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Publisher: Elsevier   (Total: 3043 journals)

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Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.434, h-index: 14)
Air Medical J.     Hybrid Journal   (Followers: 5, SJR: 0.234, h-index: 18)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.285, h-index: 3)
Alcohol     Hybrid Journal   (Followers: 11, SJR: 0.922, h-index: 66)
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Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 1, SJR: 0.436, h-index: 12)
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Journal Cover Advances in Plant Biochemistry and Molecular Biology
  [8 followers]  Follow
    
   Full-text available via subscription Subscription journal
   ISSN (Print) 1755-0408
   Published by Elsevier Homepage  [3043 journals]
  • Contributors to Volume 1
    • Abstract: 2008
      Publication year: 2008
      Source:Advances in Plant Biochemistry and Molecular Biology, Volume 1



      PubDate: 2012-12-17T18:14:06Z
       
  • Introduction to the Series and Acknowledgements
    • Abstract: 2008
      Publication year: 2008
      Source:Advances in Plant Biochemistry and Molecular Biology, Volume 1



      PubDate: 2012-12-17T18:14:06Z
       
  • Preface to volume 1
    • Abstract: 2008
      Publication year: 2008
      Source:Advances in Plant Biochemistry and Molecular Biology, Volume 1



      PubDate: 2012-12-17T18:14:06Z
       
  • Prologue
    • Abstract: 2008
      Publication year: 2008
      Source:Advances in Plant Biochemistry and Molecular Biology, Volume 1



      PubDate: 2012-12-17T18:14:06Z
       
  • Metabolic Organization in Plants: A Challenge for the Metabolic Engineer
    • Abstract: 2008
      Publication year: 2008
      Source:Advances in Plant Biochemistry and Molecular Biology, Volume 1

      Predictive models of plant metabolism with sufficient power to identify suitable targets for metabolic engineering are desirable, but elusive. The problem is particularly acute in the pathways of primary carbon metabolism, and ultimately it stems from the complexity of the plant metabolic network and the plethora of interacting components that determine the observed fluxes. This complexity is manifested most obviously in the remarkable biosynthetic capacity of plant metabolism, and in the extensive subcellular compartmentation of steps and pathways. However it is argued that while these properties provide a considerable challenge at the level of identifying enzymes and metabolic interconversions ‐ indeed the definition of the plant metabolic network is still incomplete ‐ the real obstacle to predictive modelling lies in identifying the complete set of regulatory mechanisms that influence the function of the network. These mechanisms operate at two levels: one is the molecular crosstalk between effectors and enzymes; and the other is gene expression, where the relationship between fluctuations in expression and network performance is still poorly understood. The tools that are currently available for analysing network structure and performance are described, with particular emphasis on constraints‐based network analysis, metabolic flux analysis, kinetic modelling and metabolic control analysis. Based on a varying mix of theoretical analysis and empirical measurement, all four methods provide insights into the organisation of metabolic networks and the fluxes they support. Specifically they can be used to analyse the robustness of metabolic networks, to generate flux maps that reveal the relationship between genotype and metabolic phenotype, to predict metabolic fluxes in well characterised systems, and to analyse the relationship between substrates, enzymes and fluxes. No single method provides all the information necessary for predictive metabolic engineering, although in principle kinetic modelling should achieve that goal if sufficient information is available to parameterize the models completely. The level of sophistication that is required in predictive models of primary carbon metabolism is illustrated by analysing the conclusions that have emerged from extensive metabolic studies of transgenic plants with reduced levels of Calvin cycle enzymes. These studies highlight the intricate mechanisms that underpin the responsiveness and stability of carbon fixation. It is argued that while the phenotypes of the transgenic plants can be rationalised in terms of a qualitative understanding of the components of the system, it is not yet possible to predict the behaviour of the network quantitatively because of the complexity of the interactions involved.

      PubDate: 2012-12-17T18:14:06Z
       
  • Enzyme Engineering
    • Abstract: 2008
      Publication year: 2008
      Source:Advances in Plant Biochemistry and Molecular Biology, Volume 1

      Enzymes perform the biochemical transformations that direct metabolite flow through metabolic pathways of living cells. Metabolic engineering is made possible via genetic transformation of plants with genes encoding enzymes that selectively divert fixed carbon into desired forms. Genes encoding these enzymes may be identified from natural sources or may be variants of naturally occurring enzymes that have been tailored for specific functionality. The evolution of novel enzyme activities in natural systems provides a context for discussing laboratory‐directed enzyme engineering. This process, also called directed evolution, facilitates the expansion of enzyme function beyond the range identified in nature, by altering factors such as substrate specificity, regioselectivity and enantioselectivity. Changes in kinetic parameters such as kcat, Km and kcat/Km can also be achieved. Key steps in this process are described, including the selection of starting genes, methods for introducing variability, the choice of a heterologous expression system, ways to identify improved variants, and methods for combining improved variants to achieve the desired activity. Introduction of appropriately engineered proteins into plants has great potential not only for metabolic engineering of desired storage compounds but also for enhancement of productivity by improving resistance to pathogens or abiotic stresses.

      PubDate: 2012-12-17T18:14:06Z
       
  • Genetic Engineering of Amino Acid Metabolism in Plants
    • Abstract: 2008
      Publication year: 2008
      Source:Advances in Plant Biochemistry and Molecular Biology, Volume 1

      Amino acids are not only building blocks of proteins but also participate in many metabolic networks that control growth and adaptation to the environment. In young plants, amino acid biosynthesis is regulated by a compound metabolic network that links nitrogen assimilation with carbon metabolism. This network is strongly regulated by the metabolism of four central amino acids, namely glutamine, glutamate, aspartate, and asparagine (Gln, Glu, Asp, and Asn), which are then converted into all other amino acids by various biochemical processes. Amino acids also serve as major transport molecules of nitrogen between source and sink tissues, including transport of nitrogen from vegetative to reproductive tissues. Amino acid metabolism is subject to a concerted regulation by physiological, developmental, and hormonal signals. This regulation also appears to be different between source and sink tissues. The importance of amino acids in plants does not only stem from being central regulators of plant growth and responses to environmental signals, but amino acids are also effectors of the nutritional quality of human foods and animal feeds. Since mammals cannot synthesize about half of the 20‐amino acid building blocks of proteins, they rely on obtaining them from foods and feeds. Yet, the major crop plants contain limited amounts of some of these so‐called “essential amino acids,” which decreases nutritional value. Recent genetic engineering and more recently genomic approaches have significantly boosted our understanding of the regulation of amino acid metabolism in plants and their participation in growth, stress response, and reproduction. In addition, genetic engineering approaches have improved the content of essential amino acids in plants, particularly the contents of lysine and methionine, which are often most limiting.

      PubDate: 2012-12-17T18:14:06Z
       
  • Engineering Photosynthetic Pathways
    • Abstract: 2008
      Publication year: 2008
      Source:Advances in Plant Biochemistry and Molecular Biology, Volume 1

      Improvements of metabolic reactions in photosynthetic pathways, and prospects for successfully altering photosynthetic carbon reduction (PCR) cycle in particular, have become possible through technologies developed during the last decade. This chapter outlines recent strategies and achievements in engineering enzymes of primary CO2 fixations. We emphasize antisense approaches, attempts at engineering the chloroplast genome, and the transfer into C3 species of reactions and enzymes typical for C4 species or cyanobacteria. In addition, we point to the importance of studying the evolutionary diversity of enzymes in primary metabolism. The resulting transgenic lines then provide material suitable for precise flux control analysis. Discussed are enzymes of the photosynthetic reaction (PCR) cycle, ribulose 1,5‐bisphosphate carboxylase/oxygenase (RuBisCO), fructose 1,6‐bisphosphatase (FBPase), sedoheptulose 1,7‐bisphosphatase (SBPase), aldolase, and transketolase that exert control in a rate‐limiting fashion. The PCR cycle, initiated by reactions that are catalyzed by RuBisCO, represents a major energy‐consuming process in photosynthesis, justifying the large amount of research effort directed toward engineering this important enzyme. We also discuss progress in fine‐tuning the two competing reactions catalyzed by RuBisCO, and in defining the roles and importance of PCR components, such as FBPase and SBPase. Lasting success is still elusive in improving crops by increasing primary productivity, but new tools have provided promising new avenues.

      PubDate: 2012-12-17T18:14:06Z
       
  • Genetic Engineering of Seed Storage Proteins
    • Abstract: 2008
      Publication year: 2008
      Source:Advances in Plant Biochemistry and Molecular Biology, Volume 1

      Seeds synthesize and accumulate variable amounts of carbohydrate, lipid, and protein to support their growth, development, and germination. The process of desiccation during seed maturation preserves these nutrients for long periods, making seeds an excellent food source and livestock feed. Over the millennia, human selection for high‐yielding seed crops has resulted in dramatic increases in the accumulation of valuable nutrients and the reduction of toxic compounds and chemicals that affect the taste of foods made from seeds. However, in some cases, selection has resulted in a reduction in the amount or quality of certain nutrients. Many types of seeds are adequate in one nutritional aspect but inadequate in others. Genetic engineering has created the opportunity to use the beneficial traits of certain types of seeds and ameliorate the negative aspects of others. This chapter summarizes the progress that has been made toward the improvement of seed and nonseed crops using transgenic expression of seed storage proteins. We explain the limitations of these approaches and describe promising areas of research such as reduction of allergenic seed components. We also discuss economic and ethical issues that impact this field.

      PubDate: 2012-12-17T18:14:06Z
       
  • Biochemistry and Molecular Biology of Cellulose Biosynthesis in Plants:
           Prospects for Genetic Engineering
    • Abstract: 2008
      Publication year: 2008
      Source:Advances in Plant Biochemistry and Molecular Biology, Volume 1

      Cellulose is a major component of the plant cell wall, and understanding the mechanism of synthesis of this polysaccharide is a major challenge for plant biologists. Cellulose microfibrils are synthesized and assembled by membrane‐localized protein complexes that are visualized as rosettes by freeze‐fracture electron microscopy. Cellulose synthase is required for cellulose synthesis. So far only this enzyme has been localized to these cellulose‐synthesizing complexes. Although it has not been possible to purify and fully characterize cellulose synthase activity from plants, it has been possible to obtain cellulose synthesis in vitro using membranes and detergent‐solubilized membrane fractions. Cellulose synthase uses uridine 5′‐diphosphate (UDP)‐glucose as a substrate and polymerizes glucose residues into long β‐1,4‐linked glucan chains in a single‐step reaction. Cellulose synthases are encoded by genes belonging to a superfamily, and each plant synthesizes a number of different cellulose synthases. Genetic analysis suggests that each cellulose‐synthesizing complex contains at least three nonredundant cellulose synthases and mutation in any one of these cellulose synthases results in cellulose deficiency. More interestingly, different cellulose synthases perform cellulose synthesis in the primary cell wall and the secondary cell wall. Apart from the cellulose synthases, a number of other proteins have been suggested to play a role in cellulose synthesis, but so far their functions are not clearly understood. Genetic manipulation of cellulose synthesis in plants will therefore require not only a complete understanding of the different cellulose synthases but also other proteins that regulate the temporal and spatial synthesis and assembly of this very important polysaccharide.

      PubDate: 2012-12-17T18:14:06Z
       
  • Metabolic Engineering of the Content and Fatty Acid Composition of
           Vegetable Oils
    • Abstract: 2008
      Publication year: 2008
      Source:Advances in Plant Biochemistry and Molecular Biology, Volume 1

      This chapter discusses engineering of plants for yield and composition of edible and industrial triacylglycerols (TAGs). Total oil production has been increased moderately by overexpression of genes for the first and last steps of oil synthesis, acetyl‐CoA carboxylase (ACCase), and diacylglycerol acyltransferase (DGAT), respectively. However, the single enzyme approach has proved less than satisfactory, and further progress may depend on identification of regulatory genes affecting overall expression of the lipid synthesis pathways and partitioning of carbon between oil and other plant products. The fatty acid composition of oilseeds has been more amenable to modification. Development of edible oils rich in monounsaturated fatty acids (18:1) has been achieved in several oilseeds normally dominated by polyunsaturated fatty acids such as 18:2. Approaches have included both chemical mutagenesis and transgenic alteration of the FAD2 genes responsible for desaturation of 18:1 to 18:2. Proportions of 16:0 have been reduced substantially by reduction of FatB, the gene for the thioesterase that releases 16:0 from the acyl carrier protein (ACP) on which it is assembled. The last major goal in edible oil modification, production of a temperate crop sufficiently rich in saturated fatty acids for use without hydrogenation and its associated trans‐fatty acid production, remains elusive. Mechanisms for minimizing transfer of the upregulated saturated fatty acids to plant membranes are currently lacking. Excess saturated fatty acids in plant membranes are particularly damaging in colder temperature ranges. Finally, a wide range of genes have been identified that encode enzymes for synthesis of unusual fatty acids with potential as food additives or industrial feedstocks. Genes for production of γ‐linolenic acid (GLA) and polyunsaturated ω‐3 fatty acids have been introduced into plants, as have genes permitting production of 10:0 and 12:0 for the detergents industry, long‐chain fatty acids for plastics and nylons, novel monounsaturated and conjugated fatty acids, and fatty acids with useful epoxy‐, hydroxy‐, and cyclic moieties. With the notable exception of the shorter‐chain fatty acids, these efforts have been hampered by inadequate yields of the novel products. Given that plants from which many of the applicable genes were isolated do produce oils with high proportions of unusual fatty acids, increased yields in transgenic crops should be achievable. It is probable that introduction of the novel fatty acids must be coupled with appropriate modifications of the enzymes responsible for their flux into vegetable oils.

      PubDate: 2012-12-17T18:14:06Z
       
  • Pathways for the Synthesis of Polyesters in Plants: Cutin, Suberin, and
           Polyhydroxyalkanoates
    • Abstract: 2008
      Publication year: 2008
      Source:Advances in Plant Biochemistry and Molecular Biology, Volume 1

      Plants naturally produce the lipid‐derived polyester cutin, which is found in the plant cuticle that is deposited at the outermost extracellular matrix of the epidermis covering nearly all aboveground tissues. Being at the interface between the cell and the external environment, cutin and the cuticle play important roles in the protection of plants from several stresses. A number of enzymes involved in the synthesis of cutin monomers have recently been identified, including several P450s and one acyl‐CoA synthetase, thus representing the first steps toward the understanding of polyester formation and, potentially, polyester engineering to improve the tolerance of plants to stresses, such as drought, and for industrial applications. However, numerous processes underlying cutin synthesis, such as a controlled polymerization, still remain elusive. Suberin is a second polyester found in the extracellular matrix, most often synthesized in root tissues and during secondary growth. Similar to cutin, the function of suberin is to seal off the respective tissue to inhibit water loss and contribute to resistance to pathogen attack. Being the main constituent of cork, suberin is a plant polyester that has already been industrially exploited. Genetic engineering may be worth exploring in order to change the polyester properties for either different applications or to increase cork production in other species. Polyhydroxyalkanoates (PHAs) are attractive polyesters of 3‐hydroxyacids because of their properties as bioplastics and elastomers. Although PHAs are naturally found in a wide variety of bacteria, biotechnology has aimed at producing these polymers in plants as a source of cheap and renewable biodegradable plastics. Synthesis of PHA containing various monomers has been demonstrated in the cytosol, plastids, and peroxisomes of plants. Several biochemical pathways have been modified in order to achieve this, including the isoprenoid pathway, the fatty acid biosynthetic pathway, and the fatty acid β‐oxidation pathway. PHA synthesis has been demonstrated in a number of plants, including monocots and dicots, and up to 40% PHA per gram dry weight has been demonstrated in Arabidopsis thaliana. Despite some successes, production of PHA in crop plants remains a challenging project. PHA synthesis at high level in vegetative tissues, such as leaves, is associated with chlorosis and reduced growth. The challenge for the future is to succeed in synthesis of PHA copolymers with a narrow range of monomer compositions, at levels that do not compromise plant productivity. This goal will undoubtedly require a deeper understanding of plant biochemical pathways and how carbon fluxes through these pathways can be manipulated, areas where plant “omics” can bring very valuable contributions.

      PubDate: 2012-12-17T18:14:06Z
       
  • Plant Sterol Methyltransferases: Phytosterolomic Analysis, Enzymology, and
           Bioengineering Strategies
    • Abstract: 2008
      Publication year: 2008
      Source:Advances in Plant Biochemistry and Molecular Biology, Volume 1

      So far as is known, the biosynthesis of phytosterols is a ubiquitous property of plants and microbes, whereas insects fail to synthesize the sterol nucleus. All of them require phytosterols to grow and mature. In recent years, the availability of stable isotopes, modern instrumentation such as high‐field nuclear magnetic resonance spectroscopy and molecular biology have offered new insights into the evolutionary development of sterol structure–enzyme function relationships, pathway sequencing, chemical ecology, and in the case of bioengineering provides a mechanism to generate value‐added traits. Here we describe results obtained with these techniques in relation to the critical enzyme that controls the pattern of C‐24 side‐chain diversity, the (S)‐adenosyl‐L‐methionine: Δ24‐sterol methyltransferase (SMT).

      PubDate: 2012-12-17T18:14:06Z
       
  • Engineering Plant Alkaloid Biosynthetic Pathways: Progress and Prospects
    • Abstract: 2008
      Publication year: 2008
      Source:Advances in Plant Biochemistry and Molecular Biology, Volume 1

      With the successful application of molecular genetic methods to the plant alkaloid field, we now have sophisticated tools at our disposal to study regulation of enzymatic biosynthesis, as well as determining the cellular and subcellular localization of these enzymes. The availability of ever‐increasing numbers of recombinant enzymes has enabled thorough analyses of selected alkaloid biosynthetic enzymes at the biochemical and structural levels. We are just beginning to use this knowledge to metabolically engineer alkaloid metabolism in plants and in in vitro cultures. Multicellular compartmentation of alkaloid pathways must be considered if meaningful metabolic engineering experiments are to be designed; for example, we will need to use promoters that drive transgene expression in the correct cell types. Regulation of these pathways at the gene and enzyme level is complex and there is still much to be learned about metabolite levels, multienzyme complexes, and pathway interconnections, as we systematically overexpress and suppress gene transcription. Today, pathway engineering in plants remains highly variable. When we perturb cellular physiology, metabolite homeostasis and intra‐ and intercellular partitioning can be affected in unpredictable ways. Predictive metabolic engineering to generate plants with tailored alkaloid profiles for basic research and for commercial production is clearly a challenge for the future.

      PubDate: 2012-12-17T18:14:06Z
       
  • Engineering Formation of Medicinal Compounds in Cell Cultures
    • Abstract: 2008
      Publication year: 2008
      Source:Advances in Plant Biochemistry and Molecular Biology, Volume 1

      Higher plants are rich sources of medicinal compounds. Many medicinal plants, however, are still harvested in the wild due to technical difficulties of cultivation, as well as for economic reasons. The increased demand and drastic reduction in plant availability increase the pressure to produce medicinal compounds via alternative ways, especially using cell/tissue cultures and transgenic plants. Furthermore, the demands for quality materials have also increased. Before 1970, the reported yields from cell cultures were generally lower than those in plants. However, several cell cultures can have considerable productivity, and in some cases their production exceeds that present in intact plants. The current advancements in understanding and manipulating the molecular and cellular biology of secondary metabolism provide a basis for optimism regarding the commercial production of secondary products in cell/organ cultures and/or transgenic plants. We summarize recent progress in alkaloid research as a principal model and discuss the factors that control productivity and quality, focusing on organ differentiation, genetic instability, rate‐limiting enzyme steps in metabolism, transcriptional regulators, transport, and storage.

      PubDate: 2012-12-17T18:14:06Z
       
  • Genetic Engineering for Salinity Stress Tolerance
    • Abstract: 2008
      Publication year: 2008
      Source:Advances in Plant Biochemistry and Molecular Biology, Volume 1

      Multiple biotic and abiotic environmental factors may constitute stresses that affect plant growth and yield in crop species. With a focus on ionic stress exerted by the presence of sodium, and the associated water deficit, recent advances in our understanding are reviewed. Established physiological, biochemical, and genetic approaches are made more meaningful by the inclusion of genomics‐type tools, which have been most helpful by making available a global view of transcriptome responses to salinity stress, and by providing lines from the global mutagenesis of model species, in particular for Arabidopsis thaliana. Many of the genetic elements that assure ion homeostasis and ion transport have become known, as have several elements that control ion homeostasis. Genes that respond to salinity stress have been identified through mutant screens, from comparative functional studies that relied on known physiological and phenotypic parameters. Until now, the resulting concepts and strategies for engineering salinity stress tolerance in their majority targeted single genes in biochemical pathways, which represent end points of response cascades, but engineering of upstream master switches that regulate the activity of many downstream genes and proteins is increasingly attempted. The rapidly growing body of results on (salinity) stress sensing and signaling promises to lead to the identification of those genes that are of superior significance in salt stress response pathways, and abiotic stresses in general.

      PubDate: 2012-12-17T18:14:06Z
       
  • Metabolic Engineering of Plant Allyl/Propenyl Phenol and Lignin Pathways:
           Future Potential for Biofuels/Bioenergy, Polymer Intermediates, and
           Specialty Chemicals'
    • Abstract: 2008
      Publication year: 2008
      Source:Advances in Plant Biochemistry and Molecular Biology, Volume 1

      Exciting recent developments in the enzymology and molecular biology of plant phenylpropanoids offer numerous opportunities to re‐engineer the composition of plant biomass. Two main targets of such modifications are the optimized production of valuable compounds and reductions in the levels of less desirable products, such as the structural biopolymeric lignins. For example, the amounts of lignin biopolymers in (woody) species might be reduced, with carbon flow concurrently redirected toward production of related nonpolymeric phenylpropanoids, such as the more valuable allyl/propenyl phenols (e.g., eugenol, chavicol). Lignins are monolignol‐derived polymeric end‐products of the phenylpropanoid pathway (originating from the amino acids phenylalanine and tyrosine). In general, lignins represent a formidable technical challenge, particularly due to their intractable nature, for improved plant biomass utilization, for example, when considering the use of woody biomass for bioethanol production, as well as for wood, pulp, and paper manufacture. Other species‐specific outcomes of the phenylpropanoid pathway, however, include metabolites such as lignans, flavonoids, and allyl/propenyl phenols. The recent discovery of the biochemical pathway resulting in the production of the more valuable liquid allyl/propenyl phenols (e.g., eugenol, chavicol, estragole, and anethole), important components of plant spice aromas and flavors, presents one potential approach to the engineering of plant metabolism in new directions. These compounds are synthesized from monolignols in two consecutive enzymatic reactions: (1) acylation of the terminal (C‐9) oxygen of the monolignol forming an ester and (2) regiospecific, NAD(P)H‐dependent reduction of the phenylpropanoid side chain with displacement of the carboxylate ester as leaving group. The proteins involved in the latter step are homologous to well‐characterized phenylpropanoid reductases (pinoresinol‐lariciresinol, isoflavone, phenylcoumaran‐benzylic ether, and leucoanthocyanidin reductases), with similar catalytic mechanisms being operative. The proteins (and corresponding genes) involved in these transformations have been isolated and characterized and offer the potential of engineering plants to partially redirect carbon flow from lignin (or lignans) into these liquid volatile compounds in oilseeds, leafy or heartwood‐forming tissues, or woody stems. The emerging knowledge could also potentially facilitate wood processing in pulp/paper industries and offer sources of renewable plant‐derived biofuels, intermediate chemicals in polymer industries, or specialty chemicals in perfume and flavor industries.

      PubDate: 2012-12-17T18:14:06Z
       
 
 
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