Annexin D1 promotes potyvirus infection through interaction with nuclear inclusion protein b and Ca2+-dependent phosphorylation

Annexins are a family of calcium- and phospholipid-binding proteins with immunomodulatory roles. However, whether annexins regulate plant virus infection has not been studied in detail. Here, we report that annexin D1 of Nicotiana benthamiana (NbANXD1) forms dimers and interacts with nuclear inclusion protein b (NIb) of tobacco vein banding mosaic virus (TVBMV) by binding the C domain of NIb. NIb can recruit NbANXD1 to the perinuclear region, and the NIb-NbANXD1 interaction complex is found to co-localize with TVBMV 6K2. Further analysis showed that phosphokinase 29 of N. benthamiana (NbKIN29) interacts with and specifically phosphorylates NbANXD1 at amino acid residues T204, T276, and S286. Furthermore, Ca2+ may regulate TVBMV infection by modulating the phosphorylation of NbANXD1 by NbKIN29. Gene silencing, overexpression, knockout, and mutation experiments showed that annexin D1 positively regulates potyviral replication and systemic infection. In summary, our study supports that annexin D1 is recruited to promote potyvirus infection through interaction with NIb and Ca2+-dependent phosphorylation by phosphokinase 29. Our results provide important insights into the potyvirus infections.