A Plant Protein NbP3IP Induces Autophagy and Mediates the Autophagic Degradation of RSV p3 to Inhibit Viral Infection

ABSTRACT In plants, autophagy is involved in responses to viral infection. However, understanding of new host factors mediating autophagic clearance of plant viruses is very limited. We here identified a new host factor NbP3IP participating in autophagy-mediated plant defense against viral infection. NbP3IP interacted with p3, a RNA silencing suppressor encoded by Rice stripe virus (RSV), a negative-strand RNA virus, and mediated its autophagic degradation. NbP3IP could also interact with NbATG8f, which was required for NbP3IP-miediated p3 degradation. Overexpression of NbP3IP induced autophagy and down-regulation of NbP3IP reduced autophagy. Both overexpression of NbP3IP and silencing of GAPC, which also induces autophagy, inhibited RSV infection. In contrast, silencing of ATG7 promoted RSV infection. Thus, through identification of a new potential selective autophagy receptor P3IP, we revealed a new mechanism of autophagy-mediated plant defense against plant viruses and provided the first evidence that plant autophagy can also play an antiviral role against negative-strand RNA viruses.