G-protein (gpa) genes are involved in dauer larvae formation Richard R. Zwaal and Ronald H. A. Plasterk Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands Guanine nucleotide regulatory proteins (G-proteins)are involved in signal transduction over the cell membrane. An activated receptor induces a conformational change in the G-protein, thereby uncoupling the a- and the b-gamma subunits, which can propagate the signal down to a diversity of enzymes and ion channels. Apart from the homologs of the mammalian G-protein a-subunits Gsa, Goa and Gqa, C. elegans contains at least 3 other a-subunit genes that cannot be classified as such. These genes are called gpa-1, gpa-2 and gpa-3 and are all located on LGV within 2 map units of each other. Transgenic animals carrying a presumptive dominant mutation in either gpa-2 or gpa-3 form dauer larvae under non-inducing conditions (7percent and 40percent respectively; Jane Mendel and Paul Sternberg (WBG 13#1 p.80)). To obtain animals in which the gpa-genes are inactivated we isolated mutants with a Tc1 insertion in these genes, followed by the isolation of Tc1 mediated deletion alleles (Zwaal etal., PNAS 90 (1993) 7431-7435). Furthermore we isolated the different double mutants, and the gpa- 1, gpa-2, gpa-3 triple mutant, using PCR to recognize recombinant chromosomes with linked gpa alleles. The response of these mutants to a fixed amount of pheromone (5 to 10 units) at 25C was tested (many thanks to Betsy Malone and Jim Thomas for help with the assay). Although the gpa-1 deletion mutant shows a slight reduction in response, this effect is more clear with the gpa-2 and gpa-3 single mutants. Under these conditions the gpa-2 gpa-3 double mutant and the triple mutant show drastic response defects, so that GPA-2 and GPA-3 seem to have (partially) redundant functions. Since lowering the food concentration, at constant concentration of pheromone, results in an increase in the number of dauer larvae formed (for the triple mutant), the gpa genes do not seem to be involved in the dauer execution program but instead in measuring the balance between the concentration of pheromone and food present. We are currently studying at which site(s) in the genetic pathway these mutants act by analyzing epistatic interactions with different daf genes.