KANADI regulates organ polarity in Arabidopsis

Leaves and floral organs are polarized along their adaxial-abaxial (dorsal- ventral) axis. In Arabidopsis, this difference is particularly obvious in t he first two rosette leaves, which possess trichomes (leaf hairs) on their adaxial surface but not their abaxial surface(1-3). Mutant alleles of KANAD I (KAN) were identified in a screen for mutants that produce abaxial tricho mes on these first two leaves. kan mutations were originally identified as enhancers of the mutant floral phenotype of crabs claw (crc), a gene that s pecifies abaxial identity in carpels(4,5). Here we show that KAN is require d for abaxial identity in both leaves and carpels, and encodes a nuclear-lo calized protein in the GARP family of putative transcription factors. The e xpression pattern of KAN messenger RNA and the effect of ectopically expres sing KAN under the regulation of the cauliflower mosaic virus (CAMV) 35S pr omoter indicate that KAN may also specify peripheral identity in the develo ping embryo.