Generation of infectious cDNA clones of a Korean strain of tomato aspermy virus.

Infectious full-length cDNA clones of the Korean strain of tomato aspermy cucumovirus (KC-TAV) were constructed using a long-template reverse transcription-polymerase chain reaction. The in vitro RNA transcripts, which were produced using T7 RNA polymerase from full-length cDNAs, could systemically infect the Nicotiana tabacum cv. Xanti-nc plants and induce systemic symptoms on the upper leaves that are similar to the wildtype KC-TAV. The complete nucleotide sequences of genomic RNAs of KC-TAV were determined from the infectious full-length cDNA clones. RNA1 and RNA2 of KC-TAV contain 3412 nucleotides and 3074 nucleotides, respectively. RNA3 of KC-TAV, 2222 nucleotides long, encodes the 3a protein and coat protein (CP) that are separated by 295 nucleotides intergenic region. The overall sequence analysis of the whole genome of KC-TAV revealed a strong homology (99%) to the genome of the V-TAV strain, the only strain whose entire genomic nucleotide sequence was available in the database, and an overall 60% homology to those of other cucumber mosaic virus and peanut stunt virus strains. A sequence comparison analysis of the deduced amino acid sequences of cDNAs of KC-TAV RNA 1, 2, and 3 indicates that there is no genetic diversity in the TAV population, although the virus exists in different geographical distributions.