Highly divergent sequences of the pollen self-incompatibility (S) gene in class-I S haplotypes of Brassica campestris (syn. rapa) L.

Self-incompatibility (SI) enables flowering plants to discriminate between self- and non-self-pollen. In Brassica, SI is controlled by the highly poly morphic S locus. The recently identified male determinant, termed SP11 or S CR, is thought to be the ligand of S receptor kinase, the female determinan t. To examine functional and evolutionary properties of SP11, we cloned 14 alleles from class-I S haplotypes of Brassica campestris and carried out se quence analyses. The sequences of mature SP11 proteins are highly divergent , except for the presence of conserved cysteines. The phylogenetic trees su ggest possible co-evolution of the genes encoding the male and female deter minants. (C) 2000 Federation of European Biochemical Societies.