Characterization of DCL4 missense alleles provides novel insights into its ability to process distinct classes of dsRNA substrates

In the model plant Arabidopsis thaliana, four Dicer-like proteins (DCL1-4) mediate the production of various classes of small RNAs (sRNAs). Among these four proteins, DCL4 is by far the most versatile RNaseIII-like enzyme and previously identified dcl4 missense alleles were shown to uncouple the production of the various classes of DCL4-dependent sRNAs. Yet, little is known about the molecular mechanism pertaining this uncoupled production. Here, by studying the subcellular localization, interactome and binding to the sRNA precursors of three distinct dcl4 missense alleles, we simultaneously highlight the absolute requirement of its helicase domain for efficient production of all DCL4-dependent sRNAs, and identify an important determinant of DCL4 versatility within its PAZ domain that is mandatory for efficient processing of intramolecular foldback dsRNA precursors but dispensable for the production of siRNAs from RDR-dependent dsRNA susbtrates. This study not only provides novel insights into DCL4 mode of action in plants but also delineates interesting tools to further study the complexity of plant RNA silencing pathways. Overall design: RNA library of immunoprecipitated RNA from Col-0 (WT), pDCL4-DCL4-6:FHA/dcl4-2 and pDCL4-DCL4-8:FHA/dcl4-2 Arabidopsis flowers or seedlings were generated by deep sequencing, using Illumina HiSeq 2500 v4.

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Montavon T, Kwon Y, Zimmermann A, Hammann P, Vincent T, Cognat V, Bergdoll M, Michel F, Dunoyer P