CLCuMuV V2 Interacts With Plant AGO4 And Its Function In Virus Infection

Geminiviridae is the largest family of plant virus known to us at present.In plants,RNA-directed DNA methylation(RdDM)-mediated transcriptional gene silencing(TGS)is a natural antiviral defense against geminiviruses.Therefore,the further study of this mechanism has physiological significance for resisting plant virus infection,and increasing cash crop yield.Several geminiviral proteins have been shown to target the enzymes related to methylcycle or histone modification;however,it remains largely unknown whether and by which mechanism geminiviruses directly inhibit RdDM-mediated TGS.In this study,we show that Cotton Leaf Curl Multan virus(CLCuMuV)V2 directly interacts with NbAGO4 and the L76S mutation in V2(V2L76S)abolishes such interaction.We further showed that V2,but not V2L76S can suppresses RdDM and TGS.Silencing of NbAGO4 inhibits TGS and enhances CLCuMuV DNA accumulation.In contrast,the V2L76S substitution mutant attenuates CLCuMuV infection.These findings reveal that CLCuMuV V2 contributes to viral infection by interaction with NbAGO4 to suppress RdDM-mediated TGS in plants.Our work provides the evidence that a geminiviral protein is able to directly target core RdDM component to counter RdDM-mediated TGS antiviral defense in plants,which extends our current understanding of viral counter-host antiviral defense.We further applied V2 into a wide-used tobacco rattle virus introduced gene silencing vector.With the TGS-suppressing function of V2,the modified TRV vector owns an enhanced ability of expressing foreign proteins in the whole plant.