+RNA Viruses Enhance Plant Drought Tolerance Through Modulation of Phospholipase Dα1 (PLDα1)-Derived Phosphatidic Acid (PA).

Numerous studies suggest that virus infections can improve drought resistance in host plants, but the underlying mechanisms remain unclear. In this study, we used Turnip mosaic virus (TuMV), Potato virus Y (PVY), Tomato bushy stunt virus (TBSV) and the host Nicotiana benthamiana as model systems to investigate these mechanisms. Our findings reveal that the abscisic acid (ABA) signalling pathway is strongly and durably induced by +RNA virus infection and is essential for virus-induced drought tolerance. Notably, although ABA content increased following virus infection, this elevation was not necessary for downstream ABA signalling or virus-induced drought tolerance. Instead, +RNA virus-induced drought tolerance relies on N. benthamiana phospholipase Dα1 (NbPLDα1)-derived phosphatidic acid (PA). Knockout of NbPLDα1 or disruption of the interaction between viral proteins and NbPLDα1 impaired the ability of +RNA viruses to activate ABA signalling and enhance drought tolerance. The virus-induced increase in ABA levels appears to result from feedback regulation by PA-activated ABA signalling. Overall, our results suggest that +RNA viruses improve plant drought tolerance by modulating NbPLDα1-derived PA rather than by promoting ABA production.