Jan. 17, 2012, Neuchâtel, Switzerland — A research team at the University of Neuchâtel has shown for the first time that stimulating a plant’s natural defences also increases the capacity for disease resistance in its descendants.
The substances that were used to stimulate these defences are harmless to the environment and are simple to apply, which are desirable traits for agricultural tools. Carried out within the framework of the National Centre of Competence in Research (NCCR) Plant Survival, this study was recently published in the journal Plant Physiology.
“We apply treatments to plants in order to increase their natural ability to stimulate their own defences against pathogenic organisms, a well known method among specialists called priming,” explains Brigitte Mauch-Mani, research director in the Laboratory of cell and molecular biology at the University of Neuchâtel.
“These treatments do not act directly on the genes, but on molecules situated close to the DNA. It is an epigenetic phenomenon, which means that changes in genome function are heritable. They occur without manipulating the plant’s DNA and then are passed on to their progeny.”
The experiments were carried out using Arabidopsis thaliana, a model plant used in research. The researchers compared the plants’ reactions when their defence mechanisms had been primed with either β-amino-butyric acid (BABA) or with an avirulent isolate of bacteria from the genus Pseudomonas.
The control plants were simply treated with tap water.
Compared to the progeny of control plants, the descendants of primed plants defended themselves faster and better against a vector of mildew and a pathogenic bacterium. Furthermore, the researchers observed that these plants showed a more rapid and higher accumulation of transcripts (i.e., copies of genetic information) of defence-related genes.
Similar research carried out by Jurriaan Ton, a former post-doc of the NCCR Plant Survival, and his group at the University of Sheffield (U.K.) arrived at the same conclusion.
This mechanism is also effective against herbivorous insects. In the same edition of the journal Plant Physiology, Sergio Rasmann, a former member of the NCCR Plant Survival, observed during his post-doc at Cornell University (U.S.) that priming of defence responses in Arabidopsis against caterpillars persisted during two generations.
In this case, the resistance was stimulated using methyl jasmonate or by exposing the parent plants to insect feeding. The results showed that caterpillars feeding on Arabidopsis plants whose parents had been primed developed much slower and saw their sized reduced by 50 per cent.
“Applying this method could help to reduce pesticide use,” says Sergio Rasmann, who is currently working at the University of Lausanne.
“By reducing the amount of pesticides applied in fields, plants end up being more exposed to insect wounds. Paradoxically, these wounds reinforce the plant’s resistance, which will then be transmitted to the next generation. This is an interesting strategy that could benefit various plants since similar results were also obtained in tomato plants.”
This natural mechanism helps plants to adapt to a hostile environment, notes Brigitte Mauch-Mani.
“However, the phenomenon is reversible. If the second generation is not subjected to a priming treatment, then resistance will be strongly diminished in the descendants and will eventually return to its normal state in future generations.”
All of these characteristics make the application of defence elicitors a very promising strategy for sustainable agriculture that respects the environment.