Minisymposium 1: Cell Walls

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Abs # M0101: Expression regulation and functions of Arabidopsis xyloglucan endotransglucosylase/hydrolases

Presenter:	Mezzari, Melissa P       Contact Presenter
Authors	Mezzari, Melissa P (A)   Becnel, Jaime  (A)   Pao, Sharon  (A)   Braam, Janet  (A)
Affiliations:	(A): Rice University
Web Site:	http://bioc.rice.edu/~braam/

The cell wall, a major structural determinant of plants, must undergo regulated architectural alterations to contribute to the dynamic morphogenetic changes that accompany plant growth and development. Xyloglucan endotransglucosylase/hydrolases (XTHs) are predicted to be important players in wall structure regulation because of their ability to modify xyloglucan interactions with cellulose microfibrils. XTHs are encoded by a 33-member gene family. XTH::GUS reporter expression patterns and Genevestigator compilations reveal differential sites of potential action. Characterization of insertion mutants begins to reveal physiological function. For example, insertion mutations in XTH15 result in defective hypocotyl elongation. The cellular basis of the growth defect is revealed by microscopy cross-sections. Cells of xth15-1 and xth15-2 collapse and fail to align properly. Pronounced changes in the morphology of the hypocotyl endodermis and cortex are observed, including cell-shape changes and incomplete cell walls. In roots, the pericycle cell layer may also be collapsed. GUS transgenics report putative XTH15 cell-specific expression in patterns consistent with the cellular defects. Thus, XTH15 function is required for integrity of specific cell types in the elongating hypocotyl and root. This material is based upon work supported by the National Science Foundation under Grant number IBN 0313432.