Item

Abstract

Environmental cues can have profound effects on organismal development and phenotype, often regulated by small RNAs. We have used long-term environmental induction experiments to study the influence of shifts in microbial diet on mouth- form plasticity in Pristionchus pacificus. This nematode exhibits a mouth dimorphism with the eurystomatous (Eu) form being a potential predator on nematodes, whereas the stenostomatous (St) form is a strict bacterial feeder. We used a wild isolate of P. pacificus that is preferentially St on E. coli OP50. Directed evolution of 110 genetically identical lines for 101 generations on a Novosphingobium diet revealed immediate and systemic diet-induced plasticity, resulting exclusively in the formation of the Eumorph. Periodic diet-reversals to OP50 starting in F15, F25 etc revealed transgenerational memory that entails multigenerational plasticity. We combined these long-term induction experiments with unbiased forward genetic screens by performing an EMS mutagenesis in generation F14 on Novosphingobium to find mutants defective in transgenerational inheritance. From a screen of 9,900 ‘F2’ progeny of mutagenized animals, we found 165 potential candidates for transgenerational inheritance defective (tid) after food reversal. Whole genome sequencing revealed that multiple candidate genes were hit several times independent- ly (i.e. >3 alleles). Indeed, generating clean CRISPR mutants in the first five tid candidate genes revealed a tid phenotype after diet reversal from Novosphingobium to OP50. We will describe novel molecular mechanisms and epigenetic factors identified through the analysis of these tid mutants, providing novel insight into transgenerational inheritance and its conservation in C. elegans.