Oligomeric SWEET1g of Solanum tuberosum confers resistance to potato virus Y and Potato virus X.

How the protein sugars will eventually be exported transporter (SWEET) affects plant virus infection remains largely unknown. Here, our findings showed that potato virus Y (PVY) coat protein (CP) directly interacted with SWEET1g of Solanum tuberosum (StSWEET1g). Silencing of StSWEET1g promoted PVY infection while overexpressing StSWEET1g in Nicotiana benthamiana inhibited PVY replication. Mutation of glycine (G) at position 80 to aspartic acid (D) impaired the self-interaction and attenuated the antiviral activity of StSWEET1g, indicating that oligomerization of StSWEET1g is indispensable for restricting PVY replication. The mutation of G to D also abolished the interaction between StSWEET1g and PVY CP. Moreover, StSWEET1g interacted with the CPs of tobacco vein banding mosaic virus (TVBMV; genus Potyvirus) and potato virus X (PVX; genus Potexvirus) similarly. We further demonstrated that the heat shock protein 70 of potato (StHSP70), a pro-viral factor of PVY, interacted with both StSWEET1g and CP. Our findings further provided evidence that StSWEET1g exerted its antiviral function via interfering with CP-StHSP70 interaction and initiating jasmonic acid (JA) defense pathway. To sum up, our results indicate that oligomeric StSWEET1g jointly manipulates StHSP70 and JA signaling pathway to regulate plant immunity and confer broad-spectrum resistance to plant RNA viruses of different genera.