sur-2, a novel gene, functions late in the let-60 ras-mediated signaling pathway during Caenorhabditis elegans vulval induction.

We describe here a new gene acting downstream of let-60 ras in the vulval signaling pathway of Caenorhabditis elegans. The sur-2 (suppressor of ras) gene is defined by eight mutations identified in a genetic screen for suppressors of the Multivulva phenotype of let-60(n1046), an activated let-60 ras mutation. sur-2 mutations result in pleiotropic, incompletely penetrant phenotypes that include a Vulvaless phenotype in hermaphrodites, defects in development of the male tail, gonadal abnormalities, and larval lethality, indicating a role for the sur-2 gene product in multiple developmental events. Genetic epistasis analyses suggest that sur-2 is required late in the vulval signaling pathway, downstream of let-60 Ras, and is likely to act downstream of the Raf/MAP Kinase cascade. We cloned the sur-2 gene by DNA-mediated transformation and have shown that it encodes a novel protein. We also show that a sur-2::lacZ transgene is expressed in the vulval precursor cells at the time of vulval determination.