Abstract
Self-incompatibility (SI) is a mechanism for preventing self-fertilization in flowering plants. In Brassica, it is controlled by a single multi-allelic locus, S, and it is believed that two highly polymorphic genes in the S locus, SLG and SRK, play central roles in self-recognition in stigmas. SRK is a putative receptor protein kinase, whose extracellular domain exhibits high similarity to SLG. We analyzed two pairs of lines showing cross-incompatibility (S2 and S2-b; S13 and S13-b). In S2 and S2-b, SRKs were more highly conserved than SLGs. This was also the case with S13 and S13-b. This suggests that the SRKs of different lines must be conserved for the lines to have the same self-recognition specificity. In particular, SLG2-b showed only 88.5% identity to SLG2, which is comparable to that between the SLGs of different S haplotypes, while SRK2-b showed 97.3% identity to SRK2 in the S domain. These findings suggest that the SLGs in these S haplotypes are not important for self-recognition in SI.
Determining the Physical Limits of the Brassica S Locus by Recombinational Analysis
