Role of phosphorylation on the silencing suppressor activity of the movement protein TGBp1 of the Potato X virus and the relationship with its ATPase activity

BINAGHI M., MÓDENA N., CONTE F., MENTABERRY A, ZELADA A

Quebec

Congreso; XIV International Congress on Molecular Plant-Microbre Interactions; 2009

Society for Molecular Plant-Microbe Interactions

Role of phosphorylation on the silencing suppressor activity of themovement protein TGBp1 of the Potato X virus and the relationship withits ATPase activityM. BINAGHI (1), N. Módena (1), A. Mentaberry (1), A. Zelada (1)(1) Laboratorio de Agrobiotecnología, FCEN Universidad de Buenos Aires,Buenos Aires, ARGENTINAPresenter’s E-mail: maria_binaghi@hotmail.comIS-MPMI 2009 XIV Congress 40Potato virus X (PVX) is a member of the potexvirus whose RNA genomecodes for the viral replicase, three movement proteins (MPs: TGBp1, TGBp2and TGBp3) and the viral capsid protein. Mounting evidence suggests thatphosphorylation events can regulate MP functions. We have previouslydemonstrated that PVX TGBp1 is phosphorylated by a Nicotiana tabacumCK2-like kinase (Módena et al., 2008). The aim of this project is to evaluatethe role of phosphorylation on the silencing suppressor and ATPase activitiesof the PVX TGBp1. Based on in silico analysis of sequences from differentpotexvirus TGBp1s, we identified two threonine residues possibly subjectedto phosphorylation. We have developed different TGBp1 mutants where theidentified threonines (T193 and T215) have been replaced by alanine (A) oraspartate (D) residues. Silencing experiments show that the TGBp1-T215Amutant is partially defective on its silencing suppressor activity whereasTGBp1-T215D loses all silencing suppressor activity. On the other hand, weobserved that TGBp1-T193A has less suppressor activity due to the fact that itis less stable than wild-type TGBp1. We also show that although protein levelsof TGBp1-T193D mutant are normal, it was not able to restore wild-type suppressoractivity. Finally, ATP hydrolysis assays show that the ATPase activitiesof TGBp1-T193A and TGBp1-T215A were similar to wild-type TGBp1,whereas the revertant versions were significantly reduced. These results suggestthat phosphorylation of PVX TGBp1 plays an important role in regulating theATPase activity which might be necessary for silencing suppression.