Multi-Omics Analysis Uncovers the Salicylic Acid and Ethylene-Responsive Transcription Factor-Mediated Defence Mechanism of Panax notoginseng to Panax notoginseng Virus Y.

Panax notoginseng is an edible traditional medicinal plant, but it is highly susceptible to Panax notoginseng virus Y (PnVY). This study revealed that salicylic acid (SA) treatment decreases this susceptibility. The underlying molecular mechanism was elucidated by integrating physiological, multi-omics and genetic approaches. SA application alleviated PnVY-induced photosynthetic inhibition and activated antioxidant enzymes, thereby decreasing reactive oxygen species levels and maintaining redox homeostasis. Upon PnVY inoculation, SA triggered a range of defence responses. The exogenous application of SA promoted the accumulation of phenylpropanoids, alkaloids and flavonoids, which was consistent with the upregulated expression of phenylpropanoid biosynthesis-related genes. Transcriptional regulatory network analysis revealed that the ethylene-responsive transcription factor PnERF120 may positively regulate the biosynthesis of phenolic acids including SA. Overexpressing PnERF120 enhanced the resistance of P. notoginseng to PnVY, activated SA biosynthesis and signal transduction pathway, upregulated the RNA-silencing-related genes and improved phenolic acid accumulation. However, silencing PnERF120 in P. notoginseng had the opposite effect. Additionally, yeast one-hybrid and dual-luciferase assays indicated that PnERF120 binds to the promoter of PnPAL1 and activates PnPAL1 expression. In conclusion, PnERF120 positively regulates defence against PnVY infection by modulating SA biosynthesis and the SA signalling pathway.