Ningnanmycin Activates Defense Systems against Potato Virus Y in Nicotiana benthamiana

Ningnanmycin has been proven to effectively inhibit infection by potato virus Y (PVY), although its underlying mechanisms remain unclear. In this study, we report a novel finding that ningnanmycin affects PVY replication. Two approaches were employed: studies using PVY movement-deficient mutants suggest that ningnanmycin, at a concentration of 500 μg/mL, inhibits PVY replication. Ningnanmycin interacts with the PVY-encoded coat protein (CP) with a binding constant of 1.34 μmol/L, and key amino acids Glu¹⁶⁸ and Thr²⁰⁶ are involved in this interaction. Additionally, ningnanmycin induces the expression of antiviral response genes in Nicotiana benthamiana, including PRXIIB, PRXIIE, PUB4, and PER42. Furthermore, studies revealed that the overexpression of PUB4 in N. benthamiana confers resistance to PVY infection. These findings highlight the mechanisms by which ningnanmycin activates the PUB4 gene and suppresses CP assembly, thereby inhibiting PVY in N. benthamiana. This study represents an important step toward elucidating the molecular mechanism underlying the antiviral activity of ningnanmycin.