Sneha Singhal, Jaypee Institute of information technology, Noida
A well-documented evolutionary driving phenomenon has been found in prokaryotes and eukaryotes known as HGT (Horizontal gene transfer), but its impact has remained elusive on the plant kingdom. HGT between a plant and insect in which the transferred genetic material performs a useful function, has been shown in one species of white fly. This is the first known example of a natural gene transfer also called horizontal gene transfer (HGT) from a plant to an insect. Why the whitefly Bemisia tabaci is so adept at munching on crops has been explained by this example. An aphid-like insect, the whitefly Bemisia tabaci is a cosmopolitan, highly polyphagous agricultural pest that incorporated a portion of plant DNA into its genome by the mechanism of HGT that protects it from leaf toxins.
Ted Turlings and his colleagues at the University of Neuchâtel in Switzerland discovered, the silverleaf whitefly has acquired the plant-derived phenolic glucoside malonyltransferase gene BtPMaT1, which is found in plants but never previously seen in insects. In whiteflies this gene neutralizes the phenolic glucosides, a compound found in tomato plants. By disrupting the gene’s function this made the whiteflies susceptible to this compound. All white flies has been died after feeding on tomato plants that had been genetically modified to produce the RNA molecules that silence BtPMaT1, and thus impairing the whiteflies’ detoxification ability.
Andrew Gloss, who studies plant–pest interactions at the University of Chicago says, how studying evolution can inform new approaches for applications like crop protection is a remarkable example. Bemisia tabaci are vectors for more than 100 pathogenic plant viruses, on this Turlings says that genome of the viruses can get incorporated into their host cells.
BtPMaT1 gene may have important function in plants as it helps plant to store harmless toxins in such a way that plant don’t get poisoned. Similarly, when these whiteflies eat the plants, the gene may help to avoid being poisoned.
Byrt says “For targeting the resistance of crops, there’s a mechanism that we could use to plant pests” although she points out that to our genetic engineering allows the pests to evolve resistance by mechanism of HGT.
Caitlin Byrt at the Australian National University in Canberra says, the extent to which HGT occurs in nature is probably underestimated. Through gene transfer event the whiteflies may transmit viruses that cause disease in plants. Virus may take some DNA from a plant and transmit it to the whiteflies and then subsequently assimilated into the insects’ genomes.
We highlighted the evolutionary implications for plant-insect interactions and show the potential of these findings for pest control by silencing the BtPMaT1 gene via genetically transformed tomato plants. These studies provide compelling evidences in a polyphagous arthropod herbivore, which support the idea that a plant-derived gene allows for the detoxification of plant defence metabolites.
So, in the end we concluded that the gene that gets horizontally transferred into whiteflies (BtPMaT1) enables Bemisia tabaci to neutralise the phenolic glycosides, which is a toxic compound for many insect herbivores and silencing of this gene conferred full resistance of tomatoes to these silverleaf whiteflies.
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References:
- Xia, J., Guo, Z., Yang, Z., Han, H., Wang, S., Xu, H., Yang, X., Yang, F., Wu, Q., Xie, W., Zhou, X., Dermauw, W., Turlings, T. C. J., & Zhang, Y. (2021). Whitefly hijacks a plant detoxification gene that neutralizes plant toxins. Cell, 184(7), 1693-1705.e17. https://doi.org/10.1016/j.cell.2021.02.014
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