The regulation of members of the knotted1 -like homeobox ( knox ) gene family is required for the normal initiation and development of lateral organs. The maize rough sheath2 ( rs2 ) gene, which encodes a Myb-domain protein, is expressed in lateral organ primordia and their initials. Mutations in the rs2 gene permit ectopic expression of knox genes in leaf and floral primordia, causing a variety of developmental defects. Ectopic KNOX protein accumulation in rs2 mutants occurs in a subset of the normal rs2 -expressing cells. This variegated accumulation of KNOX proteins in rs2 mutants suggests that rs2 represses knox expression through epigenetic means.