[Analysis of the Complete Tomato Aspermy Virus Genomes Suggests Reassortment in Russian Isolates from Chrysanthemum]

Tomato aspermy virus (TAV, genus Cucumovirus from the family Bromoviridae) is one of the most common and harmful chrysanthemum viruses, causing severe flower distortion, size reduction, and color breaking. Metatranscriptome sequencing of chrysanthemum plants of the Ribonette and Golden Standard cultivars from the collection of the Nikita Botanical Garden (Yalta, Republic of Crimea) generated TAV-related RNA reads. The complete genomes of two Russian isolates of the virus were assembled from the reads. This is the first report of full-length TAV genomes from Russia. Typically of cucumoviruses, the segmented TAV genome is represented by three single-stranded positive-sense linear RNA molecules of 3412 (RNA1), 3097 (RNA2) and 2219 (RNA3) nucleotides. Five open reading frames (ORF) have been identified that encode replicase (ORF1), RNA-dependent RNA polymerase (ORF2a), silencing suppressor protein (OFR2b), movement protein (OFR3a) and the coat protein (ORF3b). The identity of TAV genomes from the two chrysanthemum cultivars was 99.8% for all three viral RNAs; with other TAV isolates from GenBank it was 97.5-99.7% (RNA1), 93.8-99.8% (RNA2), and 89.3-99.3% (RNA3). Phylogenetic analysis showed that RNA1 and RNA3 of the Russian isolates were assigned to heterogeneous groups of TAV isolates found on various plant species in different regions of the world. At the same time, RNA2 clearly clustered with tomato isolates SKO20ST2 from Slovenia and PV-0220 from Bulgaria and, to a lesser extent, with the Iranian isolate Ker.Mah.P from petunia and the Chinese isolate Henan from chrysanthemum. The incongruence of phylogenetic trees reconstructed from different genome segments suggests pseudo-recombination (reassortment) in the Russian TAV isolates.

[Epitope mapping of the recombinant movement protein of the tobacco mosaic virus using monoclonal antibodies]

The movement protein (MP) of the tobacco mosaic virus (TMV) provides the intercellular transport of the viral RNA through plasmodesmata. The MP fulfills its function while interacting with host cell factors over the whole path of its intracellular movement from the subcellular site of its synthesis to the plasmodesmata of cellular walls. The MP conformation during its intracellular movement and fulfillment of the transport function still remains unknown. In this study, we describe the preparation of murine monoclonal antibodies (MAs) to TMV MP and mapping of the MP epitopes. Stable hybridoma lines that produce MAs to the partially denatured recombinant MP (MPr) were obtained. MAs were tested by immunoblotting and ELISA with the use of deletion variants of MPr. The epitopes of TMV MPr that recognize specific MAs were determined.