Existence of s-glycoprotein-like proteins in anthers of self-incompatible species of brassica

Experimental evidence is presented that there exists an anther protein that is reactive with a polyclonal antiserum raised against the stigma S-glycoprotein of the S⁸-homozygote of Brassica campestris. The antiserum did not react with extracts of seeds, ovaries or leaves. Since this antiserum did not react with the polysaccharide residues similar to those in S-glycoprotein, it was considered capable of identifying S-glycoprotein-like proteins in anthers (SA-protein: S-glycopro-tein-like anther protein). The SA-protein generated a single distinct band at a pI of about 5.0 on blots of gels after isoelectric focusing and three spots at 29 kDa and 83 kDa on blots of two-dimensional gels, which were different from those of stigma S-glycoprotein. The SA-protein did not contain polysaccharide residue that reacted with Con A. No allelic differences in pI were found for the SA-protein within a given species, while such differences are common in stigma S-glycoprotein. The SA-protein appeared in anthers at the uninucleate microspore stage which is much earlier than the stage at which the stigma S-xglycoprotein appears. It is present in anther walls rather than in the pollen of mature anthers. The SA-protein is considered to play an important role in sporophytic control of self-incompatibility.