Arabidopsis thaliana (Thale Cress) | Photo Credit: Getty Images

Animals often use highly specific signals to warn their herd about approaching predators. Surprisingly, a similar behaviour is also observed in plants. Shedding more light on this phenomenon, Tokyo University of Science researchers have discovered one such mechanism. Using Arabidopsis thaliana as a model system, the researchers have shown that herbivore-damaged plants give off volatile chemical ‘scents’ that trigger epigenetic modifications in the defence genes of neighbouring plants. These genes subsequently trigger anti-herbivore defence systems.

Prior studies have shown that when grown near mint plants, soybean and field mustard (Brassica rapa) plants display heightened defence properties against herbivore pests by activating defence genes in their leaves, as a result of "eavesdropping" on mint volatiles. Put simply, if mint leaves get damaged after a herbivore attack, the plants in their immediate vicinity respond by activating their anti-herbivore defence systems in response to the chemical signals released by the damaged mint plant. To understand this mechanism better, a team led by Tokyo University of Science, studied these responses in Arabidopsis thaliana, a model plant used widely in biological studies (Plant Physiology).

First, researchers exposed the plants to beta-ocimene, a volatile organic compound often released by plants in response to attacks by herbivores like Spodoptera litura. Next, the researchers tried to determine the exact mechanism of action of volatile-chemical-activated plant defence. They found that the volatile chemicals released by the damaged plants enhanced histone acetylation and the expression of defence gene regulators. The team found a specific set of enzymes were responsible for the induction and maintenance of the anti-herbivore properties, a press release says.

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