Influence of modeled microgravity on tobacco mosaic virus

Сlinorotation is an effective method of treating diseases caused by some plant viruses. Therefore, we researched the influence of microgravity (modeled by сlinorotation) on a tobacco mosaic virus (TMV) that infects many agricultural crops. It is known that cells of plants (infected with TMV) contain viral inclusion bodies or viroplasms and amount of viral inclusion bodies correlates with harmfulness of TMV. Therefore, the purpose of this study was to find out the effect of influence of modeled microgravity on inclusion bodies of TMV. In this study, we cultivated Nicotiana tabacum L. and inoculated them with TMV that was isolated from Norway maple (Acer platanoides L.). Then we divided these plants into two groups and cultivated these plants under normal and microgravitation conditions. Microgravity conditions were modeled by сlinorotation at 2 rpm for 4 hours a day. This experiment lasted 36 days. Changes of the amount of TMV inclusion bodies in cells of plants that cultivated under normal and microgravitation conditions was investigated by luminescence microscopy. We found that formation of TMV inclusion bodies under microgravitation conditions is first slowed down compared to formation under normal conditions and then their amount quickly decreasing. These results demonstrate the gravisensitivity of TMV. It was suggested hypothesis that this viroplasm pattern caused by the disorganization of cortical microtubule-associated ER sites (C-MERS) that are nodes of cellular transport pathways and nucleation centers of cortical microtubules and cortical microfilaments. It is known that under microgravity conditions there is a disorganization and disorientation of cortical microtubules, which stabilize C-MERS on which TMV viroplasms are formed. Thus, the disorganization and disorientation of cortical microtubules probably causes the disorganization of C-MERS, which leads to a decrease in the number of TMV viroplasms under the influence of microgravity. In this context, it is worth noting that some plant viruses, such as a Wheat streak mosaic virus (WSMV), a Potato virus M (PVM) and Potato curly dwarf virus (PCDV), are gravisensitive. These viruses belong to different taxa, for example WSMV belong to genus Tritimovirus (family Potyviridae), PVM belong to genus Carlavirus (family Betaflexiviridae) and PCDV belong to plant rhabdoviruses (uncertain taxonomic position), and differ both structurally and functionally. Therefore, the gravisensitivity of these viruses can occur by other mechanisms. Thus, antiviral therapeutic effect of clinorotation based on gravisensitivity of TMV and can be used in the production of virus-free seeds. To confirm this hypothesis, it is necessary to conduct a systematic review, as well as experimentally establish the fact of the disorganization of the C-MERS under microgravity conditions.