FEATURES OF THE EXTRACELLULAR DOMAIN OF THE S-LOCUS RECEPTOR KINASE FROM BRASSICA

An S-receptor kinase (SRK) gene associated with self-incompatibility i n a Brassica napus subsp. oleifera line has been characterized. The SR K-A14 cDNA shows the highest levels of homology in the 5' end to the S LG-A14 cDNA present at the same locus. RNA blot analysis shows that th e SRK-A14 gene is expressed predominantly in the pistil, and at lower levels in the anthers. The predicted amino acid sequences from the ext racellular domain of the SRK-A14 gene and three other SRK genes were c ompared. The different SRK extracellular domains were for the most par t very similar, with the exception of two variable regions containing a high level of amino acid alterations. These extracellular domains al so contain a region of similarity to the immunoglobulin domains presen t in members of the immunoglobulin superfamily. These findings may def ine regions of the SRK protein that are necessary for interactions bet ween SRK and other proteins.