Genetic analysis of rolled, which encodes a Drosophila mitogen-activated protein kinase

Genetic and molecular characterization of the dominant suppressors of D-raf (c110) on the second chromosome identified two gain-of-function alleles of rolled (rl), which encodes a mitogen-activated protein (MAP) kinase in Dros ophila. One of the alleles, rl(Su23), was found to bear the same molecular lesion as rl(Sem), which has been reported to be dominant female sterile. H owever, rl(Su23) and the current stock of rl(Sem) showed only a weak domina nt female sterility. Detailed analyses of the rl mutations demonstrated mod erate dominant activities of these alleles in the Torso (Tor) signaling pat hway, which explains the weak dominant female sterility observed in this st udy. The dominant rl mutations failed to suppress the terminal class matern al-effect mutations, suggesting that activation of Rl is essential, but not sufficient, for Tor signaling. Involvement of rl in cell proliferation was also demonstrated by clonal analysis. Branching and integration of signals in the MAP kinase cascade is discussed.