Genome analysis and characterization of a tobacco mosaic virus
isolate infecting balsam (Impatiens balsamina)
Seung-Kook Choi Æ Ju-Yeon Yoon Æ
Received: 15 January 2009 / Accepted: 30 March 2009 / Published online: 19 April 2009
Ó Springer-Verlag 2009
Abstract The complete RNA genomic sequence of a
tobacco mosaic virus isolate infecting Impatiens balsamina,
designated as TMV-IM, has been determined. The genomic
sequence and the predicted gene products of TMV-IM were
similar to those of other members of the genus Tobamovirus.
The CP ORF of TMV-IM showed sequence identities of
95.0–99.5% with the corresponding ORFs of other TMV
strains. Full-length cDNA of TMV-IM was ampliﬁed by
RT-PCR with a 5
-end primer harboring a T7 promoter
sequence and a 3
-end TMV-speciﬁc primer. Subsequently,
the full-length cDNA was cloned into plasmid vectors.
Capped transcripts synthesized from the cDNA clone were
highly infectious and caused characteristic symptoms in
balsam plants, similar to wild-type TMV-IM and TMV-U1.
These results provide deﬁnitive evidence for the natural
occurrence of TMV in balsam.
Tobacco mosaic virus (TMV) is an extensively studied model
virus that has a worldwide distribution and infects over 200
plant species [10, 23]. Several tobamoviruses that were for-
merly considered TMV strains, causing severe losses in
tobacco, tomato, pepper and other crops, have been classiﬁed
recently as members of new species of the genus Tobamo-
virus on the basis of differences in host range, serological
properties and amino acid sequences of encoded virus pro-
teins [1, 12]. The genus currently consists of 22 deﬁnitive and
one tentative species [9, 11, 13], which are further divided
into three subgroups based on natural host range, genome
organization, and phylogenetic clustering [1, 9, 12, 16]. The
complete nucleotide sequences of numerous members of the
genus Tobamovirus have been reported [1, 2, 9, 14–16, 23].
Tobamovirus particles are rod-shaped, about 300 9
18 nm. The single-stranded, positive-sense RNA genome
of the U1 isolate (TMV-U1) has been completely
sequenced and shown to consist of 6,359 nucleotides .
The TMV genome encodes the replicase proteins 126 and
183 K; the latter protein, generated by read-through of an
amber stop codon, is directly translated from the 5
the viral genomic RNA [7, 17]. Two further proteins are
produced from subgenomic mRNA including the 30 K
cell-to-cell movement protein and the 17.5 K coat protein
[7, 18, 22].
So far, few viruses have been identiﬁed as infecting
plants of the family Balsaminaceae . We observed rod-
shaped virus particles in the leaf tissues of balsam plant
(Impatiens balsamina) showing yellow ring symptoms in
Korea in 2006. In this paper, we identiﬁed the causal agent
as an impatiens-infecting isolate of TMV (TMV-IM) and
determined the complete genome sequence of TMV-IM.
The biological properties of TMV-IM were further ana-
lyzed by using an infectious cDNA clone, showing that
both TMV-IM and TMV-U1 infected balsam systemically.
Fresh samples of balsam leaves showing yellow ring
symptoms were collected from greenhouse-grown commercial
S.-K. Choi (&)
Division of Biosciences and Bioinformatics,
College of Natural Science, Myong-Ji University,
Yongin 449-728, South Korea
PVGB, Division of Environmental and Life Sciences,
Seoul Women’s University, Seoul 139-774, South Korea
Division of Horticultural environment,
National Institute of Horticultural and Herbal Science,
RDA, Suwon 440-310, South Korea
Arch Virol (2009) 154:881–885