A functional S locus anther gene is not required for the self-incompatibility response in Brassica oleracea.

International audienceThe self-incompatibility (SI) response in Brassica involves recognition of self-pollen by the papillar cells of the stigma and is mediated by the products of genes localized at the S (self-incompatibility) locus. Two S locus genes, SRK and SLG, are thought to encode components of a receptor complex present in the female partner. The putative gene product of SLA, a third S locus-linked gene that is expressed specifically in anthers, is a candidate for the male component of the SI recognition system. The identification of a mutant SLA allele, interrupted by a large insert resembling a ret-rotransposon, in self-compatible Brassica napos initially suggested that SLA played an essential role in the SI response. In this study, we have characterized an SLA allele from a self-compatible B. oleracea var acephala line and show that it too is interrupted by a large insert. However, analysis of seven B. oleracea var bofryfis lines exhibiting both self-compatible and self-incompatible phenotypes showed that these lines carry an S allele very similar or identical t o that of the B. oleracea var acephala line and that the SLA gene is interrupted by an insert in all seven lines. The insertion of the putative retrotransposon was shown t o interfere with gene expression, with no SLA transcripts being detected by RNA gel blot analysis in a self-incompatible B. oleracea var bofryfis line carrying an interrupted SLA gene. These data indicate that a functional SLA gene is not required for the SI response in Brassica