35 million years ago, a self-defence gene was passed from a plant to a fly, which now allows it to be a pest immune to natural pesticides. This passing of DNA not to offspring, but to environmental partners, is the first case of horizontal gene transfer observed between a plant and a complex animal, and it works.

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Just over 35 million years ago, a decisive and unusual genetic hijacking took place. Somehow, a self-defence gene from a plant passed into the cellular interior of the whitefly. Once inside, it stayed there and was inherited from there until it spread to all of them. Since then, the whitefly uses its function as a shield and is able to resist the attacks that many plants launch against all kinds of insects. Today, by virtue of that gene, the whitefly is one of the world’s most destructive pests.

The evolutionary leap can be understood with the example of Lynn Margulis: “It’s a bit like going into a swimming pool, going in with brown eyes and coming out with blue eyes, just because you’ve swallowed water”.

Hijacking is a case of what is known in the jargon as horizontal gene transfer. This involves the passing of genetic material not to offspring, as happens in the traditional, vertical way, but to environmental partners.

In some cases, the result is an almost immediate evolutionary leap and can be understood with the comparison made by microbiologist Lynn Margulis: “It’s a bit like going into a swimming pool, going in with brown eyes and coming out with blue eyes, just because you’ve swallowed water”. It is very common among microorganisms, but much rarer in cells such as those of plants or animals.

This is the first time such a jump with such an obvious function has been described between a plant and an animal. The inaugural study is published in the journal Cell and, in the words of Charles Davis, an evolutionary biologist at Harvard University, “it’s really cool”.