Stomata Study Provides New Insights in Plant Response to High Temperatures and Drought

We are increasingly confronted with the impacts of climate change, with failed harvests being only one example. Addressing these challenges requires multifaceted approaches, including making plants more resilient.

An international research team led by researchers at VIB-UGent has unraveled how the opening and closing of stomata—tiny pores on leaves—is regulated in response to high temperatures and drought. These new insights, published in Nature Plants, pave the way for developing climate change-ready crops.

Global climate change affects more and more people, with extreme weather conditions steadily becoming the norm. Beyond the immediate impacts like floods and severe droughts, it also significantly affects our natural ecosystems and crops, making it challenging in many regions to grow the food we rely on or to identify the right climate-adapted plants.

Prof. Ive De Smet (VIB-UGent Center for Plant Systems Biology) said, "For years our research has focused on the impact of extreme weather conditions on plants. The molecular insights we gain can lead to solutions to enhance plant resilience. In essence, we learn from the natural mechanisms that plants themselves deploy.

"For instance, how stomata on leaves play a crucial role in the plant's interaction with the environment. This makes insights into their activation mechanisms highly valuable."

Conflicting responses in stomata, the 'sweat glands' of plants

Plants respond to changing environmental conditions among others via opening or closing little pores in their epidermis. These stomata regulate gas and water vapor exchange with the environment, function as entry points for pathogens, and are pivotal in shielding plants against abiotic stress.

When temperatures are high, the stomata open to cool down. In dry conditions, they close to prevent water loss. So, when conditions are dry and hot, this may evoke conflicting—and therefore less efficient—stomatal responses. The VIB-UGent team of Prof. Ive De Smet joined forces with research teams from the universities of Utrecht (NL), Valencia (Spain), and Wageningen (NL) and set out to unravel the underlying cellular mechanisms.

A well-regulated signaling axis

Dr. Xiangyu Xu (VIB-UGent), first author of the study said, "Opening and closing of stomata are rapid responses that require switch-like signaling mechanisms. We know that phosphorylation-encoded switches within protein networks are reversible and tend to be faster than genetic switches. That's why we studied the role of kinase-mediated phosphorylation relays in stomata opening and closing."

Xu and his colleagues succeeded in identifying and characterizing a novel phosphorylation-dependent signaling axis that regulates stomatal aperture under high temperature and/or drought conditions. They demonstrated that TOT3, a high temperature-associated kinase, controls stomatal opening under high-temperature conditions, and that OST1, which regulates stomatal closure during drought stress, directly inactivates TOT3 through phosphorylation.