Arch Virol (2003) 148: 199–205
An unusual large intergenic region in the S-RNA of a Bulgarian
tomato spotted wilt virus isolate
C. Heinze, P. Willingmann, F. Schwach, and G. Adam
Institute of Applied Botany, Department of Phytopathology, University of Hamburg,
Received November 29, 2001; accepted July 2, 2002
Published online November 4, 2002
Summary. The complete S-RNA sequences of four Bulgarian and one German
isolate of tomato spotted wilt tospovirus were determined. All isolates show a
high conservation in their N proteins, while the NSs proteins and the intergenic
regions (IGR) are more variable. The Bulgarian isolate 10HK96 has the largest
S-RNA (3364 nucleotides) among tomato spotted wilt virusesreported sofar. The
enlargement is based on an insertion of 365nts in the IGR that may have resulted
from stuttering of the viral polymerase or non-homologous recombination. This
insertion is present in the N protein gene subgenomic messenger, upstream of a
proposed transcription termination signal.
RNA viruses evolvemainly bymutations caused by the high errorratesof the viral
RNA-dependent RNA polymerases (RdRp). In addition, the exchange of genetic
material (homologous recombination) or the acquisition of genetic material from
a non-related virus in mixed infections or even from the hosts (non-homologous
with unrelated sequences from the host or other virus species is a rare event.
Tomato spotted wilt tospovirus (TSWV) is the type member of the genus
Tospovirus, the only phytopathogenic genus within the family Bunyaviridae.
Tospoviruses have lipid-enveloped particles, quasispherical in shape and 80–
110nm in diameter. The genome consists of three single stranded RNAs (L,
M and S). The L-RNA is of negative polarity and encodes the putative virale
polymerase , while the M and S-RNAs have an ambisense character .
The M-RNA encodes a precursor of the viral glycoproteins G1 and G2, that
are integral components of the lipid envelope and the putative viral movement