Sporophytic Self-Incompatibility

Most flowering plants are hermaphrodites with flowers that have both male and female reproductive organs. Despite being able to self-fertilize, numerous mechanisms have evolved to prevent this from happening. The most common of these mechanisms is self-incompatibility (SI), a genetically controlled system that enables the female reproductive organ of the flower to recognize the source of each male pollen grain it receives; and to reject all 'self' pollen grains, those originating from the plant itself or one of its close relatives. Although SI systems are found in many different taxa, the underlying mechanisms appear to have arisen independently many times during flowering plant diversification because the molecules that mediate recognition are generally not the same. Here, we discuss one of the two generally recognized forms of SI, sporophytic SI, and what is currently known about the cellular mechanism that regulates this system in one plant family, the Brassicaceae.