Characterization of molecular mechanisms of sporophytic self-incompatibility in Ipomoea trifida

为了鉴定野生型甘薯（Ipomoea trifida）自交不亲和相关基因（s基因），对S1、53、S10、S29自交不亲和系和Sc自交不亲和系的s位点进行了分离和测序。通过表达分析和序列多态性分析，确定了多个s -候选基因；AB1 ~ AB4为男性s基因候选者，SE1 ~ SE2和SEA为女性s基因候选者。其中，AB2、A83、SE2和SEA基因均存在于s座序列中。然而，在Sc s -单倍型中，一些s -候选基因的启动子序列和基因本身发生了一些突变。这些突变可能使sc -单倍型自相容。为了确定这四个候选s基因的时空表达，进行了原位杂交分析。原位分析表明，雄性s -候选基因在绒毡层发育早期全部表达，雌性s -候选基因在柱头乳头细胞成熟阶段全部表达。这些结果表明，所有s候选基因都具有s基因的充分必要条件。5个s -单倍型的基因组序列比较表明，存在一个高度序列多态性的区域，称为s -位点多样化区（SDRs）。在该sdr中，定位到3个s候选基因，分别是AB2、AB3和SEA，因此这些基因产物可能在自交不亲和性反应中起关键作用。此外，自交不亲和系的SDR长度比较表明，最显性s单倍型的SDR长度最长，最隐性系的SDR长度最短，且SDR长度的排序与自交不亲和系的显性-隐性层次结构一致。显性系中存在隐性系之外的附加序列，如转座子样序列、重复序列和细胞器基因组样序列片段。由此可以认为，三叶草自交不亲和性等级较高的系是由隐性系发育而来的。少

To identify genes correlated to self-incompatibility(S-genes)of wild type sweet potato(Ipomoea trifida), genomic sequences of S-locus from S1, 53, S10, S29 self-incompatible lines and Sc, the self-compatible line, were isolated and sequenced.By the expression analysis and sequence polymorphism, several S-gene candidates were identified ; AB1 to AB4 as male S-gene candidates and SE1 to SE2 and SEA as female S-gene candidates. Among these genes, AB2, A83, SE2 and SEA were found from all analyzed S-locus sequence. In the Sc S-haplotype, however, some mutations were observed in the promoter sequence and gene itself in some of the S-gene candidates. These mutations may contribute the Sc-haplotype as self-compatible.To determine spatial and temporal expression of these four S-gene candidates, in situ hybridization analyses were carried out. In situ analyses indicated that all of the male part S-candidate genes were expressed in the tapetum at early developmental stage, and all of the female … More part S-candidate genes were expressed in the papilla cells of stigma at mature stage. These results indicated that all S-candidate genes share a necessary and sufficient condition for S-genes.Comparison between the genomic sequences of five S-haplotypes indicated that the existence of a regions which have highly sequence polymorphisms, designated as S-locus diversed regions(SDRs). Within this SDRs, three S-candidate genes were located, which are AB2, AB3 and SEA, therefore, these gene products might play key roles in the self-incompatibility reaction.Furthermore, comparison of the length of the SDRs from self-incompatible lines indicated that SDR length is longest in the most dominant S-haplotype and is shortest in the most recessive line, and the order of the SDR length is consistent with the dominance-recessive hierarchy of the self-incompatibility. In the dominance line have additional sequence to recessive line, such as transposon-like sequences, repetitive sequences, and fragments of organelle genome-like sequences. From this observation, it was considered that the lines at the higher hierarchy in the self-incompatibility of Ipomoea trifida was developed from recessive line. Less