Self-incompatibility (SI), the cellular recognition system that limits inbreeding, has sewed as a paradigm for the study of cell-to-cell communication in plants since the phenomenon was first described by Darwin. Recent studies indicate that SI is achieved by diverse molecular mechanisms in different plant species. in the mustard family, the mechanism of SI shows parallels to the signaling systems found in animals that are mediated by cell-surface receptors with signal-transducing protein kinase activity.