Bioinformation Analysis And RNAi Of BraSDG2

Histone methyltransferase SDG2 (SET domain group 2) is highly conserved in plants and broadly involveded in the development of Arabidopsis thaliana. The function loss of SDG2 leads to severe pleiotropic phenotypes, smaller and shorter plants, curled leaves, smaller rosette leaves and shorter roots, as well as many target genes in disorder. Two homologous SDG2 genes have been found in Brassica rapa by bioinformation analysis. In this study, we firstly analyzed the bioinformation characters of BraSDG2a and BraSDG2b genes, constructed RNA interference vector of BraSDG2, and geneticly transformated A. thaliana or B. rapaand obtainedtwo kinds of transgenic plants. The results laid the solid foundations for the further research the function of BraSDG2 in the future.1. The bioimformation analysis of BraSDG2. It indicated that B. rapa has two homologous genes of SDG2, which were named BraSDG2a and BraSDG2b, respectively, and their CDS were 7191 bp and 7161 bp, encoding 2396 and 2386 amino acidpoly peptides. Their relative molecular mass were 273328.5 D and 272217.6 D and the theoretical isoelectric points were 6.23 and 6.11. Both of them had a SET domain and 9 or 8 low complexity domains. The two genes were an hydrophilic protein without signal peptide and transmembrane structure.2. Semiquantitative RT-PCR was used for the analysis of BraSDG2. The results showed that BraSDG2b expressed in the each developmental stages of Brassica rapa, especially in the fourth week; It also expressed in the roots, stems, leafs and buds, especially in the buds. The expression level of BraSDG2a is much lessen than BraSDG2a.3. BraSDG2 interference vector was constructed and transformed A. thaliana and B. rapa. Compared with wild-type Arabidopsis, transgenetic Arabidopsis was a smaller and shorter plant with little rosette leaves and almost sterile. These phenotypes were much similar to sdg2.4. Using the petiolate cotyledon of B. rapa as the explant, we optimize the in vitro regeneration and genetic transformation system. Optimum meidium for adventitious bud regeneration medium was MS+ 6-BA 3.0 mg/L+ NAA 0.05 mg/L+30g sucrose+1.6g phytagar, and the differentiation rate was 55.8%. One transgenetic seedling of B. rapa with BraSDG2 RNAi was obtained.