Pseudomonas fluorescens 15 small RNAs mediate the species-specific transgenerational epigenetic inheritance of avoidance in C. elegans

Abstract

C. elegans are exposed to a variety of pathogenic and non-pathogenic bacteria species in their natural environment. Correspondingly, C. elegans has evolved an ability to discern between nutritive and infectious bacterial food sources. Here we show that C. elegans can learn to avoid the pathogenic bacteria Pseudomonas fluorescens 15 (Pf15), and that this learned avoidance behavior can then be passed on to their progeny for four generations, as we previously demonstrated for PA14. In addition, the transgenerational avoidance of Pf15 requires both the TGF-β ligand DAF-7 and Cer1 retrotransposon encoded virus-like particles. Pf15 small RNAs sufficient to induce this transgenerational avoidance behavior. However, unlike our previous findings with PA14, Pf15 does not use P11 or a P11 homolog for this avoidance; instead, an unrelated Pf15 small RNA is required for learned avoidance. Our results suggest that worms have evolved multiple small RNA-dependent mechanisms to avoid different pathogenic bacteria species, thereby providing progeny with a survival advantage in a dynamic environment.