Variation of S-alleles and S-glycoproteins in a naturalized population of self-incompatible Brassica campestris L.

Abstract

Variation of S-alleles and S-glycoproteins associated with self-incompatibility was studied in a naturalized population of Brassica campestris growing in Oguni-machi, Japan. Of 58 plants collected from the population, 45 were self-incompatible and 8 were self-compatible. Of 32 families investigated on their selfed progenies, 30 families showed segregation fitting to one locus S-allele model of sporophytic self-incompatibility. From cross-pollination experiments between 35 S-homozygotes so far isolated, 16 different S-alleles were identified, and the number of S-alleles involved in this population was estimated to be 20-30. S-glycoproteins corresponding to each S-allele were determined by immunoblotting with polyclonal antibody against S8-glycoprotein. Concanavalin A and Coomassie Blue stainings were also applied to determining corresponding S-glycoproteins, but were not so clear as the antibody cross reaction. It is pointed out that a stigma involves a number of proteins with different pI points, which are cross-reactive with anti-S-glycoprotein-antiserum. Many of these proteins are heritable in correlation with major S-glycoproteins. Since the content of these proteins was variable, we tentatively classified major and minor S-glycoproteins, and assumed that these S-glycoproteins were controlled by S-like DNA sequences with closely linked S-locus. Beside these S-glycoproteins, presence of heterozygote specific proteins was also pointed out, suggesting occurrence of post-transcriptional modification of these proteins. The pI values of major S-glycoproteins ranged from 5.0-9.0 and those at 7.0-9.0 were frequent.