The Ras/MAPK pathway is required for pachytene exit during meiosis in the germline of C. elegans . We have used a temperature-sensitive MAPK mutant allele,
mpk-1(
ga111) , which produces a phenotype only in the germline, resulting in pachytene arrest of germ cells at 25 o C. Shifting
mpk-1(
ga111) adults back to the permissive temperature restores MAPK signaling, as evidenced by resumption of meiotic progression and production of functional oocytes by 15 hours at 15 o C. By comparing gene expression of
mpk-1(
ga111) and control animals through a timecourse microarray analysis, we can examine the global genome response to loss and restoration of MAPK signaling in the germline. We have compared mRNA extracts from control and mutant adults raised at 25 o C and then at 3,6,9,12, and 15 hours after shifting the
mpk-1(
ga111) mutants to 15 o C. We also collected mRNA from control animals after 15 hours at 15 o C. We required that candidate genes must be enriched in the control as compared to the
mpk-1 mutant (1.5-fold, p<.05) at the restrictive temperature, which indicates that MAPK signaling is required for their transcription. We also required that the genes show no change in the control population after 15 hours at 15 o C. These two criteria define a set of 78 genes. We then divided the genes into groups based on their expression changes during the timecourse. The 5 'early' genes showed statistically significant change in expression within 3 hours at the permissive temperature, while the 30 'middle' genes show statistically significant change within 6 hours at the permissive temperature. The remaining 43 genes are 'late' genes and are not likely to be direct signaling targets. The five early genes are the best candidates for direct MAPK signaling targets as they change immediately after downshifting the animals. We have begun to study the five early genes for their potential functions downstream of MAPK in the germline. One of these genes, T05G11.1, is a C2H2 zinc finger containing protein, which is a potential transcription factor. We have isolated a deletion mutant of T05G11.1, (
vr3) , and it enhances the brood size reduction of
mpk-1(
ga111) . Another early gene, K02B9.2, is closely related to a neighboring C. elegans gene, K02B9.1. K02B9.1 was identified as a middle gene. K02B9.1/K02B9.2 (RNAi) causes a highly penetrant sterile progeny phenotype with a severely underproliferated germline. Further characterization of the phenotypes of these genes will be presented.