title: Comparison of the genome structure of the self-incompatibility (S) locus in interspecific pairs of S haplotypes.
abstract: The determinants of recognition specificity of self-incompatibility in Brassica are SRK in the stigma and SP11/SCR in the pollen, both of which are encoded in the S locus. The nucleotide sequence analyses of many SRK and SP11/SCR alleles have identified several interspecific pairs of S haplotypes having highly similar sequences between B. oleracea and B. rapa. These interspecific pairs of S haplotypes are considered to be derived from common ancestors and to have maintained the same recognition specificity after speciation. In this study, the genome structures of three interspecific pairs of S haplotypes were compared by sequencing SRK, SP11/SCR, and their flanking regions. Regions between SRK and SP11/SCR in B. oleracea were demonstrated to be much longer than those of B. rapa and several retrotransposon-like sequences were identified in the S locus in B. oleracea. Among the seven retrotransposon-like sequences, six sequences were found to belong to the ty3 gypsy group. The gag sequences of the retrotransposon-like sequences were phylogenetically different from each other. In Southern blot analysis using retrotransposon-like sequences as probes, the B. oleracea genome showed more signals than the B. rapa genome did. These findings suggest a role for the S locus and genome evolution in self-incompatible plant species.
authors.affiliation: Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Fujimoto
authors.forename: Keiichi
authors.initials: K
authors.lastname: Okazaki
authors.forename: Eigo
authors.initials: E
authors.lastname: Fukai
authors.forename: Makoto
authors.initials: M
authors.lastname: Kusaba
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nishio
mesh_terms: D001937:Brassica / Q000145:classification / Q000235:genetics*; D029741:Brassica rapa / Q000235:genetics; D002874:Chromosome Mapping; D018744:DNA, Plant / Q000235:genetics; D019143:Evolution, Molecular; D017343:Genes, Plant; D018745:Genome, Plant; D006239:Haplotypes; D008969:Molecular Sequence Data; D018626:Retroelements / Q000235:genetics; D013045:Species Specificity
chemical_list: D018744:DNA, Plant; D018626:Retroelements