Sequence comparisons among dispersed members of the Brassica S multigene family in an S-9 genome

Self-incompatibility (SI) systems prevent self-pollination and promote outb reeding. In Brassica, the SI genes SLG (for S-locus glycoprotein) and SRK ( for S-receptor kinase) are members of the S multigene family, which share t he SLG-like domain (S domain), which encodes a putative receptor. We have c loned members of the S multigene family from the S-9 haplotype of B. campes tris (syn. rapa). In addition, eight distinct genomic regions harboring 10 SLG/SRK-like genes were characterized in the present study. Sequence analys is revealed two novel SRK-like genes, BcRK3 and BcRK6 (for B. campestris re ceptor kinases 3 and 6, respectively). Other genes that were characterized included SFR2 (for S gene family receptor 2), SLR2 (for S locus related gen e 2), and a pseudogene. Based on phylogenetic analysis of the nucleotide se quences of the S domain regions, SLG and SRK appear to be distinct from oth er members of the S multigene family. Linkage analysis showed that most mem bers of the S multigene family are dispersed in the Brassica genome, and th at SLR1 (S Locus related gene 1) is not linked to the SLR2 in B. campestris .