Lectins in pistils play a key role in self-incompatibility in the heterostylous Linum perenne

Self-incompatibility is one of the mechanisms preventing inbreeding in populations, based on the failure of pollen grains to germinate or of pollen tubes to grow normally in incompatible crosses. A unique model for studying this process are heterostylous species, in which self-incompatibility alleles are closely linked to flower morphological traits. One such species is L. perenne, a classic distylous species with reciprocal herkogamy and complete self-incompatibility strongly linked. The mechanism of self-pollen recognition is poorly understood in most heterostylous species, including L. perenne. As self-incompatibility in other systems is based on protein-protein interactions and many extracellular proteins are glycosylated, one of the possible participants in this process may be lectins. Therefore, we aimed to investigate the lectin activity in pistils and stamens of L. perenne L-morph and S-morph plants and to establish whether these lectins take part in self-incompatibility. We show that pistil-derived galactose-specific Ca2+-independent lectins from the respective other morph can overcome self-incompatibility in heterostylous L. perenne. This may be due to the presence of some lectins that are specific for arabinose and xylose. Our results suggest that lectins participate in signaling pathways for recognition at the pollen-stigma interface and are involved in the regulation of the self-incompatibility process in L. perenne.