DEPARTMENT OF PLANT VIRUS BIOCHEMISTRY

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In the early works of the Department, the complementation analysis has been implemented for the first time in application to the plant viruses. Formation of the "mixed" viruses, composed of heterologous RNA and protein, has been demonstrated in vivo, thus allowing studying the protein-RNA "recognition" in the infected cell. A novel type of non-complemented ts-mutations (cis-mutations) influencing only the RNA conformation, was described. New concept of the intercellular transport of the plant virus genetic material has been proposed and developed.

Group of Dr. N.P.Rodionova developed a new approach in genetic engineering of viruses basing on direct manipulations of virus RNA genomes. New original methods for addressed cleavage of polycistronic RNAs and ligation allowed to restore biological activity of viral RNAs cleaved in vitro.

In collaborative research of a group headed by Dr. N.P.Rodionova and a laboratory of molecular biology of plant viruses (a head - Dr. Yu.L.Dorokhov) the genome structure and expression of a new tobamovirus (crTMV) has been studied. It has been shown that, in contrast to the other tobamoviruses, the genome of crTMV contains an internal ribosome entry site (IRES, 148 nt) that allows independent translation of the internal coat protein gene. The IRES was found to be effective in the cell-free translation systems derived from plants and animals, and to stimulate translation of both the natural and homeric templates. Evidence has been obtained that the coat protein of crTMV may be synthesized by the mechanism of internal initiation of translation in vivo. These data open an avenue for constructing transgenic plants that simultaneously express two (or more) introduced genes.

Dr. S.Yu.Morozov and co-workers (laboratory of plant virus genetic engineering) developed a new approach for construction of virus-resistant transgenic plants, and the resistant transgenes were produced expressing a defective (partially functional) viral transport protein. The genomes of hordeiviruses (multipartite genome) and potexviruseses have been sequenced. It has been found that the 5'-terminal (ab-leader) sequence in the potexvirus RNA possesses the activity of a translational enhancer that strongly stimulates expression of the heterologous genes. A new approach for movement protein complementation has been developed basing on microprojectile bombardment.

Group of Dr. A.A.Agranovsky the genome organization of a closterovirus (monopartite genomes) has studied. A novel type of the virion architecture was unraveled for a closterovirus - a "rattlesnake" structure built of two capsid proteins.

A group of Dr. E.N.Dobrov studied RNA structure and protein-nucleic acid interactions in particles of elongated plant viruses with helix symmetry. It was found that spatial organization of small region in the tobacco mosaic virus coat protein may play important role in determination of symptom expression.

1. Agranovsky A.A., Lesemann D.E., Maiss E., Hull R. and Atabekov J.G. "Rattlesnake" structure of a filamentous plant RNA virus built of two capsid proteins. Proc. Natl. Acad. Sci. USA (1995) 92, 2470-2473.

2. Solovjev A.G., Zelenina D.A., Savenkov E.J., Grdzelishvili V.Z., Morozov S.Yu., Lesemann D.E., Maiss E., Casper R., Atabekov J.G. Movement of a Barley Stripe Mosaic Virus Chimera witn a Tobacco Mosaic Virus Movement Protein. Virology (1996) 217, 435-441.

3. Morozov S.Yu., Fedorkin O.N., Juttner, G., Schiemann, J., Baulcombe D.C., Atabekov J.G. Complementation of a potato virus X mutant mediated by bombardment of plant tissues with cloned viral movement protein genes. J.Gen.Virology (1997) 78,. 2077-2083. 4. Karpova O.V., Ivanov K.I., Rodionova N.P., Dorokhov Yu.L., Atabekov J.G.). Nontranslatability and dissimilar behavior in plants and protoplasts of viral RNA and movement protein complexes formed in vitro.Virology (1997) 230, 11-21.

5. Ivanov P.A., Karpova O.V., Skulachev M.V., Tomashevskaya O.L., Rodionova N.P., Dorokhov Yu.L., Atabekov J.G. A tobamovirus genome that contains an internal ribosome entry site functional in vitro. Virology (1997), 232, 32-43.