Tomato yellow leaf curl virus
| Tomato yellow leaf curl virus | |
|---|---|
| Virus classification | |
| Group: | Group II (ssDNA) |
| Family: | Geminiviridae |
| Genus: | Begomovirus |
| Species: | Tomato yellow leaf curl virus |
Tomato yellow leaf curl virus (TYLCV) is a DNA virus from the genus Begomovirus and the family Geminiviridae. TYLCV causes the most destructive disease of tomato, and it can be found in tropical and subtropical regions causing severe economic losses. This virus is transmitted by an insect vector from the family Aleyrodidae and order Hemiptera, the whitefly Bemisia tabaci, commonly known as the silverleaf whitefly or the sweet potato whitefly. The primary host for TYLCV is the tomato plant, and other plant hosts where TYLCV infection has been found include eggplants, potatoes, tobacco, beans, and peppers. Due to the rapid spread of TYLCV in the last few decades, there is an increased focus in research trying to understand and control this damaging pathogen. Some interesting findings include virus being sexually transmitted from infected males to non-infected females (and vice versa), and an evidence that TYLCV is transovarially transmitted to offspring for two generations.
This virus consists of a single circular single-stranded (ss) DNA molecule (2787 nt in size) which is a common distinction among viruses in the family Geminiviridae. The coat protein is an essential component for successful insect transmission of this virus. The ssDNA genome encodes for six open reading frames (ORF): two in the virion sense orientation, V1 and V2, and four in the complementary orientation, C1, C2, C3, and C4. The V1 and V2 protein encoded by the v1 and v2 gene are the coat protein and pre-coat protein, respectively. The function of the V1 protein, identified as the coat protein, is to encapsulate the ssDNA and form the virus particle to protect the viral DNA, while the pre-coat protein is believed to be involved in movement of the virus.
The six open reading frames encoded by the TYLCV genome are V1, V2, C1, C2, C3, and C4. V1 protein is the coat protein and its function is to protect the viral DNA by encapsulating it. V2 protein is the pre-coat protein, which function is still not clear, but it might be associated with viral movement. C1 protein is also known as the viral replication protein, which makes it essential for virus replication. C2, C3, and C4 proteins have been associated to function as a post-transcriptional gene silencing suppressor, a virus accumulation enhancer, and a symptom induction determinant, respectively. In the insect vector, a study found that TYLCV had a high binding affinity to a GroEL homolog, a molecular chaperon essential for protein folding. Therefore, after feeding B. tabaci with a diet containing antiserum against GroEL, they found TYLCV transmission to be reduced. This study demonstrated that the GroEL homolog is involved in the virus transmission.
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