Lily virus X
| Lily virus X (LVX) | |
|---|---|
| Virus classification | |
| Group: | Group IV ((+)ssRNA) |
| Order: | Tymovirales |
| Family: | Alphaflexiviridae |
| Genus: | Potexvirus |
| Species: | Lily virus X |
Lily virus X (LVX) is a pathogenic ssRNA(+) plant virus of the family Alphaflexiviridae and the order Tymovirales. It is the type species of the genus Potexvirus.
LVX is described in the 4th report of the ICTV (1982). It is found primarily in lilies, although more plants are susceptible, and the virus is thought to be only transmitted mechanically. There are no known vectors; however, the application of insecticides effectively reduced the spread of LVX, from which it may be gathered that the virus’ transmission is insect-mediated. Symptoms of this virus are as of yet unknown, obfuscating the capability to examine the extent of natural infection and spread.
LVX is a non-enveloped virus with helical symmetry. All potexviruses, including LVX are believed to have slightly less than 9 protein subunits per helical turn. This pattern of nucleocapsid formation causes the nucleocapsid to be an elongated, flexible, filamentous virus like most plant viruses. Unlike other potexviruses (average length of 550 nm), LVX has a length of 470 nm and a width of 13 nm. LVX is distinguishable from lily symptomless carlavirus (LSV) by serological tests, such as immunogold labeling tests.
The LVX genome consists of one single stranded (+)RNA sequence of 5.9-7 kilobases in size. The genome contains only three Open Reading Frames (ORFs), coding for five proteins (RdRp, TGBp1, TGBp2, TGBp3, CP). The 5’ end is capped and the 3’ terminus is polyadenylated.
These proteins are 24 kilodaltons (kDa), 12 kDa, and 22 kDa, with the third being the coat protein, while also encoding for RNA-dependent RNA polymerase (RdRp). The stop codon of the 24 kDa ORF and the start codon of the 12 kDa ORF overlap one another. While many potexvirus genomes contain a small ORF that is immediately 5’ of this coat protein ORF, this is not found in the LVX genome. This difference is surprising as this ORF has been identified in at least six other potexvirus genomes. However, when looking at the proteins encoded by LVX and other potexviruses, there were significant similarities between the amino acid sequences. At the 5’ end of LVX, there is a truncated ORF, which encodes for a polypeptide which contains a GDD motif. This motif is also found in the C-terminal end of proteins encoded by other potexviruses. Examination of the 24 kDa protein of LVX reveals that it contains a nucleoside triphosphate binding motif (GXXGXGKS/T). This motif also found in the lily symptomless virus 25 kDa protein, as well as the 25-26 kDa proteins of other potexviruses, such as potato virus X and potato virus S.
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