Glycobiology_Course_lesson_3

Glycobiology_Course_lesson_3 - Glycobiology Course 2 Plant...

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Glycobiology Course 2 Plant cell walls as photosynthetic energy repository Kathleen Piens Unit Molecular Glycobiology March 2007
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Introduction Plant cell wall ü Strenghtens the plant body, but has also key roles in plant growth, cell differentiation, intercellulair communication, water movement and defence ü A complex polysaccharide wall which constitutes the raw material that is used to manufacture textiles, paper, films, thickeners and other products ü Primary source of cellulose, the most abundant biopolymer on the Earth ü Interesting composite material How is it made? How is it broken down?
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Introduction Outline ü Plant cell wall composition, primary cell wall, secondairy cell wall Intermezzo 1: Structure of the main polysaccharides that are present in the plant cell wall ü How do plant cells synthesize wall polysaccharides? Biosynthesis of cellulose and matrix polysaccharides How is a strong fibrous network assembled? Physico-chemical interactions and enzymatic crosslinking What about wall expansion during cell growth? Enzymes involved in this process
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Introduction Intermezzo 2: CAZy or carbohydrate active enzymes database Glycoside Hydrolases (GH), GlycosylTransferases (GT), Carbohydrate Esterases (CE) Mechanism of GHs Intermezzo 3: Plant cell wall enzymes … tools for the design of new composite materials Example: xyloglucan endotransglycosylase ü Biodegradation and utilization of lignocellulose Biomass recalcitrance: Engineering plants and enzymes for biofuel production The path forward for biofuels?
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Plant cell wall composition Plant comprise ~35 cell types, each of which is distinctive in its size, shape, position and wall characteristics Zone A: Cambial Meristem Zone A-C: Cell Division and Expansion Zone D: Xylem Formation and Secondary Wall Deposition. Zone E: Xylem Maturation and Cell Death Wood formation in hybrid aspen, Populus tremula x P. tremuloides KTH, SLU Umeå, Umeå University Cross section of a hybrid aspen stem stained with Toluidine blue Hertzberg et al , (2001), PNAS , 98 ,14732–14737.
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Plant cell wall composition PRIMARY CELL WALL (PCW): flexible extracellular matrix that is deposited while the cell is expanding SECONDAIRY CELL WALL: laid down inside the PCW when expansion ceases, making the cell wall stronger (lignin = a polymer of monolignols) MIDDLE LAMELLA: thin layer that connects two plant cells and is rich in pectin
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Plant cell wall composition PCW = growing cell wall - strong but pliant extracellular layer CELLULOSE MICROFIBRILS embedded in a matrix of complex polysaccharides two classes: 1) PECTINS 2) HEMICELLULOSES
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Plant cell wall composition Intermezzo 1: Structure of the main polysaccharides that are present in the plant cell wall Cellulose: unbranched (1,4)-linked β - D -glucan (cellobiose is the repeating unit) - parallel glucans form a crystalline microfibril - intra- en intermolecular H-bonds
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Plant cell wall composition: Intermezzo 1 Hemicelluloses: xyloglucan and arabinoxylan are the most abundant hemicelluloses in the PCW
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Glycobiology_Course_lesson_3 - Glycobiology Course 2 Plant...

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