AV2 protein of tomato leaf curl Palampur virus interacts with F-box Kelch protein of tomato and enhances phenylalanine ammonia-lyase activity during virus infection

Abstract Leaf curl diseases caused by tomato leaf curl Palampur virus (ToLCPalV) is responsible for considerable yield losses and pathogenicity of virus is attributed to the expression of a viral protein, AV2. The present study was designed to elucidate role of AV2 in virus infection and characterize its interaction with tomato F-box Kelch protein (KFB). The interaction between AV2 and KFB was assayed using several approaches including yeast two hybrid screening (Y2H) and bimolecular fluorescence complementation (BiFC). Interestingly, transient co-expression of AV2 and KFB in Nicotiana benthamiana resulted in destabilization of the KFB protein. This in turn was associated with ~3.4-fold downregulation of KFB transcripts in ToLCPalV infected leaves. The N. benthamiana plants inoculated with wild-type or mutant ToLCPalV strains also showed a significant difference in phenylalanine ammonia-lyase (PAL) activity. These results provide valuable insights into molecular steps underlying virulence of ToLCPalV on tomato plants.