同形化型 自家不和合性에 관한 硏究動向 Ⅰ. 胞子體型 自家不和合性에 관한 遺傳分析 및 分子的 硏究

Research trend on homomorphic self-incompatibility Ⅰ. Genetic analysis and molecular research on sporophytic self-incompatibility

In self-incompatibility, the rejection if self pollen occurs at the initial site of pollination, the stigma, where pollen germination either does not commence or is aborted before invasion of the papillar cell wall by the pollen tube. Recently, analysis of self-incompatibility in Brassica has focused on the study of a class of stigma glycoproteins, the S-locus glycoprotein(SLG). The level of SLG corresponds with the onset of self-incompatibility and the polymorphisms of these molecules correlate with S-allele polymorphism and genetic segregation of S-allele. In these decades, knowledge have been accumulated explosively on S-alleles at DNA and protein levels. An evidence that the function of SLG was suggested by a database survey in respective systems tells us recent trends of studies in this area. These studies revealed the difference of the structure and function of S-alleles in sporophytic and gametophytic systems. Siganl transduction system as found in vertebrates seems to be involved in sporophytic incompatibility, since SRK(S-receptor kinase) genes were found. SRK gene was shown to encode a putative receptor protein kinase with a cytoplasmic domain exhibiting homology to serine/threonine protein kinase and an SLG-homologous extracelluar domain was speculated to be involved in ligand binding. Despite of the explosive increase of data, many important question are still unsolved What is the pollen specific substance that participate in the recognition reaction? Can variation of S-alleles be explained only by the structural difference of SLG? How is the whole structure of S-genes? These situation give us an impression that we are still very poverty in our knowledege of self-incompatibility, but the rush of papers in a couple of years gives us also a hope that the mechanism of self-incompatibility will be recongnized by us on a sound basis in very near future.