Complete Nucleotide
Sequence and Possible Genomic Expression Strategy of a Chinese Isolate of Broad
Bean Wilt Virus
ZHOU Xue-Ping, QI Yi-Jun, Li Fan, HUANG Xiao-Zao, LI De-Bao
( Institute of Biotechnology, Zhejiang University, Hangzhou 310029,
China )
Abstract The
complete nucleotide sequence of isolate B935 of the RNAs of broad bean wilt
virus2 (BBWV2) was determined. RNA1 contained 5956 nucleotide (nt) residues in
length exclusive the 3′ terminal poly(A)tail, and encoded a single long open
reading frame (ORF) with a molecular weight of 210 063 (210 kD). RNA2 was
composed of 3 601 nt residues exclusive of the poly(A) at the 3′ end, and
encoded a single long ORF with a molecular weight of 119 002 (119 kD). The
determination of the N terminal sequences of large coat protein (LCP) and small
coat protein (SCP) indicated that the polyprotein of RNA2 was cleaved at
Q/G(465/466) residues and Q/A(867/868) residues, to release three mature
proteins：a
N-terminal protein, LCP and SCP. The N-terminal protein shared homology with 58
kD/48 kD movement protein of cowpea mosaic virus and contained a similar
rNTP binding domain, indicating that this protein may have the function of
movement. Comparisons between the RNA1-encoded polyprotein and proteins encoded
by several species in Comoviridae revealed that the 210 kD
polyprotein could be cleaved into proteins such as RdRp, protease, NTP-binding
domain (NTBM), protease co-factor and Vpg. The phylogenetic tree based on the
amino acid sequences of LCP and SCP confirmed that the two serotypes of BBWV
should be regarded as different viruses.
Key words broad bean wilt virus 2；genome；genomic expression strategy
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