title: Coevolution of the S-locus genes SRK, SLG and SP11/SCR in Brassica oleracea and B. rapa.
abstract: Brassica self-incompatibility (SI) is controlled by SLG and SRK expressed in the stigma and by SP11/SCR expressed in the anther. We determined the sequences of the S domains of 36 SRK alleles, 13 SLG alleles, and 14 SP11 alleles from Brassica oleracea and B. rapa. We found three S haplotypes lacking SLG genes in B. rapa, confirming that SLG is not essential for the SI recognition system. Together with reported sequences, the nucleotide diversities per synonymous and nonsynonymous site (pi(S) and pi(N)) at the SRK, SLG, and SP11 loci within B. oleracea were computed. The ratios of pi(N):pi(S) for SP11 and the hypervariable region of SRK were significantly >1, suggesting operation of diversifying selection to maintain the diversity of these regions. In the phylogenetic trees of 12 SP11 sequences and their linked SRK alleles, the tree topology was not significantly different between SP11 and SRK, suggesting a tight linkage of male and female SI determinants during the evolutionary course of these haplotypes. Genetic exchanges between SLG and SRK seem to be frequent; three such recent exchanges were detected. The evolution of S haplotypes and the effect of gene conversion on self-incompatibility are discussed.
authors.affiliation: Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555, Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Sato
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nishio
authors.forename: Ryo
authors.initials: R
authors.lastname: Kimura
authors.forename: Makoto
authors.initials: M
authors.lastname: Kusaba
authors.forename: Tohru
authors.initials: T
authors.lastname: Suzuki
authors.forename: Katsunori
authors.initials: K
authors.lastname: Hatakeyama
authors.forename: David J
authors.initials: DJ
authors.lastname: Ockendon
authors.forename: Yoko
authors.initials: Y
authors.lastname: Satta
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D029741:Brassica rapa / Q000235:genetics*; D019143:Evolution, Molecular; D005785:Gene Conversion; D014644:Genetic Variation; D006023:Glycoproteins / Q000235:genetics*; D006239:Haplotypes; D016013:Likelihood Functions; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics*; D011494:Protein Kinases / Q000235:genetics*; D016415:Sequence Alignment
chemical_list: D006023:Glycoproteins; D010940:Plant Proteins; C431526:SP11 protein, Brassica; C064156:self-incompatibility locus specific glycoprotein, Brassica; D011494:Protein Kinases; C079832:S-receptor kinase