How could a gene “jump” from a plant to an insect?

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This is about horizontal gene transfer, an evolutionary mechanism widely understood by science. Usually, the latter is observed between bacteria or between plants, but recently, researchers have witnessed a great first. Indeed, a gene has “jumped” from a plant to an insect.

An unknown gene in insects

We already mentioned it in 2016 for its strong presence in the state of Florida (United States): the tobacco whitefly (Bemisia tabaci). Affectionate the plantations of tobacco, cotton, melons, tomatoes or even beans, this white fly is a real plague. At the time, the US authorities were concerned about a particular phenomenon: its resistance to pesticides.

Researchers from the Chinese Academy of Agricultural Sciences conducted a study published in the journal Cell April 1, 2021. The goal? Understanding how the tobacco whitefly is able to escape the defense mechanism plants in order to transmit many pathogenic viruses to them. However, their discovery is surprising and constitutes a great first.

Scientists first sequenced the genome of the tobacco whitefly. They found there an unknown gene until today: BtPMaT1. However, this gene codes for a protein whose function is to neutralize phenolic glycosides, metabolites toxic to herbivorous insects. Surprised, the researchers tried to understand where this gene, never before observed in an insect, could come from. Chinese scientists eventually found genes similar to BtPMaT1, but only in plants, fungi as well as bacteria.

Credits: CSIRO / Wikimedia Commons

GMO plants targeting the tobacco whitefly?

Ted Turlings, ecologist at the University of Neuchâtel (Switzerland), also took part in the work. The interested party mentioned in an article published in Nature the probability that a virus present in a plant has integrated the gene into its genome, and then that a whitefly has eaten that infected plant. Then the virus transferred the gene to the insect’s genome. This gene transfer is said to have occurred between 35 and 80 million years ago when the tobacco whitefly is separated from other whiteflies not having the famous gene. For the study leaders, this is the very first horizontal gene transfer observed between a plant and an insect.

In a way, the tobacco whitefly appropriated the combat strategy of his adversaries to resist it. In order to test their hypothesis, the scientists turned off the gene by genetically modifying tomato plants. The goal ? Make these plants produce a small piece of RNA interfering with the gene. When whiteflies fed on these plants, their mortality was higher. This suggests that it is possible to use GM plants. targeting this white fly and why not, other plant pests.

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