Study of sel/non-selfrecognition system in sel/cross incompatibility of wild type and cultivated sweet potato

野生型甘薯（Ipomoea trifida）具有孢子体自交不亲和（SSI）系统，但该系统不是基于芸苔属植物的SPII/SCR和SRK系统。为了鉴定番薯SSI系统的S基因，分离并分析了几种S单倍型，包括自交亲和（Sc）突变体的S基因座基因组区域。对4种S单倍型的S位点基因组区域进行鸟枪法测序，结果表明，S位点基因组区域的长度与S基因的显性-隐性层次相平行，显性的S位点基因组区域较长，隐性的S位点基因组区域较短。在Sc突变系中，所有的S候选基因（雄性的AB 2和雌性的SE 2和SEA）都位于Sc-S-位点上，但AB 2和SEA基因是重复的，其中两个SEA基因在雄性生殖器官中异位表达。这可能是SEA基因的异位表达使Sc系自交亲和的原因之一。对野生型和栽培型甘薯的S候选基因分析表明，Ltrifzda的S_3单倍型在甘薯中是保守的。这一结果表明，在栽培甘薯自交/杂交不亲和性是基于相同的分子机制，在I. trifida自交不亲和性。

Wild type sweet potato (Ipomoea trifida) has sporophytic self-incompatibility (SSI) system, but this system is not based on the SPII/SCR and SRK system, which is observed in Brassica. To identify S genes of Ipomoea SSI system, S-locus genomic regions from several S-haplotypes, including self-compatible (Sc) mutant, were isolated and analyzed. According to the shotgun sequencing of S-locus genomic regions from four S-haplotypes, the length of the S-locus genomic region was parallel to the dominant-recessive hierarchy of S-genes ; longer in dominants, shorter in recessives. In the Sc mutant line, all S-candidate genes ; AB2 for male, and SE2 and SEA for female ; were located in the Sc-S-locus, however, AB2 and SEA genes were duplicated, and two SEA genes indicated ectopic expression in the male reproductive organs. It is possible to consider that this ectopic expression of SEA genes make Sc line as self-compatible. S-candidate gene analyses of wild type (I.trifida) and cultivated (I.batatas) indicated that S_3 haplotype ofLtrifzda is conserved in the I.batatas. This result indicates that the self/cross-incompatibility in cultivated sweet potato is based on the same molecular mechanism as in the self-incompatibility of I.trifida.