Researchers first learned that plants can detect carbon dioxide (CO2) concentrations more than 50 years ago. Stomata, or “breathing” pores in leaves, open and close in response to changes in CO2 levels, regulating water evaporation, photosynthesis, and plant growth. More than 90% of the water in plants evaporates through the stomata. Due to the increased impacts of carbon dioxide on the climate and water supplies in a warming world, the regulation of stomatal pore openings by CO2 is essential for deciding how much water plants lose.
The location of the carbon dioxide sensor and an explanation of how it functions in plants, however, have long been a mystery.
Scientists at the University of California, San Diego, recently made a significant advancement in the identification of the long-sought carbon dioxide sensor in Arabidopsis plants and unraveled its functional components. The carbon dioxide sensor mechanism was identified by UC San Diego project scientist Yohei Takahashi, School of Biological Sciences Distinguished Professor Julian Schroeder, and his associates, who also described its genetic, biochemical, physiological, and anticipated structural characteristics. Science Advances published their findings on December 7.
Stomatal pores regulate plant water loss; hence, the sensor is essential for water management and has implications for managing droughts brought on by climate change, wildfires, and agricultural crops.
“A typical plant loses between 200 and 500 water molecules to evaporation through the stomatal holes for each carbon dioxide molecule absorbed,” said Schroeder, Novartis Chair and professor in the Department of Cell and Developmental Biology. The sensor is very important because it can tell when CO2 concentrations rise and how much water a plant loses as a result of absorbing carbon dioxide.
The composition of the sensor was a key discovery from the recent research. The researchers discovered that the sensor functions as a result of two plant proteins cooperating, rather than linking it to a single source or protein. These were recognized as 1) a “high leaf temperature 1” protein kinase known as HT1 and 2) certain MPK4 and MPK12 MAP kinase enzyme members of the mitogen-activated protein kinase family.
The reversible interaction of two proteins, which controls stomatal motions, allows plants to monitor changes in CO2 concentration, according to Takahashi, who is currently working at the Institute of Transformative Biomolecules in Japan. This could give us a new chemical and engineering objective for effective plant water usage and atmospheric CO2 absorption.
The team’s discoveries, which have been documented in a UC San Diego patent, may inspire improvements in how well plants use water as CO2 levels rise.
According to Schroeder, “This conclusion is crucial for crops as well as trees and their deep roots, which can dry out soil if there isn’t rain for an extended length of time, which can lead to wildfires.” “The soil may dry out more gradually if we can use this new knowledge to assist trees in responding better to rises in atmospheric CO2.” Similar to this, crops’ water consumption efficiency could be increased, yielding more crop per drop.
The researchers worked with professor Andrew McCammon from the Department of Chemistry and Biochemistry as well as graduate student Christian Seitz to further investigate their sensor discoveries. Seitz and McCammon developed a thorough model of the complex sensor structure using cutting-edge methods. The model identified regions in which genetic alterations are known to limit a plant capacity to control transpiration in response to carbon dioxide. The updated imaging revealed that the mutants congregate along the interface between 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 research, “This work is a wonderful example of curiosity-driven research that brings together several disciplines—ffrom genetics to modeling to systems biology—aand results in new knowledge with the ability to aid society, in this case by making more robust crops.”
The complete list of authors for the paper is as follows: Yohei Takahashi, Krystal Bosmans, Po-Kai Hsu, Karnelia Paul, Christian Seitz, Dmitry Yarmolinsky, Maija Sierla, Triin Vahisalu, J. Andrew McCammon, Jaakko Kangasjarvi, Li Zhang, Hannes Kollist, Thien Trac, and Julian I. Schroeder.
