STUDIES ON THE EXPRESSION OF DOMINANCE/RECESSIVENESS IN THE SELF-INCOMPATIBILITY OF BRASSICEAE

本研究旨在调查十字花科油菜自交不亲和性中S等位基因的显性/隐性关系，并探讨显性/隐性关系的机理。在柱头杂合子中，S等位基因可分为两组：共显性组和显性组。在花药杂合子的情况下，它们被分为三个组：共显性组、显性组和隐性组。S等位基因的显性/隐性关系在柱头和花粉之间是独立的。有14个组合的杂合子与两个亲本菌株都是亲和的，但它们是自交不亲和的。这些S等位基因被认为是独立的弱化基因。在S9纯合子中，SLG和SRK在1.7kb左右的启动子区域和S结构域的序列完全相同，这可能与柱头端的显性关系有关。在S29纯合子中，分离到SLG和SRB克隆，并发现它们之间具有很高的同源性。由于本项目研究周期较短，不能获得完整的SLG和SRK数据。然而，随着这一研究方向的发展，本研究的目标有望在不久的将来达到。

Objective of this research is to carry out a survey on the dominant/recessive relationships of S-alleles in the self-incompatibility of Brassicaceae and to investigate the mechanism of the dominant/recessive relationships.Out of 300 possible combinations between 25 S-allele homozygotes of Brassica campestris, 275 F_1s were raised and their dominant/recessive relationships were surveyed in the two cases, ie heterozygotes in stigma or anther, separately. In the case of stigma heterozygotes, the S-alleles were classified into two groups ; codominant and dominant groups. In the case of anther heterozygotes, they were classified into three groups ; codominat, dominant and recessive groups. The dominant/recessive relationships of S-alleles were indepent between stigma and pollen. There were 14 combinations where the heterozygotes were compatible to both parental strains, whereas they were self-incompatible. These S-alleles are considered to be independent weakening genes.Several SLG,SRK genes were isolated from cDNA or genomic DNA libraries. In S9-homozygotes, the sequences through the promoter region and S-domain across about 1.7kb were completely identical between SLG and SRK.This identity should be concerned with the dominance relationship at the stigma side. In S29 homozygotes, SLG and SRB clones were isolated, and it was revealed that they are highly homologous to each other. Because of short period of this project research, we could not obtain whole the SLG and SRKs. However it is expected that the objective of this study will be attained in near future by the development of this line of study.