Certain chemicals can activate the innate defence mechanisms of plants, and researchers at the Tokyo University of Science are working on ways to use such chemicals as alternatives to harmful agricultural pesticides.
These researchers have found that a compound derived from menthol can boost the expression of defence-related genes in soybeans, corn, peas, and other crop species. This finding may pave the way to green agricultural technologies that shield crops from pests while minimizing damage to the environment.
Professor Gen-ichiro Arimura of the Tokyo University of Science, Japan, notes that “the development of agricultural technology to date has been largely reliant on the use of pesticides and chemical fertilizers, which has resulted in
environmental pollution and the destruction of ecosystems.”
As a greener alternative to pesticides, terpenoid signalling molecules may help farmers continue their production of vital foodstuffs while lessening the associated environmental costs.
In pursuit of this goal, Prof. Arimura and his colleagues chose to investigate the terpenoid compound menthol, which is derived from mint leaves and can activate plant immune
systems. The aim of this project, which the researchers describe in an article recently published in the journal Plant Molecular Biology, was to develop compounds that are structurally similar to menthol but improve upon menthol’s ability to activate
plant immune systems.
The researchers therefore experimented with chemically modifying menthol by attaching amino acids, which are a structurally diverse set of compounds that living cells use to construct proteins. In total, the researchers synthesized six different menthol derivatives with attached amino acids.
The researchers then tested the resulting menthol derivatives to see whether the modified compounds could outperform unmodified menthol at activating plant defense mechanisms. To do this, they treated soybean leaves with either menthol or one of the six menthol derivatives to see which of the derivatives, if any, could outclass menthol itself at boosting the expression levels of two defense-related soybean genes after 24 hours of exposure. The found that only one of the modified compounds bested menthol, and this compound
is called valine menthyl ester, or “ment-Val” for short.
The researchers found that spraying soybean leaves once with a ment-Val solution boosted expression of the defence-related genes for three days, and second spraying on the fourth day worked to boost the expression of those genes again.
These findings suggest that ment-Val could provide sustainable pest control for farmers growing soybeans. Further experiments showed that ment-Val also increased the expression of defence-related genes in other crops, including peas, tobacco, lettuce, and corn. Ment-Val also proved to be quite stable under various conditions, which suggests that farmers would probably not lose the compound to degradation during storage.
Overall, these results suggest that ment-Val could be extremely useful as an alternative to the chemical pesticides that so many farmers rely on. Prof. Arimura notes that spraying ment-Val may be an effective way “to reduce pest damage to soybeans and other crops.”
He has applied for a patent on ment-Val’s use as a crop protection agent, and he predicts that the commercialization of ment-Val “will generate billions of yen in economic benefits through its usage by companies operating in the fields of horticulture and agriculture.”
He also notes that ment-Val’s anti-inflammatory properties could make it useful for human medicine.