M 6 A Modification of Plant Virus Enables Host Recognition by NMD Factors in Plants

N 6 -methyladenosine (m 6 A) is the most abundant eukaryotic mRNA modification and is involved in various biological processes. Increasing evidence has implicated that m 6 A modification is an important anti-viral defense mechanism in mammals and plants, but it is largely unknown how m 6 A regulates viral infection in plants. Here we report the dynamic changes and functional anatomy of m 6 A in Nicotiana benthamiana and Solanum lycopersicum during Pepino mosaic virus (PepMV) infection. m 6 A modification in the PepMV RNA genome is conserved in these two species. Overexpression of the m 6 A writers, mRNA adenosine methylase A (MTA), and HAKAI inhibit the PepMV RNA accumulation accompanied by increased viral m 6 A modifications, whereas deficiency of these writers decreases the viral RNA m 6 A levels but enhances virus infection. Further study reveals that the cytoplasmic YTH-domain family protein NbECT2A/2B/2C as m 6 A readers are involved in anti-viral immunity. Protein-protein interactions indicate that NbECT2A/2B/2C interact with nonsense-mediated mRNA decay (NMD)-related proteins, including NbUPF3 and NbSMG7, but not with NbUPF1. m 6 A modification-mediated restriction to PepMV infection is dependent on NMD-related factors. These findings provide new insights into the functionality of m 6 A anti-viral activity and reveal a distinct immune response that NMD factors recognize the m 6 A readers-viral m 6 A RNA complex for viral RNA degradation to limit virus infection in plants.