Although highly related proteins often perform redundant functions, there are rare cases of homologous proteins taking on opposing roles in certain contexts. We discovered one such example where the activities of Argonaute-like-gene 1 (
alg-1) and
alg-2 diverge in adult C. elegans. These Argonaute (AGO) proteins are specific to the miRNA pathway and seem to perform overlapping and complementary roles in regulating gene expression during embryogenesis and larval development. Surprisingly, we found that loss of
alg-1 leads to a shorter lifespan and loss of
alg-2 results in an extended lifespan. Gene expression analyses revealed that distinct sets of genes are mis-regulated in each of the AGO mutant backgrounds. Consistent with the longevity phenotypes of
alg-1 and
alg-2 mutant animals, many of the differentially expressed genes are regulated by the insulin/ IGF-1 signaling (IIS) pathway. Furthermore, genetic experiments demonstrate that the long lifespan of animals deficient in insulin receptor activity (
daf-2 mutants) is partially dependent on
alg-1, while the extended lifespan of
alg-2 mutants requires the FOXO DAF-16 transcription factor. These findings prompt the question of how two proteins that are over 80% identical in amino acid sequence and exhibit similar expression patterns and functions during development take on opposing roles in adulthood. To address this problem, we have used CRISPR to fuse fluorescent tags to the endogenous
alg-1 and
alg-2 genes, which will enable detailed analyses of the expression and activity of these AGOs in aging animals. These strains will allow us to test the hypothesis that in adults ALG-1 and ALG-2 bind distinct miRNAs and targets, which contributes to their opposing longevity roles. To understand the molecular basis for the different activities of these two AGOs, regulatory and coding sequences will be swapped between
alg-1 and
alg-2 to identify the elements responsible for their divergent roles in adult animals. Overall, I aim to elucidate how two miRNA AGOs promote opposite longevity fates in C. elegans.