1. | Plant cell wall | All plant cells are surrounded by a thin primary cell wall. This is a main distinguishing feature of plants. It provides protection and shape to a plant cell. These primary walls are made up of polysaccharides (chains of sugar molecules) and some other components such as proteins and enzymes. Some plant cells like xylem (wood) also have two or three additional cell wall layers (S1, S2, S3). These walls are called secondary walls and are made up of cellulose, hemicellulose and lignin. |
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Plant cell wall | ||||
Plant cell wall | ||||
Plant cell wall | ||||
2. | Major components of wood cell wall | Primary wall composition is 25% cellulose, 25% hemicellulose, 35% pectins and 2-5% structural proteins. In contrast, xylem secondary walls are 50% cellulose, 25% hemicelluloses and 20% pectinsand 5% proteins etc. | ||
Major components of wood cell wall | ||||
Major components of wood cell wall | ||||
3. | lignin biosynthesis | Review of secondary growth, secondary cell wall structure and the lignin biosynthetic pathway Experimental approaches to studying the lignin pathway • Purification of enzymes and cloning of genes • Regulation of lignin biosynthesis via transgenics • Genomics |
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lignin biosynthesis | ||||
lignin biosynthesis | ||||
4. | cell wall synthesis | Primary cell wall is formed at the phragmoplast that develops between two newly formed daughter cells. Wall polysaccharides aggregate spontaneously into organized structure. Also during wall formation, glucanfibers automatically form hydrogen bonds between chains forming cellulose microfibrils. Hemicelluloses can be dissolved in strong alkali and upon removal of alkali reform the original ordered network. Wall enzymes put cell wall together or remodel it as needed. See XET on next slide. XETs cut the backbone of XGs and put it with acceptor XGs. Also glycosidases, PMEs and oxidasesare important. | ||
cell wall synthesis | ||||
cell wall synthesis | ||||
7. | cellulose synthase | Poplar genome contains 17CesAs. Nine types of duplicated CesAs are distributed on different chromosomes. Comparison of cell wall contents in transgenic and control aspen with respect to each other. Transgenic poplar trees transformed with three CesA genes also grew faster | ||
cellulose synthase | ||||
cellulose synthase | ||||
8. | Lignin Biosynthesis | Misconceptions about biotechnology and bioenergy.Any plant can be transformed. Genetic manipulation of lignin reduces recalcitrance and improves ethanol production from swithchgrass. | ||
Lignin Biosynthesis | ||||
Lignin Biosynthesis | ||||
9. | student presentation | student presentation | ||
student presentation | ||||
student presentation | ||||
10. | student presentation | |||
student presentation |