ИСТИНА

The coat protein (CP) of Tobacco mosaic virus (TMV) is the well-studied one both structurally and functionally among CPs of helical plant viruses with the positive RNA genome. Besides canonical functions including virion assembly and dissociation the TMV CP is involved in noncanonical (nonstructural) functions such as virus movement through the plant vascular system (long-distance transport) and modulation of the host responses to viral infection. In our work we tested the role of the intrinsically unfolded C-terminus of the TMV CP exposed on the surface of viral particle for characteristics of viral infection. We obtained TMV U1 infectious cDNA clones with a set of deletions inside the gene CP encoding mutant CPs without 3, 6, 9, 15 and 20 amino acids residues from C-terminus respectively. Nicotiana benthamiana plants were infected using leave infiltration by Agrobacterium tumefaciens comprising wild type (wt) and mutant TMV U1 cDNA clones. Symptoms of viral infection and level of viral RNA in infected and systemic (non-infected) leaves were analyzed. This study demonstrates that the deletion of the CP C-terminal 3 a.a. only does not affect the infection characteristics (symptoms, cell-to-cell and long-distance movement, TMV RNA levels and virion appearance) in comparison with wt TMV infection. All other deletions inside the gene CP abolished infection in inoculated leaves: neither viral RNA nor virions were detected in these plants. However infected plants demonstrated similar mild symptoms such as curling of upper systemic leaves during two weeks post infiltration. We believe that the TMV CP C-terminus contain functional determinant/determinants which might interact with viral/cellular proteins involved in previously assumed participation of the TMV CP regulation of TMV RNA replication, production of viral movement protein or cell-to-cell transport.