[Construction of a full-length cDNA of tobacco mosaic virus strain V-69 genome].

The genome of the tobacco mosaic virus (TMV) strain V-69 was sequenced by us earlier. The comparison of its nucleotide sequence with those of well-known attenuated strains (using published data) demonstrated considerable homology between strain V-69 and tomato strain L of TMV. In this study, full-length cDNA copy of TMV strain V-69 genomic RNA has been cloned in vector pBS(+) under the control of the T7 promoter and with an SmaI site at the 3'-terminus. The in vitro transcription of this construction with the use of phage T7 RNA polymerase in the presence of a cap analog (m7GpppG) has yielded an infectious RNA. This RNA has induced the same symptoms as those caused by TMV strain V-69 in infected indicator plants. Three point mutations inactivating one of two HindIII sites have been introduced into the cDNA. The absence of the HindIII site at position 1449 of the viral nucleotide sequence and the corresponding mutations serve as markers of the construction obtained. The full-length cDNA copy of the TMV strain V-69 RNA can be used both as a research tool and for constructing a vector for transit gene expression.