A 7-KDA POLLEN COATING-BORNE PEPTIDE FROM BRASSICA-NAPUS INTERACTS WITH S-LOCUS GLYCOPROTEIN AND S-LOCUS-RELATED GLYCOPROTEIN

Two S(self-incompatibility)-family glycoproteins have been identified in stigmas of self-compatible (SC) Brassica napus L. by their ability to interact, in vitro, with a peptide fraction from the pollen coating containing a PCP7-like peptide, PCP7 (pollen coat peptide 7[kDa]) bei ng a pollen coat peptide from self-incompatible (SI) Brassica oleracea L. which has been shown to interact with S-locus glycoproteins (SLGs) . Electrophoretic purification and N-terminal amino-acid sequencing of these stigmatic glycoproteins confirmed one to be an SLG and the othe r to be a class 1 S-locus-related glycoprotein (SLR1). This is the fir st reported isolation of SLG and SLR1 proteins from SC B. napus and th e first time that a PCP7-like peptide has been shown to interact with an S-class glycoprotein other than SLG. On the basis of these findings we suggest that an ability to interact with PCP7 or a PCP7-like pepti de is a property of SLGs, SLR1s and possibly other S-glycoproteins and may thus provide a novel route to the identification of these glycopr oteins in stigmatic extracts. The levels of the SLG in stigmas of SC B . napus were relatively much lower than the levels of the SLR1-the opp osite to the situation in SI B. oleracea. This finding is discussed in terms of translational control of SLGs and SLR1, and the possible imp lications for self-incompatibility in B. oleracea and self-compatibili ty in B. napus.