Regulated cell expansion is an important determinant of organ shape in higher plants. The sabre mutation results in abnormal cell expansion in Arabidopsis. There is a shift in the orientation of expansion evident primarily in root cortex cells. The SABRE gene has been cloned and found to encode a novel protein. Reduction of effective levels of the plant phytohormone ethylene through use of inhibitors and an insensitive mutant resulted in partial rescue of the sabre phenotype. This suggested that one of the roles of SABRE is to counter the action of ethylene in promoting radial expansion in plant cells.