One species of whitefly, an aphid-like insect, has incorporated a portion of plant DNA into its genome that protects it from leaf toxins. It seems to be the first known example of so-called horizontal gene transfer between a plant and insect in which the transferred genetic material performs a useful function.

While sequencing the genome of the silverleaf whitefly (Bemisia tabaci), Ted Turlings at the University of Neuchâtel in Switzerland and his colleagues discovered a gene known as BtPMaT1, which is found in plants but never previously seen in insects.

This gene may have an important function in plants. The plants generate toxins to defend themselves from attack by animals. The team suspects that the BtPMaT1 gene may help plants store these toxins in a harmless form so the plants don’t poison themselves.

Similarly, the gene may help the whitefly avoid being poisoned when it eats the plant.

Turlings says the gene transfer event occurred between 35 million and 80 million years ago, when the sweet potato whitefly and other whitefly species that lack the gene split from a common ancestor.

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The gene transfer event may have involved viruses that cause disease in plants and are transmitted via the whiteflies. Some DNA from a plant may have been taken up by a virus, transmitted to the whiteflies and then subsequently assimilated into the insects’ genomes.

“[Some] viruses basically incorporate their own genome into the cells of their hosts,” says Turlings.

The research suggests that the extent to which horizontal gene transfer occurs in nature is probably underestimated, says Caitlin Byrt at the Australian National University in Canberra.

“What this shows is that where there’s a really strong pressure for survival on an organism, it can actually borrow genetic information that helps it do that from other organisms,” says Byrt.

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The researchers demonstrated the function of BtPMaT1 in whiteflies by selectively interfering with the gene using small molecules of RNA.

Disrupting the gene’s function made the whiteflies susceptible to compounds known as phenolic glycosides that are present in tomato plants.

After feeding on tomato plants that had been genetically modified to produce the RNA molecules, all whiteflies subsequently died.

“This demonstrates a mechanism that we could use in engineering crops to basically target plant pests, and target the resistance of crops to plant pests,” says Byrt, although she points out that horizontal gene transfer may then allow the pests to evolve resistance to our genetic engineering.

Journal reference: Cell, DOI: 10.1016/j.cell.2021.02.014