Zhou, Shaohua , Carpita, Nicholas C , McCann, Maureen C .
Is rhamnogalacturonan-I a key scaffolding element in the pectin network of arabidopsis cell walls?
Cell walls constrain the sizes and shapes of plant cells. Primary (growing) plant cell walls contain highly hydrated biopolymer networks. The structures of some of the component polysaccharides and their cross-links are known, but the architectures of the networks are not defined, compromising the interpretation of biophysical or biological properties in terms of molecular mechanisms. Pectins account for 20 to 50% of dry mass of dicotyledonous cell walls. Pectins comprise rhamnogalacturonan I (RG-I) and homogalacturonan (HG) polymers that can be variously substituted with acetyl and ester groups, and side chains, and are developmentally regulated in different cell types. We have identified a 7-member gene family in Arabidopsis, the MYST gene family, that encode rhamnogalacturonan lyases, an enzyme activity more commonly associated with plant pathogens for cell wall hydrolysis. Two allelic mutants of MYST6 have bulging root hair and early senescence phenotypes that are complemented by expression of MYST6 cDNA. We hypothesize that the failure to turn over RG-I in root epidermal cell walls arrests elongation of root hairs. RNAi-knockdown of MYST4 expression results in highly dwarfed plants. By modulating the activity of endogenous RG lyase, we aim to modulate the content of RG-I in cell walls and define the function of this polysaccharide in cell wall architecture. Phenotypic analyses of over-expressing and knockdown transgenic lines reveal dramatic phenotypes indicating crucial functions for these proteins and their substrate in plant growth and development.
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1 - Purdue University, Biological Sciences
2 - Purdue University, Botany and Plant Pathology
3 - Purdue University, Biological Sciences, West Lafayette, IN, 47907, USA
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM