Self-incompatibility, the rejection of self pollen, is the most widespread
mechanism by which flowering plants prevent inbreeding. In Brassica, the S
receptor kinase (SRK) has been implicated in the self-incompatibility respo
nse, but the molecular mechanisms involving SRK are unknown. One putative d
ownstream effector for SRK is ARC1, a protein that binds to the SRK kinase
domain. Here it is shown that suppression of ARC1 messenger RNA levels in t
he self-incompatible Brassica napus W1 line is correlated with a partial br
eakdown of self-incompatibility, resulting in seed production. This provide
s strong evidence that ARC1 is a positive effector of the Brassica self-inc
ompatibility response.