Anti-TMV Activity and Functional Mechanisms of Two Diterpenoid Alkaloids Isolated from Dendrobium findlayanum

Tobacco mosaic virus (TMV) is a major threat to crops, making the discovery of green biopesticides essential. Herein, we present two active ingredients derived from the medicinal plant Dendrobium findlayanum, findlayine A (1) and dendrofindline B (2), as promising precursor compounds for TMV inhibitors. Among them, 2 inhibited TMV infestation on tobacco leaves at a rate of 38.6%, which was close to that of the commercial antiviral agent ningnanmycin (43.1%). Both 1 and 2 could effectively alleviate the destruction of tobacco leaf protoplasts by TMV infestation, and enhance the resistance of tobacco to TMV by affecting the activities of phenylalaninammo-nialyase (PAL), peroxidase (POD) and superoxide dismutase (SOD). Additionally, 1 and 2 significantly down-regulated the expression of TMV coat protein (CP) and inhibited CP-mediated aggregation of TMV, thereby reducing its infestation capacity. This study systematically investigated the mechanism of anti-TMV activity of diterpenoid alkaloids from D. findlayanum, with a view to providing new insights into the creation of novel green antiviral agents.