Scientists learned that plants can detect levels of carbon dioxide (CO2) in the air more than 50 years ago. In response to variations in atmospheric carbon dioxide concentration, “breathing” holes in leaves known as stomata open and shut, controlling transpiration, photosynthesis, and plant development. More than 90% of a plant’s water supply is lost to evaporation through its stomata. Due to increased carbon dioxide impacts on climate and water resources in a warming environment, the control of stomatal pore openings by CO2 is vital for deciding how much water plants lose.
However, locating the plant component that detects carbon dioxide and describing how it works has been a long-standing mystery.
Scientists at the University of California, San Diego, used a number of methods and techniques to finally locate and decipher the CO2 sensor in Arabidopsis plants. The CO2 sensor mechanism was discovered by UC San Diego’s Yohei Takahashi, School of Biological Sciences Distinguished Professor Julian Schroeder, and his colleagues, who revealed its genetic, biochemical, physiological, and anticipated structural features. Their findings were released on the 7th of December in Science Advances.
The sensor is important for water management and has implications for climate-induced drought, wildfires, and agricultural crop management due to the stomatal pores’ regulation of plant water loss.
Schroeder, the Novartis Chair and faculty member in the Department of Cell and Developmental Biology, said that for every molecule of carbon dioxide a plant takes in, 200 to 500 molecules of water are lost to evaporation via the stomatal holes. The sensor is crucial because it detects rising CO2 levels and calculates the amount of water a plant loses when CO2 is absorbed.
The new research’s composition of the sensor was a major surprise. Rather than isolating a single protein, the researchers determined that the sensor is activated by the cooperation of two proteins found in plants. The first is a protein kinase called HT1, and the second are two members of the MAP kinase family, MPK4 and MPK12.
Research by Takahashi, currently at Japan’s Institute for Transformative Bio-Molecules, shows that plants may detect shifts in CO2 concentration through the reversible interaction of two proteins that control stomata motions. For more effective plant water utilization and atmospheric CO2 absorption, this may offer a new plant engineering and chemical target.
The research team has submitted a patent application to UC San Diego that might lead to improvements in plant efficiency with regard to water consumption as CO2 levels rise.
This result is crucial for crops but also for trees and their deep roots that can dry up soils if there is no rain for extended periods, which can lead to wildfires. This new knowledge may help the trees to better adapt to rising CO2 levels, resulting in less soil drying up. It is also possible to improve agricultural yields while decreasing water usage via farming practices.
Their sensor finding was subsequently investigated with the help of Christian Seitz, a doctoral student, and Andrew McCammon, a professor in the Department of Chemistry and Biochemistry. Seitz and McCammon used state-of-the-art methods to simulate the complex sensor’s architecture in great detail. Plants’ capacity to control transpiration in response to carbon dioxide levels was predicted to be impaired in several locations where mutations have been found. Recent imaging has revealed that the mutants congregate around the junction of the two sensor proteins, HT1 and MPK.
According to Matthew Buechner, a program director in the U.S. National Science Foundation’s Directorate for Biological Sciences, which funded the study, this work is a great example of curiosity-driven research that draws together many disciplines—from genetics to modeling to systems biology and results in newfound information with the potential to aid society, in this particular instance by making more robust farmland.
Yohei Takahashi, Krystal C. Bosmans, Po-Kai Hsu, Karnelia Paul, Christian Seitz, Chung-Yueh Yeh, Yuh-Shuh Wang, Dmitry Yarmolinsky, Maija Sierla, Triin Vahisalu, J. Andrew McCammon, Jaakko Kangasjärvi, Li Zhang, Hannes Kollist, Thien Trac, Julian I. Schroeder. Stomatal CO 2 /bicarbonate sensor consists of two interacting protein kinases, Raf-like HT1 and non-kinase-activity activity requiring MPK12/MPK4. Science Advances, 2022; 8 (49) DOI: 10.1126/sciadv.abq6161