Genes that prevent the deleterious effects of inbreeding in monoecious plants by controlling the rate of growth of the pollen tube down the style. Self-incompatibility is controlled by a highly polymorphic S locus. Growth of a pollen tube in the style is arrested when the S allele carried by the pollen matches one of the two S alleles carried by the pistil. S genes have been cloned and shown to encode glycoproteins with RNase activity. In self-pollinations, the RNase is internalized by receptors on the pollen tube surface. Once inside the pollen tube, the enzyme degrades RNAs essential to its further growth.
Subjects: Genetics and Genomics.