Kusaba M, Nishio T
Institute of Radiation Breeding National Institute of Agrobiological Resources, Ministry of Agriculture, Forestry and Fisheries, Ibaraki, Japan.
Plant J. 1999 Jan;17(1):83-91. doi: 10.1046/j.1365-313x.1999.00355.x.
Self-incompatibility in Brassica is controlled by a single multi-allelic locus (the S locus) which harbors at least two highly polymorphic genes, SLG and SRK. SRK is a putative transmembrane receptor kinase and its amino acid sequence of the extracellular domain of SRK (the S domain) exhibits high homology to that of SLG. The amino acid sequences of the SLGs of S8 and S46 haplotypes of B. rapa are very similar and those of S23 and S29 haplotypes of B. oleracea were also found to be almost identical. In both cases, SLG and the S domain of SRK of the same haplotype were less similar. This seems to contradict the idea that SLG and SRK of the same haplotype have the same self-recognition specificity. In the transmembrane-kinase domain, the SRK alleles of the S8 and S46 haplotypes had almost identical nucleotide sequences in spite of their lower homology in the S domain. Such a cluster of nucleotide substitutions is probably due to recombination or related events, although recombination in the S locus is thought to be suppressed. Based on our observations, the recognition mechanism and the evolution of self-incompatibility in Brassica are discussed.
芸苔属植物的自交不亲和性由单个多等位基因位点（S位点）控制，该位点包含至少两个高度多态的基因，即SLG和SRK。SRK是一种假定的跨膜受体激酶，其SRK胞外结构域（S结构域）的氨基酸序列与SLG的氨基酸序列具有高度同源性。白菜S8和S46单倍型的SLG氨基酸序列非常相似，甘蓝S23和S29单倍型的SLG氨基酸序列也几乎相同。在这两种情况下，同一单倍型的SLG和SRK的S结构域相似度较低。这似乎与同一单倍型的SLG和SRK具有相同的自我识别特异性这一观点相矛盾。在跨膜激酶结构域中，S8和S46单倍型的SRK等位基因尽管在S结构域中的同源性较低，但其核苷酸序列几乎相同。这种核苷酸替换的聚集可能是由于重组或相关事件导致的，尽管S位点的重组被认为受到抑制。基于我们的观察结果，对芸苔属植物自交不亲和性的识别机制和进化进行了讨论。
