Genomic organization of the SLG/SRK region of the S locus in Brassica species

Self-incompatibility in Brassica species is controlled by a single S locus with multiple alleles. Recent experimental data suggest that SLG (S locus g lycoprotein) and/or SRK (S receptor kinase) are the stigmatic S determinant s of self-incompatibility in Brassica. A 76-kb genomic fragment containing both SLG and SRK was isolated and characterized in the Sg haplotype of B. c ampestris. This fragment contains at least 14 expressed genes and three put ative open reading frames (ORFs), suggesting that the S locus is embedded i n a gene-rich region. Within this fragment, both anther and/or stigma-speci fic genes are clustered around the SLG and SRK genes. Some members of the S multigene family are also closely linked to the S locus. In this review we discuss the complex genomic structure of the S locus in Brassica species. (C) 2000 Annals of Botany Company.