Protein arginine methyltransferase 6 mediates antiviral immunity in plants

Highlights•PRMT6 plays a positive role in resistance against tomato bush stunt virus (TBSV)•PRMT6 inhibits the silencing suppressor activity of TBSV P19•PRMT6 reduces P19 dimerization and sRNA binding by methylating conserved R43 and R115•PRMT6 natural alleles contribute to TBSV resistance in tomato accessionsSummaryViral suppressor RNA silencing (VSR) is essential for successful infection. Nucleotide-binding and leucine-rich repeat (NLR)-based and autophagy-mediated immune responses have been reported to target VSR as counter-defense strategies. Here, we report a protein arginine methyltransferase 6 (PRMT6)-mediated defense mechanism targeting VSR. The knockout and overexpression of PRMT6 in tomato plants lead to enhanced and reduced disease symptoms, respectively, during tomato bush stunt virus (TBSV) infection. PRMT6 interacts with and inhibits the VSR function of TBSV P19 by methylating its key arginine residues R43 and R115, thereby reducing its dimerization and small RNA-binding activities. Analysis of the natural tomato population reveals that two major alleles associated with high and low levels of PRMT6 expression are significantly associated with high and low levels of viral resistance, respectively. Our study establishes PRMT6-mediated arginine methylation of VSR as a mechanism of plant immunity against viruses.Graphical abstract