Non-self- and self-recognition models in plant self-incompatibility.

The mechanisms by which flowering plants choose their mating partners have interested researchers for a long time. Recent findings on the molecular mechanisms of non-self-recognition in some plant species have provided new insights into self-incompatibility (SI), the trait used by a wide range of plant species to avoid self-fertilization and promote outcrossing. In this Review, we compare the known SI systems, which can be largely classified into non-self- or self-recognition systems with respect to their molecular mechanisms, their evolutionary histories and their modes of evolution. We review previous controversies on haplotype evolution in the gametophytic SI system of Solanaceae species in light of a recently elucidated non-self-recognition model. In non-self-recognition SI systems, the transition from self-compatibility (SC) to SI may be more common than previously thought. Reversible transition between SI and SC in plants may have contributed to their adaptation to diverse and fluctuating environments.