Engineering compounds to protect crops from drought

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Every year, more crops are lost to excessive heat and drought worldwide. Researchers have strived to find an affordable and safe protection method. Ghent University Professor Chris Stevens has brought that goal within reach. His lab has synthesized a new compound that has the ability to make plant stomata close, preventing water evaporation. He has joined forces with the group of Professor Danny Geelen, who handles the functional tests and unravels the pathways involved. The UK-based company Plant Impact has joined the project and supports the creation of a market-ready product.

Currently, few methods exist to protect plants against drought. The hormone abscisic acid (ABA) is known to close the stomata, but is expensive to produce and not sufficiently stable. Its practical value is limited to niche applications, such as in viticulture.

Applying your expertise in other domains

In a recent study, American researchers have described the ability of the compound pyrabactin to make plant stomata close. The molecule was patented, but researchers have indicated that a practical application is highly unlikely. While the reason was not disclosed, assuming that toxicity might be an issue is not far-fetched. “The molecule contains a sulfonamide group that will form a strong acid upon hydrolysis in the cells, which is lethal to the plant,” Stevens explains. “When I read the pyrabactin publication, I saw an opportunity to apply our expertise in phosphorous chemistry,” Stevens states. “From standard, readily available precursors, we were able to synthesize a phosphonamide pyrabactin analogue, which is not toxic to cells. We then created a library of analogues with varying functional groups on different positions to optimize its activity.”

Finding out what works, and why

This library was screened for the ability to close the stomata in the In Vitro Biology and Horticulture lab of Professor Geelen. Some of the analogues proved to be active, whereas others failed. Based on these insights, new modifications could be introduced more rationally in newer libraries. “Surprisingly, some analogues had the opposite effect. They induced the stomata to open,” Stevens says. “This indicates a very delicate regulation, driven by multiple receptors.” This process is being studied in Professor Geelen’s lab. A better insight into the pathway involved will allow engineering the analogue even further. The existing pyrabactin patent does not pose a threat to Ghent University’s phosphonamide analogues. “It’s a completely different class of molecules, which means it isn’t self-evident that it would show the same activity as pyrabactin,” Stevens states. This allowed the researchers to take out a patent on the analogues themselves.

Joining forces for commercialization

While the activity is demonstrated in early tests, there is still a long way to go before the product will reach the market. Nevertheless, the company Plant Impact has already shown great interest in the commercialization of the product. A deal was prepared by Ghent University’s tech transfer office, and Plant Impact supports further development. The initial hurdle was ruling out ecotoxicity, which was achieved in initial experiments. Further experiments are ongoing to rule out any type of toxicity. In parallel, additional tests are being performed on plants to characterize the activity. An important parameter is the sustainability of the effect. “Having a product that protects plants against dehydration is great, but it has no use when the effect transpires after just a few hours,” Steven explains. In addition to further engineering the molecular structure, product formulation is essential to achieve this. Finally, the lab has started scaling up the production process and is moving to continuous production to ensure that production does not become a bottleneck when the product is ready to go to the market. This case is one of the results of Ghent University’s conscious effort to stimulate green chemistry. It has established a cluster of researchers within the university that is active in this field. Furthermore, international partnerships in the domain are promoted, as well. Researchers are highly willing to collaborate and move the field forward, leading to a sustainable chemistry that creates added-value products with green processes.