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Clinical Lipidology     Full-text available via subscription  
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology     Hybrid Journal   (Followers: 4)
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Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology     Hybrid Journal   (Followers: 5)

        1 2 3     

Journal Cover   Insect Biochemistry and Molecular Biology
  [SJR: 1.703]   [H-I: 75]   [6 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0965-1748
   Published by Elsevier Homepage  [2588 journals]
  • Silencing the odorant receptor co-receptor RproOrco affects the physiology
           and behavior of the Chagas disease vector Rhodnius prolixus
    • Abstract: Publication date: Available online 4 March 2015
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Thiago A. Franco , Daniele S. Oliveira , Monica F. Moreira , Walter S. Leal , Ana C.A. Melo
      Olfaction is one of the main sensory modalities that allow insects to interpret their environment. Several proteins, including odorant-binding proteins (OBPs) and odorant receptors (ORs), are involved in this process. Odorant receptors are ion channels formed by a binding unit OR and an odorant receptor co-receptor (Orco). The main goal of this study was to characterize the Orco gene of Rhodnius prolixus (RproOrco) and to infer its biological functions using gene silencing. The full-length RproOrco gene sequence was downloaded from VectorBase. This gene has 7 introns and is located in the genome SuperContig GL563069: 1,017,713-1,023,165. RproOrco encodes a protein of 473 amino acids, with predicted 7 transmembrane domains, and is highly expressed in the antennae during all R. prolixus developmental stages. The RNAi technique effectively silenced RproOrco, reducing the gene’s expression by approximately 73%. Interestingly, the effect of gene silencing persisted for more than 100 days, indicating a prolonged effect of dsRNA that was maintained even after molting. The phenotypic effects of silencing involved the following: (1) loss of the ability to find a vertebrate host in a timely manner, (2) decreased ingested blood volume, (3) delayed and decreased molt rate, (4) increased mortality rate, and (5) decreased egg laying. Our data strongly suggest that dsOrco disrupts R. prolixus host-finding behavior, which is further reflected in the blood ingestion, molting, mortality, and egg laying data. This study clearly demonstrates that Orco is an excellent target for controlling triatomine populations. Thus, the data presented here open new possibilities for the control of vector-borne diseases.
      Graphical abstract image

      PubDate: 2015-03-05T15:01:14Z
  • Domain organization and phylogenetic analysis of the chitinase-like family
           of proteins in three species of insects
    • Abstract: Publication date: April 2008
      Source:Insect Biochemistry and Molecular Biology, Volume 38, Issue 4
      Author(s): Qingsong Zhu , Yasuyuki Arakane , Debarshi Banerjee , Richard W. Beeman , Karl J. Kramer , Subbaratnam Muthukrishnan
      A bioinformatics-based investigation of three insect species with completed genome sequences has revealed that insect chitinase-like proteins (glycosylhydrolase family 18) are encoded by a rather large and diverse group of genes. We identified 16, 16 and 13 putative chitinase-like genes in the genomic databases of the red flour beetle, Tribolium castaneum, the fruit fly, Drosophila melanogaster, and the malaria mosquito, Anopheles gambiae, respectively. Chitinase-like proteins encoded by this gene family were classified into five groups based on phylogenetic analyses. Group I chitinases are secreted proteins that are the most abundant such enzymes in molting fluid and/or integument, and represent the prototype enzyme of the family, with a single copy each of the catalytic domain and chitin-binding domain (ChBD) connected by an S/T-rich linker polypeptide. Group II chitinases are unusually larger-sized secreted proteins that contain multiple catalytic domains and ChBDs. Group III chitinases contain two catalytic domains and are predicted to be membrane-anchored proteins. Group IV chitinases are the most divergent. They usually lack a ChBD and/or an S/T-rich linker domain, and are known or predicted to be secreted proteins found in gut or fat body. Group V proteins include the putative chitinase-like imaginal disc growth factors (IDGFs). In each of the three insect genomes, multiple genes encode group IV and group V chitinase-like proteins. In contrast, groups I–III are each represented by only a singe gene in each species.

      PubDate: 2015-03-01T14:54:01Z
  • Domain organization and phylogenetic analysis of proteins from the chitin
           deacetylase gene family of Tribolium castaneum and three other species of
    • Abstract: Publication date: April 2008
      Source:Insect Biochemistry and Molecular Biology, Volume 38, Issue 4
      Author(s): Radhika Dixit , Yasuyuki Arakane , Charles A. Specht , Chad Richard , Karl J. Kramer , Richard W. Beeman , Subbaratnam Muthukrishnan
      A bioinformatics investigation of four insect species with annotated genome sequences identified a family of genes encoding chitin deacetylase (CDA)-like proteins, with five to nine members depending on the species. CDAs (EC are chitin-modifying enzymes that deacetylate the β-1,4-linked N-acetylglucosamine homopolymer. Partial deacetylation forms a heteropolysaccharide that also contains some glucosamine residues, while complete deacetylation produces the homopolymer chitosan, consisting exclusively of glucosamine. The genomes of the red flour beetle, Tribolium castaneum, the fruit fly, Drosophila melanogaster, the malaria mosquito, Anopheles gambiae, and the honey bee, Apis mellifera contain 9, 6, 5 and 5 genes, respectively, that encode proteins with a chitin deacetylase motif. The presence of alternative exons in two of the genes, TcCDA2 and TcCDA5, increases the protein diversity further. Insect CDA-like proteins were classified into five orthologous groups based on phylogenetic analysis and the presence of additional motifs. Group I enzymes include CDA1 and isoforms of CDA2, each containing in addition to a polysaccharide deacetylase-like catalytic domain, a chitin-binding peritrophin-A domain (ChBD) and a low-density lipoprotein receptor class A domain (LDLa). Group II is composed of CDA3 orthologs from each insect species with the same domain organization as group I CDAs, but differing substantially in sequence. Group III includes CDA4s, which have the ChBD domain but do not have the LDLa domain. Group IV comprises CDA5s, which are the largest CDAs because of a very long intervening region separating the ChBD and catalytic domains. Among the four insect species, Tribolium is unique in having four CDA genes in group V, whereas the other insect genomes have either one or none. Most of the CDA-like proteins have a putative signal peptide consistent with their role in modifying extracellular chitin in both cuticle and peritrophic membrane during morphogenesis and molting.

      PubDate: 2015-03-01T14:54:01Z
  • Annotation of Tribolium nuclear receptors reveals an increase in
           evolutionary rate of a network controlling the ecdysone cascade
    • Abstract: Publication date: April 2008
      Source:Insect Biochemistry and Molecular Biology, Volume 38, Issue 4
      Author(s): François Bonneton , Arnaud Chaumot , Vincent Laudet
      The Tribolium genome contains 21 nuclear receptors, representing all of the six known subfamilies. This first complete set for a coleopteran species reveals a strong conservation of the number and identity of nuclear receptors in holometabolous insects. Two novelties are observed: the atypical NR0 gene knirps is present only in brachyceran flies, while the NR2E6 gene is found only in Tribolium and in Apis. Using a quantitative analysis of the evolutionary rate, we discovered that nuclear receptors could be divided into two groups. In one group of 13 proteins, the rates follow the trend of the Mecopterida genome-wide acceleration. In a second group of five nuclear receptors, all acting early during the ecdysone cascade, we observed an even higher increase of the evolutionary rate during the early divergence of Mecopterida. We thus extended our analysis to the 12 classic ecdysone transcriptional regulators and found that six of them (ECR, USP, HR3, E75, HR4 and Kr-h1) underwent an increase in evolutionary rate at the base of the Mecopterida lineage. By contrast, E74, E93, BR, HR39, FTZ-F1 and E78 do not show this divergence. We suggest that coevolution occurred within a network of regulators that control the ecdysone cascade. The advent of Tribolium as a powerful model should allow a better understanding of this evolutionary event.

      PubDate: 2015-03-01T14:54:01Z
  • Identification and characterization of nuclear receptors from the red
           flour beetle, Tribolium castaneum
    • Abstract: Publication date: April 2008
      Source:Insect Biochemistry and Molecular Biology, Volume 38, Issue 4
      Author(s): Anjiang Tan , Subba Reddy Palli
      Nuclear receptors (NRs) are classified by the presence of a well-conserved DNA-binding domain and a less conserved ligand-binding domain and function as key control points in diverse signaling and metabolic pathways. NRs are switched on and off by small molecule ligands with properties similar to insecticides. Therefore, NRs are attractive targets for developing new insecticides. Nineteen canonical and two Knirps family NRs were identified in the genome of Tribolium castaneum. RNAi analysis showed that 10 out of the 19 canonical NRs, TcE75, TcHR3, TcHR4, TcEcR, TcUSP, TcFTZ-F1, TcHR51, SVP, TcHR38, TcHR39 are important for metamorphosis. Knocking down the expression of five NRs, TcTll, TcDsf, TcHNF4 and TcHR78 caused defects in production of offspring. TcHNF4, TcHR78, TCHR51 and TcDsf affected egg production and TcTll affected embryonic development. Knocking down the expression of non-canonical NR Knirps-like affected adults and caused reduction in egg production. The other Knirps family member, Eagle, and five canonical NRs, TcE78, TcHR83, TcHR96, TcPNR-like and TcERR did not show much effect on metamorphosis or production of offspring. Quantitative real-time reverse transcriptase analysis showed that the mRNA levels of all NRs tested were reduced in DsRNA injected larvae when compared to their levels in control larvae injected with bacterial malE DsRNA suggesting that the RNAi worked well but reduction in expression levels of some of the NRs did not affect metamorphosis or production of offspring.

      PubDate: 2015-03-01T14:54:01Z
  • The SNMP/CD36 gene family in Diptera, Hymenoptera and Coleoptera:
           Drosophila melanogaster, D. pseudoobscura, Anopheles gambiae, Aedes
           aegypti, Apis mellifera, and Tribolium castaneum
    • Abstract: Publication date: April 2008
      Source:Insect Biochemistry and Molecular Biology, Volume 38, Issue 4
      Author(s): Zachary Nichols , Richard G. Vogt
      Sensory neuron membrane proteins (SNMPs) are membrane bound proteins initially identified in olfactory receptor neurons of Lepidoptera and are thought to play a role in odor detection; SNMPs belong to a larger gene family characterized by the human protein CD36. We have identified 12–14 candidate SNMP/CD36 homologs from each of the genomes of Drosophila melanogaster, D. pseudoobscura, Anopheles gambiae and Aedes aegypti (Diptera), eight candidate homologs from Apis mellifera (Hymenoptera), and 15 from Tribolium castaneum (Coleoptera). Analysis (sequence similarity and intron locations) suggests that the insect SNMP/CD36 genes fall into three major groups. Group 1 includes the previously characterized D. melanogaster emp (epithelial membrane protein). Group 2 includes the previously characterized D. melanogaster croquemort, ninaD, santa maria, and peste. Group 3 genes include the SNMPs, which fall into two subgroups referred to as SNMP1 and SNMP2. D. melanogaster SNMP1 (CG7000) shares both significant sequence similarity and five of its six intron insertion sites with the lepidopteran Bombyx mori SNMP1. The topological conservation of this gene family within the three major holometabolous lineages indicates that it predates the coleopteran and hymenoptera/dipera/lepidoptera split 300+ million years ago. The current state of knowledge of the characterized insect members of this gene family is discussed.

      PubDate: 2015-03-01T14:54:01Z
  • The evolution of insecticide resistance in the peach potato aphid, Myzus
    • Abstract: Publication date: August 2014
      Source:Insect Biochemistry and Molecular Biology, Volume 51
      Author(s): Chris Bass , Alin M. Puinean , Christoph T. Zimmer , Ian Denholm , Linda M. Field , Stephen P. Foster , Oliver Gutbrod , Ralf Nauen , Russell Slater , Martin S. Williamson
      The peach potato aphid, Myzus persicae is a globally distributed crop pest with a host range of over 400 species including many economically important crop plants. The intensive use of insecticides to control this species over many years has led to populations that are now resistant to several classes of insecticide. Work spanning over 40 years has shown that M. persicae has a remarkable ability to evolve mechanisms that avoid or overcome the toxic effect of insecticides with at least seven independent mechanisms of resistance described in this species to date. The array of novel resistance mechanisms, including several ‘first examples’, that have evolved in this species represents an important case study for the evolution of insecticide resistance and also rapid adaptive change in insects more generally. In this review we summarise the biochemical and molecular mechanisms underlying resistance in M. persicae and the insights study of this topic has provided on how resistance evolves, the selectivity of insecticides, and the link between resistance and host plant adaptation.
      Graphical abstract image

      PubDate: 2015-03-01T14:54:01Z
  • Large diversity of the piggyBac-like elements in the genome of Tribolium
    • Abstract: Publication date: April 2008
      Source:Insect Biochemistry and Molecular Biology, Volume 38, Issue 4
      Author(s): Jianjun Wang , Yuzhou Du , Suzhi Wang , Susan J. Brown , Yoonseong Park
      The piggyBac transposable element (TE), originally discovered in the cabbage looper, Trichoplusia ni, has been widely used in insect transgenesis including the red flour beetle Tribolium castaneum. We surveyed piggyBac-like (PLE) sequences in the genome of T. castaneum by homology searches using as queries the diverse PLE sequences that have been described previously. The search yielded a total of 32 piggyBac-like elements (TcPLEs) which were classified into 14 distinct groups. Most of the TcPLEs contain defective functional motifs in that they are lacking inverted terminal repeats (ITRs) or have disrupted open reading frames. Only one single copy of TcPLE1 appears to be intact with imperfect 16bp ITRs flanking an open reading frame encoding a transposase of 571 amino acid residues. Many copies of TcPLEs were found to be inserted into or close to other transposon-like sequences. This large diversity of TcPLEs with generally low copy numbers suggests multiple invasions of the TcPLEs over a long evolutionary time without extensive multiplications or occurrence of rapid loss of TcPLEs copies.

      PubDate: 2015-03-01T14:54:01Z
  • Characterization and expression of the β-N-acetylhexosaminidase gene
           family of Tribolium castaneum
    • Abstract: Publication date: April 2008
      Source:Insect Biochemistry and Molecular Biology, Volume 38, Issue 4
      Author(s): David G. Hogenkamp , Yasuyuki Arakane , Karl J. Kramer , Subbaratnam Muthukrishnan , Richard W. Beeman
      Enzymes belonging to the β-N-acetylhexosaminidase family cleave chitin oligosaccharides produced by the action of chitinases on chitin into the constituent N-acetylglucosamine monomer. Four genes encoding putative chitooligosaccharidolytic β-N-acetylhexosaminidases (hereafter referred to as N-acetylglucosaminidases (NAGs)) in the red flour beetle, Tribolium castaneum, namely TcNAG1, TcFDL, TcNAG2, and TcNAG3, and three other related hexosaminidases were identified by searching the recently completed genome [Tribolium Genome Sequencing Consortium, 2007. The first genome sequence of a beetle, Tribolium castaneum, a model for insect development and pest biology. Nature, submitted for publication]. Full-length cDNAs for all four NAGs were cloned and sequenced, and the exon–intron organization of the corresponding genes was determined. Analyses of their developmental expression patterns indicated that, although all four of the NAGs are transcribed during most developmental stages, each gene had a distinct spatial and temporal expression pattern. TcNAG1 transcripts are the most abundant, particularly at the late pupal stage, while TcNAG3 transcripts are the least abundant, even at their peak levels in the late larval stages. The function of each NAG during different developmental stages was assessed by observations of lethal phenotypes after gene-specific double-stranded RNA (dsRNA)-mediated transcript depletion as verified by real-time PCR. TcNAG1 dsRNA was most effective in interrupting all three types of molts: larval–larval, larval–pupal, and pupal–adult. Treated insects died after failing to completely shed their old cuticles. Knockdown of transcripts for the other three NAG genes resulted in phenotypes similar to those of TcNAG1 dsRNA-treated insects, but the effects were somewhat variable and less severe. Sequence comparisons with other enzymatically characterized insect homologs suggested that TcFDL, unlike the other NAGs, may have a role in N-glycan processing in addition to its apparent role in cuticular chitin turnover. These results support the hypothesis that TcNAGs participate in chitin turnover and/or N-glycan processing during insect development and that each NAG fulfills an essential and distinct function.

      PubDate: 2015-03-01T14:54:01Z
  • Characterization of recombinant chitinase-like proteins of Drosophila
           melanogaster and Tribolium castaneum
    • Abstract: Publication date: April 2008
      Source:Insect Biochemistry and Molecular Biology, Volume 38, Issue 4
      Author(s): Qingsong Zhu , Yasuyuki Arakane , Richard W. Beeman , Karl J. Kramer , Subbaratnam Muthukrishnan
      Insect chitinase (CHT) family proteins are encoded by as many as 16 genes depending upon the species of interest. We have classified these proteins in three species into five different groups based on amino acid sequence similarities (Zhu et al., companion paper). The functions of most of the individual proteins of this family during growth and development are largely unknown. To help determine their enzymatic properties and physiological roles, we expressed representative members belonging to this protein family from Drosophila melanogaster (Dm) and Tribolium castaneum (Tc), and characterized their kinetic and carbohydrate-binding properties. Seven proteins, including DmCHT 4, 5, 9 and DmDS47 from Drosophila, and TcCHT5, TcIDGF2 and TcIDGF4 from Tribolium, belonging to groups I, IV or V of the chitinase-like family were expressed in a baculovirus-insect cell line expression system, purified and characterized. Their enzymatic and chitin-binding properties were compared to those of the well-characterized chitinase, MsCHT535, from Manduca sexta (Ms). All of these proteins, except those belonging to group V that are related to imaginal disc growth factors (IDGFs), exhibited chitinolytic activity against the long polymeric substrate, CM-Chitin-RBV, and/or the short oligomeric substrate, MU-(GlcNAc)3. TcCHT5, DmCHT5 and MsCHT535, which are members of group I chitinases, cleaved both polymeric and oligomeric substrates. Their enzymatic properties, including pH optima, kinetic parameters, and susceptibility to substrate inhibition by chitooligosaccharides, were similar. Two group IV chitinases, DmCHT4 and DmCHT9, also were characterized. DmCHT4 had one optimum pH of 6 towards the polymeric substrate and no detectable chitinolytic activity towards an oligosaccharide substrate. DmCHT9 had high activity from pH 4 to 8 towards the polymeric substrate and exhibited low activity towards the oligosaccharide substrate. The group V proteins, TcIDGF2 and TcIDGF4, contain all of the catalytically critical residues within conserved region II of family 18 chitinases but neither exhibited chitinolytic activity. Another group V protein, DmDS47, which lacks the critical glutamate residue in region II and the C-terminal CBD, also exhibited no chitinolytic activity. However, all three of the group V proteins bound to chitin tightly. A comparison of the amino acid sequences and homology model structures of group V proteins with enzymatically active members of the chitinase family indicated that the presence of additional loops of amino acids within the (βα)8-barrel structure of these proteins interferes with productive substrate binding and/or catalysis.

      PubDate: 2015-03-01T14:54:01Z
  • New insight into the RNA interference response against cathepsin-L gene in
           the pea aphid, Acyrthosiphon pisum: Molting or gut phenotypes specifically
           induced by injection or feeding treatments
    • Abstract: Publication date: August 2014
      Source:Insect Biochemistry and Molecular Biology, Volume 51
      Author(s): Panagiotis Sapountzis , Gabrielle Duport , Séverine Balmand , Karen Gaget , Stéphanie Jaubert-Possamai , Gérard Febvay , Hubert Charles , Yvan Rahbé , Stefano Colella , Federica Calevro
      RNA interference (RNAi) has been widely and successfully used for gene inactivation in insects, including aphids, where dsRNA administration can be performed either by feeding or microinjection. However, several aspects related to the aphid response to RNAi, as well as the influence of the administration method on tissue response, or the mixed success to observe phenotypes specific to the gene targeted, are still unclear in this insect group. In the present study, we made the first direct comparison of two administration methods (injection or feeding) for delivery of dsRNA targeting the cathepsin-L gene in the pea aphid, Acyrthosiphon pisum. In order to maximize the possibility of discovering specific phenotypes, the effect of the treatment was analyzed in single individual aphids at the level of five body compartments: the bacteriocytes, the gut, the embryonic chains, the head and the remaining body carcass. Our analysis revealed that gene expression knockdown effect in each single body compartment was dependent on the administration method used, and allowed us to discover new functions for the cathepsin-L gene in aphids. Injection of cathepsin-L dsRNA was much more effective on carcass and head, inducing body morphology alterations, and suggesting a novel role of this gene in the molting of these insects. Administration by feeding provoked cathepsin-L knockdown in the gut and specific gut epithelial cell alteration, therefore allowing a better characterization of tissue specific role of this gene in aphids.
      Graphical abstract image

      PubDate: 2015-03-01T14:54:01Z
  • The red flour beetle's large nose: An expanded odorant receptor gene
           family in Tribolium castaneum
    • Abstract: Publication date: April 2008
      Source:Insect Biochemistry and Molecular Biology, Volume 38, Issue 4
      Author(s): Patamarerk Engsontia , Alan P. Sanderson , Matthew Cobb , Kimberly K.O. Walden , Hugh M. Robertson , Stephen Brown
      The Tribolium castaneum genome sequence reveals a large number of odorant receptor (Or) genes compared to those found in other insects whose olfactory genomes have been studied—341 Or genes and pseudogenes, encoding 259 intact odorant receptor proteins. An RT-PCR study of larvae and adults revealed that only 145 (64%) of 233 genes with successful genomic DNA amplifications were expressed. No expression of the other 87 genes was detected at any age, suggesting either that these genes are not expressed in this particular strain, or that they are induced only in certain environmental or developmental conditions. TcOR1, the ortholog of the Drosophila Or83b (DmOr83b) gene, which is required for the function of olfactory receptor proteins in Drosophila, was expressed in extracts from adult and larval heads and in extracts from adult bodies. Expression of 41 TcOr genes was detected in extracts from larval head tissue and 111 in extracts from adult head tissue (both figures exclude TcOr1). Twenty-eight TcOrs were detected only in adult bodies. Beetle pupae were injected with TcOr1 dsRNA; unlike sham-injected and control beetles, these knock-down beetles showed no significant response to the Tribolium aggregation pheromone, supporting the hypothesis that TcOr1 plays a similar decisive role in olfaction to DmOr83b. The substantial number of Ors poses the question of why Tribolium has such a large olfactory receptor repertoire, and underlines the need for more studies of the natural history of this species.

      PubDate: 2015-03-01T14:54:01Z
  • The beetle by the name of Tribolium Typology and etymology of Tribolium
           castaneum Herbst, 1797
    • Abstract: Publication date: April 2008
      Source:Insect Biochemistry and Molecular Biology, Volume 38, Issue 4
      Author(s): François Bonneton

      PubDate: 2015-03-01T14:54:01Z
  • Analysis of transcriptome data in the red flour beetle, Tribolium
    • Abstract: Publication date: April 2008
      Source:Insect Biochemistry and Molecular Biology, Volume 38, Issue 4
      Author(s): Yoonseong Park , Jamie Aikins , L.J. Wang , Richard W. Beeman , Brenda Oppert , Jeffrey C. Lord , Susan J. Brown , Marcé D. Lorenzen , Stephen Richards , George M. Weinstock , Richard A. Gibbs
      The whole genome sequence of Tribolium castaneum, a worldwide coleopteran pest of stored products, has recently been determined. In order to facilitate accurate annotation and detailed functional analysis of this genome, we have compiled and analyzed all available expressed sequence tag (EST) data. The raw data consist of 61,228 ESTs, including 10,704 obtained from NCBI and an additional 50,524 derived from 32,544 clones generated in our laboratories. These sequences were amassed from cDNA libraries representing six different tissues or stages, namely: whole embryos, whole larvae, larval hindguts and Malpighian tubules, larval fat bodies and carcasses, adult ovaries, and adult heads. Assembly of the 61,228 sequences collapsed into 12,269 clusters (groups of overlapping ESTs representing single genes), of which 10,134 mapped onto 6463 (39%) of the 16,422 GLEAN gene models (i.e. official Tribolium gene list). Approximately 1600 clusters (13% of the total) lack corresponding GLEAN models, despite high matches to the genome, suggesting that a considerable number of transcribed sequences were missed by the gene prediction programs or were removed by GLEAN. We conservatively estimate that the current EST set represents more than 7500 transcription units.

      PubDate: 2015-03-01T14:54:01Z
  • Identification and distribution of a GABA receptor mutation conferring
           dieldrin resistance in the malaria vector Anopheles funestus in Africa
    • Abstract: Publication date: July 2011
      Source:Insect Biochemistry and Molecular Biology, Volume 41, Issue 7
      Author(s): Charles S. Wondji , Roch K. Dabire , Zainab Tukur , Helen Irving , Rousseau Djouaka , John C. Morgan
      Growing problems of pyrethroid resistance in Anopheles funestus have intensified efforts to identify alternative insecticides. Many agrochemicals target the GABA receptors, but cross-resistance from dieldrin resistance may preclude their introduction. Dieldrin resistance was detected in An. funestus populations from West (Burkina Faso) and central (Cameroon) Africa, but populations from East (Uganda) and Southern Africa (Mozambique and Malawi) were fully susceptible to this insecticide. Partial sequencing of the dieldrin target site, the γ-aminobutyric acid (GABA) receptor, identified two amino acid substitutions, A296S and V327I. The A296S mutation has been associated with dieldrin resistance in other species. The V327I mutations was detected in the resistant sample from Burkina Faso and Cameroon and consistently associated with the A296S substitution. The full-length of the An. funestus GABA-receptor gene, amplified by RT-PCR, generated a sequence of 1674 bp encoding 557 amino acid of the protein in An. funestus with 98% similarity to that of Anopheles gambiae. Two diagnostic assays were developed to genotype the A296S mutation (pyrosequencing and PCR-RFLP), and use of these assays revealed high frequency of the resistant allele in Burkina Faso (60%) and Cameroon (82%), moderate level in Benin (16%) while low frequency or absence of the mutation was observed respectively in Uganda (7.5%) or 0% in Malawi and Mozambique. The distribution of the RdlR mutation in An. funestus populations in Africa suggests extensive barriers to gene flow between populations from different regions.
      Graphical abstract image Highlights ► Dieldrin resistance detected in An. funestus from West and Central Africa. ► Identification of the A296S conferring dieldrin resistance after sequencing. ► V327I mutation detected in resistant samples and associated with the A296S mutation. ► Two diagnostic assays were developed to genotype the A296S mutation. ► High frequency of RdlR in West Africa but complete absence in southern Africa.

      PubDate: 2015-03-01T14:54:01Z
  • Identification of mutations associated with pyrethroid resistance in the
           voltage-gated sodium channel of the tomato leaf miner (Tuta absoluta)
    • Abstract: Publication date: July 2012
      Source:Insect Biochemistry and Molecular Biology, Volume 42, Issue 7
      Author(s): Khalid Haddi , Madeleine Berger , Pablo Bielza , Dina Cifuentes , Linda M. Field , Kevin Gorman , Carmelo Rapisarda , Martin S. Williamson , Chris Bass
      The tomato leaf miner, Tuta absoluta (Lepidoptera) is a significant pest of tomatoes that has undergone a rapid expansion in its range during the past six years and is now present across Europe, North Africa and parts of Asia. One of the main means of controlling this pest is through the use of chemical insecticides. In the current study insecticide bioassays were used to determine the susceptibility of five T. absoluta strains established from field collections from Europe and Brazil to pyrethroids. High levels of resistance to λ cyhalothrin and tau fluvalinate were observed in all five strains tested. To investigate whether pyrethroid resistance was mediated by mutation of the para-type sodium channel in T. absoluta the IIS4–IIS6 region of the para gene, which contains many of the mutation sites previously shown to confer knock down (kdr)-type resistance to pyrethroids across a range of different arthropod species, was cloned and sequenced. This revealed that three kdr/super-kdr-type mutations (M918T, T929I and L1014F), were present at high frequencies within all five resistant strains at known resistance ‘hot-spots’. This is the first description of these mutations together in any insect population. High-throughput DNA-based diagnostic assays were developed and used to assess the prevalence of these mutations in 27 field strains from 12 countries. Overall mutant allele frequencies were high (L1014F 0.98, M918T 0.35, T929I 0.60) and remarkably no individual was observed that did not carry kdr in combination with either M918T or T929I. The presence of these mutations at high frequency in T. absoluta populations across much of its range suggests pyrethroids are likely to be ineffective for control and supports the idea that the rapid expansion of this species over the last six years may be in part mediated by the resistance of this pest to chemical insecticides.
      Graphical abstract image Highlights ► Pyrethroid resistance in Tuta absoluta is associated with multiple mutations (L1014F, M918T and T929I) in the sodium channel. ► This is the first description of these three mutations together in any insect population. ► The L1014F mutation was fixed in T. absoluta populations from 12 countries. ► L1014F is always found with either the M918T or T929I mutations in these populations. ► The combination of these mutations seen in field strains is likely to compromise control with pyrethroids.

      PubDate: 2015-03-01T14:54:01Z
  • Global and comparative proteomic profiling of overwintering and developing
           mountain pine beetle, Dendroctonus ponderosae (Coleoptera: Curculionidae),
    • Abstract: Publication date: December 2012
      Source:Insect Biochemistry and Molecular Biology, Volume 42, Issue 12
      Author(s): Tiffany R. Bonnett , Jeanne A. Robert , Caitlin Pitt , Jordie D. Fraser , Christopher I. Keeling , Jörg Bohlmann , Dezene P.W. Huber
      Background Mountain pine beetles, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae), are native to western North America, but have recently begun to expand their range across the Canadian Rocky Mountains. The requirement for larvae to withstand extremely cold winter temperatures and potentially toxic host secondary metabolites in the midst of their ongoing development makes this a critical period of their lives. Results We have uncovered global protein profiles for overwintering mountain pine beetle larvae. We have also quantitatively compared the proteomes for overwintering larvae sampled during autumn cooling and spring warming using iTRAQ methods. We identified 1507 unique proteins across all samples. In total, 33 proteins exhibited differential expression (FDR < 0.05) when compared between larvae before and after a cold snap in the autumn; and 473 proteins exhibited differential expression in the spring when measured before and after a steady incline in mean daily temperature. Eighteen proteins showed significant changes in both autumn and spring samples. Conclusions These first proteomic data for mountain pine beetle larvae show evidence of the involvement of trehalose, 2-deoxyglucose, and antioxidant enzymes in overwintering physiology; confirm and expand upon previous work implicating glycerol in cold tolerance in this insect; and provide new, detailed information on developmental processes in beetles. These results and associated data will be an invaluable resource for future targeted research on cold tolerance mechanisms in the mountain pine beetle and developmental biology in coleopterans.
      Graphical abstract image Highlights ► We used iTRAQ proteomics to examine overwintering physiology of Dendroctonus ponderosae larvae sampled in autumn and spring. ► Autumn larvae accumulate proteins involved in oxidative stress tolerance, cryoprotectant metabolism, and energy metabolism. ► Carbohydrate metabolism, oxidative stress tolerance, and cryoprotectant metabolism protein levels decrease in the spring. ► Ferritin, and enzymes that synthesize 2-deoxyglucose, glycerol, and trehalose seem to be important for winter survival. ► Levels of cytochromes P450, glutathione-S-transferases, and esterases indicate an early larval response to tree toxins.

      PubDate: 2015-03-01T14:54:01Z
  • Resistance to Bt maize in Mythimna unipuncta (Lepidoptera: Noctuidae) is
           mediated by alteration in Cry1Ab protein activation
    • Abstract: Publication date: August 2013
      Source:Insect Biochemistry and Molecular Biology, Volume 43, Issue 8
      Author(s): Joel González-Cabrera , Matías García , Pedro Hernández-Crespo , Gema P. Farinós , Félix Ortego , Pedro Castañera
      Bt maize cultivars based on the event MON810 (expressing Cry1Ab) have shown high efficacy for controlling corn borers. However, their efficiency for controlling some secondary lepidopteran pests such as Mythimna unipuncta has been questioned, raising concerns about potential outbreaks and its economic consequences. We have selected a resistant strain (MR) of M. unipuncta, which is capable of completing its life cycle on Bt maize and displays a similar performance when feeding on both Bt and non-Bt maize. The proteolytic activation of the protoxin and the binding of active toxin to brush border membrane vesicles were investigated in the resistant and a control strain. A reduction in the activity of proteolytic enzymes, which correlates with impaired capacity of midgut extracts to activate the Cry1Ab protoxin has been observed in the resistant strain. Moreover, resistance in larvae of the MR strain was reverted when treated with Cry1Ab toxin activated with midgut juice from the control strain. All these data indicate that resistance in the MR strain is mediated by alteration of toxin activation rather than to an increase in the proteolytic degradation of the protein. By contrast, binding assays performed with biotin labelled Cry1Ab suggest that binding to midgut receptors does not play a major role in the resistance to Bt maize. Our results emphasize the risk of development of resistance in field populations of M. unipuncta and the need to consider this secondary pest in ongoing resistance management programs to avoid the likely negative agronomic and environmental consequences.
      Graphical abstract image

      PubDate: 2015-03-01T14:54:01Z
  • Impact of environment on mosquito response to pyrethroid insecticides:
           Facts, evidences and prospects
    • Abstract: Publication date: April 2013
      Source:Insect Biochemistry and Molecular Biology, Volume 43, Issue 4
      Author(s): Theresia Estomih Nkya , Idir Akhouayri , William Kisinza , Jean-Philippe David
      By transmitting major human diseases such as malaria, dengue fever and filariasis, mosquito species represent a serious threat worldwide in terms of public health, and pose a significant economic burden for the African continent and developing tropical regions. Most vector control programmes aiming at controlling life-threatening mosquitoes rely on the use of chemical insecticides, mainly belonging to the pyrethroid class. However, resistance of mosquito populations to pyrethroids is increasing at a dramatic rate, threatening the efficacy of control programmes throughout insecticide-treated areas, where mosquito-borne diseases are still prevalent. In the absence of new insecticides and efficient alternative vector control methods, resistance management strategies are therefore critical, but these require a deep understanding of adaptive mechanisms underlying resistance. Although insecticide resistance mechanisms are intensively studied in mosquitoes, such adaptation is often considered as the unique result of the selection pressure caused by insecticides used for vector control. Indeed, additional environmental parameters, such as insecticides/pesticides usage in agriculture, the presence of anthropogenic or natural xenobiotics, and biotic interactions between vectors and other organisms, may affect both the overall mosquito responses to pyrethroids and the selection of resistance mechanisms. In this context, the present work aims at updating current knowledge on pyrethroid resistance mechanisms in mosquitoes and compiling available data, often from different research fields, on the impact of the environment on mosquito response to pyrethroids. Key environmental factors, such as the presence of urban or agricultural pollutants and biotic interactions between mosquitoes and their microbiome are discussed, and research perspectives to fill in knowledge gaps are suggested.
      Graphical abstract image Highlights ► Impact of environment on mosquito response to pyrethroids is reviewed. ► Main known pyrethroid resistance mechanisms are described. ► Environmental factors potentially affecting these mechanisms are identified. ► Research perspectives are proposed.

      PubDate: 2015-03-01T14:54:01Z
  • RNAi-based demonstration of direct link between specific odorant receptors
           and mosquito oviposition behavior
    • Abstract: Publication date: October 2013
      Source:Insect Biochemistry and Molecular Biology, Volume 43, Issue 10
      Author(s): Fen Zhu , Pingxi Xu , Rosângela M.R. Barbosa , Young-Moo Choo , Walter S. Leal
      The Southern house mosquito, Culex quinquefasciatus – a vector of West Nile virus – is equipped with 130 odorant receptors (ORs), which enable young females to locate plants and blood-meal sources and older females to find suitable sites for oviposition. In our attempts to de-orphanize ORs expressed in female antennae, we identified CquiOR37 and CquiOR99, which were narrowly tuned to two phenolic compounds, 4-methylphenol and 4-ethylphenol. When tested in the Xenopus oocyte recording system the observed EC50s for 4-methylphenol and 4-ethylphenol were 6.4 and 18.2 μM for CquiOR37 and 14.4 and 0.74 μM for CquiOR99 (goodness of fit, R 2 = 0.88–0.99), respectively. Indoor behavioral assays demonstrated that gravid female mosquitoes laid significantly more eggs in water trays spiked with these compounds than in control water trays. Field studies with gravid traps corroborated that 4-ethylphenol is active in a wide range of doses from 0.1 to 10 μg/l, as required for practical applications. A dsRNA construct based on the two genes, CquiOR37/99-dsRNA was stable in pupa hemolymph for up to 3 h. Pupae injected with CquiOR37/99-dsRNA, β-galactosidase-dsRNA or water had more than 40% survival rate at the peak of oviposition (day-9). qPCR analysis showed individual variation, but significant mean reduction in CquiOR37 and CquiOR99 transcript levels in CquiOR37/99-dsRNA-treated mosquitoes. Water-injected females and those treated with the control gene laid significantly more eggs in trays containing 4-ethylphenol than in water trays, whereas CquiOR37/99-dsRNA-treated mosquitoes laid normal number of eggs, but could not discriminate treatment from control. This study linked for the first time specific receptors for 4-ethylphenol with increased oviposition in the important vector Cx. quinquefasciatus.
      Graphical abstract image

      PubDate: 2015-03-01T14:54:01Z
  • An abundant LEA protein in the anhydrobiotic midge, PvLEA4, acts as a
           molecular shield by limiting growth of aggregating protein particles
    • Abstract: Publication date: November 2013
      Source:Insect Biochemistry and Molecular Biology, Volume 43, Issue 11
      Author(s): Rie Hatanaka , Yuka Hagiwara-Komoda , Takao Furuki , Yasushi Kanamori , Mika Fujita , Richard Cornette , Minoru Sakurai , Takashi Okuda , Takahiro Kikawada
      LEA proteins are found in anhydrobiotes and are thought to be associated with the acquisition of desiccation tolerance. The sleeping chironomid Polypedilum vanderplanki, which can survive in an almost completely desiccated state throughout the larval stage, accumulates LEA proteins in response to desiccation and high salinity conditions. However, the biochemical functions of these proteins remain unclear. Here, we report the characterization of a novel chironomid LEA protein, PvLEA4, which is the most highly accumulated LEA protein in desiccated larvae. Cytoplasmic-soluble PvLEA4 showed many typical characteristics of group 3 LEA proteins (G3LEAs), such as desiccation-inducible accumulation, high hydrophilicity, folding into α-helices on drying, and the ability to reduce aggregation of dehydration-sensitive proteins. This last property of LEA proteins has been termed molecular shield function. To further investigate the molecular shield activity of PvLEA4, we introduced two distinct methods, turbidity measurement and dynamic light scattering (DLS). Turbidity measurements demonstrated that both PvLEA4, and BSA as a positive control, reduced aggregation in α-casein subjected to desiccation and rehydration. However, DLS experiments showed that a small amount of BSA relative to α-casein increased aggregate particle size, whereas PvLEA4 decreased particle size in a dose-dependent manner. Trehalose, which is the main heamolymph sugar in most insects but also a protectant as a chemical chaperone in the sleeping chironomid, has less effect on the limitation of aggregate formation. This analysis suggests that molecular shield proteins function by limiting the growth of protein aggregates during drying and that PvLEA4 counteracts protein aggregation in the desiccation-tolerant larvae of the sleeping chironomid.
      Graphical abstract image

      PubDate: 2015-03-01T14:54:01Z
  • Unlinked genetic loci control the reduced transcription of aminopeptidase
           N 1 and 3 in the European corn borer and determine tolerance to Bacillus
           thuringiensis Cry1Ab toxin
    • Abstract: Publication date: December 2013
      Source:Insect Biochemistry and Molecular Biology, Volume 43, Issue 12
      Author(s): Brad S. Coates , Douglas V. Sumerford , Blair D. Siegfried , Richard L. Hellmich , Craig A. Abel
      Transgenic expression of Bacillus thuringiensis (Bt) crystalline (Cry) toxins by crop plants result in reduced insect feeding damage, but sustainability is threatened by the development of resistance traits in target insect populations. We investigated Bt toxin resistance trait in a laboratory colony of the European corn borer, Ostrinia nubilalis, selected for increased survival when exposed to Cry1Ab and correlated survival on Cry1Ab toxin with a constitutive ∼146.2 ± 17.3-fold reduction in midgut aminopeptidase N1 (apn1) transcript levels. A 7.1 ± 1.9-fold reduction apn3 transcript level was also correlated with Cry1Ab resistance. Quantitative trait locus (QTL) mapping identified a single major genome region controlling Cry1Ab resistance on linkage group 24 (LG24), and a minor QTL on LG27. Both QTL were independent of apn1 and apn3 loci on LG02. Positional mapping identified genetic markers that may assist in the identification of causal gene(s) within QTL intervals. This study indicates that genetic factor(s) may act in trans to reduce both apn1 and apn3 expression in Cry1Ab resistant O. nubilalis larvae, and suggest that gene regulatory pathways can influence Bt resistance traits. These findings show that gene interactions (epistasis) may influence Bt resistance in target insect populations.
      Graphical abstract image

      PubDate: 2015-03-01T14:54:01Z
  • 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: February 2014
      Source:Insect Biochemistry and Molecular Biology, Volume 45
      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 chloride 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.
      Graphical abstract image

      PubDate: 2015-03-01T14:54:01Z
  • The ABC gene family in arthropods: Comparative genomics and role
           in insecticide transport and resistance
    • Abstract: Publication date: February 2014
      Source:Insect Biochemistry and Molecular Biology, Volume 45
      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 protein subfamilies, to infer orthologous relationships that might suggest conserved function. Most orthologous relationships were found in the ABCB half transporter, 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: 2015-03-01T14:54:01Z
  • Evolutionary implications of dipluran hexamerins
    • Abstract: Publication date: March 2014
      Source:Insect Biochemistry and Molecular Biology, Volume 46
      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.
      Graphical abstract image

      PubDate: 2015-03-01T14:54:01Z
  • 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: April 2014
      Source:Insect Biochemistry and Molecular Biology, Volume 47
      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 30 μg 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.
      Graphical abstract image

      PubDate: 2015-03-01T14:54:01Z
  • 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: May 2014
      Source:Insect Biochemistry and Molecular Biology, Volume 48
      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.
      Graphical abstract image

      PubDate: 2015-03-01T14:54:01Z
  • The progress and future of enhancing antiviral capacity by transgenic
           technology in the silkworm Bombyx mori
    • Abstract: Publication date: May 2014
      Source:Insect Biochemistry and Molecular Biology, Volume 48
      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: 2015-03-01T14:54:01Z
  • Identification of candidate odorant degrading gene/enzyme systems in the
           antennal transcriptome of Drosophila melanogaster
    • Abstract: Publication date: October 2014
      Source:Insect Biochemistry and Molecular Biology, Volume 53
      Author(s): Faisal Younus , Thomas Chertemps , Stephen L. Pearce , Gunjan Pandey , Françoise Bozzolan , Christopher W. Coppin , Robyn J. Russell , Martine Maïbèche-Coisne , John G. Oakeshott
      The metabolism of volatile signal molecules by odorant degrading enzymes (ODEs) is crucial to the ongoing sensitivity and specificity of chemoreception in various insects, and a few specific esterases, cytochrome P450s, glutathione S-transferases (GSTs) and UDP-glycosyltransferases (UGTs) have previously been implicated in this process. Significant progress has been made in characterizing ODEs in Lepidoptera but very little is known about them in Diptera, including in Drosophila melanogaster, a major insect model. We have therefore carried out a transcriptomic analysis of the antennae of D. melanogaster in order to identify candidate ODEs. Virgin male and female and mated female antennal transcriptomes were determined by RNAseq. As with the Lepidoptera, we found that many esterases, cytochrome P450 enzymes, GSTs and UGTs are expressed in D. melanogaster antennae. As olfactory genes generally show selective expression in the antennae, a comparison to previously published transcriptomes for other tissues has been performed, showing preferential expression in the antennae for one esterase, JHEdup, one cytochrome P450, CYP308a1, and one GST, GSTE4. These largely uncharacterized enzymes are now prime candidates for ODE functions. JHEdup was expressed heterologously and found to have high catalytic activity against a chemically diverse group of known ester odorants for this species. This is a finding consistent with an ODE although it might suggest a general role in clearing several odorants rather than a specific role in clearing a particular odorant. Our findings do not preclude the possibility of odorant degrading functions for other antennally expressed esterases, P450s, GSTs and UGTs but, if so, they suggest that these enzymes also have additional functions in other tissues.
      Graphical abstract image

      PubDate: 2015-03-01T14:54:01Z
  • The structural sheath protein of aphids is required for phloem feeding
    • Abstract: Publication date: Available online 17 December 2014
      Source:Insect Biochemistry and Molecular Biology
      Author(s): Torsten Will , Andreas Vilcinskas
      Aphids produce two types of saliva that mediate their interactions with plants. Watery saliva is secreted during cell penetration and ingestion, whereas gel saliva is secreted during stylet movement through the apoplast where it forms a sheath around the stylet to facilitate penetration and seal puncture sites on cell membranes. In order to study the function of the sheath when aphids interact with plants, we used RNA interference (RNAi) to silence the aphid structural sheath protein (SHP) in the pea aphid Acyrthosiphon pisum. The injection of 50 ng of double stranded RNA completely disrupted sheath formation, as confirmed by scanning electron microscopy. Aphid behavior was monitored using the electrical penetration graph technique, revealing that disrupted sheath formation prevented efficient long-term feeding from sieve tubes, with a silencing effect on reproduction but not survival. We propose that sealing the stylet penetration site in the sieve tube plasma membrane is part of a two-step mechanism to suppress sieve-tube occlusion by preventing calcium influx into the sieve tube lumen. The SHP is present in several aphid species and silencing has a similar impact to aphid-resistant plants, suggesting that SHP is an excellent target for RNAi-mediated pest control.
      Graphical abstract image

      PubDate: 2014-12-19T06:47:25Z
  • An atypical residue in the pore of Varroa destructor GABA-activated RDL
           receptors affects picrotoxin block and thymol modulation
    • Abstract: Publication date: December 2014
      Source:Insect Biochemistry and Molecular Biology, Volume 55
      Author(s): Kerry L. Price , Sarah C.R. Lummis
      GABA-activated RDL receptors are the insect equivalent of mammalian GABAA receptors, and play a vital role in neurotransmission and insecticide action. Here we clone the pore lining M2 region of the Varroa mite RDL receptor and show that it has 4 atypical residues when compared to M2 regions of most other insects, including bees, which are the major host of Varroa mites. We create mutant Drosophila RDL receptors containing these substitutions and characterise their effects on function. Using two electrode voltage clamp electrophysiology we show that one substitution (T6′M) ablates picrotoxin inhibition and increases the potency of GABA. This mutation also alters the effect of thymol, which enhances both insect and mammalian GABA responses, and is widely used as a miticide. Thymol decreases the GABA EC50 of WT receptors, enhancing responses, but in T6′M-containing receptors it is inhibitory. The other 3 atypical residues have no major effects on either the GABA EC50, the picrotoxin potency or the effect of thymol. In conclusion we show that the RDL 6′ residue is important for channel block, activation and modulation, and understanding its function also has the potential to prove useful in the design of Varroa-specific insecticidal agents.
      Graphical abstract image

      PubDate: 2014-12-15T09:05:32Z
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