Self/non-self discrimination in angiosperm self-incompatibility

► Many angiosperms employ self-incompatibility (SI) system to avoid inbreeding. ► Most SI is controlled by the S-locus, which encodes both male and female determinants. ► Self/non-self recognition is achieved by direct interaction between two determinants. ► Mechanistically, SI is not a single system but contains divergent molecular systems. ► SI can be classified into two distinct systems – self recognition and non-self recognition. Self-incompatibility (SI) in angiosperms prevents inbreeding and promotes outcrossing to generate genetic diversity. In many angiosperms, self/non-self recognition in SI is accomplished by male-specificity and female-specificity determinants (S-determinants), encoded at the S-locus. Recent studies using genetic, molecular biological and biochemical approaches have revealed that angiosperms utilize diverse self/non-self discrimination systems, which can be classified into two fundamentally different systems, self-recognition and non-self recognition systems. The self-recognition system, adopted by Brassicaceae and Papaveraceae, depends on a specific interaction between male and female S-determinants derived from the same S-haplotype. The non-self recognition system, found in Solanaceae, depends on non-self (different S-haplotype)-specific interaction between male and female S-determinants, and the male S-determinant genes are duplicated to recognize diverse non-self female S-determinants.