Genomic sequence of an SRK-like gene linked to the S-locus of a self-incompatible Brassica oleracea line

Abstract

A cDNA clone of an S-locus glycoprotein gene (SLG) from Brassica oleracea specific to the S29 self-incompatibility allele was used to detect homologous gene sequences in the S63 haplotype. Two genomic fragments hybridised by this probe appeared to comprise an SLG and S-receptor kinase (SRK) gene pair, as previously described in B.oleracea. The complete DNA sequence of the putative receptor kinase gene was determined and found to predict a polypeptide structurally homologous to SRK proteins. Combined RFLP, stigma glycoprotein and pollination analysis of a segregating F2 family of plants indicated that the gene pair is linked to the S63 incompatibility allele. Transcripts originating from the SRK-like gene were identified in stigma mRNA by DNA sequencing of amplified RT-PCR products but homologous transcripts were also found in leaf. An associated stigma-specific SLG transcript was not detected, suggesting that this SRK-like gene may have a function and tissue-specificity unrelated to SI and that the true SRK63 allele may have a diverged DNA sequence.