The Ras/MAP kinase pathway is involved in many developmental processes in C. elegans, including meiotic progression. We are examining the effects of MAPK signaling using a temperature sensitive MAPK mutant allele,
mpk-1(
ga111), which produces a phenotype only in the germline, resulting in pachytene arrest of germ cells. Shifting these adults back to the permissive temperature restores MAPK signaling, as evidenced by resumption of meiotic progression and production of functional oocytes. Oocytes are detected in these animals 12 hours after shifting and oocyte production is similar to wild type by 18 hours. By comparing gene expression of these MAPK mutants to control animals through microarray analysis, we can examine the global genome response to loss of MAPK signaling in the germline. We have compared mRNA extracts from control and mutant adults raised at the restrictive temperature and obtained a set of candidate genes that are enriched in the control. To distinguish early from late targets, we have also shifted the animals to the permissive temperature and compared their gene expression after 9 hours by microarray. Comparing the gene expression ratios, control/mpk-1, at the two timepoints provides temporal information about the gene expression changes that occur after resumption of MAPK signaling. These timepoints define two groups of MAPK responsive genes. The early-induced category includes genes that are enriched in the control/mpk-1 comparison before shifting, but are no longer enriched after 9 hours at the permissive temperature. These early-induced genes change prior to observable oocyte formation and are candidates for direct targets of MAPK signaling. The late-induced category includes genes that are enriched at both timepoints. We were able to define 50 early-induced and 162 late-induced genes. Of these, 35 and 52 genes are germline-enriched, respectively, based on previous microarray analysis. Further temporal and spatial data support that this group of genes is specifically transcribed at the pachytene region of the germline. In situ expression data available from NEXTDB reveals that many of these early-induced genes have expression that is restricted to the proximal germline, beginning at the bend in the gonad arm where MAPK is active. Additionally, these genes co-regulate over time in a microarray analysis of germline gene expression in a wild-type timecourse. Functional characterization of these targets is in progress. A more detailed temporal microarray analysis of
mpk-1(
ga111), including timepoints from 3 to 15 hours after shifting to the permissive temperature, will also be presented.