Poster: Cell Walls

Abs # 1255: Maintenance of cell wall strength in Arabidopsis thaliana by xyloglucan endotransglycosylase

Presenter:	Carpita, Nick , carpita@purdue.edu
Authors	Carpita, Nick  (A)   Peña, María J. (A)   Ryden, Peter  (B)   Madson, Michael  (A)   Smith, Andrew  (B)
Affiliations:	(A): Dept. of Botany & Plant Path, Purdue University, W. Lafayette, IN, USA (B): Institute of Food Research, Norwich, U.K.

In land plants, xyloglucans tether cellulose microfibrils into a strong but extensible cell wall. MUR2 and MUR3 encode xyloglucan-specific fucosyl and galactosyl transferases, respectively. Mutations of these genes give precisely altered xyloglucan structures missing one or both of these subtending sugar residues. Tensile strength measurements of etiolated hypocotyls revealed that galactosylation rather fucosylation of the side-chains is responsible for maintenance of wall strength. In contrast, galactosylation of the xyloglucans is not strictly required for cell elongation, for lengthening the polymers that occurs in the wall after they are secreted, or for binding of the xyloglucans to cellulose. Rather, the galactosyl residues markedly enhance the activity of the enzyme xyloglucan endotransglycosylase and the accessibility of xyloglucan to its action, establishing a role for this enzyme in xyloglucan restructuring in the wall during growth for maintenance of tensile strength.