The SHORT-ROOT gene controls radial patterning of the Arabidopsis root through radial signaling

Asymmetric cell divisions play an important role in the establishment and p ropagation of the cellular pattern of plant tissues. The SHORT-ROOT (SHR) g ene is required for the asymmetric cell division responsible for formation of ground tissue (endodermis and cortex) as well as specification of endode rmis in the Arabidopsis root. We show that SHR encodes a putative transcrip tion factor with homology to SCARECROW (SCR). From analyses of gene express ion and cell identity in genetically stable and unstable alleles of shr, we conclude that SHR functions upstream of SCR and participates in a radial s ignaling pathway. Consistent with a regulatory role in radial patterning, e ctopic expression of SHR results in supernumerary cell divisions and abnorm al cell specification in the root meristem.