The genome of Beet cryptic virus 1 shows high homology to certain  cryptoviruses present in phylogenetically distant hosts.
This study determined the complete nucleotide sequence of Beet cryptic virus 1 (BCV1). As expected by analogy to previously sequenced alphacryptoviruses, dsRNA1 (2008 bp) encodes a 72.5-kDa protein containing sequence motifs characteristic for RNA-dependent RNA polymerases (RdRp). In addition to the full-length dsRNA1, a truncated form was also detected in dsRNA extracts. dsRNA2 (1783 bp) codes for the viral coat protein (CP) as proven by the identity of the predicted CP sequence to peptide sequences of the purified virion protein. The amino acid sequence of BCV1 RdRp as well as the 5'- and 3'-UTRs show 81-85% identity to the corresponding regions of Vicia cryptic virus (VCV), White clover cryptic virus 1 (WCCV1) and Carrot cryptic virus (CaCV). The amino acid sequence identity of the CP is about 55-62%, moreover, a strong conservation of predicted alpha-helical regions was observed. The high degree of similarity of these seed- and pollen-transmitted viruses persisting in phylogenetically distant hosts, together with their high similarity to fungal partitiviruses strongly supports the hypothesis that horizontal transfer by a fungus played a role in the emergence of the present cryptovirus species. The change in the distribution of cryptic viruses may also be due to human influence: While earlier BCV1 occurred frequently in sugar beet cultivars, it is very rare in cultivars currently used in agricultural practice and was detected in only one of the 28 cultivars investigated in our experiments.


BACKGROUND
The online version of this article (doi:10.1007/s11262-009-0432-4) contains supplementary material, which is available to authorized users.
Szego
Anita
A
Department of Plant Physiology and Plant Biochemistry, Corvinus University of Budapest, Ménesi út 44, 1118 Budapest, Hungary.
Enünlü
Natalya
N
Deshmukh
Sachin D
SD
Veliceasa
Dorina
D
Hunyadi-Gulyás
Eva
E
Kühne
Thomas
T
Ilyés
Pál
P
Potyondi
László
L
Medzihradszky
Katalin
K
Lukács
Noémi
N
D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D000595:Amino Acid Sequence; D027461:Beta vulgaris / Q000821:virology*; D036022:Capsid Proteins / Q000235:genetics; D016000:Cluster Analysis; D016679:Genome, Viral; D008969:Molecular Sequence Data; D010802:Phylogeny; D010942:Plant Viruses / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification*; D017433:Protein Structure, Secondary; D012328:RNA Viruses / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification*; D012367:RNA, Viral / Q000235:genetics; D012324:RNA-Dependent RNA Polymerase / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid
D020413:3' Untranslated Regions; D020121:5' Untranslated Regions; D036022:Capsid Proteins; D012367:RNA, Viral; D012324:RNA-Dependent RNA Polymerase