The gravitropic tomato mutant lazy-2 is altered in signal transduction

Abstract

Plant gravitropism involves many cell types and several mechanistic steps. One approach to dissecting such complex processes is with the use of genetic mutants. Such an approach has already proven successful in the elucidation of the gibberellin biosynthetic pathway in maize and pea (Reid, 1987) and is currently proving useful in the study of flower development (Bowman et al., 1989). The study of gravitropism in tomato is an especially attractive system due to the existence of three gravitropic mutants whose phenotypes suggest they carry lesions in three distinct components of the gravitropic pathway: lazy-1, an agravitropic mutant which does not contain sedimenting amyloplasts and therefore probably does not perceive gravity (Roberts, 1984), lazy-2, which we postulate in the present paper to be a lesion in the gravitropic mechanism after perception but prior to response, and diageotropica, which is thought to be an auxin-receptor mutant (Kelly and Bradford, 1986; Hicks et al., 1989).