Molecular Genetics and Biology of Self-Incompatibility in Nicotiana alata, an Ornamental Tobacco

Abstract

Glycoproteins are present in the styles of several self-incompatible species within the Solanaceae which segregate with particular alleles of the S-(self-incompatibility) gene. The amino acid sequences of style glycoproteins corresponding to different S-alleles of N. alata are homologous in some regions and variable in others. Homologous regions include N-terminal sequences as well as most of the glycosylation sites and cysteine residues. The isolated style S-glycoproteins inhibit in vitro growth of pollen tubes of several S-genotypes, with some specificity in the interaction. The isolated S-glycoproteins have ribonuclease activity which may be involved in their action in arrest of growth of incompatible (self) pollen.