DIFFERENTIAL ACTIVITY OF RAS1 DURING PATTERNING OF THE DROSOPHILA DORSOVENTRAL AXIS

In Drosophila, the Ras1 gene is required downstream of receptor tyrosi ne kinases for correct eye development, embryonic patterning, wing vei n formation, and border cell migration. Here we characterize a P-eleme nt allele of Ras1, Ras1(5703), that affects viability, eye morphogenes is, and early and late stages of oogenesis. Flies transheterozgyous fo r Ras1(5703) and existing EMS-induced Ras1 alleles are viable and exhi bit a range of eye and eggshell defects. Differences in the severity o f these phenotypes in different tissues suggest that there are allele- specific effects of Ras1 in development. Analysis of rescue constructs demonstrates that these differential phenotypes are due to loss of fu nction in Ras1 alone and not due to effects on neighboring genes. Fema les mutant at the Ras1 locus lay dorsal eggshell structures. We observ e dominant interactions between Ras1 mutants and other dorsoventral pa thway mutants, including Egfr(top) and gurken. Ras1 is also epistatic to K10. Unlike Egfr(top) and gurken mutants, however, Ras1 females are moderately fertile, laying eggs with ventralized eggshells that can h atch normal larvae. These results suggest that Ras1 may have a differe nt requirement in the patterning of the eggshell axis than in the patt erning of the embryonic axis during oogenesis.