sRNA profiles of control adults, postdauer adults, larva L3, and dauer stages of C. elegans. Caenorhabditis elegans

Early environmental experiences and life histories profoundly influence adult phenotypes via as yet poorly understood mechanisms. We previously showed that wild-type adult C. elegans that transiently passed through the stress-induced dauer larval stage (post-dauers) exhibit different gene expression patterns, genome-wide chromatin structure, and life history traits when compared to adults that bypassed the dauer stage (controls). Here we show that endogenous small inhibitory RNAs (endo-siRNAs) and siRNA pathways may mediate developmental history-dependent phenotypic diversity. Deep sequencing of small RNA libraries show changes in endo-siRNA levels in post-dauer as compared to control animals, and meta analyses indicate that specific endo-siRNA pathways are targets of developmental history-dependent reprogramming. We demonstrate that mutations in specific endo-siRNA pathways affect the expected gene expression and chromatin state changes in post-dauer animals, and also disrupt their increased brood size phenotype. We find that the chromatin state and endo-siRNA distribution in dauers is also distinct and suggest that this remodeling in dauers provides a template for the subsequent establishment of adult post-dauer profiles. Together, our results imply a critical mechanistic role for endo-siRNA pathways in mediating early experience-dependent phenotypic divergence in adults, and suggest that regulation of these pathways contribute to increased fitness via non-genetic mechanisms. Overall design: We deep-sequenced small RNA libraries from 2 biological replicates each of control and postdauer adults, and one biological each of larval L3 and dauer stages.