Complete nucleotide sequence of a new strain of Tobacco necrosis virus A infecting soybean in China and infectivity of its full-length cDNA clone.

The complete nucleotide sequence of a virus isolated from soybean (Glycine max (L.) Merr.) in China, previously identified as a new strain of Tobacco necrosis virus A (TNV-A) based on its biological, serological properties, and coat protein (CP) sequence and named as TNV-A C, was determined and compared with that of TNV-A and other closely related Necroviruses and Carmoviruses. The viral RNA genome consists of 3,682 nucleotides and contains five open reading frames (ORFs). TNV-A C showed 86.4% overall nucleotide sequence identity to TNV-A. The CP and putative RNA-dependent RNA polymerase (RdRp) showed 88.8 and 95.9% amino acid identity, respectively, to that of TNV-A. The greatest difference between TNV-A C and TNV-A was in the 3' terminal region: the p7K ORF region present in TNV-A was absent in TNV-A C. Phylogenetic analysis of RdRp, CP, and small ORF regions of Necroviruses confirmed TNV-A C as a new strain of TNV-A. A full-length cDNA clone of TNV-A C was constructed and used as template for run-off transcription based on the obtained sequence. The results indicate that the in vitro-synthesized viral RNA faithfully represented the biological activity of wild-type TNV-A C.