Co-operative Research on Genes Associated with Self-incompatibility

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Aims : To understand the molecular mechanisms fo self-incompatibility systems of higher plants, proteins and the DNAs associated with the self-incompatibility were analyzed and their functions were studied.Results : As for Brassica plants, which is belonging to the sporophytic self-incompatibility, several genes of SLG (S-locus glycoprotein) and SRK (S-receptor protein kinase) were cloned and sequenced. Furthermore their related genes, SRA and SRB were also isolated. Analysis of the inheritance of these genes revealed that the former groups are linked to S-locus and the latters are not. Analysis of the genomic DNA indicated that so many traces of the related genes to SRK and SLG are present. At least one gene among them was linked to S-locus. To analyze the S-genotypes of the plants, an RFLP system using a PCR method was devised. Using this system most of the S-genotypes can be determined. For the transformation of Brassica plants, several varieties were tested for the ability of transformation and regeneration. Some specific varieties were revealed useful for this purpose. In the self-incompatibility system of lpomea, similar genes with SRK in Brassica and S-RNase in tobacco were isolated, but these genes were not linked to S-locus. From protein analysis with 2D-electrophoresis specific spots linked to S-genotypes were found and will be analyzed further. For a gametophytic system, Japanese pear was studied and several S-RNases were isolated and their amino acid sequences were established. A similar RNase but not linked to the S-locus was also isolated and analyzed. The effects of various RNases were analyzed for their activity of pollen tubes elongation of Japanese pear. In the case of lilium, a system associated with cAMP was suggested to inhibit elongation of the self pollens throught the style.