Poster: Cell walls
Abs #
606: Deciphering the roles of xyloglucan galactosylation in the assembly of a functional plant cell wall
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Presenter: |
Li, Xuemei |
Authors | Li, Xuemei (A) Peña, María (B) Cordero, Israel (A) Link, Bruce (A) Amin, Amy (A) Carpita, Nick (B) Reiter, Wolf-Dieter (A) | | Affiliations: |
(A): Department of Molecular and Cell Biology, University of Connecticut
(B): Department of Botany and Plant Pathology, Purdue University
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| Web Site: | http://www.sp.uconn.edu/~mcbstaff/reiter/index.html | |
Xyloglucans (XyGs) consist of a β(1,4)-linked glucan backbone, which is substituted by xylose residues in an "XXXG" repeat pattern. Some of the second and third xylosyl residues within this core structure carry galactosyl and fucosyl-galactosyl side chains, respectively. The main function of XyGs is the binding and cross-linking of cellulose microfibrils, which is considered essential for cell wall assembly and remodeling during cell growth. XyGs of the mur3 mutant of Arabidopsis lack the fucosyl-galactosyl side chain because of a defect in xyloglucan galactosyltransferase I, which converts XXXG to its galactosylated derivative XXLG. Although XyG binding to cellulose is unaffected, mur3 hypocotyls exhibit abnormal cell swelling and greatly reduced tensile strength. Shoots of chemically induced mur3 alleles do not show obvious visible phenotypes, but three independent T-DNA insertion lines are slightly stunted, show reduced cellulose content and decreased tensile strength of elongating inflorescence stems. A knockout mutant in the MUR3 paralog AtGT18 contains only small amounts of galactose on the central xylose residue within the XyG repeat unit, suggesting that this gene encodes xyloglucan galactosyltransferase II, which converts XXXG to XLXG. The atgt18 plants show a "droopy" phenotype and abnormal patterns of lignin deposition. Preliminary results on the F2 population from a mur3 x atgt18 cross indicate segregation for plants with severe growth defects, which appear to be double mutants. Comparative analysis of the various mutant lines should lead to meaningful insights into the functional significance of xyloglucan galactosylation. Supported by grants from NSF-IBN and the Plant Genome Research Program.
