Transgenic Expression of Pectin Methylesterase Inhibitors in Arabidopsis and Tobacco limits Tobamovirus spreading

Viral infection is a complex process influenced by the balance of virus-encoded proteins and host factors which support virus replication, cell-to-cell and long distance movement through the plant. Virus-encoded movement proteins (MPs) are necessary to allow cell-to-cell spread through plasmodesmata (PD). The interaction of MP with plant pectin methylesterase (PME) is required for Tobacco mosaic virus (TMV) local spreading in tobacco. The viral exit out of the vascular system is also partly PME-dependent. 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 expression of a PME inhibitor from Actinidia chinensis (AcPMEI) in Nicotiana tabacum decreases the overall PME activity and increases the level of pectin methylesterification of the wall without affecting plant morphology and development. After inoculation with TMV the transformed plants expressing AcPMEI exhibited a significant delay of viral spreading. A reduced susceptibility against Turnip vein clearing virus (TVCV) infection was also observed in Arabidopsis plants overexpressing the AtPMEI-2 inhibitor. Overall, our results indicate PMEIs as efficient tools to limit Tobamovirus infection.