Primary and secondary siRNA synthesis triggered by RNAs from food bacteria in the ciliate Paramecium tetraurelia - Sorbonne Université Access content directly
Journal Articles Nucleic Acids Research Year : 2015

Primary and secondary siRNA synthesis triggered by RNAs from food bacteria in the ciliate Paramecium tetraurelia

Abstract

In various organisms, an efficient RNAi response can be triggered by feeding cells with bacteria producing double-stranded RNA (dsRNA) against an endoge-nous gene. However, the detailed mechanisms and natural functions of this pathway are not well understood in most cases. Here, we studied siRNA bio-genesis from exogenous RNA and its genetic overlap with endogenous RNAi in the ciliate Parame-cium tetraurelia by high-throughput sequencing. Using wild-type and mutant strains deficient for dsRNA feeding we found that high levels of primary siR-NAs of both strands are processed from the ingested dsRNA trigger by the Dicer Dcr1, the RNA-dependent RNA polymerases Rdr1 and Rdr2 and other factors. We further show that this induces the synthesis of secondary siRNAs spreading along the entire en-dogenous mRNA, demonstrating the occurrence of both 3-to-5 and 5-to-3 transitivity for the first time in the SAR clade of eukaryotes (Stramenopiles, Alve-olates, Rhizaria). Secondary siRNAs depend on Rdr2 and show a strong antisense bias; they are produced at much lower levels than primary siRNAs and hardly contribute to RNAi efficiency. We further provide evidence that the Paramecium RNAi machinery also processes single-stranded RNAs from its bacterial food, broadening the possible natural functions of exoge-nously induced RNAi in this organism.
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hal-01279181 , version 1 (25-02-2016)

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Attribution - NonCommercial

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Quentin Carradec, U. Gotz, O. Arnaiz, J. Pouch, M. Simon, et al.. Primary and secondary siRNA synthesis triggered by RNAs from food bacteria in the ciliate Paramecium tetraurelia. Nucleic Acids Research, 2015, 43 (3), pp.1818-1833. ⟨10.1093/nar/gku1331⟩. ⟨hal-01279181⟩
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