Poster: Cell Walls
Abs #
1277: Characterization of putative galactosyltransferase genes in Arabidopsis thaliana
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Presenter: |
Egelund, Jack , j.egelund@dias.kvl.dk |
Authors | Egelund, Jack (A) L. Petersen, Bent (A) Geshi, Naomi (A) Ulvskov, Peter (A) | | Affiliations: |
(A): Biotechnology Group, Danish Institute of Agricultural Sciences, DK-1871 Copenhagen, Denmark
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Using a bioinformatics approach five Arabidopsis sequences were identified as putative galactosyltransferases (GalTs) with function in synthesis of b-(1,4)-linked-D-galactan of pectic rhamnogalacturonan I (RG I). The genes fall into two distinct groups consisting of highly identical group-members (Group I: GalT1, GalT2 & GalT5 with 90 and 73 % identity and Group II: GalT4 & GalT6 with 72 % identity) but with only 11 % identity between the two groups. Validation of the presumed function of the five genes all supported that these genes were indeed GT, even though they are not listed in the Carbohydrat-Active enZYmes (CAZy) database.
GUS analysis of transgenic Arabidopsis containing a fusion between either the GalT2 (group I) or GalT4 promoter (group II) and the gusA reporter gene, revealed that the two genes were differentially expressed. The GalT2 promoter-gusA construct was active in siliques, carples and weakly expressed in petals. Expression was only observed in tissue in which senescence had begun. The GalT4 promoter-gusA construct was active in meristematic tissue starting at the development of the first true leaves.
T-DNA insertion lines for two (GalT4 and GalT6) of the GalTs, showed a delayed growth phenotype in comparison with wild-type plants. Cell wall specific polysaccharide epitopes in primary roots were investigated using a range of antibodies. However, no significant differences were found compared to wild type.
A putative relationship to CAZy GT-family-8 was identified using the Pfam, 3D-PSSM and mGenTHREADER servers. The fact that GTs in this family all posses retaining activities, raises questions as to the acceptor substrates for the putative GalTs. These questions as well as the interpretation of the T-DNA knock-out phenotypes will be discussed.
