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Subcellular Localization and Detection of Tobacco mosaic virus ORF6 Protein by Immunoelectron Microscopy

T. N. Erokhina1*, E. A. Lazareva2, K. R. Richert-Pöggeler3, E. V. Sheval2, A. G. Solovyev2, and S. Y. Morozov2

1Shemyakin–Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia; E-mail: tne@mx.ibch.ru

2Lomonosov Moscow State University, Belozersky Institute of Physico-Chemical Biology, 119991 Moscow, Russia; E-mail: morozov@genebee.msu.ru

3Julius-Kühn-Institut, Institute for Epidemiology and Pathogen Diagnostics, Messeweg 11/12, 38104 Braunschweig, Germany; E-mail: katja.richert-poeggeler@julius-kuehn.de

* To whom correspondence should be addressed.

Received June 19, 2016; Revision received August 17, 2016
Members of the genus Tobamovirus represent one of the best-characterized groups of plant positive, single stranded RNA viruses. Previous studies have shown that genomes of some tobamoviruses contain not only genes coding for coat protein, movement protein, and the cistron coding for different domains of RNA-polymerase, but also a gene, named ORF6, coding for a poorly conserved small protein. The amino acid sequences of ORF6 proteins encoded by different tobamoviruses are highly divergent. The potential role of ORF6 proteins in replication of tobamoviruses still needs to be elucidated. In this study, using biochemical and immunological methods, we have shown that ORF6 peptide is accumulated after infection in case of two isolates of Tobacco mosaic virus strain U1 (TMV-U1 common and TMV-U1 isolate A15). Unlike virus particles accumulating in the cytoplasm, the product of the ORF6 gene is found mainly in nuclei, which correlates with previously published data about transient expression of ORF6 isolated from TMV-U1. Moreover, we present new data showing the presence of ORF6 genes in genomes of several tobamoviruses. For example, in the genomes of other members of the tobamovirus subgroup 1, including Rehmannia mosaic virus, Paprika mild mottle virus, Tobacco mild green mosaic virus, Tomato mosaic virus, Tomato mottle mosaic virus, and Nigerian tobacco latent virus, sequence comparisons revealed the existence of a similar open reading frame like ORF6 of TMV.
KEY WORDS: Tobacco mosaic virus, ORF6 protein, overlapping genes, subcellular localization, monoclonal antibodies, immunoelectron microscopy

DOI: 10.1134/S0006297917010060