Fujimoto Ryo, Okazaki Keiichi, Fukai Eigo, Kusaba Makoto, Nishio Takeshi
Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
Genetics. 2006 Jun;173(2):1157-67. doi: 10.1534/genetics.104.037267. Epub 2006 Apr 19.
The determinants of recognition specificity of self-incompatibility in Brassica are SRK in the stigma and SP11/SCR in the pollen, both of which are encoded in the S locus. The nucleotide sequence analyses of many SRK and SP11/SCR alleles have identified several interspecific pairs of S haplotypes having highly similar sequences between B. oleracea and B. rapa. These interspecific pairs of S haplotypes are considered to be derived from common ancestors and to have maintained the same recognition specificity after speciation. In this study, the genome structures of three interspecific pairs of S haplotypes were compared by sequencing SRK, SP11/SCR, and their flanking regions. Regions between SRK and SP11/SCR in B. oleracea were demonstrated to be much longer than those of B. rapa and several retrotransposon-like sequences were identified in the S locus in B. oleracea. Among the seven retrotransposon-like sequences, six sequences were found to belong to the ty3 gypsy group. The gag sequences of the retrotransposon-like sequences were phylogenetically different from each other. In Southern blot analysis using retrotransposon-like sequences as probes, the B. oleracea genome showed more signals than the B. rapa genome did. These findings suggest a role for the S locus and genome evolution in self-incompatible plant species.
芸苔属植物中自交不亲和识别特异性的决定因素是柱头中的SRK和花粉中的SP11/SCR，二者均由S位点编码。对许多SRK和SP11/SCR等位基因的核苷酸序列分析已鉴定出几个种间S单倍型对，其在甘蓝和白菜之间具有高度相似的序列。这些种间S单倍型对被认为源自共同祖先，并且在物种形成后保持了相同的识别特异性。在本研究中，通过对SRK、SP11/SCR及其侧翼区域进行测序，比较了三对种间S单倍型的基因组结构。结果表明，甘蓝中SRK和SP11/SCR之间的区域比白菜中的长得多，并且在甘蓝的S位点鉴定出了几个类似逆转座子的序列。在七个类似逆转座子的序列中，有六个序列属于ty3 gypsy组。这些类似逆转座子序列的gag序列在系统发育上彼此不同。在使用类似逆转座子序列作为探针的Southern印迹分析中，甘蓝基因组比白菜基因组显示出更多的信号。这些发现表明S位点和基因组进化在自交不亲和植物物种中的作用。
