Cell-to-Cell Movement and Protein Interactions of Potato mop top virus

27 28 Functions of viral proteins can be regulated through phosphorylation by serine/threonine kinases 29 in plants but little is known about involvement of tyrosine kinases in plant virus infection. In this 30 study, TGBp3, one of the three movement proteins encoded by a triple gene block (TGB) of 31 Potato mop-top virus (PMTV), was detected for the first time in PMTV-infected plants and 32 found to be tyrosine-phosphorylated. Phosphorylation sites (Tyr87–89 and Tyr120) were located in 33 two amino acid motifs conserved in the TGB-containing, rod-shaped plant viruses. Substitution 34 of these tyrosine residues in both motifs was needed to abolish tyrosine phosphorylation of 35 TGBp3. Substitution of Tyr87–89 with alanine residues enhanced the interaction between TGBp3 36 and TGB protein 2 (TGBp2) and inhibited cell-to-cell movement of PMTV. On the other hand, 37 substitution of Tyr120 with alanine resulted in no alteration in the interaction of TGBp3 with 38 TGBp2, but the mutant virus was not infectious. The results suggest that tyrosine 39 phosphorylation is a mechanism regulating the functions of plant virus movement proteins. 40 41 42 on July 8, 2017 by gest http/jvi.asm .rg/ D ow nladed fom