Sakamoto K, Kusaba M, Nishio T
Institute of Radiation Breeding, NIAR, MAFF, Ibaraki, Japan.
Mol Gen Genet. 1998 May;258(4):397-403. doi: 10.1007/s004380050747.
The S-locus glycoprotein gene, SLG, which participates in the pollen-stigma interaction of self-incompatibility, and its unlinked homologue, SLR1, were analyzed in Raphanus sativus and three self-incompatible ornamental plants in the Brassicaceae. Among twenty-nine inbred lines of R. sativus, eighteen S haplotypes were identified on the basis of DNA polymorphisms detected by genomic Southern analysis using Brassica SLG probes. DNA fragments of SLG alleles specifically amplified from eight S haplotypes by PCR with class I SLG-specific primers showed different profiles following polyacrylamide gel electrophoresis, after digestion with a restriction endonuclease. The nucleotide sequences of the DNA fragments of these eight R. sativus SLG alleles were determined. Degrees of similarity of the nucleotide sequences to a Brassica SLG (S6SLG) ranged from 85.6% to 91.9%. Amino acid sequences deduced from these had the twelve conserved cysteine residues and the three hypervariable regions characteristic of Brassica SLGs. Phylogenetic analysis of the SLG sequences from Raphanus and Brassica revealed that the Raphanus SLGs did not form an independent cluster, but were dispersed in the tree, clustering together with Brassica SLGs. These results suggest that diversification of the SLG alleles of Raphanus and Brassica occurred before differentiation of these genera. Although SLR1 sequences from Orychophragmus violaceus were shown to be relatively closely related to Brassica and Raphanus SLR1 sequences, DNA fragments that are highly homologous to the Brassica SLG were not detected in this species. Two other ornamental plants in the Brassicaceae, which are related more distantly to Brassica than Orychophragmus, also lacked sequences highly homologous to Brassica SLG genes. The evolution of self-incompatibility in the Brassicaceae is discussed.
参与自交不亲和花粉-柱头相互作用的S-位点糖蛋白基因（SLG）及其不连锁的同源基因SLR1，在萝卜和十字花科三种自交不亲和观赏植物中进行了分析。在29个萝卜自交系中，基于使用芸薹属SLG探针通过基因组Southern分析检测到的DNA多态性，鉴定出了18种S单倍型。通过PCR用I类SLG特异性引物从8种S单倍型特异性扩增的SLG等位基因的DNA片段，在用限制性内切酶消化后，经聚丙烯酰胺凝胶电泳显示出不同的图谱。测定了这8个萝卜SLG等位基因的DNA片段的核苷酸序列。这些核苷酸序列与芸薹属SLG（S6SLG）的相似程度在85.6%至91.9%之间。从这些序列推导的氨基酸序列具有芸薹属SLG特有的12个保守半胱氨酸残基和3个高变区。对萝卜和芸薹属的SLG序列进行系统发育分析表明，萝卜的SLG没有形成一个独立的簇，而是分散在树中，与芸薹属SLG聚集在一起。这些结果表明，萝卜和芸薹属的SLG等位基因的多样化发生在这些属分化之前。虽然诸葛菜的SLR1序列显示与芸薹属和萝卜的SLR1序列相对密切相关，但在该物种中未检测到与芸薹属SLG高度同源的DNA片段。十字花科另外两种与芸薹属的亲缘关系比诸葛菜更远的观赏植物，也缺乏与芸薹属SLG基因高度同源的序列。文中讨论了十字花科自交不亲和性的进化。
