A synthetic Multivulva phenotype is produced by two mutations, one in each of two classes of genes, A and B. Mutations in one or more class A genes or one or more class B genes do not produce a Multivulva phenotype. For example, neither a
lin-8 (class A) nor a
lin-9 (class B) mutation alone produces a Multivulva phenotype; however, a
lin-8; lin- 9 double mutant is Multivulva. One locus,
lin-15, has genetically separable class A and class B activities. It has been proposed that the class A and class B genes define two functionally redundant pathways that act to specify the non-vulval fate of the vulval precursor cells. 1 We are isolating new mutations that cause a synthetic Multivulva phenotype. To isolate class B mutations, we have mutagenized
lin-8(nl l l ) animals with EMS and screened the F2 generation for Multivulva animals. In a screen of about 6000 haploid genomes, we isolated 15 putative synthetic Multivulva mutants. The new mutations include five
lin-15 alleles, four
lin-35 alleles, three
lin-36 allelcs, and one lin- 37 allele. We are currently analyzing the other two new putative class B mutations. We are mutagenizing lin-lS
(n767) to isolate more class B alleles, and
lin36(n766) and lin-lS
(n744) to isolate new class A alleles. We have started analyzing
lin-36 in greater detail. Iin-36 mutants seem to differ in phenotype from other class B mutants in that strains carrying
lin-36 mutations do not suffer from a reduction in fertility as do strains carrying mutations in
lin-9,
lin-35, or
lin-37. We have mapped
lin-36 between egl-S and
unc-36 on linkage group III. We have rescued the Multivulva phenotype of animals containing
lin-36 with cosmids C04Hl 1, E02E3, and F44B9. To help elucidate the mechanism by which the synthetic Multivulva genes act, we have planned a mosaic analysis of
lin-36, which is tightly linked to the cell-autonomous marker ncl-l. This experiment should indicate whether or not
lin-36 acts cell-autonomously in the vulval precursor cells. Herman and Hedgecock2 have shown that
lin-15 acts in a cell-non-autonomous manner and have proposed that
lin-15 acts in
hyp7 to inhibit the expression of vulval cell fates. Mosaic analysis should reveal whether
lin-36, a class B gene, acts in a manner similar to
lin-15, a gene with both class A and class B activities.