Novel functional microRNAs from virus-free and infected Vitis vinifera plants under water stress

Micro(mi)RNAs have fundamental roles in plant development and adaptation to stresses through post-transcriptional control of several physiological pathway intermediates. Plants are simultaneously exposed to several environmental stresses, however, to date there are few data about the roles of miRNAs in plant simultaneously subjected to a biotic and abiotic stress. We adopted a biological system consisting of Vitis vinifera infected by Grapevine rupestris stem pitting-associated virus (GRSPaV), likely the most prevalent among grapevine viruses, subjected to drought in greenhouse conditions. The analysis of small RNAs (from GRSPaV-free and infected plants, both in well watered and stress conditions) allowed us to highlight as GRSPaV alters the expression profile of several miRNAs, both known miRNAs and novel miRNA candidates, including those involved in adaptation to water stresses. Targets of known (i.e. miR396, miR164, miR156) and novel miRNAs (miRC121, miRC129, miRs409712_2) annotated as players in drought stress adaptations were indeed validated. These molecular changes suggested the possibility that GRSPaV could influence the response of V. vinifera to drought. By investigating key ecophysiological parameters, we show that infected plants show higher rate of photosynthesis, stomatal conductance, and low hydraulic resistance to water transport. Molecular and physiological changes induced by GRSPaV in grapevine under drought are therefore discussed.