S-RNase-mediated gametophytic self-incompatibility is ancestral in eudicots.

The evolutionary relationship between self-incompatibility systems in different families of flowering plants has long been a topic of interest. Physiological differences in the mode of gene action and the enormous sequence differences between genes with different modes of action suggest that many instances of self-incompatibility have arisen independently. In contrast, previous analyses of the S-RNase associated with gametophytic self-incompatibility in the eudicot families (Solanaceae, Scrophulariaceae, and Rosaceae) have suggested that sequences within families form well-supported and distinct lineages. In this study we demonstrate that in fact, S-RNase-mediated gametophytic self-incompatibility evolved only once in the eudicots.