SEXUAL INCOMPATIBILITY, A GENETIC MECHANISM THAT PREVENTS SELF-FERTILIZATION AND CONTRIBUTES TO PLANT DIVERSITY

Abstract

Proximity between sexual organs in hermaphrodite flowers highly increases the likelihood of self-fertilization. To avoid it, several species evolved the sexual incompatibility (SI) system, a mechanism present in several angiosperm families which allows the pistil to reject self-pollen and to accept non-self-pollen, thus encouraging outcrossing to prevent inbreeding. The SI is genetically controlled by male and female determinants, both encoded in the highly polymorphic S-locus. In this paper we review and discuss the current advances in the molecular control of the gametophytic SI, present in the Solanaceae, Rosaceae and Plantaginaceae families, in which the specificity of pollen rejection is determined by the S-specific interaction between the S-RNase (female determinant) and SLF (S locus F-box protein; male determinant). In addition, we discuss the potential biochemical leading to pollen rejection in S-RNase based systems, and we propose a combined model.