Phylogenetic analysis of Brassicaceae plants and molecular evolution of self-incompatibility

本研究以十字花科19种植物为材料，测定了SLR1(S座位相关基因1)、RbcL(Rubisco大亚基)和叶绿体ID亚型的核苷酸序列，并对它们进行了系统发育分析。SLR1分析表明，黑菜与甘蓝、油菜虽然同属，但亲缘关系较远，海南芥菜和萝卜与甘蓝和油菜的亲缘关系较近。RbcL和叶绿体亚型ID的分析表明，这些物种可分为白菜型油菜/油菜型油菜和白菜型油菜型油菜/黑菜型油菜两大类群，而油菜型油菜与油菜型油菜有较远的亲缘关系。我们正在研究这些基因的种内变异，并计算这些物种的物种形成年份。在决定自交不亲和的自我/非自我识别特异性的SLG和SRK基因的比较中，甘蓝、油菜和甘蓝型油菜之间发现了高度相似的等位基因集。这组等位基因被认为在这三个物种的物种形成之前是相同的等位基因。大蒜的SLG等位基因没有形成一个独立于甘蓝型油菜的类群，说明S基因座的多样性发生在这些属分离之前。对S基因座的长片段分析表明，S基因座复合体中的插入或缺失发生在物种形成时或之后。

Using 19 species of Brassicaceae plants, we determined nucleotide sequences of SLR1 (S-locus related gene 1), rbcL (Large subunit of RuBisCO), and Plastid subtype ID, and compared them for phylogenetic analysis. Analysis of SLR1 showed that Brassica nigra is distantly related to Brassica oleracea and Brassica rapa though they belong to the same genus, and that Erucastrum abyssinicum and Raphanus sativus are more closely related to B. oleracea and B. rapa. Analyses of rbcL and Plastid subtype ID indicated that these species can be separated into two groups, B. rapa/B. oleracea group and Sinapis alba/B. nigra group, and that B. nigra is distantly related to B. oleracea. We are now investigating the intra-specific variation of these genes, and going to calculate the year of speciation of these species.In the comparison of SLG and SRK genes, which determine the self/non-self recognition specificity of self-incompatibility, highly similar set of alleles among B. oleracea, B. rapa, and B. napus were found. This set of alleles are considered to have been the same allele before the speciation of these three species. SLG alleles of R. sativus did not form a group independent from those of Brassica, indicating that diversification of S locus occurred before the separation of these genus. Analysis of long DNA fragments of S locus suggested that insertion or deletion of DNA fragments occurred in the S locus complex at the time of or after the speciation.