ya Zheng , En-Juan Xiong , Jing-Jing Li , Lin-Ling Yuan , Xiao-Qiang Yu , Yu-Feng Wang
      Wolbachia are endosymbionts that infect many insect species. They can manipulate the host’s reproduction to increase their own maternal transmission. Cytoplasmic incompatibility (CI) is one such manipulation, which is expressed as embryonic lethality when Wolbachia-infected males mate with uninfected females. However, matings between males and females carrying the same Wolbachia strain result in viable progeny. The molecular mechanisms of CI are currently not clear. We have previously reported that the gene Juvenile hormone-inducible protein 26 (JhI-26) exhibited the highest upregulation in the 3rd instar larval testes of Drosophila melanogaster when infected by Wolbachia. This is reminiscent of an interaction between Wolbachia and juvenile hormone (JH) pathway in flies. Considering that Jhamt gene encodes JH acid methyltransferase, a key regulatory enzyme of JH biosynthesis, and that methoprene-tolerant (Met) has been regarded as the best JH receptor candidate, we first compared the expression of Jhamt and Met between Wolbachia-infected and uninfected fly testes to investigate whether Wolbachia infection influence the JH signaling pathway. We found that the expressions of Jhamt and Met were significantly increased in the presence of Wolbachia, suggesting an interaction of Wolbachia with the JH signaling pathway. Then, we found that overexpression of JhI-26 in Wolbachia-free transgenic male flies caused paternal-effect lethality that mimics the defects associated with CI. JhI-26 overexpressing males resulted in significantly decrease in hatch rate. Surprisingly, Wolbachia-infected females could rescue the egg hatch. In addition, we showed that overexpression of JhI-26 caused upregulation of the male accessory gland protein (Acp) gene CG10433, but not vice versa. This result suggests that JhI-26 may function at the upstream of CG10433. Likewise, overexpression of CG10433 also resulted in paternal-effect lethality. Both JhI-26 and CG10433 overexpressing males resulted in nuclear division defects in the early embryos. Finally, we found that Wolbachia-infected males decreased the propensity of the mated females to remating, a phenotype also caused by both JhI-26 and CG10433 overexpressing males. Taken together, our results provide a working hypothesis whereby Wolbachia induce paternal defects in Drosophila probably by interaction with the JH pathway via JH response genes JhI-26 and CG10433.
      Graphical abstract image

      PubDate: 2014-04-11T02:14:26Z
  • Editorial Board
    • Abstract: Publication date: May 2014
      Source:Insect Biochemistry and Molecular Biology, Volume 48

      PubDate: 2014-04-11T02:14:26Z
  • bmnpv-miR-3 facilitates BmNPV infection by modulating the expression of
           viral P6.9 and other late genes in Bombyx mori
    • Abstract: Publication date: Available online 1 April 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): C.P. Singh , J. Singh , J. Nagaraju
      During the last decade, microRNAs (miRNAs) have emerged as fine tuners of gene expression in various biological processes including host-pathogen interactions. Apart from the role of host encoded miRNAs in host-virus interactions, recent studies have also indicated the key role of virus-encoded miRNAs in the regulation of host defense responses. In the present study, we show that bmnpv-miR-3, a Bombyx mori nucleopolyhedrovirus (BmNPV) encoded miRNA, regulates the expression of DNA binding protein (P6.9) and other late genes, vital for the late stage of viral infection in the host, Bombyx mori. We have performed both cell culture and in vivo experiments to establish the role of bmnpv-miR-3 in the infection cycle of BmNPV. Our findings showed that bmnpv-miR-3 expresses during early stage of infection, and negatively regulates the expression of P6.9. There was an upregulation in P6.9 expression upon blocking of bmnpv-miR-3 by Locked Nucleic Acid (LNA), whereas overexpression of bmnpv-miR-3 resulted in a decreased expression of P6.9. Besides, a remarkable enhancement and reduction in the viral loads were observed upon blocking and overexpression of bmnpv-miR-3, respectively. Furthermore, we have also assessed the host immune response using one of the Lepidoptera-specific antimicrobial proteins, Gloverin-1 upon blocking and overexpression of bmnpv-miR-3, which correlated viral load with the host immune response. All these results together; clearly imply that bmnpv-miR-3-mediated controlled regulation of BmNPV late genes in the early stage of infection helps BmNPV to escape the early immune response from the host.
      Graphical abstract image

      PubDate: 2014-04-06T00:13:08Z
  • Molecular Biology of Insect Sodium Channels and Pyrethroid Resistance
    • Abstract: Publication date: Available online 3 April 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Ke Dong , Yuzhe Du , Frank Rinkevich , Yoshiko Nomura , Peng Xu , Lingxin Wang , Kristopher Silver , Boris S. Zhorov
      Voltage-gated sodium channels are essential for the initiation and propagation of the action potential in neurons and other excitable cells. Because of their critical roles in electrical signaling, sodium channels are targets of a variety of naturally occurring and synthetic neurotoxins, including several classes of insecticides. This review is intended to provide an update on the molecular biology of insect sodium channels and the molecular mechanism of pyrethroid resistance. Although mammalian and insect sodium channels share fundamental topological and functional properties, most insect species carry only one sodium channel gene, compared to multiple sodium channel genes found in each mammalian species. Recent studies showed that two posttranscriptional mechanisms, alternative splicing and RNA editing, are involved in generating functional diversity of sodium channels in insects. More than 50 sodium channel mutations have been identified to be responsible for or associated with knockdown resistance (kdr) to pyrethroids in various arthropod pests and disease vectors. Elucidation of molecular mechanism of kdr led to the identification of dual receptor sites of pyrethroids on insect sodium channels. Most of the kdr mutations appear to be located within or close to the two receptor sites. The accumulating knowledge of insect sodium channels and their interactions with insecticides provides a foundation for understanding the neurophysiology of sodium channels in vivo and the development of new and safer insecticides for effective control of arthropod pests and human disease vectors.
      Graphical abstract image

      PubDate: 2014-04-06T00:13:08Z
  • Highly Efficient Multiplex Targeted Mutagenesis and Genomic Structure
           Variation in Bombyx mori Cells Using CRISPR/Cas9
    • Abstract: Publication date: Available online 31 March 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Yuanyuan Liu , Sanyuan Ma , Xiaogang Wang , Jiasong Chang , Jie Gao , Run Shi , Jianduo Zhang , Wei Lu , Yue Liu , Ping Zhao , Qingyou Xia
      Bombyx mori is an economically important insect and a model organism for studying lepidopteran and arthropod biology. Using a highly efficient CRISPR/Cas9 system, we showed that this system could mediate highly efficient targeted genome editing of a single gene locus, large chromosomal deletion or inversion, and also multiplex genome editing of 6 genes simultaneously in BmNs cell line derived from B. mori. The simplicity and high efficiency of our system provide unprecedented possibilities for researchers to implement precise and sophisticated manipulation of a chosen B. mori gene in BmNs cells easily in a limited time course, and perhaps new opportunities for functional genomics of B. mori and other lepidopteran insects.
      Graphical abstract image

      PubDate: 2014-03-31T20:20:00Z
  • Two essential peritrophic matrix proteins mediate matrix barrier functions
           in the insect midgut
    • Abstract: Publication date: Available online 26 March 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Sinu Agrawal , Marco Kelkenberg , Khurshida Begum , Steinfeld Lea , Clay E. Williams , Karl J. Kramer , Richard W. Beeman , Yoonseong Park , Subbaratnam Muthukrishnan , Hans Merzendorfer
      The peritrophic matrix (PM) in the midgut of insects consists primarily of chitin and proteins and is thought to support digestion and provide protection from abrasive food particles and enteric pathogens. We examined the physiological roles of 11 putative peritrophic matrix protein (PMP) genes of the red flour beetle, Tribolium castaneum (TcPMPs). TcPMP genes are differentially expressed along the length of the midgut epithelium of feeding larvae. RNAi of individual PMP genes revealed no abnormal developmental phenotypes for 9 of the 11 TcPMPs. However, RNAi for two PMP genes, TcPMP3 and TcPMP5-B, resulted in depletion of the fat body, growth arrest, molting defects and mortality. In situ permeability assays after oral administration of different-sized FITC-dextran beads demonstrated that the exclusion size of the larval peritrophic matrix (PM) decreases progressively from >2 MDa to <4 kDa from the anterior to the most posterior regions of the midgut. In the median midguts of control larvae, 2 MDa dextrans were completely retained within the PM lumen, whereas after RNAi for TcPMP3 and TcPMP5-B, these dextrans penetrated the epithelium of the median midgut, indicating loss of structural integrity and barrier function of the larval PM. In contrast, RNAi for TcPMP5-B, but not RNAi for TcPMP3, resulted in breakdown of impermeability to 4 and 40 kDa dextrans in the PM of the posterior midgut. These results suggest that specific PMPs are involved in the regulation of PM permeability, and that a gradient of barrier function is essential for survival and fat body maintenance.
      Graphical abstract image

      PubDate: 2014-03-31T20:20:00Z
  • A Major Facilitator Superfamily protein encoded by TcMucK gene is not
           required for cuticle pigmentation, growth and development in Tribolium
    • Abstract: Publication date: Available online 28 March 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Seulgi Mun , Mi Young Noh , Mizuko Osanai-Futahashi , Subbaratnam Muthukrishnan , Karl J. Kramer , Yasuyuki Arakane
      Insect cuticle pigmentation and sclerotization (tanning) are vital physiological processes for insect growth, development and survival. We have previously identified several colorless precursor molecules as well as enzymes involved in their biosynthesis and processing to yield the mature intensely colored body cuticle pigments. A recent study indicated that the Bombyx mori (silkmoth) gene, BmMucK, which encodes a protein orthologous to a Culex pipiens quiquefasciatus (Southern house mosquito) cis,cis, muconate transporter, is a member of the “Major Facilitator Superfamily” (MFS) of transporter proteins and is associated with the appearance of pigmented body segments of naturally occurring body color mutants of B. mori. While RNA interference of the BmMucK gene failed to result in any observable phenotype, RNAi using a dsRNA for an orthologous gene from the red flour beetle, Tribolium castaneum, was reported to result in molting defects and darkening of the cuticle and some body parts, leading to the suggestion that orthologs of MucK genes may differ in their functions among insects. To verify the role and essentiality of the ortholog of this gene in development and body pigmentation function in T. castaneum we obtained cDNAs for the orthologous gene (TcMucK) from RNA isolated from the GA-1 wild-type strain of T. castaneum. The sequence of a 1524 nucleotides-long cDNA for TcMucK which encodes the putatively full-length protein, was assembled from two overlapping RT-PCR fragments and the expression profile of this gene during development was analyzed by real-time PCR. This cDNA encodes a 55.8 kDa protein consisting of 507 amino acid residues and includes 11 putative transmembrane segments. Transcripts of TcMucK were detected throughout all of the developmental stages analyzed. The function of this gene was explored by injection of two different double-stranded RNAs targeting different regions of the TcMucK gene (dsTcMucKs) into young larvae to down-regulate transcripts during subsequent stages of insect development until the adult stage. RNA interference of TcMucK had no observable effects on larval, pupal or adult pigmentation. In addition, it did not affect larval-larval, larval-pupal and pupal-adult molting or survival. Thus, in contrast to the results of Zhao et al. (2012), our study demonstrates that TcMucK is not essential for growth, development or cuticle pigmentation of T. castaneum.
      Graphical abstract image

      PubDate: 2014-03-31T20:20:00Z
  • Effects of different dietary conditions on the expression of trypsin- and
           chymotrypsin-like protease genes in the digestive system of the migratory
           locust, Locusta migratoria
    • Abstract: Publication date: Available online 17 March 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Jornt Spit , Sven Zels , Senne Dillen , Michiel Holtof , Niels Wynant , Jozef Vanden Broeck
      While technological advancements have recently led to a steep increase in genomic and transcriptomic data, and large numbers of protease sequences are being discovered in diverse insect species, little information is available about the expression of digestive enzymes in Orthoptera. Here we describe the identification of Locusta migratoria serine protease transcripts (cDNAs) involved in digestion, which might serve as possible targets for pest control management. A total of 5 putative trypsin and 15 putative chymotrypsin gene sequences were characterized. Phylogenetic analysis revealed that these are distributed among 3 evolutionary conserved clusters. In addition, we have determined the relative gene expression levels of representative members in the gut under different feeding conditions. This study demonstrated that the transcript levels for all measured serine proteases were strongly reduced after starvation. On the other hand, larvae of L. migratoria displayed compensatory effects to the presence of Soybean Bowman Birk (SBBI) and Soybean Trypsin (SBTI) inhibitors in their diet by differential upregulation of multiple proteases. A rapid initial upregulation was observed for all tested serine protease transcripts, while only for members belonging to class I, the transcript levels remained elevated after prolonged exposure. In full agreement with these results, we also observed an increase in proteolytic activity in midgut secretions of locusts that were accustomed to the presence of protease inhibitors in their diet, while no change in sensitivity to these inhibitors was observed. Taken together, this paper is the first comprehensive study on dietary dependent transcript levels of proteolytic enzymes in Orthoptera. Our data suggest that compensatory response mechanisms to protease inhibitor ingestion may have appeared early in insect evolution.
      Graphical abstract image

      PubDate: 2014-03-22T01:14:10Z
  • Identification of life-stage and tissue-specific splice variants of an
           inward rectifying potassium (Kir) channel in the yellow fever mosquito
           Aedes aegypti
    • Abstract: Publication date: Available online 18 March 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Matthew F. Rouhier , Peter M. Piermarini
      Inward-rectifier potassium (Kir) channels play key roles in nerve, muscle, and epithelial cells in mammals, but their physiological roles in insects remain to be determined. The yellow fever mosquito (Aedes aegypti) possesses five different genes encoding Kir channel subunits: Kir1, Kir2A, Kir2B, Kir2B′, and Kir3. We have recently cloned and characterized the Kir1, Kir2B, and Kir3 cDNAs in the renal (Malpighian) tubules of adult female Ae. aegypti. Here we characterize the expression of the Kir2A gene in Ae. aegypti, which was not abundantly expressed in Malpighian tubules. We find that the 1) Kir2A gene is expressed primarily in the midgut and hindgut of adult female mosquitoes, and 2) Kir2A mRNAs are alternatively spliced into three distinct variants (Kir2A-a, -b, and -c). The deduced Kir2A proteins from these splice forms share a completely conserved transmembrane domain (a pore-forming domain flanked by two transmembrane-spanning segments), but possess novel NH2-terminal and/or COOH-terminal domains. Semi-quantitative RT-PCR analyses indicate that the splice variants exhibit both developmental- and tissue-specific expression. Lastly, we provide insights into the conservation of alternative splicing among the Kir2A genes of dipterans, which may add molecular diversity that compensates for the relatively limited number of Kir channel genes in insects compared to mammals.
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      PubDate: 2014-03-22T01:14:10Z
  • Insulin receptor-mediated nutritional signalling regulates juvenile
           hormone biosynthesis and vitellogenin production in the German cockroach
    • Abstract: Publication date: Available online 21 March 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Marc Abrisqueta , Songül Süren-Castillo , José L. Maestro
      Female reproductive processes, which comprise, amongst others, the synthesis of yolk proteins and the endocrine mechanisms which regulate this synthesis, need a considerable amount of energy and resources. The role of communicating that the required nutritional status has been attained is carried out by nutritional signalling pathways and, in particular, by the insulin receptor (InR) pathway. In the present study, using the German cockroach, Blattella germanica, as a model, we analysed the role of InR in different processes, but mainly those related to juvenile hormone (JH) synthesis and vitellogenin production. We first cloned the InR cDNA from B. germanica (BgInR) and then determined that its expression levels were constant in corpora allata and fat body during the first female gonadotrophic cycle. Results showed that the observed increase in BgInR mRNA in fat body from starved compared to fed females was abolished in those females treated with systemic RNAi in vivo against the transcription factor BgFoxO. RNAi-mediated BgInR knockdown during the final two nymphal stages produced significant delays in the moults, together with smaller adult females which could not spread the fore- and hindwings properly. In addition, BgInR knockdown led to a severe inhibition of juvenile hormone synthesis in adult female corpora allata, with a concomitant reduction of mRNA levels corresponding to 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase-1, HMG-CoA synthase-2, HMG-CoA reductase and methyl farnesoate epoxidase. BgInR RNAi treatment also reduced fat body vitellogenin mRNA and oocyte growth. Our results show that BgInR knockdown produces similar phenotypes to those obtained in starved females in terms of corpora allata activity and vitellogenin synthesis, and indicate that the InR pathway mediates the activation of JH biosynthesis and vitellogenin production elicited by nutrition signalling.
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      PubDate: 2014-03-22T01:14:10Z
  • Identification and characterization of plant cell wall degrading enzymes
           from three glycoside hydrolase families in the cerambycid beetle Apriona
    • Abstract: Publication date: Available online 21 March 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Yannick Pauchet , Roy Kirsch , Sandra Giraud , Heiko Vogel , David G. Heckel
      Xylophagous insects have evolved to thrive in a highly challenging environment. For example, wood-boring beetles from the family Cerambycidae feed exclusively on woody tissues, and to efficiently access the nutrients present in this sub-optimal environment, they have to cope with the lignocellulose barrier. Whereas microbes of the insect’s gut flora were hypothesized to be responsible for the degradation of lignin, the beetle itself depends heavily on the secretion of a range of enzymes, known as plant cell wall degrading enzymes (PCWDEs), to efficiently digest both hemicellulose and cellulose networks. Here we sequenced the larval gut transcriptome of the Mulberry longhorn beetle, Apriona japonica (Cerambycidae, Lamiinae), in order to investigate the arsenal of putative PCWDEs secreted by this species. We combined our transcriptome with all available sequencing data derived from other cerambycid beetles in order to analyze and get insight into the evolutionary history of the corresponding gene families. Finally, we heterologously expressed and functionally characterized the A. japonica PCWDEs we identified from the transcriptome. Together with a range of endo-β-1,4-glucanases, we describe here for the first time the presence in a species of Cerambycidae of (i) a xylanase member of the subfamily 2 of glycoside hydrolase family 5 (GH5 subfamily 2), as well as (ii) an exopolygalacturonase from family GH28. Our analyses greatly contribute to a better understanding of the digestion physiology of this important group of insects, many of which are major pests of forestry worldwide.
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      PubDate: 2014-03-22T01:14:10Z
  • Editorial Board
    • Abstract: Publication date: April 2014
      Source:Insect Biochemistry and Molecular Biology, Volume 47

      PubDate: 2014-03-17T02:21:19Z
  • Induction of soluble AChE expression via alternative splicing by chemical
           stress in Drosophila melanogaster
    • Abstract: Publication date: Available online 15 March 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Young Ho Kim , Deok Ho Kwon , Hyo Min Ahn , Young Ho Koh , Si Hyeock Lee
      Various molecular forms of acetylcholinesterase (AChE) have been characterized in insects. Post-translational modification is known to be a major mechanism for the molecular diversity of insect AChE. However, multiple forms of Drosophila melanogaster AChE (DmAChE) were recently suggested to be generated via alternative splicing (Kim and Lee, 2013). To confirm alternative splicing as the mechanism for generating the soluble form of DmAChE, we generated a transgenic fly strain carrying the cDNA of DmAChE gene (Dm_ace) that predominantly expressed a single transcript variant encoding the membrane-anchored dimer. 3′ RACE (rapid amplification of cDNA ends) and western blotting were performed to compare Dm_ace transcript variants and DmAChE forms between wild-type and transgenic strains. Various Dm_ace transcripts and DmAChE molecular forms were observed in wild-type flies, whereas the transgenic fly predominantly expressed Dm_ace transcript variant encoding the membrane-anchored dimer. This supports alternative splicing as the major determinant in the generation of multiple forms of DmAChE. In addition, treatment with DDVP as a chemical stress induced the expression of the Dm_ace splice variant without the glycosylphosphatidylinositol anchor site in a dose-dependent manner and, accordingly, the soluble form of DmAChE in wild-type flies. In contrast, little soluble DmAChE was expressed in the transgenic fly upon exposure to DDVP. DDVP bioassays revealed that transgenic flies, which were unable to express a sufficient amount of soluble monomeric DmAChE, were more sensitive to DDVP compared to wild-type flies, suggesting that the soluble monomer may exert non-neuronal functions, such as chemical defense against xenobiotics.
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      PubDate: 2014-03-17T02:21:19Z
  • Sequence similarity and functional comparisons of pheromone receptor
           orthologs in two closely related Helicoverpa species
    • Abstract: Publication date: Available online 14 March 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Xiao-Jing Jiang , Hao Guo , Chang Di , Shanlin Yu , Ligui Zhu , Ling-Qiao Huang , Chen-Zhu Wang
      The olfactory system of moth species in subfamily Heliothinae is an attractive model to study the evolution of the pheromone reception because they show distinct differentiation in sex pheromone components or ratios that activate pheromone receptors (PRs). However, functional assessment of PRs in closely related species remains largely untried. Here we present a special cloning strategy to isolate full-length cDNAs encoding candidate odorant receptors (ORs) from Helicoverpa armigera (Harm) and Helicoverpa assulta (Hass) on the basis of Heliothis virescens ORs, and investigate the functional properties of PRs to determine how the evolution of moth PRs contribute to intraspecific mating choice and speciation extension. We cloned 11 OR orthologs from H. armigera and 10 from H. assulta. We functionally characterized the responses of PRs of both species to seven pheromone compounds using the heterologous expression system of Xenopus ooctyes. HassOR13 was found to be highly tuned to the sex pheromone component Z11-16:Ald, and unexpectedly, both HarmOR14b and HassOR16 were specific for Z9-14:Ald. However, HarmOR6 and HassOR6 showed much higher specificity to Z9-16:OH than to Z9-16:Ald or Z9-14:Ald. HarmOR11, HarmOR14a, HassOR11 and HassOR14b failed to respond to the tested chemicals. Based on our results and previous research, we can show that some PR orthologs from H. armigera, H. assulta and H. virescens such as OR13s have similar ligand selectivity, but others have different ligand specificity. The combined PR function and sex pheromone component analysis suggests that the evolution of PRs can meet species-specific demands.
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      PubDate: 2014-03-17T02:21:19Z
  • Duplication of acetylcholinesterase gene in diamondback moth strains with
           different sensitivities to acephate
    • Abstract: Publication date: Available online 13 March 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Shoji Sonoda , Xueyan Shi , Dunlun Song , Pei Liang , Xiwu Gao , Youjun Zhang , Jianhong Li , Yong Liu , Ming Li , Masaya Matsumura , Sachiyo Sanada , Chieka Minakuchi , Toshiharu Tanaka , Tadashi Miyata
      This study examined the acetylcholinesterase 1 gene (AChE1) in P. xylostella strains with different sensitivities to acephate. Multiple haplotypes of the gene were found in the field-collected strains including distinct haplotypes carrying one or both previously reported mutations (A298S and G324A). Moreover, sequencing results indicated the presence of duplicated copies of the gene in the field-collected strains. No correlation was found between copy numbers of AChE1 and levels of resistance to acephate suggesting that extensive AChE1 duplication is not a major resistance factor at least in some P. xylostella strains. Proportions of the A298S and G324A mutations showed no correlation with levels of resistance to acephate. This suggests that acephate resistance of P. xylostella is complex and cannot be evaluated based on the AChE1 copy number or proportions of the resistance mutations alone.
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      PubDate: 2014-03-17T02:21:19Z
  • Identification of Pheromone Components and their Binding Affinity to the
           Odorant Binding Protein CcapOBP83a-2 of the Mediterranean Fruit Fly,
           Ceratitis capitata
    • Abstract: Publication date: Available online 7 March 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): P. Siciliano , X.L. He , C. Woodcock , J.A. Pickett , L.M. Field , M.A. Birkett , B. Kalinova , L.M. Gomulski , F. Scolari , G. Gasperi , A.R. Malacrida , J.J. Zhou
      The Mediterranean fruit fly (or medfly), Ceratitis capitata (Wiedemann; Diptera: Tephritidae), is a serious pest of agriculture worldwide, displaying a very wide larval host range with more than 250 different species of fruit and vegetables. Olfaction plays a key role in the invasive potential of this species. Unfortunately, the pheromone communication system of the medfly is complex and still not well established. In this study, we report the isolation of chemicals emitted by sexually mature individuals during the “calling” period and the electrophysiological responses that these compounds elicit on the antennae of male and female flies. Fifteen compounds with electrophysiological activity were isolated and identified in male emissions by gas chromatography coupled to electroantennography (GC-EAG). Within the group of 15 identified compounds, 11 elicited a response in antennae of both sexes, whilst 4 elicited a response only in female antennae. The binding affinity of these compounds, plus 4 additional compounds known to be behaviourally active from other studies, was measured using C. capitata OBP, CcapOBP83a-2. This OBP has a high homology to Drosophila melanogaster OBPs OS-E and OS-F, which are associated with trichoid sensilla and co-expressed with the well-studied Drosophila pheromone binding protein LUSH. The results provide evidence of involvement of CcapOBP83a-2 in the medfly’s odorant perception and its wider specificity for (E,E)-α-farnesene, one of the five major compounds in medfly male pheromone emission. This represents the first step in the clarification of the C. capitata and pheromone reception pathway, and a starting point for further studies aimed towards the creation of new powerful attractants or repellents applicable in the actual control strategies.
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      PubDate: 2014-03-11T23:14:12Z
  • Cross-linking in the silks of bees, ants and hornets
    • Abstract: Publication date: Available online 7 March 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Peter M. Campbell , Holly E. Trueman , Qiang Zhang , Katsura Kojima , Tsunenori Kameda , Tara D. Sutherland
      Silk production is integral to the construction of nests or cocoons for many Aculeata, stinging Hymenopterans such as ants, bees and wasps. Here we report the sequences of new aculeate silk proteins and compare cross-linking among nine native silks from three bee species (Apis mellifera, Bombus terrestris and Megachile rotundata), three ant species (Myrmecia forficata, Oecophylla smaragdina and Harpegnathos saltator) and three hornets (Vespa analis, Vespa simillima and Vespa mandarinia). The well studied silks of spiders and silkworms are comprised of large proteins that are cross-linked and stabilized predominantly by intra and intermolecular beta sheet structure. In contrast, the aculeate silks are comprised of relatively small proteins that contain central coiled coil domains and comparatively reduced amounts of beta sheet structure. The hornet silks, which have the most beta sheet structure and the greatest amount of amino acid sequence outside the coiled-coil domains, dissolve in concentrated LiBr solution and appear to be stabilized predominantly by beta sheet structure like the classic silks. In contrast, the ant and bee silks, which have less beta sheet and less sequence outside the coiled-coil domains, could not be dissolved in LiBr and appear to be predominantly stabilized by covalent cross-linking. The iso-peptide cross-linker, ε-(γ-glutamyl)-lysine that is produced by transglutaminase enzymes, was demonstrated to be present in all silks by mass spectrometry, but at greater levels in silks of ants and bees. The bee silks and ant cocoons, but not the Oecophylla nest silks, appeared to be further stabilized by tanning reactions.
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      PubDate: 2014-03-11T23:14:12Z
  • The Maxillary Palp of Aedes aegypti, a Model of Multisensory Integration
    • Abstract: Publication date: Available online 6 March 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Jonathan D. Bohbot , Jackson T. Sparks , Joseph C. Dickens
      Female yellow-fever mosquitoes, Aedes aegypti, are obligate blood-feeders and vectors of the pathogens that cause dengue fever, yellow fever and Chikungunya. This feeding behavior concludes a series of multisensory events guiding the mosquito to its host from a distance. The antennae and maxillary palps play a major role in host detection and other sensory-mediated behaviors. Compared to the antennae, the maxillary palps are a relatively simple organ and thus an attractive model for exploration of the neuromolecular networks underlying chemo- and mechanosensation. In this study, we surveyed the expressed genetic components and examined their potential involvement with these sensory modalities. Using Illumina sequencing, we identified the transcriptome of the maxillary palps of physiologically mature female Ae. aegypti. Genes expressed in the maxillary palps included those involved in sensory reception, signal transduction and neuromodulation. In addition to previously reported chemosensory genes, we identified candidate transcripts potentially involved in mechanosensation and thermosensation. This survey lays the groundwork to explore sensory networks in an insect appendage. The identification of genes involved in thermosensation provides prospective molecular targets for the development of chemicals aimed at disrupting the behavior of this medically important insect.
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      PubDate: 2014-03-06T21:23:09Z
  • Global distribution and origin of target site insecticide resistance
           mutations in Tetranychus urticae
    • Abstract: Publication date: Available online 3 March 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): A. Ilias , J. Vontas , A. Tsagkarakou
      The control of Tetranychus urticae, a worldwide agricultural pest, is largely dependent on pesticides. However, their efficacy is often compromised by the development of resistance. Recent molecular studies identified a number of target site resistance mutations, such as G119S, A201S, T280A, G328A, F331W in the acetylcholinesterase gene, L1024V, A1215D, F1538I in the voltage-gated sodium channel gene, G314D and G326E in glutamate-gated chloride channel genes, G126S, I136T, S141F, D161G, P262T in the cytochrome b and the I1017F in the chitin synthase 1 gene. We examined their distribution, by sequencing the relevant gene fragments in a large number of T. urticae collections from a wide geographic range. Our study revealed that most of the resistance mutations are spread worldwide, with remarkably variable frequencies. Furthermore, we analyzed the variability of the ace locus, which has been subjected to longer periods of selection pressure historically, to investigate the evolutionary origin of ace resistant alleles and determine whether they resulted from single or multiple mutation events. By sequencing a 1540 bp ace fragment, encompassing the resistance mutations and downstream introns in 139 T. urticae individuals from 27 countries, we identified 6 susceptible and 31 resistant alleles which have arisen from at least three independent mutation events. The frequency and distribution of these ace haplotypes varied geographically, suggesting an interplay between different mutational events, gene flow and local selection.
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      PubDate: 2014-03-06T21:23:09Z
  • The genetics of chemoreception in the labella and tarsi of Aedes aegypti
    • Abstract: Publication date: Available online 26 February 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Jackson T. Sparks , Jonathan D. Bohbot , Joseph C. Dickens
      The yellow-fever mosquito Aedes aegypti is a major vector of human diseases, such as dengue, yellow fever, chikungunya and West Nile viruses. Chemoreceptor organs on the labella and tarsi are involved in human host evaluation and thus serve as potential foci for the disruption of blood feeding behavior. In addition to host detection, these contact chemoreceptors mediate feeding, oviposition and conspecific recognition; however, the molecular landscape of chemoreception in these tissues remains mostly uncharacterized. Here we report the expression profile of all putative chemoreception genes in the labella and tarsi of both sexes of adult Ae. aegypti and discuss their possible roles in the physiology and behavior of this important disease vector.
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      PubDate: 2014-03-01T23:49:44Z
  • Semi-quantitative analysis of changes in the plasma peptidome of Manduca
           sexta larvae and their correlation with the transcriptome variations upon
           immune challenge
    • Abstract: Publication date: Available online 22 February 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Shuguang Zhang , Xiaolong Cao , Yan He , Steve Hartson , Haobo Jiang
      The tobacco hornworm, Manduca sexta, has been used as a biochemical model for studying insect physiological processes. While the transcriptomes of its fat body, hemocytes, midgut, and antennae have been examined in several studies, limited information is available for proteins in tissues, cells, or body fluids of this insect. In keeping pace with the M. sexta genome project, we launched a pilot study to identify differences in the peptidome of cell-free hemolymph samples from larvae injected with buffer or a mixture of bacteria. At 24 h after injection, plasma was collected and treated with 50% acetonitrile to precipitate large proteins. The supernatants, containing peptides (<25 kDa) and other stable proteins (>25 kDa), were digested with trypsin and analyzed by nano-liquid chromatography and nano-electrospray tandem mass spectrometry (nanoLC-MS/MS) on an LTQ Orbitrap XL mass spectrometer. Known M. sexta cDNA sequences and gene transcripts from the draft genome were translated in silico to generate a database of polypeptides (i.e. peptides and proteins) in this species. By searching the database, we identified 268 hemolymph polypeptides, 50 of which showed 1.67 to 200 fold abundance increases after the immune challenge, as judged by significant changes in normalized spectral counts between the control and induced plasma. These included a total of 33 antimicrobial peptides (attacins, cecropins, defensins, diapausins, gallerimycin, gloverin, lebocins, lysozymes), pattern recognition receptors, and proteinase inhibitors. Although there was no strong parallel (correlation coefficients: -0.13, 0.11, 0.39 and 0.62) between plasma peptide levels and their transcript levels in control or induced hemocytes or fat body, we observed the mRNA level changes in hemocytes and fat body concurred with their peptide level changes with correlation coefficients of 0.67 and 0.76, respectively. These data suggest that fat body contributed a significant portion of the plasma polypeptides involved in various aspects of innate immunity after the bacterial injection.
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      PubDate: 2014-02-25T02:54:19Z
  • The progress and future of enhancing antiviral capacity by transgenic
           technology in the silkworm Bombyx mori
    • Abstract: Publication date: Available online 20 February 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Liang Jiang , Qingyou Xia
      Bombyx mori is a common lepidopteran model and an important economic insect for silk production. B. mori nucleopolyhedrovirus (BmNPV) is a typical pathogenic baculovirus that causes serious economic losses in sericulture. B. mori and BmNPV are a model of insect host and pathogen interaction including invasion of the host by the pathogen, host response, and enhancement of host resistance. The antiviral capacity of silkworms can be improved by transgenic technology such as overexpression of an endogenous or exogenous antiviral gene, RNA interference of the BmNPV gene, or regulation of the immune pathway to inhibit BmNPV at different stages of infection. Antiviral capacity could be further increased by combining different methods. We discuss the future of an antiviral strategy in silkworm, including possible improvement of anti-BmNPV, the feasibility of constructing transgenic silkworms with resistance to multiple viruses, and the safety of transgenic silkworms. The silkworm model could provide a reference for disease control in other organisms.

      PubDate: 2014-02-20T07:15:48Z
  • Yolk proteins in the male reproductive system of the fruit fly Drosophila
           melanogaster: spatial and temporal patterns of expression
    • Abstract: Publication date: Available online 17 February 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Magdalena M. Majewska , Agnieszka Suszczynska , Joanna Kotwica-Rolinska , Tomasz Czerwik , Bohdan Paterczyk , Marta A. Polanska , Piotr Bernatowicz , Piotr Bebas
      In insects, spermatozoa develop in the testes as clones of single spermatogonia covered by specialized somatic cyst cells (cc). Upon completion of spermatogenesis, spermatozoa are released to the vas deferens, while the cc remain in the testes and die. In the fruit fly Drosophila melanogaster, the released spermatozoa first reach the seminal vesicles (SV), the organ where post-testicular maturation begins. Here, we demonstrate the temporal (restricted to the evening and early night hours) accumulation of membranous vesicles containing proteins in the SV lumen of D. melanogaster. When SV vesicles were isolated from the semen and co-incubated with testis-derived spermatozoa in vitro, their contents bound to the spermatozoa along their tails. The proteins of the SV vesicles were then characterized using 2-D electrophoresis. We identified a prominent protein spot of around 45-47 kDa, which disappears from the SV vesicles in the night, i.e. shortly after they appear in the SV lumen. Sequencing of peptides derived from this spot by mass spectrometry revealed identity with three yolk proteins (YP1-3). This unexpected result was confirmed by western blotting, which demonstrated that SV vesicles contain proteins that are immunoreactive with an antibody against D. melanogaster YP1-3. The expression of all yp genes was shown to be a unique feature of testis tissues. Using RNA probes we found that their transcripts localize exclusively to the cc that cover fully developed spermatozoa in the distal part of each testis. Temporally, the expression of yp genes was found to be restricted to a short period during the day and is followed by the evening accumulation of YP proteins in the cc. Immunohistochemical staining confirmed that cc are the source of SV vesicles containing YPs that are released into the SV lumen. These vesicles interact with spermatozoa and as a result, YPs become extrinsic proteins of the sperm membrane. Thus, we describe for the first time the expression of yolk proteins in the male reproductive system of D. melanogaster under physiological conditions, and show that somatic cells of the testes are the source of these proteins.
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      PubDate: 2014-02-20T07:15:48Z
  • Editorial Board
    • Abstract: Publication date: March 2014
      Source:Insect Biochemistry and Molecular Biology, Volume 46

      PubDate: 2014-02-15T04:15:42Z
  • Identification of conserved and novel microRNAs in Manduca sexta and their
           possible roles in the expression regulation of immunity-related genes
    • Abstract: Publication date: Available online 5 February 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Xiufeng Zhang , Yun Zheng , Guru Jagadeeswaran , Ren Ren , Ramanjulu Sunkar , Haobo Jiang
      The tobacco hornworm Manduca sexta has served as a model for insect biochemical and physiological research for decades. However, knowledge of the posttranscriptional regulation of gene expression by microRNAs is still rudimentary in this species. Our previous study (Zhang et al., 2012) identified 163 conserved and 13 novel microRNAs in M. sexta, most of which were present at low levels in pupae. To identify additional M. sexta microRNAs and more importantly to examine their possible roles in the expression regulation of immunity-related genes, we constructed four small RNA libraries using fat body and hemocytes from naïve or bacteria-injected larvae and obtained 32.9 million reads of 18-31 nucleotides by Illumina sequencing. Mse-miR-929 and mse-miR-1b (antisense microRNA of mse-miR-1) were predicted in the previous study and now found to be conserved microRNAs in the tissue samples. We also found four novel microRNAs, two of which result from a gene cluster. Mse-miR-281-star, mse-miR-965-star, mse-miR-31-star, and mse-miR-9b-star were present at higher levels than their respective mature strands. Abundance changes of microRNAs were observed after the immune challenge. Based on the quantitative data of mRNA levels in control and induced fat body and hemocytes as well as the results of microRNA target site prediction, we suggest that certain microRNAs and microRNA*s regulate gene expression for pattern recognition, prophenoloxidase activation, cellular responses, antimicrobial peptide synthesis, and conserved intracellular signal transduction (Toll, IMD, JAK-STAT, MAPK-JNK-p38, and small interfering RNA pathways). In summary, this study has enriched our knowledge on M. sexta microRNAs and how some of them may participate in the expression regulation of immunity-related genes.
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      PubDate: 2014-02-05T07:20:02Z
  • Genomic analysis of the interactions between social environment and social
           communication systems in honey bees (Apis mellifera)
    • Abstract: Publication date: Available online 31 January 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Osnat Malka , Elina L. Niño , Christina M. Grozinger , Abraham Hefetz
      Social context is often a primary regulator of social behavior, but genes that affect or are affected by social context have rarely been investigated. In social insects, caste specific pheromones are key modulators of social behavior, e.g., in honey bees the queen mandibular gland (MG) pheromone mediates reproductive dominance, its absence prompting ovary activation and queen pheromone production in workers. Here, we investigate the effect of social environment on genome-wide expression patterns in the MG, to determine how social context modulates expression of genes that, in turn alter social environment. We used microarrays to examine the MGs of virgin and mated queens, and queenright (QR) and queenless (QL) workers with or without activated ovaries. Approximately 2554 transcripts were significantly differentially expressed among these groups, with caste and social context being the main regulators of gene expression patterns, while physiological state (ovary activation) only minimally affecting gene expression. Thus, social context strongly regulates expression of genes, which, in turn, shape social environment. Among these, 25 genes that are putatively involved in caste selective production of the fatty-acid derived MG pheromone were differentially expressed in queens and workers. These genes whose functions correspond with enzymatic or transport processes emphasize the occurrence of disparate pheromone biosynthetic pathways for queens and workers, adding another dimension regarding the regulation of these important pheromones. Gene ontology analysis also revealed genes of different functional categories whose expression was impacted by caste or by the social environment, suggesting that the MG has broader functions than pheromone biosynthesis.
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      PubDate: 2014-02-05T07:20:02Z
  • Editorial Board
    • Abstract: Publication date: February 2014
      Source:Insect Biochemistry and Molecular Biology, Volume 45

      PubDate: 2014-02-05T07:20:02Z
  • A recombinant fusion protein containing a spider toxin specific for the
           insect voltage-gated sodium ion channel shows oral toxicity towards
           insects of different orders
    • Abstract: Publication date: Available online 29 January 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Sheng Yang , Prashant Pyati , Elaine Fitches , John A. Gatehouse
      Recombinant fusion protein technology allows specific insecticidal protein and peptide toxins to display activity in orally-delivered biopesticides. The spider venom peptide δ-amaurobitoxin-PI1a, which targets insect voltage-gated sodium channels, was fused to the "carrier" snowdrop lectin (GNA) to confer oral toxicity. The toxin itself (PI1a) and an amaurobitoxin / GNA fusion protein (PI1a/GNA) were produced using the yeast Pichia pastoris as expression host. Although both proteins caused mortality when injected into cabbage moth (Mamestra brassicae) larvae, the PI1a/GNA fusion was approximately 6 times as effective as recombinant PI1a on a molar basis. PI1a alone was not orally active against cabbage moth larvae, but a single 30μg dose of the PI1a/GNA fusion protein caused 100% larval mortality within 6 days when fed to 3rd instar larvae, and caused significant reductions in survival, growth and feeding in 4th - 6th instar larvae. Transport of fusion protein from gut contents to the haemolymph of cabbage moth larvae, and binding to the nerve chord, was shown by Western blotting. The PI1a/GNA fusion protein also caused mortality when delivered orally to dipteran (Musca domestica; housefly) and hemipteran (Acyrthosiphon pisum; pea aphid) insects, making it a promising candidate for development as a biopesticide.
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      PubDate: 2014-01-31T22:19:54Z
  • Identification of two acetylcholinesterases in Pardosa pseudoannulata and
           the sensitivity to insecticides
    • Abstract: Publication date: Available online 23 January 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Yixi Zhang , Ying Shao , Feng Jiang , Jian Li , Zewen Liu
      Pardosa pseudoannulata is an important predatory enemy against insect pests, such as rice planthoppers and leafhoppers. In order to understand the insecticide selectivity between P. pseudoannulata and insect pests, two acetylcholinesterase genes, Pp-ace1 and Pp-ace2, were cloned from this natural enemy. The putative proteins encoded by Pp-ace1 and Pp-ace2 showed high similarities to insect AChE1 (63% to Liposcelis entomophila AChE1) and AChE2 (36% to Culex quinquefasciatus AChE2) with specific functional motifs, which indicated that two genes might encode AChE1 and AChE2 proteins respectively. The recombinant proteins by expressing Pp-ace1 and Pp-ace2 genes in insect sf9 cells showed high AChE activities. The kinetic parameters, V max and K m , of two recombinant AChE proteins were significantly different. The sensitivities to six insecticides were determined in two recombinant AChEs. Pp-AChE1 was more sensitive to all tested insecticides than Pp-AChE2, such as fenobucarb (54 times in K i ratios), isoprocarb (31 times), carbaryl (13 times) and omethoate (6 times). These results indicated that Pp-AChE1 might be the major synaptic enzyme in the spider. By sequence comparison of P. pseudoannulata and insect AChEs, the key amino acid differences at or close to the functional sites were found. The locations of some key amino acid differences were consistent with the point mutation sites in insect AChEs that were associated with insecticide resistance, such as Phe331 in Pp-AChE2 corresponding to Ser331Phe mutation in Myzus persicae and Aphis gossypii AChE2, which might play important roles in insecticide selectivity between P. pseudoannulata and insect pests. Of course, the direct evidences are needed through further studies.
      Graphical abstract image

      PubDate: 2014-01-27T12:18:59Z
  • Abamectin is metabolized by CYP392A16, a cytochrome P450 associated with
           high levels of acaricide resistance in Tetranychus urticae
    • Abstract: Publication date: Available online 23 January 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): M. Riga , D. Tsakireli , A. Ilias , E. Morou , A. Myridakis , E.G. Stephanou , R. Nauen , W. Dermauw , T. Van Leeuwen , M. Paine , J. Vontas
      Abamectin is one of the most important insecticides worldwide. It is used against major agricultural pests and insects of public health importance, as well as against endoparasites in animal health. Abamectin has been used successfully for the control of the spider mite Tetranychus urticae, a major agricultural pest with global distribution, an extremely diverse host range, and a remarkable ability to develop resistance against insecticides including abamectin. Target site resistance mutations may explain a large part of resistance, although genetic evidence and transcriptomic data indicated that additional mechanisms may also be implicated in the abamectin resistant phenotype. To investigate a functional link between cytochrome P450-mediated metabolism and abamectin resistance, we recombinantly expressed three cytochrome P450s (CYP392A16, CYP392D8 and CYP392D10) that have been associated with high levels of abamectin resistance in a resistant T. urticae strain isolated from Greece. CYP392A16 was expressed predominately in its P450 form however, both CYP392D8 and CYP392D10 were expressed predominately as P420, despite optimization efforts on expression conditions. CYP392A16 catalyses the hydroxylation of abamectin (Kcat= 0.54 pmol/min/pmol P450; Km= 45.9 μM), resulting in a substantially less toxic compound as confirmed by bioassays with the partially purified metabolite. However, CYP392A16 did not metabolize hexythiazox, clofentezine and bifenthrin, active ingredients that also showed reduced toxicity in the abamectin resistant strain. Among a number of fluorescent and luminescent substrates screened, Luciferin-ME EGE was preferentially metabolized by CYP392A16, and it may be a potential diagnostic probe for metabolic resistance detection and monitoring.
      Graphical abstract image

      PubDate: 2014-01-27T12:18:59Z
  • Comparative analysis of two phenologically divergent populations of the
           pine processionary moth (Thaumetopoea pityocampa) by de novo transcriptome
    • Abstract: Publication date: Available online 24 January 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Bernhard Gschloessl , Heiko Vogel , Christian Burban , David Heckel , Réjane Streiff , Carole Kerdelhué
      The pine processionary moth Thaumetopoea pityocampa is a Mediterranean lepidopteran defoliator that experiences a rapid range expansion towards higher latitudes and altitudes due to the current climate warming. Its phenology - the time of sexual reproduction - is certainly a key trait for the local adaptation of the processionary moth to climatic conditions. Moreover, an exceptional case of allochronic differentiation was discovered ca. 15 years ago in this species. A population with a shifted phenology (the summer population, SP) co-exists near Leiria, Portugal, with a population following the classical cycle (the winter population, WP). The existence of this population is an outstanding opportunity to decipher the genetic bases of phenology. No genomic resources were so far available for T. pityocampa. We developed a high-throughput sequencing approach to build a first reference transcriptome, and to proceed with comparative analyses of the sympatric SP and WP. We pooled RNA extracted from whole individuals of various developmental stages, and performed a transcriptome characterisation for both populations combining Roche 454-FLX and traditional Sanger data. The obtained sequences were clustered into ca. 12,000 transcripts corresponding to 9,265 unigenes. The mean transcript coverage was 21.9 reads per bp. Almost 70% of the de novo assembled transcripts displayed significant similarity to previously published proteins and around 50% of the transcripts contained a full-length coding region. Comparative analyses of the population transcriptomes allowed to investigate genes specifically expressed in one of the studied populations only, and to identify the most divergent homologous SP/WP transcripts. The most divergent pairs of transcripts did not correspond to obvious phenology-related candidate genes, and 43% could not be functionally annotated. This study provides the first comprehensive genome-wide resource for the target species T. pityocampa. Many of the assembled genes are orthologs of published Lepidoptera genes, which allows carrying out gene-specific re-sequencing. Data mining has allowed the identification of SNP loci that will be useful for population genomic approaches and genome-wide scans of population differentiation to identify signatures of selection.
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      PubDate: 2014-01-27T12:18:59Z
  • Retrotransposon “Qian” mediated segmental duplication in
           silkworm, Bombyx mori
    • Abstract: Publication date: Available online 21 January 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Yunmin Xu , Ning Jiang , Ziliang Zou , Zhijian Tu , Anli Chen , Qiaoling Zhao , Zhonghuai Xiang , Ningjia He
      Transposable elements constitute a large fraction of the eukaryotic genomes. They have the potential to alter genome structure and play a major role in genome evolution. Here, we report a segmental duplication mediated by a novel long terminal repeat (LTR) retrotransposon as the cause of an egg-shell recessive lethal mutant (l-e m mutant) in silkworm (Bombyx mori). The segmental duplication resulted in the duplication of six genes and the disruption of two genes. Disruption of BmEP80 (B. mori egg protein 80), a gene encoding a major egg-shell structure protein, is likely responsible for the lethal water-loss phenotype in the l-e m /l-e m mutant. Our data revealed that BmEP80 is present in the inner egg-shell layer and plays important roles in resistance to water efflux form eggs. A novel LTR retrotransposon (named as “Qian”) was identified and the model for the Qian-mediated chromosomal segmental duplication was proposed. Detail biochemical and genomic analyses on the l-e m mutant offer an opportunity to demonstrate that an LTR retrotransposon could trigger duplication of a chromosomal segment (∼96.3 kb) and confer novel phenotype.
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      PubDate: 2014-01-23T04:30:19Z
  • Evolutionary implications of dipluran hexamerins
    • Abstract: Publication date: Available online 22 January 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Wei Xie , Yun-Xia Luan
      Hexamerin, as a member of the highly conserved arthropod hemocyanin superfamily, has been shown to be a good marker for the phylogenetic study of insects. However, few studies have been conducted on hexamerins in basal hexapods. The first Diplura hexamerin CspHex1 was reported only recently (Pick and Burmester, 2009). Remarkably, CspHex1 was suggested to have evolved from hexapod hemocyanin subunit type 2, which is very different from all insect hexamerins originated from hexapod hemocyanin subunit type 1. Does this finding suggest double or even multiple origins of hexamerins in Hexapoda? To find more evidence on the evolution of dipluran hexamerins, eight putative hexamerin gene sequences were obtained from three dipluran species, as were three hemocyanin genes from two collembolan species. Unexpectedly, after adding the new sequences into the phylogenetic analyses, all dipluran hexamerins including CspHex1 grouped together and as sister to the insect hexamerins, with high likelihood and Bayesian support. Our analysis supports a single origin of the hexamerins in Hexapoda, and suggests the close relationship between Diplura and Insecta. In addition, our study indicates that a relatively comprehensive taxa sampling is essential to solve some problems in phylogenetic reconstruction.
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      PubDate: 2014-01-23T04:30:19Z
  • Identification, functional characterization and phylogenetic analysis of
           double stranded RNA degrading enzymes present in the gut of the desert
           locust, Schistocerca gregaria
    • Abstract: Publication date: Available online 10 January 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Niels Wynant , Dulce Santos , Rik Verdonck , Jornt Spit , Pieter Van Wielendaele , Jozef Vanden Broeck
      RNA interference (RNAi) has become a widely used reverse genetics tool in eukaryotes and holds great potential to contribute to the development of novel strategies for insect pest control. While previous studies clearly demonstrated that injection of dsRNA into the body cavity of the desert locust, Schistocerca gregaria, is highly effective to induce gene silencing effects, we observed that the RNAi response is much less sensitive to orally delivered dsRNA. In line with this, we report on the presence of a potent dsRNA degrading activity in the midgut juice. Four different dsRNase sequences that belong to the DNA/RNA Non-specific Nuclease superfamily were retrieved from a transcriptome database of the desert locust. Surprisingly, we have found that, in the publicly available eukaryote nucleotide sequence databases, the presence of this group of enzymes is restricted to insects and crustaceans. Nonetheless, phylogenetic analyses predict a common origin of these enzymes with the Endonuclease G (EndoG) Non-specific Nucleases that display a widespread taxonomic distribution. Moreover, in contrast to the Sg-endoG transcript, the four Sg-dsRNase transcripts appear to be specifically expressed in the gut. Finally, by means of RNAi, we provide evidence for an important contribution of dsRNase2 to the dsRNA degrading activity that is present in the gut lumen of S. gregaria.
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      PubDate: 2014-01-11T07:16:02Z
  • Activation of Bombyx neuropeptide G protein-coupled receptor A4 via a
           Gαi-dependent signaling pathway by direct interaction with
           neuropeptide F from silkworm, Bombyx mori
    • Abstract: Publication date: Available online 27 December 2013
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Xiaoyan Deng , Huipeng Yang , Xiaobai He , Yuan Liao , Congxia Zheng , Qi Zhou , Chenggang Zhu , Guozheng Zhang , Jimin Gao , Naiming Zhou
      Members of the mammalian neuropeptide Y (NPY) family serve as neurotransmitters and contribute to a diversity of physiological functions. Although neuropeptide F (NPF), the NPY-like orthologs from insects, have been identified, the NPF receptors and their signaling and physiological functions remain largely unknown. In this study, we established the stable and transient functional expression of a Bombyx orphan G protein-coupled receptor, BNGR-A4, in both mammalian HEK293 and insect SF21 cells. We identified Bombyx mori NPFs as specific endogenous ligands for the Bombyx Neuropeptide GPCR A4 (BNGR-A4) and, accordingly, named the receptor BomNPFR. Our results demonstrated that BomNPFR was activated by synthetic BomNPF1a and BomNPF1b at a high efficacy and by BomNPF2 at a low efficacy. This activation led to a decrease of forskolin or adipokinetic hormone peptide-stimulated adenylyl cyclase activity, an increase of intracellular Ca2+, the activation of ERK1/2 signaling and receptor internalization. Moreover, a Rhodamine-labeled BomNPF1a peptide was found to bind specifically to BomNPFR. The results derived from quantitative RT-PCR analysis and dsRNA-mediated knockdown experiments demonstrated the possible role of BomNPFR in the regulation of food intake and growth. Our results provide the first in-depth information on BomNPFR-mediated signaling for the further elucidation of the BomNPF/BomNPFR system in the regulation of fundamental physiological processes.
      Graphical abstract image

      PubDate: 2013-12-28T22:29:21Z
  • The novel isoxazoline ectoparasiticide fluralaner: Selective inhibition of
           arthropod γ-aminobutyric acid- and l-glutamate-gated chloride
           channels and insecticidal/acaricidal activity
    • Abstract: Publication date: Available online 21 December 2013
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Michael Gassel , Christian Wolf , Sandra Noack , Heike Williams , Thomas Ilg
      Isoxazolines are a novel class of parasiticides that are potent inhibitors of γ-aminobutyric acid (GABA)-gated chloride channels (GABACls) and l-glutamate-gated chloride channels (GluCls). In this study, the effects of the isoxazoline drug fluralaner on insect and acarid GABACl (RDL) and GluCl and its parasiticidal potency were investigated. We report the identification and cDNA cloning of Rhipicephalus (R.) microplus RDL and GluCl genes, and their functional expression in Xenopus laevis oocytes. The generation of six clonal HEK293 cell lines expressing Rhipicephalus microplus RDL and GluCl, Ctenocephalides felis RDL-A285 and RDL-S285, as well as Drosophila melanogaster RDLCl-A302 and RDL-S302, combined with the development of a membrane potential fluorescence dye assay allowed the comparison of ion channel inhibition by fluralaner with that of established insecticides addressing RDL and GluCl as targets. In these assays fluralaner was several orders of magnitude more potent than picrotoxinin and dieldrin, and performed 5-236 fold better than fipronil on the arthropod RDLs, while a rat GABACl remained unaffected. Comparative studies showed that R. microplus RDL is 52-fold more sensitive than R. microplus GluCl to fluralaner inhibition, confirming that the GABA-gated ion channel is the primary target of this new parasiticide. In agreement with the superior RDL on-target activity, fluralaner outperformed dieldrin and fipronil in insecticidal screens on cat fleas (Ctenocephalides felis), yellow fever mosquito larvae (Aedes aegypti) and sheep blowfly larvae (Lucilia cuprina), as well as in acaricidal screens on cattle tick (R. microplus) adult females, brown dog tick (Rhipicephalus sanguineus) adult females and Ornithodoros moubata nymphs. These findings highlight the potential of fluralaner as a novel ectoparasiticide.
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      PubDate: 2013-12-25T12:19:14Z
  • Juvenile hormone signaling during reproduction and development of the
           linden bug, Pyrrhocoris apterus
    • Abstract: Publication date: Available online 19 December 2013
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Vlastimil Smykal , Adam Bajgar , Jan Provaznik , Silvie Fexova , Marcela Buricova , Keiko Takaki , Magdalena Hodkova , Marek Jindra , David Dolezel
      Juvenile hormone (JH), a sesquiterpenoid produced by the insect corpus allatum gland (CA), prevents metamorphosis in larvae and stimulates vitellogenesis in adult females. Whether the same JH signaling pathway regulates both processes is presently unknown. Here, we employ the robust JH response during reproduction and development of the firebug, Pyrrhocoris apterus, to compare the function of key JH-signaling genes encoding the JH receptor, Methoprene-tolerant (Met), its binding partner Taiman (Tai), and a JH-inducible protein, Krüppel-homolog 1 (Kr-h1). RNA interference (RNAi) with Met or Tai, but not Kr-h1, blocked ovarian development and suppressed vitellogenin gene expression in the fat body of females raised under reproduction-inducing conditions. Loss of Met and Tai matched the effects of CA ablation or the natural absence of JH during reproductive diapause. Stimulation of vitellogenesis by treatment of diapausing females with a JH mimic methoprene also required both Met and Tai in the fat body, whereas Kr-h1 RNAi had no effect. Therefore, the Met-Tai complex likely functions as a JH receptor during vitellogenesis. In contrast to Met and Kr-h1 that are both required for JH to prevent precocious metamorphosis in P. apterus larvae, removal of Tai disrupted larval ecdysis without causing premature adult development. Our results show that while Met operates during metamorphosis in larvae and reproduction in adult females, its partner Tai is only required for the latter. The diverse functions of JH thus likely rely on a common receptor whose actions are modulated by distinct components.
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      PubDate: 2013-12-21T10:33:31Z
  • TGL-mediated lipolysis in Manduca sexta fat body: possible roles for
           lipoamide-dehydrogenase (LipDH) and high-density lipophorin (HDLp)
    • Abstract: Publication date: Available online 12 December 2013
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Zengying Wu , Jose L. Soulages , Bharat D. Joshi , Stuart M. Daniel , Zachary J. Hager , Estela L. Arrese
      Triglyceride-lipase (TGL) is a major fat body lipase in Manduca sexta. The knowledge of how TGL activity is regulated is very limited. A WWE domain, presumably involved in protein-protein interactions, has been previously identified in the N-terminal region of TGL. In this study, we searched for proteins partners that interact with the N-terminal region of TGL. Thirteen proteins were identified by mass spectrometry, and the interaction with four of these proteins was confirmed by immunoblot. The oxidoreductase lipoamide-dehydrogenase (LipDH) and the apolipoprotein components of the lipid transporter, HDLp, were among these proteins. LipDH is the common component of the mitochondrial α-keto acid dehydrogenase complexes whereas HDLp occurs in the hemolymph. However, subcellular fractionation demonstrated that these two proteins are relatively abundant in the soluble fraction of fat body adipocytes. The cofactor lipoate found in typical LipDH substrates was not detected in TGL. However, TGL proved to have critical thiol groups. Additional studies with inhibitors are consistent with the notion that LipDH acting as a diaphorase could preserve the activity of TGL by controlling the redox state of thiol groups. On the other hand, when TG hydrolase activity of TGL was assayed in the presence of HDLp, the production of diacylglycerol (DG) increased. TGL-HDLp interaction could drive the intracellular transport of DG. TGL may be directly involved in the lipoprotein assembly and loading with DG, a process that occurs in the fat body and is essential for insects to mobilize fatty acids. Overall the study suggests that TGL occurs as a multi-protein complex supported by interactions through the WWE domain.
      Graphical abstract image

      PubDate: 2013-12-14T04:40:40Z
  • De novo biosynthesis of linoleic acid and its conversion to the
           hydrocarbon (Z,Z)-6,9-heptadecadiene in the astigmatid mite, Carpoglyphus
           lactis: Incorporation experiments with 13C-labeled glucose
    • Abstract: Publication date: Available online 11 December 2013
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Nobuhiro Shimizu , Michiya Naito , Naoki Mori , Yasumasa Kuwahara
      De novo biosynthesis of linoleic acid (LA) and its conversion to (Z,Z)-6,9-heptadecadiene were examined in Carpoglyphus lactis (Acarina, Carpoglyphidae). Experiments involving 13C-administration using [1-13C]-d-glucose revealed that 13C atoms were incorporated into LA of total lipid extracted from the mite, resulting in labeling of all even-numbered carbons. This result demonstrated that LA was produced from 13C-labeled acetyl-CoA, which is indicative of direct de novo biosynthesis. In these feeding experiments involving [1-13C]-d-glucose, 13C atoms were also incorporated into (Z,Z)-6,9-heptadecadiene, which is one of the major secretory components in the mite. The labeling pattern of (Z,Z)-6,9-heptadecadiene at odd-numbered carbons agreed well with that of LA after loss of the carboxyl carbon. It was concluded that the mites could stably convert LA into (Z,Z)-6,9-heptadecadiene without the dietary requirement of this essential fatty acid.
      Graphical abstract image

      PubDate: 2013-12-14T04:40:40Z
  • Chromatin-induced spindle assembly plays an important role in metaphase
           congression of silkworm holocentric chromosomes
    • Abstract: Publication date: Available online 1 December 2013
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Hiroaki Mon , Jae Man Lee , Kazuei Mita , Marian R. Goldsmith , Takahiro Kusakabe
      The kinetochore plays important roles in cell cycle progression. Interactions between chromosomes and spindle microtubules allow chromosomes to congress to the middle of the cell and to segregate the sister chromatids into daughter cells in mitosis. The chromosome passenger complex (CPC), composed of the Aurora B kinase and its regulatory subunits INCENP, Survivin, and Borealin, plays multiple roles in these chromosomal events. In the genome of the silkworm, Bombyx mori, which has holocentric chromosomes, the CPC components and their molecular interactions were highly conserved. In contrast to monocentric species, however, the silkworm CPC co-localized with the chromatin-driven spindles on the upper side of prometaphase chromosomes without forming bipolar mitotic spindles. Depletion of the CPC by RNAi arrested the cell cycle progression at prometaphase and disrupted the microtubule network of the chromatin-driven spindles. Interestingly, depletion of mitotic centromere-associated kinesin (MCAK) recovered formation of the microtubule network but did not overcome the cell cycle arrest at prometaphase. These results suggest that the CPC modulates the chromatin-induced spindle assembly and metaphase congression of silkworm holocentric chromosomes.
      Graphical abstract image

      PubDate: 2013-12-06T07:19:36Z
  • Expression pattern and function of alternative splice variants of
           glutamate-gated chloride channel in the housefly Musca domestica
    • Abstract: Publication date: Available online 1 December 2013
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Tomo Kita , Fumiyo Ozoe , Yoshihisa Ozoe
      Glutamate-gated chloride channels (GluCls) mediate fast inhibitory neurotransmission in invertebrate nervous systems. cDNAs encoding two alternative splice variants (MdGluClB and C) of the GluCl subunit were cloned from the housefly Musca domestica. The expression patterns of three variants, including the previously reported MdGluClA, differed among the body parts (head, thorax, abdomen, and leg) of the adult housefly and among developmental stages (embryo, larva, pupa, and adult). The MdGluClA and B transcripts were abundant in the central nervous system of the adult, whereas the MdGluClC transcript was expressed in the central nervous system and as the predominant variant in the peripheral tissues. The sensitivities to the agonist glutamate and the allosteric activator ivermectin B1a did not differ between channels containing MdGluCl variants when they were singly or co-expressed in Xenopus oocytes. By contrast, MdGluClA and B channels were more sensitive to the channel blockers fipronil and picrotoxinin than was MdGluClC channels. Heteromeric channels containing different subunit variants were more sensitive to picrotoxinin than were homomeric channels. Heteromeric channels were more sensitive to fipronil than were homomeric MdGluClC channels but not than homomeric MdGluClA and B channels. These results suggest that functionally indistinguishable but pharmacologically distinct GluCls are expressed in a spatially and temporally distinct manner in the housefly.
      Graphical abstract image

      PubDate: 2013-12-06T07:19:36Z
  • Molecular and functional characterization of CYP6BQ23, a cytochrome P450
           conferring resistance to pyrethroids in European populations of pollen
           beetle, Meligethes aeneus
    • Abstract: Publication date: Available online 4 December 2013
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Christoph T. Zimmer , Chris Bass , Martin S. Williamson , Martin Kaussmann , Katharina Wölfel , Oliver Gutbrod , Ralf Nauen
      The pollen beetle (Meligethes aeneus F.) is widespread throughout much of Europe where it is is a major coleopteran pest of oilseed rape (Brassica napus). The reliance on synthetic insecticides for control, particularly the pyrethroid class, has led to the development of populations with high levels of resistance. Resistance to pyrethroids is now widespread throughout Europe and is thought to be mediated by enhanced detoxification by cytochrome P450´s and/or mutation of the pyrethroid target-site, the voltage-gated sodium channel. However, in the case of cytochrome P450 mediated detoxification, the specific enzyme(s) involved has (have) not yet been identified. In this study a degenerate PCR approach was used to identify ten partial P450 gene sequences from pollen beetle. Quantitative PCR was then used to examine the level of expression of these genes in a range of pollen beetle populations that showed differing levels of resistance to pyrethroids in bioassays. The study revealed a single P450 gene, CYP6BQ23, which is significantly and highly overexpressed (up to ∼900-fold) in adults and larvae of pyrethroid resistant strains compared to susceptible strains. CYP6BQ23 overexpression is significantly correlated with both the level of resistance and with the rate of deltamethrin metabolism in microsomal preparations of these populations. Functional recombinant expression of full length CYP6BQ23 along with cytochrome P450 reductase in an insect (Sf9) cell line showed that it is able to efficiently metabolise deltamethrin to 4-hydroxy deltamethrin. Furthermore we demonstrated by detection of 4-hydroxy tau-fluvalinate using ESI-TOF MS/MS that functionally expressed CYP6BQ23 also metabolizes tau-fluvalinate. A protein model was generated and subsequent docking simulations revealed the predicted substrate-binding mode of both deltamethrin and tau-fluvalinate to CYP6BQ23. Taken together these results strongly suggest that the overexpression of CYP6BQ23 is the primary mechanism conferring pyrethroid resistance in pollen beetle populations throughout much of Europe.
      Graphical abstract image

      PubDate: 2013-12-06T07:19:36Z
  • E93 predominantly transduces 20-hydroxyecdysone signaling to induce
           autophagy and caspase activity in Drosophila fat body
    • Abstract: Publication date: Available online 4 December 2013
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Hanhan Liu , Jin Wang , Sheng Li
      During the larval-prepupal transition in Drosophila, a balancing crosstalk occurs between autophagy and caspase activity in the remodeling fat body: the inhibition of autophagy induces caspase activity and the inhibition of caspases induces autophagy. Both autophagy and caspase activity are induced by a pulse of molting hormone (20-hydroxyecdysone, 20E) via the 20E nuclear receptor complex, EcR-USP. We here demonstrate that E93, a 20E primary-response gene encoding an HTH transcription factor, predominantly transduces 20E signaling to induce autophagy and caspase activity in the remodeling fat body. RNAi knockdown or mutation of E93 blocks autophagy and caspase activity, E93 overexpression induces them both, while E93 overexpression has a better rescuing effect on the inhibition of autophagy than caspase activity caused by EcR DN overexpression. At the transcriptional level, E93 not only greatly impacts the 20E-triggered transcriptional cascade, but also upregulates essential autophagy and apoptosis genes. Meanwhile, at the phosphorylational level, E93 blocks the PI3K-TORC1 signaling to initiate autophagy. Taken together, we conclude that autophagy and caspase activity are induced by 20E and predominantly transduced by E93 in the remodeling fat body of Drosophila.
      Graphical abstract image

      PubDate: 2013-12-06T07:19:36Z
  • The ABC gene family in arthropods: comparative genomics and role in
           insecticide transport and resistance
    • Abstract: Publication date: Available online 28 November 2013
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Wannes Dermauw , Thomas Van Leeuwen
      About a 100 years ago, the Drosophila white mutant marked the birth of Drosophila genetics. The white gene turned out to encode the first well studied ABC-transporter in arthropods. The ABC gene family is now recognized as one of the largest transporter families in all kingdoms of life. The majority of ABC proteins function as primary active transporters that bind and hydrolyze ATP while transporting a large diversity of substrates across lipid membranes. Although extremely well studied in vertebrates for their role in drug resistance, less is known about the role of this family in the transport of endogenous and exogenous substances in arthropods. The ABC families of five insect species, a crustacean and a chelicerate have been annotated in some detail. We conducted a thorough phylogenetic analysis of the seven arthropod and human ABC transporter subfamilies, to infer orthologous relationships that might suggest conserved function. Most orthologous relationships were found in the ABCB HT, ABCD, ABCE and ABCF subfamilies, but specific expansions within species and lineages are frequently observed and discussed. We next surveyed the role of ABC transporters in the transport of xenobiotics/plant allelochemicals and their involvement in insecticide resistance. The involvement of ABC-transporters in xenobiotic resistance in arthropods is historically not well documented, but an increasing number of studies using unbiased differential gene expression analysis now points to their importance. We give an overview of methods that can be used to link ABC-transporters to resistance. ABC-proteins have also recently been implicated in the mode of action and resistance to Bt toxins in Lepidoptera. Given the enormous interest in Bt toxicology in transgenic crops, such findings will provide an impetus to further reveal the role of ABC transporters in arthropods.
      Graphical abstract image

      PubDate: 2013-12-02T03:01:36Z
  • Cadherin AdCad1 in Alphitobius diaperinus larvae is a receptor of Cry3Bb
           toxin from Bacillus thuringiensis
    • Abstract: Publication date: Available online 10 November 2013
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Gang Hua , Youngjin Park , Michael J. Adang
      Bacillus thuringiensis (Bt) Cry proteins are used as components of biopesticides or expressed in transgenic crops to control diverse insect pests worldwide. These Cry toxins bind to receptors on the midgut brush border membrane and kill enterocytes culminating in larval mortality. Cadherin proteins have been identified as Cry toxin receptors in diverse lepidopteran, coleopteran, and dipteran species. In the present work we report a 185 kDa cadherin (AdCad1) from larvae of the lesser mealworm (Alphitobius diaperinus) larvae as the first identified receptor for Cry3Bb toxin. The AdCad1 protein contains typical structural components for Cry toxin receptor cadherins, including nine cadherin repeats (CR9), a membrane-proximal extracellular domain (MPED) and a cytosolic region. Peptides corresponding to the CR9 and MPED regions bound Cry3Bb toxin with high affinities (23 nM and 40 nM) and significantly synergized Cry3Bb toxicity against A. diperinus larvae. Silencing of AcCad1 expression through RNA interference resulted in highly reduced susceptibility to Cry3Bb in A. diperinus larvae. The CR9 peptide fed with toxin to RNAi-treated larvae restored Cry3Bb toxicity. These results are evidence that AdCad1 is a functional receptor of Cry3Bb toxin and that exogenously fed CR9 peptide can overcome the effect of reduced AdCad1expression on Cry3Bb toxicity to larvae.
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      PubDate: 2013-11-12T03:01:55Z
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