Gene transfer from plant to insect: genetic predators on the prowl

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Tobacco whiteflies are also called whiteflies

Photo: Jack Clark / imago images

The tobacco moth scale barely gets over a millimeter in size, but farmers around the world can't afford to overlook the creature.

Because the species, also known as whitefly because of its appearance, is one of the most important pests of all.

She sucks the juice out of plants with her mouthparts, tomatoes, peppers and cucumbers are on her menu in greenhouses.

In tropical regions it also prefers to attack sweet potato or cassava plants.

And it doesn't even stop at popular flowers such as begonias, hibiscus or the poinsettia.

In addition,

Bemisia tabaci

transmits viruses to plants that can make them sick.

The insects are so adaptable that they have spread almost all over the world.

Researchers have now partially discovered the secret of the animals' success and have discovered the strategy with which they also consume defensive victims.

Plants, for their part, also develop strategies to keep pests at bay.

These include toxins, for example.

A team led by Youjun Zhang from the Chinese Academy of Agricultural Sciences in Beijing has now discovered why tobacco whiteflies are immune to a certain type of these antibodies: They have the gene that is responsible in plants for resistance to their own toxins from the plants taken over.

Gene hijacking in the plant kingdom

As the researchers were able to show in a study in the specialist magazine »Cell«, the whitefly carries the gene BtPMaT1, which does not have to come from its own genome, but rather from the genome of plants due to its structure.

The animals have "hijacked" it to a certain extent, as the researchers write in the title of their study.

BtPMaT1 enables them to neutralize so-called phenol glycosides.

These are substances that many plants use to ward off insects and that are poisonous for many species - but not for the tobacco whitefly.

The gene probably passed into the louse's genetic material many millions of years ago through an evolutionary process, possibly through a virus.

It has undergone what is known as a horizontal gene transfer.

A hereditary trait is not transferred from one generation to the next through a reproductive process, but from one organism to another.

That rarely happens in nature.

Only a few examples are known to date, for example in the case of types of bacteria.

For example, a few years ago researchers found evidence that a species of beetle had a gene for a digestive enzyme from a bacterium.

Humans, too, have probably taken over a tiny part of their genetic makeup through horizontal gene transfer from microorganisms.

The study results in an interesting approach for the tobacco moth scale: The researchers developed a tomato plant that, through genetic modification, was able to block the function of the BtPMaT1 gene in the tobacco moth scale.

If the animals ate the tomato plant, the protective effect of BtPMaT1 was switched off and the scale insects died.

In this way, the researchers succeeded in confirming their hypothesis in the experiment.

In addition, such an approach offers an effective way of combating the pests, since they are already resistant to some insecticides.

joe