Summary auto-generated
Researchers determined the complete 8890-nucleotide RNA sequence of shallot virus X (ShVX), a newly identified flexuous filamentous virus infecting shallot plants. The viral genome contains six open reading frames encoding proteins of 194, 26, 11, 42, 28, and 15 kilodaltons. Sequence analysis revealed that ShVX combines genomic elements typical of both potexviruses and carlaviruses. The largest ORF1 protein (195K) shows high homology to potexvirus RNA replicases and contains conserved domains for methyl transferase, helicase, and polymerase activities. ORFs 2, 3, 5, and 6 have identifiable homologues among potex- and carlavirus proteins, including sequences related to the triple gene block found in these viruses. However, the 42K protein encoded by ORF4 appears unique with no reliable similarity to known viral proteins in databases. The 5' untranslated region resembles that of potato virus X, while the 3' region contains a poly(A) tail. This genomic arrangement distinguishes ShVX as a previously unknown pathogen combining characteristics of established plant virus families.
Key findings
- ShVX contains six open reading frames encoding proteins ranging from 11K to 195K in molecular weight, with the 8890-nucleotide genome structure differing from typical potexviruses and carlaviruses
- The ORF1-encoded 195K replicase protein displays extensive homology to potexvirus RNA replicases, containing conserved methyl transferase, helicase, and polymerase domains
- ORF4 encodes a unique 42K protein with no homologous sequences in existing viral protein databases, distinguishing ShVX from related plant viruses
- The genome organization combines elements typical of both potexviruses and carlaviruses, including a triple gene block-like region and flanking untranslated regions with poly(A) tails
- ShVX represents a new viral species serologically distinct from known Allium potyviruses and lacking cytoplasmic inclusions characteristic of potyvirus infection
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Abstract
The 8890 nucleotide RNA sequence of shallot virus X (ShVX), a new virus isolated from shallot, has been determined. The sequence contains six open reading frames (ORFs) which encode putative proteins (in the 5' to 3' direction) of M(r) 194528 (ORF1), 26333 (ORF2), 11245 (ORF3), 42209 (ORF4), 28486 (ORF5) and 14741 (ORF6). The ORF1 protein was found to be highly homologous to the putative potexvirus RNA replicases; ORF2, -3, - 5 and -6 proteins also have analogues among the potex- and/or carlavirus-encoded proteins. ORF3 is followed by an AUG-lacking frame coding for an amino acid sequence homologous to that of the 7K to 8K proteins of the triple gene block of the above-mentioned viruses. The putative ORF4 protein has no reliable homology with proteins in the database. The results obtained testify that, except for the unique 42K protein gene, the ShVX genome combines a number of elements typical of both carla- and potexviruses.