Suppression of nbe‐miR166h‐p5 attenuates leaf yellowing symptoms of potato virus X on Nicotiana benthamiana and reduces virus accumulation

MicroRNAs (miRNAs) play essential roles in plant development. There is increasing evidence that changed expression of miRNAs in virus‐infected plants contributes to the development of viral symptoms. Here, we analysed the altered expression of miRNAs of Nicotiana benthamiana in response to Potato virus X (PVX) by Illumina Solexa sequencing. One of the 21 miRNAs significantly affected, nbe‐miR166h‐p5, was closely associated with viral symptoms. Using the Tobacco rattle virus‐based miRNA suppression (VbMS) system, we found that the suppression of nbe‐miR166h‐p5 in plants caused leaves to turn dark green with increased chlorophyll. When PVX was inoculated on nbe‐miR166h‐p5‐suppressed plants, the leaf yellowing symptom of PVX was largely attenuated with less reduction in chlorophyll content, and the accumulation of PVX was decreased. nbe‐miR166h‐p5 was also up‐regulated in plants infected by Turnip mosaic virus (TuMV), and its suppression attenuated the leaf yellowing symptom of TuMV and decreased viral accumulation. Three potential targets of nbe‐miR166h‐p5 were identified. The results indicate the association of nbe‐miR166h‐p5 with symptoms of PVX and also with those of TuMV, providing useful information on the relationship between miRNA and viral infection.