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6. Signaling and Response Mechanisms
The disassembly and hydrolysis of polysaccharides after
their function in the wall is complete. Wall disassembly is typically
associated with fruit ripening or the digestion of the storage tissue walls
during seed germination, but such processes occur throughout development in
all cells. Over 170 Arabidopsis genes are suspected to encode pectin degrading
enzymes alone (Henrissat et al. 2001). Plants with Type I and II walls have
also developed different repertories of hydrolases that function in disassembly
of their different cell wall polysaccharides (Hrmova and Fincher 2001). Part
of the disassembly of the wall by differentiating cells includes the salvage
of sugars into the nucleotide-sugar interconversion pathway. Defects in this
pathway would lead an inability to recycle sugars and potentially lead to
reduced content.
Henrissat, B., P. M. Coutinho, G. J. Davies. 2001. A census of carbohydrate-active
enzymes in the genome of Arabidopsis. Plant Mol. Biol. 47, 55-72.
Hrmova, M., G. B. Fincher. 2001. Structure-function relationships of b-D-glucan endo- and exohydrolases from higher plants. Plant Mol. Biol. 47, 73-91.
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ARA1 ARA1 encodes cytosolic C-1 arabinokinase responsible for salvaging arabinose cleaved from cell wall polymers into the nucleotide-sugar pool. The mutant was discovered by the plant’s usual inability to grow on media supplemented with arabinose. Arabinose is toxic in submillimolar amounts, and arabinokinase removes the toxic sugar. References:
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6.1 Generation of signal molecules
6.2 Reactive-oxygen species generation
6.3 Receptor-like kinases and their ligands
6.4 Glycosylphosphatidylinositol (GPI)-anchored
proteins
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