Remote precursor elements can modulate RNA induced silencing complex‐loading efficiency of miR168 in Arabidopsis

Le résumé fourni par la source

RNA interference mediated via the action of micro RNAs (miRNAs) plays a pivotal role in developmental and stress response pathways. In the nucleus, plant miRNAs are generated by subsequent enzymatic cuts of the MIRNA precursors, having specific hairpin-like secondary structures, to liberate the miRNA/miRNA* duplex. The mature miRNA strands are then loaded mostly into the ARGONAUTE 1-containing RNA induced silencing complex (RISC) with various efficiencies and trigger the down-regulation of the expression of the target mRNAs, while the miRNA* strands are eliminated. Here we revealed that MIRNA precursor structural elements, not overlapping with the miRNA/miRNA* duplex part, can have an influence on the AGO-loading efficiency of the produced miRNAs. Using transient and transgenic expression studies, we revealed that a chimeric MIR168 precursor hairpin structure containing the stem region of a hvu-MIR171 precursor can induce the enhancement of AGO-loading efficiency of the produced miR168, resulting in increased target down-regulation and in developmental defects of the transgenic plants. This effect was the most pronounced when the orientation of the wild-type miR168/miR168* duplex was inverted in the chimeric precursor, implying the cooperative action of the structural elements. In transient studies, we also showed that precursor elements of MIR168a can reduce AGO-loading efficiency of miR171. The discovery of signals on remote structures of the miRNA precursor suggests that miRNA biogenesis and AGO-loading can be spatially more connected in the nucleus and/or signalization events mediated by these non-duplex structural features during miRNA biogenesis can determine the fate of the miRNA/miRNA* duplexes in separated AGO-loading processes.

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