Self-incompatibility (SI) is the inherited ability of a flowering plant to prevent self-fertilization by discriminating between self and non-self pollen during pollination. In many species of the Solanaceae, self-incompatibility is controlled by the single, multiallelic locus S (By similarity). a ribonucleotidyl-ribonucleotide-RNA + H2O = a 3'-end 3'-phospho-ribonucleotide-RNA + a 5'-end dephospho-ribonucleoside-RNA + H(+) Monomer. Belongs to the RNase T2 family.