To warn their herd of incoming predators, animals often employ extremely specialized signals. Surprisingly, plants exhibit comparable behaviors as well. Tokyo University of Science researchers have uncovered one such mechanism that sheds further light on this phenomena.
The researchers used Arabidopsis thaliana as a model system to show that herbivore-damaged plants emit volatile chemical “scents” that cause epigenetic changes in surrounding plants’ defense genes. Anti-herbivore defense systems are triggered as a result of these genes.
Many species of animals in the wild, particularly those with known predators, use a range of tactics to warn each other of impending hazards, ranging from scent to sound. We now have cause to suspect that plants, too, can raise an alert when they are threatened by an attack, due to many studies on the subject.
Previous research has demonstrated that when planted near mint plants, soybean and field mustard (Brassica rapa) plants activate defense genes in their leaves, increasing their defense qualities against herbivore pests as a result of “eavesdropping” on mint volatiles.
Simply said, when mint leaves are damaged by herbivores, nearby plants respond by activating their anti-herbivore defense systems in response to the chemical signals sent by the wounded mint plant.
A group of researchers from various Japanese research institutes, including Tokyo University of Science, analyzed these reactions in Arabidopsis thaliana, a model plant used widely in biological investigations, to better understand this mechanism.
“Surrounding undamaged plants exposed to odors emitted from plants eaten by pests can develop resistance to the pests. Although the induction of the expression of defense genes in odor-responsive plants is key to this resistance, the precise molecular mechanisms for turning the induced state on or off have not been understood. In this study, we hypothesized that histone acetylation, or the so-called epigenetic regulation, is involved in the phenomenon of resistance development,” explains Dr. Gen-ichiro Arimura, Professor at the Tokyo University of Science and one of the authors of the study.
Their findings have recently been published in the journal Plant Physiology.
Surrounding undamaged plants exposed to odors emitted from plants eaten by pests can develop resistance to the pests. Although the induction of the expression of defense genes in odor-responsive plants is key to this resistance, the precise molecular mechanisms for turning the induced state on or off have not been understood. In this study, we hypothesized that histone acetylation, or the so-called epigenetic regulation, is involved in the phenomenon of resistance development.
Dr. Gen-ichiro Arimura
The plants were first exposed to β-ocimene, a volatile organic chemical produced by plants in response to herbivore attacks such as Spodoptera litura. The researchers then tried to figure out exactly how volatile-chemical-activated plant defense works.
Defense features were produced in Arabidopsis leaves, probably via “epigenetic” pathways, which relate to gene regulation that happens as a result of external environmental stimuli.
The ethylene response factor genes “ERF8” and “ERF104” were induced by the volatile compounds emitted by the damaged plants, which increased histone acetylation and the expression of defensive gene regulators.
The researchers discovered that a specific collection of histone acetyltransferase enzymes (HAC1, HAC5, and HAM1) were responsible for the anti-herbivore characteristics’ induction and maintenance. The researchers are ecstatic to have discovered the importance of epigenetics in plant defense.
They believe that plant communication via volatile chemicals (also known as the “talking plants” phenomenon) could be applied to organic farming systems. This could help plants become more resistant to pests and lessen our reliance on chemicals.
“The effective use of plants’ natural survival strategies in production systems will bring us closer to the realization of a sustainable society that simultaneously solves environmental and food problems,” concludes Dr. Arimura.
