Characterization of IRX10 and IRX10-like reveals an essential role in glucuronoxylan biosynthesis in Arabidopsis |
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Authors: | Brown David M Zhang Zhinong Stephens Elaine Dupree Paul Turner Simon R |
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Institution: | Faculty of Life Science, University of Manchester, Manchester M13 9PT, UK;, Biochemistry Department, Building O, Downing Site, Cambridge CB2 1QW, UK;, and Chemistry Department, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK |
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Abstract: | Xylan, the major hemicellulosic polysaccharide in Arabidopsis secondary cell walls, requires a number of glycosyltransferases (GT) to catalyse formation of the various glycosidic linkages found in the polymer. In this study, we characterized IRX10 and IRX10-like ( IRX10-L ), two highly homologous genes encoding members of the glycosyltransferase family 47 (GT47). T-DNA insertions in IRX10 gave a mild irregular xylem (irx) phenotype consistent with a minor defect in secondary cell-wall synthesis, whereas plants containing mutations in IRX10-L showed no change. However, irx10 irx10-L double mutant plants showed a much more severe irx and whole-plant phenotype, suggesting considerable functional redundancy between these two genes. Detailed biochemical analysis of the irx10 irx10-L double mutant showed a large reduction of xylan in the secondary cell walls, consistent with a specific defect in xylan biosynthesis. Furthermore, the irx10 irx10-L mutant retains the unique oligosaccharide found at the reducing end of Arabidopsis xylan, but shows a severe reduction in β(1,4) xylosyltransferase activity. These characteristics are similar to those of irx9 and irx14 , mutants that are believed to be defective in xylan chain elongation, and suggests that IRX10 and IRX10-L also play a role in elongation of the xylan backbone. |
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Keywords: | xylan glycosyltransferase secondary cell wall irregular xylem (irx) mutant NpGUT1 IRX10 |
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