Arch Virol (2002) 147: 2215–2224
Nucleotide sequence, genome organisation and phylogenetic
analysis of Indian citrus ringspot virus
, R. G. Milne, and G. P. Accotto
Istituto di Virologia Vegetale, Consiglio Nazionale delle Ricerche, Torino, Italy
Received February 26, 2002; accepted June 25, 2002
Published online September 12, 2002
Summary. The sequence of the single-stranded RNA genome of Indian citrus
ringspot virus (ICRSV) consists of 7560 nucleotides. It contains six open reading
frames(ORFs)whichencodeputativeproteins of187.3,25, 12,6.4,34 and23kDa
respectively. ORF1 encodes a polypeptide that contains all the elements of a
replicase; ORFs 2, 3 and 4 compose a triple-geneblock; ORF5encodes the capsid
protein; the function of ORF6 is unknown. Phylogenetic analysis of the complete
genome and each ORF separately, and database searches indicate that ICRSV,
though showing some similarities to potexviruses, is signiﬁcantly different, as in
the presence of ORF6, the genome and CP sizes, and particle morphology. These
differences favour its inclusion in a new virus genus.
Indian citrus ringspot virus (ICRSV) is associated with a serious disease of citrus,
especially Kinnow mandarin, in India . The virus has ﬂexuous ﬁlamentous
particles 650nm in length, with an ssRNA genome of about 7500 nucleotides
and a capsid protein (CP) of 34kDa. Two open reading frames (ORFs) have been
identiﬁed at the 3
-end of the genome, encoding the CP and a 23kDa polypeptide
of unknown function .
Here we report the complete sequence and genome organisation of an isolate
(K1) of ICRSV, the same as used previously , and the results of phylogenetic
analysis of the putative viral proteins. The virus was propagated in Phaseolus
vulgaris cv. Saxa; puriﬁcation and viral RNA extraction was as described .
Present address: The Sanger Centre, Wellcome Trust Genome Campus, Hinxton,
Cambridge CB10 1SA, U.K.
The GenBank accession number of the sequence reported in this paper is AF406744.