microRNA-mediated ribosome stalling promotes secondary siRNA biogenesis in plants

Ribosome traverse on mRNAs is not always smooth but can be impeded by various obstacles. One such example is halting of ribosome movements by microRNAs in plants. However, its exact mechanism and physiological role remain unclear. Here, by combining genome-wide ribosome profiling, in vitro biochemical analyses, and in planta assays, we found a direct link between microRNA-mediated ribosome stalling and amplification of RNA silencing. To stall ribosomes, the microRNA within Argonaute protein needs to directly interact with the double-stranded RNA-binding protein SGS3. Strikingly, ribosome stalling by microRNAs elicits the production of secondary small interfering RNAs from target mRNAs. Our results uncover a previously uncharacterized role for paused ribosomes.