Abstract: On signal transduction of self-incompatibility in Brassica, the signal molecule-SCR ligand is produced by the pollen grain, recognized by SRK receptor in stigmatic papillae, and transduced into a cellular response. The receptor-ligand pairs are two S locus-encoded highly polymorphic proteins that determine specificity of self-incompatibility. The ligand encoded by SCR gene is a small pollen coat protein present on the surface of pollen grains. The receptor localized to the plasma membrane of the stigmatic papillae on the surface of the pistil is encoded by SRK gene. During selfpollination, SCR interacts with its cognate receptor to activate SRK, which mediates the ubiquitination of substrates by ARC1. ARC1 functions downstream of the SRK. Ubiquitinated substrates, which may represent pistil compatible factors and normally promote pollen hydration, germination, and tube growth, are degraded by the proteasome/CSN, there by resulting in the response of selfincompatibility. In this paper, we give a detailed review about signal transduction of self-incompatibility in Brassica.