Ningnanmycin Activates Defense Systems against Potato Virus Y in <i>Nicotiana benthamiana</i>

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 <i>Nicotiana benthamiana</i>, including <i>PRXIIB</i>, <i>PRXIIE</i>, <i>PUB4</i>, and <i>PER42</i>. Furthermore, studies revealed that the overexpression of <i>PUB4</i> in <i>N. benthamiana</i> confers resistance to PVY infection. These findings highlight the mechanisms by which ningnanmycin activates the <i>PUB4</i> gene and suppresses CP assembly, thereby inhibiting PVY in <i>N. benthamiana</i>. This study represents an important step toward elucidating the molecular mechanism underlying the antiviral activity of ningnanmycin.