Li, Xuemei , Wang, Lijuan , Peña, María , York, William , O'Neill, Malcolm , Link, Bruce , Reiter, Wolf-Dieter .
Cell wall mutations affect the structure of the endomembrane system.
Xyloglucan is the major cross-linking glycan in the primary cell walls of flowering plants, and interacts with cellulose microfibrils to yield a load-bearing but extensible three-dimensional network. We have identified and characterized xyloglucan galactosyltransferase I (XyGAT1/MUR3) that catalyzes the conversion of the XXXG subunit of xyloglucan to the galactosylated derivative XXLG. A T-DNA knockout of this gene named mur3-3 shows thinner cell walls, elongation defects, and a clustering of intracellular vesicles. Two slightly leaky mur3 missense alleles (mur3-1 and mur3-2) have fairly normal phenotypes, but a third allele (cie1) with two missense mutations is similar to mur3-3. NMR data revealed that the residual amount of XXLG/XXFG in xyloglucan from the various mutant lines decreased in the order mur3-1 â‰ˆ mur3-2> cie1> mur3-3. No fucosylation/galactosylation was detectable in mur3-3. Additionally, the double mutants fut1 mur3-1 and fut1 mur3-2Â that are defective in xyloglucan fucosylation due to the fut1 mutation exhibited endomembrane aggregation, and a slightly dwarfed growth habit. This suggests that small amounts of XXFG suppress the phenotypes associated with tight mur3 alleles. Furthermore, the mur1 gmd1 double mutant that cannot make GDP-L-fucose for incorporation into the cell wall is dwarfed and has an abnormal endomembrane system. We suspect that the defects in cell wall polymers interfere with the normal organization of the endomembrane system, which in turn leads to cell elongation defects.
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1 - University of Connecticut, Molecular and Cell Biology, Torrey Life Sciences, Room 403, 75 North Eagleville Road, Unit 3125, Storrs, CT, 06269, United states
2 - Uni. of Connecticut, Molecular and Cell Biology
3 - Uni. of Georgia, Complex Carbohydrate Research Center
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM