30In plants, autophagy is involved in responses to viral infection. However, understanding 31 of new host factors mediating autophagic clearance of plant viruses is very limited. We 32 here identified a new host factor NbP3IP participating in autophagy-mediated plant 33 defense against viral infection. NbP3IP interacted with p3, a RNA silencing suppressor 34 encoded by Rice stripe virus (RSV), a negative-strand RNA virus, and mediated its 35 autophagic degradation. NbP3IP could also interact with NbATG8f, which was required 36 for NbP3IP-miediated p3 degradation. Overexpression of NbP3IP induced autophagy and 37 down-regulation of NbP3IP reduced autophagy. Both overexpression of NbP3IP and 38 silencing of GAPC, which also induces autophagy, inhibited RSV infection. In contrast, 39 silencing of ATG7 promoted RSV infection. Thus, through identification of a new 40 potential selective autophagy receptor P3IP, we revealed a new mechanism of 41 autophagy-mediated plant defense against plant viruses and provided the first evidence 42 that plant autophagy can also play an antiviral role against negative-strand RNA viruses. 43 KEY WORDS 44 Autophagy; Rice stripe virus; p3; NbP3IP; ATG8 45 46 Rice stripe virus (RSV), transmitted by the small brown planthopper (SBPH; Laodelphax 48 striatellus Fallén), causes serious epidemics in East Asia, including China, Japan and 49 Korea (Cheng et al., 2008). RSV belongs to the genus Tenuivirus and only infects plants 50 of the family Poaceae by natural SBPH transmission, which is a barrier to studies 51exploring the pathogenesis of RSV and its interaction with plants in the field or with its 52 3 insect vector. In the laboratory, however, RSV can infect the experimental plant Nicotiana 53 benthamiana by mechanical inoculation, which has been adopted as a very useful model 54 system for studying RSV-plant interactions (Xiong et al., 2008; Yuan et al., 2011; Zhang 55 et al., 2012; Kong et al., 2013; Fu et al., 2018). RSV has four single-stranded RNA 56 genome segments. RNA1 (~9 kb) is negative-sense and has a single open reading frame 57 (ORF), encoding the RNA-dependent RNA polymerase (RdRP), in its complementary 58 strand. Each of the other three segments (RNA2, 3.5 kb; RNA3, 2.5 kb; RNA4, 2.2 kb) 59 are ambisense and contain two non-overlapping ORFs on opposite strands, separated by a 60 non-coding intergenic region (IR) that functions in termination of transcription (Zhu et al., 61 1991; Zhu et al.