期刊
PLANT AND CELL PHYSIOLOGY
卷 59, 期 12, 页码 2624-2636出版社
OXFORD UNIV PRESS
DOI: 10.1093/pcp/pcy180
关键词
Arabidopsis; Cell wall; Galactan; Galactosyltransferases; Glycosyltransferases; Pectin; Rhamnogalacturonan-I
资金
- US Department of Energy, Office of Science, Office of Biological and Environmental Research [DE-AC02-05CH11231]
- Danish Strategic Research Council [Set4Future 11-116795]
- Australian Research Council Future Fellowships [FT160100276, FT130101165]
- Villum Foundation (PLANET project)
- Novo Nordisk Foundation
- Villum Foundation [95-300-73023]
- ARC Centre of Excellence in Plant Cell Walls [CE110001007]
Pectin is a major component of primary cell walls and performs a plethora of functions crucial for plant growth, development and plant-defense responses. Despite the importance of pectic polysaccharides their biosynthesis is poorly understood. Several genes have been implicated in pectin biosynthesis by mutant analysis, but biochemical activity has been shown for very few. We used reverse genetics and biochemical analysis to study members of Glycosyltransferase Family 92 (GT92) in Arabidopsis thaliana. Biochemical analysis gave detailed insight into the properties of GALS1 (Galactan synthase 1) and showed galactan synthase activity of GALS2 and GALS3. All proteins are responsible for adding galactose onto existing galactose residues attached to the rhamnogalacturonan-I (RG-I) back-bone. Significant GALS activity was observed with galacto-pentaose as acceptor but longer acceptors are favored. Overexpression of the GALS proteins in Arabidopsis resulted in accumulation of unbranched beta-1, 4-galactan. Plants in which all three genes were inactivated had no detectable beta-1, 4-galactan, and surprisingly these plants exhibited no obvious developmental phenotypes under standard growth conditions. RG-I in the triple mutants retained branching indicating that the initial Gal substitutions on the RG-I backbone are added by enzymes different from GALS.
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