Avoiding the incest in plants: genetic and biochemical control

Abstract

To avoid endogamy many flowering plants evolved a mechanism to recognize and reject their self-pollen, which is known as self-incompatibility (SI) system. In many cases the SI is genetically controlled by a single and highly polymorphic locus known as the S-locus. This DNA region carries two tightly linked transcriptional units. One of them encodes the female determinant (pistil expressed) and the second one the male determinant (pollen expressed). In this review, we discuss the most relevant advances in the SI mechanism in S-RNase based systems, which are present in Solanaceae, Rosaceae and Plantaginaceae. In these families, the female determinant encodes a ribonuclease named S-RNase and the male determinant encodes a protein called SLF/SFB (S-locus F-Box). We finally describe the role of the role of modifier genes, not coded by S-locus, in the pollen rejection response and propose a model including the main events so far described.