Abstract

C. elegans feeds on bacteria of diverse nature. We previously showed that animals feeding on pathogens such as P. aeruginosa PAO1 or S. Typhimurium MST1 form dauers in the second generation as a defense mechanism. We proposed that bacteria trigger an RNAi-dependent process in the worm, generating accumulation of endo-siRNAs in the germline that are transmitted to the progeny to promote diapause formation (Palominos et al., 2017). Transcriptomic analysis of worms fed during two generations with PAO1 and MST1 showed over-expression of two microRNAs, mir-243 and mir-51, when compared to worms fed with E. coli OP50. Mutant strains of mir-243 and mir-51 fail to form dauer in the presence of PAO1 and MST1, but not on starvation, indicating that both microRNAs are required for dauer formation under pathogenesis. The expression of mir-243 is higher in F1 than in F2 and it is localized in the gut of the pathogen fed worms. In addition, when mir-243::gfp animals are fed with various pathogenic and non-pathogenic bacteria, the intestinal expression of this miRNA allowed to classify bacteria according to their degree of pathogenicity. This suggests that mir-243 could be an early effector in the activation of this defense mechanism having a role in pathogen recognition. On the other hand, mir-51 is constitutively expressed in neurons, and in response to pathogens it is strongly expressed in the intestine of F2 worms, indicating a later response to pathogens than mir-243. Analysis of regulatory networks formed by these miRNAs and intestinal transcription factors, differentially expressed under pathogenesis, shows that both miRNAs are part of the same regulatory circuit composed of aly-2, ama-1, crh-2, daf-16, elt-3, fos-1, jun-1, lsy-1, mdl-1, mep-1, nhr-23, nhr-28, pha-1, pqm-1, snpc-4, unc-130, unc-62, and ztf-7. Additionally, mir-51, but not mir-243, is also regulated by msl-2 in the second generation under PAO1 infection.