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Tomato plants protect themselves against herbivorous insects with the help of tiny hairs. A team of biologists from the University of Amsterdam (UvA), supervised by dr. Rob Schuurink, in collaboration with Rijk Zwaan, has discovered that a protein called MYC1 is essential for the formation of a certain type of these hairs. In addition, this protein plays a role in the production of anti-insect compounds. Their findings were published on in The Plant Cell.

The hairs (trichomes) on a tomato plant, made visible with a scanning electron microscope .
Tomato hairs. Photo: UvA

If you have ever looked carefully at the leaves or stem of a plant, you have probably noticed that they are covered with tiny hairs. These hairs - called trichomes - protect the plant against herbivorous insects. They form a physical barrier and, additionally, some trichomes also produce volatile anti-insect compounds that are either toxic to insects or will attract their enemies. Tomato plants have such anti-insect compound producing hairs. Since tomato is economically an important crop, biologists would like to know more about how this defense system is regulated.

Regulatory protein

A team led by dr. Rob Schuurink from the Swammerdam Institute for Life Sciences at the University of Amsterdam was interested in a protein called MYC1. These researchers suspected that this protein plays an important role in the formation of a specific type of trichomes, called type VI glandular trichomes. They decided to test this by growing tomato plants that could not make the protein, and plants having lower concentrations of it. To do so they collaborated with the vegetable breeding company Rijk Zwaan.

No hairs

The hypothesis of Schuurink and his colleagues turned out to be correct: tomato plants without MYC1 are not able to make hairs of the type the biologists were interested in. When the protein was present in the plant, but in lower concentrations than normal, the hairs were smaller. These smaller hairs on the leaves produced fewer anti-insect compounds, but, in contrast, the smaller hairs on the stem produced more of some of these volatile compounds than they usually do.

Dual role

'These data show that the protein MYC1 is important for this defense system of tomato plants, and has a dual role," says Schuurink. 'The protein is essential for the production of these type VI glandular trichomes, and it also regulates the amount of anti-insect compounds they produce.'

The next step is to see if the reverse is also true. Schuurink: 'What we are interested in right now is whether increasing the concentration of MYC1 leads to more trichomes and a higher production of anti-insect compounds. So the plant is better protected against harmful insects.’ If this proves to be the case, the discovery will be of great value.