CONSTITUTIVE EXPRESSION OF PECTIN METHYLESTERASE INHIBITORS LIMITS TOBAMOVIRUS SPREADING IN TOBACCO AND ARABIDOPSIS

Plant viral infection is a complex process influenced by the interaction of virus-encoded proteins and host factors which support virus replication and movement. Successful infection requires viral movement proteins (MPs) that modify the plasmodesmata (PD) size exclusion limit during the cell-to-cell movement. Pectin methylesterase (PME) was shown to interact in vitro with the MP of different viruses and the MP-PME interaction was proposed to be necessary for Tobacco mosaic virus (TMV) cell-to-cell spreading. PME is also required for the systemic movement of TMV through the host vasculature. Pectin demethylation directed by PME is likely to be a source of methanol that has been recently found to facilitate TMV spreading by triggering PD dilation. We here report that the ectopic expression of a PME inhibitor from Actinidia chinensis (AcPMEI) in Nicotiana tabacum significantly delays the TMV cell-to-cell and systemic spreading. A reduced susceptibility against Turnip vein clearing virus (TVCV) was also observed in Arabidopsis plants overexpressing a PME inhibitor from Arabidopsis (AtPMEI-2). Overall, our results indicate PMEIs as efficient tools to limit Tobamovirus infection