Molecular Determinants and Mechanisms of Gametophytic Self-Incompatibility in Fruit Trees of Rosaceae

Abstract

Self-incompatibility is an important genetic mechanism that prevents inbreeding and promotes genetic polymorphism and heterosis in flowering plants. Many fruit species in the Rosaceae, including apple, pear, plum, apricot, sweet cherry, Japanese apricot, and almond, exhibit typical gametophytic self-incompatibility (GSI) controlled by an apparently single multi-allelic locus. This locus encodes at least two components from both the pollen and the pistil, and controls recognition of self- and non-self pollen. Recently, the GSI system has been investigated at the molecular and cellular levels in Rosaceae, and findings have provided some important insights as to how these two genes interact within pollen tubes that lead to specific inhibition of germination and/or growth of self-pollen tubes. In this review, molecular features of S-determinants of both pistil and pollen, identification of S-alleles, mechanisms of self-incompatibility break-down, and evolution of S-alleles are presented. Moreover, hypothetical signal transduction models in a self-incompatible system in Rosaceae are proposed based on recent findings that indicate that several signal factors are involved in GSI responses.