Chemical mines

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Chemical mines

Lots of our crops miss defence mechanisms against insects. A defence that is precent in their wild relatives. And to be honest, for a long time a good insect defence mechanism was not a top priority for crops. As pesticides had taken over this job. But now farmers put pesticides aside, it is time for crops to get back their defence mechanisms. This it turns out is not as easy as it seems. Dutch researchers show that a defence is more than just producing toxic chemicals.

When you look closely you see that lots of plants are hairy. Their stem and leaves are covered with tiny hairs, trichomes. These trichomes are forming an obstacle course for insects. With the added challenge that some trichomes are kitted with chemical mines. Like the stinging hairs on stinging nettles. Ideal for scaring or killing insects. But for a lot of our crops those chemical mines hardly filled at all.

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The defence is a strong as its weakest link

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To investigate if it was possible for tomato plants to obtain back their chemical mines, the researchers crossed tomato plants with their wild relatives. To their big surprise produced this prodigy scarcely more insect killing toxins than their domesticated parent. And a lot less than expected.

This it turned out was not due to the lack of essential genes. Even in the presence of these genes hardly any insect killing toxin was seen. Just as that the low production was not explained by the number of chemical mines carrying trichomes. So did the researchers also observe leaves with relatively few mine carrying trichomes that produced lots of toxin. This suggests that an up till now unknown regulator regulates the amount of insect killing toxin a plant is making.

The big question is now: who is this regulator? When this is known, then breeders can select on all the essential components of the defence mechanism and give crops their defence back. Just elsewhere, a plants defence is as strong as its weakest link.

Literature

Kortbeek RWJ, Galland MD, Muras A, Therezan R, Maia S, Haring MA, Schuurink RC and Bleeker PM (2023) Genetic and physiological requirements for high-level sesquiterpene-production in tomato glandular trichomes. Front. Plant Sci. 14:1139274. https://doi.org/10.3389/fpls.2023.1139274