Ribonuclease activity of buckwheat plant (Fagopyrum esculentum) cultivars with different sensitivities to buckwheat burn virus.

Ribonucleases (RNases) are present in base-level amounts in intact plants, but this level is able to increase greatly under stress conditions. The possible cause for such an increase is protection against plant RNA-virus attack. Buckwheat burn virus (BBV) is a highly virulent pathogen that belongs to Rhabdoviridae family. In our study, we have analyzed the correlation between RNase activity and resistance of different buckwheat cultivars to BBV infection. Two cultivars, Kara-Dag and Roksolana, with different sensitivities to BBV have been used. Kara-Dag is a cultivar with medium sensitivity to virus and Roksolana is a tolerant cultivar. It has been shown that the base level of RNase activity in Roksolana cultivar was in most cases higher than the corresponding parameter in Kara-Dag cultivar. Both infected and uninfected plants of Roksolana cultivar demonstrated high RNase activity during two weeks. Whereas infected plants of Kara-Dag cultivar demonstrated unstable levels of RNase activity. Significant decline in RNase activity was detected on the 7th day post infection with subsequent gradual increase in RNase activity. Decline of the RNase activity during the first week could promote the virus replication and therefore more successful infection of upper leaves of plants. Unstable levels of RNase activity in infected buckwheat plants may be explained by insufficiency of virus-resistant mechanisms that determines the medium sensitivity of the cultivar to BBV. Thus, plants of buckwheat cultivar having less sensitivity to virus, displayed in general higher RNase activity.

[Matrix activity of mRNP of different cell localization from plants infected by minus-genome curly potato dwarfness virus in protein-synthesizing system in vitro].

Using structures of mRNP of different cell localization isolated from plants infected by minus-genomecurly potato dwarfness virus (CPDV), it was established that synthesis of virus proteins in vitro is mainly realized on membrane-related and free polysomal mRNP capable to direct synthesis of proteins programmed in RNA in cell-free protein-synthesizing systems. The obtained results prove that synthesis of virus proteins is actively realized on membrane-related nonpolysomal mRNP - 23520 imp/min. An analogous distribution of matrix activity is observed also in the case when mRNA isolated from mRNP of different cell localization was introduced in protein-synthesizing system. The least matrix activity was observed in cytoplasmic nonpolysomal mRNPs which are low-active in the translation system in vitro - only 1890 imp/min. The function of free cytoplasmic nonpolysomal mRNP is apparently mainly reduced to the transport and reserve of genetic information in a cell.

[Effect of structural P-protein of potato curly dwarf virus on replicase activity of mRNP-complexes of infected plants].

All representatives of rhabdoviruses contain a nucleocapside phosphoprotein - P-protein which is an essential subunit of the viral RNA-dependent RNA polymerase complex. As a result of studying the effect of nucleocapside protein P(NS) on replicase activity of mRNP isolated from plants infected by potato curly dwarf virus in the system in vitro, it was established that nucleocapside P-protein stimulates considerably the replicase activity of membrane-bound polysomal m-RNP P-protein being available in concentration of 15 microg/ml in the replication system in vitro of membrane-bound polysomal mRNP, the replicase activity increased 11.7 times. This property of nucleocapside P-protein at the same concentration was displayed to a less extent with the presence of free polysomal mRNP, in the system in vitro. Thus the replicase activity mRNP-complexes in the replication system in vitro depends on the presence of nucleocapside viral P-protein in the system. Its concentration being increased or decreased, one can observe the change of the replicase activity.

[Immunospecific detection of the potato virus X by the surface plasmon resonance].

Highly specific and proximal method of laboratory diagnostics of the viral disease, has been developed using the structural protein of the potato virus X, as a model, and monospecific antibodies to it. The immunospecific determination of the potato virus X was carried out by the surface plasmon resonance method using specific IgG-antigen complexes, immobilized on the sensor surface modified by rodanide and protein A of Staphylococcus aureus.