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MRNA-seq analysis of early adult C. elegans following extended L1 arrest with reduced insulin/insulin-like signaling

ABSTRACT: We characterized the effects of early-life starvation and reduced insulin/insulin-like signaling (IIS) during larval development on adult gene expression using mRNA-seq of whole worms. In our two-factor design, 'starved' worms were cultured without food (E. coli) in L1 arrest for eight days, and 'control' worms were starved overnight for synchronization. Both populations of worms were fed ad libitum with either empty vector (EV; negative control) or daf-2/InsR RNAi food (reduced IIS). RNAi was used rather than a daf-2 mutant so that the results would not be confounded by daf-2 function during L1 arrest, instead disrupting daf-2 only after starvation in fed, developing larvae. Upon reaching adulthood, animals were collected for transcript profiling.

ORGANISM(S): Caenorhabditis elegans

PROVIDER: GSE178170 | GEO | 2022/11/08

REPOSITORIES: GEO

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Project description:Post-embryonic development of the nematode C. elegans is governed by nutrient availability. L1-stage larvae remain in a state of developmental arrest after hatching until they feed. This “L1 arrest” (or "L1 diapause") is associated with increased stress resistance, supporting starvation survival. Loss of the transcription factor daf-16/FOXO, an effector of insulin/IGF signaling, results in arrest-defective and starvation-sensitive phenotypes. We show that daf-16/FOXO regulates L1 arrest cell-nonautonomously, suggesting that insulin/IGF signaling regulates at least one additional signaling pathway. We used mRNA-seq to identify candidate signaling molecules affected by daf-16/FOXO during L1 arrest. daf-16/FOXO had overlapping but distinct effects on gene expression in L1 arrest compared to daf-2/InsR adults. Notably, dbl-1/TGF-β, a ligand for the Sma/Mab pathway, and daf-36, which encodes an upstream component of the daf-12/NHR steroid hormone signaling pathway, were up-regulated during L1 arrest in a daf-16/FOXO mutant. Using genetic epistasis analysis, we show that dbl-1/TGF-β and daf-12/NHR steroid hormone signaling pathways are required for the daf-16/FOXO arrest-defective phenotype, suggesting that daf-16/FOXO represses dbl-1/TGF-β and daf-36. The dbl-1/TGF-β and daf-12/NHR pathways have not previously been shown to affect L1 development, but we found that disruption of these pathways delayed L1 development in fed larvae, consistent with these pathways promoting development in starved daf-16/FOXO mutants. Though the dbl-1/TGF-β and daf-12/NHR pathways are epistatic to daf-16/FOXO for the arrest-defective phenotype, disruption of these pathways does not suppress starvation sensitivity of daf-16/FOXO mutants. This observation uncouples starvation survival from developmental arrest, indicating that DAF-16/FOXO targets distinct effectors for each phenotype, and revealing that inappropriate development during starvation does not cause the early demise of daf-16/FOXO mutants. Overall, this study shows that daf-16/FOXO promotes developmental arrest cell-nonautonomously by repressing pathways that promote larval development.