Poster: Cell walls
Abs #
611: Identification and characterisation of novel glycosyltransferases in Arabidopsis thaliana: Xylosyltransferases involved in the synthesis of rhamnogalacturonan II
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Presenter: |
Egelund, Jack , j.egelund@dias.kvl.dk |
Authors | Egelund, Jack (A) L. Petersen, Bent (A) Geshi, Naomi (A) Skjøt, Michael (A) Ulvskov, Peter (A) | | Affiliations: |
(A): Biotechnology Group, Danish Institute of Agricultural Sciences (DIAS), Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
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When studying the biosynthesis of complex structures such as the various polysaccharides found in the plant cell wall, a multi-disciplinary approach is called upon. In the post-genome era, where entire genomes have been sequenced, bioinformatics combined with biochemical and molecular analysis of e.g. knockout mutants and heterologous expression of the candidate genes are key tools in the non-trivial assignment of function to genes.
The work presented here comprises such a multidisciplinary approach. We have recently identified a novel pool of 27 putative GTs, which are not classified in the CAZy database. In this pool we have assigned function within pectin biosynthesis for two of these GTs.
Heterologous expressed GT1 & GT2 protein used in a biochemical assay revealed that that both GTs catalyze the transfer of xylose from UDP-xylose onto fucose and, as a side activity (20% of the xylose to fucose activity), of xylose to arabinose. The disaccharide product was specifically cleaved by a alpha-linkage specific xylosidase demonstrating that GT1 and GT2 encode alpha-xylosyltransferases. Xylose linked to fucose with an alpha-linked glucosidic bond is a rare structure in higher plants. We are only aware of this structure in the chain A of the cell wall pectic component rhamnogalacturonan II (RG-II) and propose that both GT1 and GT2 are involved in the synthesis of this particular structure. Resent analysis of RG-II isolated from GT1 and GT2 T-DNA knockout mutants as well as EGFP fusions support the proposed function in RG-II synthesis.
