Plant Carbohydrates II

In 1958, a single volume in the original series of this Encyclopedia adequately summarized the state of knowledge about plant carbohydrates. Expansion into two volumes in the New Series highlights the explosive increase in information and the heightened interest that attended this class of compounds in the interven­ ing years. Even now the search has just begun. Much remains to be accom­ plished; e.g., a full description of the plant cell wall in chemical terms. Why this growing fascination with plant carbohydrates? Clearly, much credit goes to those who pioneered the complex chemistry of polyhydroxylated compounds and to those who later sorted out the biochemical features of these molecules. But there is a second aspect, the role of carbohydrates in such biological func­ tions as host-parasite and pollen-pistil interactions, the mating reaction in fungi, symbiosis, and secretion to name a few. Here is ample reason for anyone concerned with the plant sciences to turn aside for a moment and consider how carbohydrates, so many years neglected in favor of the study of proteins and nucleic acids, contribute to the physiological processes of growth and devel­ opment in plants.

Contenu

I. Cell Walls of Higher Plants.- 1 Constitution of Plant Cell Wall Polysaccharides.- 1 The Classification of Plant Polysaccharides.- 2 The Main Structural Features.- 2.1 Cellulose, Other ?-d-Glucose and Xyloglucans.- 2.2 Rhamnogalacturonans and Associated Arabinans and Arabinogalactans.- 2.3 Mannans, Glucomannans and Galactoglucomannans.- 2.4 Xylans.- 2.5 Other Cell Wall Polysaccharides.- 3 Covalent and Non-Covalent Inter-Polymeric Linkages in the Cell Wall.- References.- 2 Ultrastructure of the Plant Cell Wall: Biophysical Viewpoint.- 1 Introduction.- 1.1 What a Plant Cell Wall Is.- 1.2 What a Plant Cell Wall Is Not.- 1.3 Functions and Biological Significance of the Plant Cell Wall.- 2 Idealized Plant Cell Wall: Structure.- 2.1 Intercellular Layer.- 2.2 Primary Cell Wall.- 2.2.1 Matrix Substances.- 2.2.2 Microfibrils of Cellulose.- 2.2.3 Local Structure of the Primary Wall.- 2.3 Secondary Cell Wall.- 2.3.1 Bordered Pits.- 2.4 Tertiary Wall.- 3 Actual Plant Cell Walls: Structure.- 3.1 Intercellular Layers of Various Species.- 3.2 Thickened Primary Wall of Axial Parenchyma Cells of Trembling Aspen.- 3.3 Secondary Wall Layers of Elm Parenchyma Cells.- 3.4 Ultrastructure of Cell Walls of Fusarium sulphureum.- 3.5 Ultrastructure of the Cell Wall of Yeasts.- 3.6 Cell Wall Structure of Algae.- 3.7 Physical Structure of Cell Walls from Protoplasts.- 3.8 Physics of Specialized Structures of Plant Cell Walls.- 4 Macromolecular Problems of Formation of Components of Plant Cell Walls.- 4.1 Physical Formation of Cellulose Microfibrils.- 4.2 Physical Formation of Chitin Microfibrils.- 4.3 Deposition of Hemicelluloses.- 4.4 Physical Self-Assembly of Plant Cell Walls.- 5 Resumé.- References.- 3 The Assembly of Polysaccharide Fibrils.- References.- 4 Ultrastructure of the Plant Cell Wall: Biochemical Viewpoint.- 1 Introduction.- 2 Microfibrillar Component.- 3 Matrix Noncellulosic Polysaccharides.- 3.1 Hemicelluloses.- 3.1.1 Xylans.- 3.1.2 Mixed ?-Glucans.- 3.1.3 Xyloglucans.- 3.1.4 Glucomannans.- 3.2 Pectic Polysaccharides.- 3.2.1 Rhamnogalacturonan.- 3.2.2 Arabinogalactans.- 3.2.3 Arabinans and Galactans.- 3.3 Glycoprotein of the Walls.- 3.4 Lignin.- 4 Polysaccharidic Association Within the Primary Cell Wall.- 4.1 Dicot Primary Cell Walls.- 4.2 Monocot Primary Cell Walls.- 5 Chemical Changes in the Cell Wall During Growth and Differentiation.- 6 Conclusion.- References.- 5 Biosynthesis and Metabolism of Cellulose and Noncellulosic Cell Wall Glucans.- 1 Introduction: Various Aspects of Cellulose Formation in Vivo and in Vitro.- 2 Possible Substrates for Cellulose Biosynthesis.- 2.1 Occurrence of NDP-Sugars (Sugar Nucleotides) in Tissues Actively Forming Cell Walls.- 2.2 Sucrose Synthetase and Pyrophosphorylase Activities.- 2.3 Different NDP-Glucoses as Hypothetical Substrates for the in Vitro Biosynthesis of Cellulose.- 2.4 In Vivo Studies on Cellulose Biosynthesis.- 3 Primer Requirement for Cellulose Biosynthesis.- 4 Involvement of Lipid-Intermediates in Cellulose Biosynthesis.- 5 Endogenous and Exogenous Factors Which Might Influence the Biosynthesis of Cellulose.- 5.1 Hormonal Control of Cellulose Biosynthesis.- 5.2 Inhibitors in the Process of Cellulose Formation.- 6 Conclusion.- References.- 6 Metabolism of Noncellulosic Polysaccharides.- 1 Cell Walls and Cell Wall Metabolism.- 2 Molecular Aspects of Polysaccharide Synthesis.- 2.1 Origins of Monosaccharides and Their Activated Forms.- 2.2 Polysaccharide Assembly.- 2.2.1 Polymerizing Systems.- 2.2.2 Lipid-Saccharide Intermediates.- 2.2.3 Chain Initiation.- 2.2.4 Chain Elongation and Direction of Growth.- 2.2.5 Sequences of Linkages and Monosaccharides, and Insertion of Side Branches.- 2.2.6 Chain Termination.- 2.3 Biosynthesis of Glycosyl Ethers and Esters.- 2.4 Control.- 2.4.1 Supply of Monosaccharide Precursors.- 2.4.2 Activation and Interconversion of Monosaccharides.- 2.4.3 Polymerization.- 3 Cellular Aspects of Polysaccharide Synthesis and Processing.- 3.1 Location of Enzymes Leading to the Establishment of the Nucleotide Sugar Pool.- 3.2 Location of Glycosyl Transferases Involving Lipid Intermediates.- 3.3 Location of Polysaccharide Synthetases.- 3.4 Subcellular Routes of Polysaccharide Assembly.- 3.4.1 Golgi Dictyosome - Golgi Vesicle - Plasma Membrane Route.- 3.4.2 Endoplasmic Reticulum - Plasma Membrane Route.- 3.4.3 Assembly at the Plasma Membrane.- 3.4.4 Deposition of Polysaccharides in the Wall.- 4 Metabolism During Cell Division, Growth, Differentiation, Senescence and Germination.- 4.1 Methodological Considerations and Interpretations.- 4.2 Molecular Strategies in Morphogenesis.- 4.3 Cell Plate Formation.- 4.4 Primary Cell Wall Deposition and Expansion.- 4.5 Secondary Cell Wall Deposition and Growth.- 4.6 Cell Wall Metabolism During Differentiation in Specific Tissues.- 4.6.1 Tracheids, Laticifers, Aerenchyma and Lateral Root Initiation.- 4.6.2 Tyloses.- 4.6.3 Formation of Plasmodesmata and Differentiation of Sieve Plates.- 4.6.4 Gametogenic Tissues.- 4.6.5 Mucilage (Slime)- and Gum-secreting Cells.- 4.7 Senescence.- 4.7.1 Abscission.- 4.7.2 Fruit Senescence.- 4.7.3 Flower and Leaf Senescence.- 4.8 Germination.- 5 Metabolism in Response to Environmental Changes and Pathogenesis.- 5.1 Tropisms.- 5.1.1 Geotropism and Phototropism.- 5.1.2 Reaction Wood.- 5.1.3 Hypogravity.- 5.2 Environmental Stress.- 5.3 Wounding Responses.- 5.4 Pathogenesis.- References.- 7 Glycoproteins and Enzymes of the Cell Wall.- 1 Introduction.- 2 Structural or Matrix Proteins.- 2.1 Higher and Lower Plants.- 2.1.1 Glycopeptide Linkages.- 2.1.2 Hydroxyproline Glycosides.- 2.1.3 Peptide Sequence and Conformation.- 2.1.4 Role of Glycosylation.- 2.1.5 Assembly.- 2.1.6 Possible Roles for the Matrix Protein Extensin.- 2.2 Algae.- 2.2.1 Occurrence of Matrix Proteins.- 2.2.2 The Chlamydomonas Type Wall.- 2.2.3 Phylogenetic Considerations.- 3 Cell Wall Enzymes.- 3.1 Introduction.- 3.2 Biological Role.- 3.2.1 Involvement in Cell Wall Assembly and Cell Extension.- 3.2.2 Involvement in Transport.- 3.2.3 Involvement in Recognition Phenomena and Disease Resistance.- 4 Arabinogalactan Proteins (AGP's) and ?-Lectins.- 4.1 General Properties.- 4.2 Chemistry, Physical Properties, and Biosynthesis.- 4.3 Biological Role.- 4.3.1 Water Relations.- 4.3.2 Mechanical Cell-Cell Interactions.- 4.3.3 Cell Recognition.- 5 Concluding Remarks.- References.- 8 The Role of Lipid-Linked Saccharides in the Biosynthesis of Complex Carbohydrates.- 1 Introduction.- 2 Nature of the Lipid Carrier.- 3 Glycoproteins or Other Complex Carbohydrates.- 4 Lipid-linked Monosaccharides.- 4.1 Mannose.- 4.2 Glucose.- 4.3 N-Acetylglucosamine.- 4.4 Other Monosaccharide Lipids.- 5 Oligosaccharide Derivatives.- 6 Protein Glycosylation.- 7 Further Reactions - Processing of Proteins.- 8 Effec…