Plants must maintain balanced levels of potassium to ensure the stability of their cells. To this end, they absorb this nutrient from the soil and store it internally to draw on this reserve in situations of water or nutritional stress. Now, a new study shows the essential role of plant pH in sensing low levels of potassium and activating proteins that recover it from the intracellular reserve.
This discovery will allow us to reduce the use of fertilizers and improve plant performance in periods of drought.
The research was conducted by a team led by Miguel Daniel-Mozo, of the Blas Cabrera Institute of Physical Chemistry (IQF), employee of the Higher Council of Scientific Research (CSIC) in Spain.
Potassium is an essential nutrient for plants, as it regulates their water status and the functioning of the stomata (small pores present in the stems and leaves that allow the exchange of gases and water with the atmosphere). Its survival, in fact, depends on the ability to maintain a stable concentration of potassium (K+) inside it. This balance is essential for cellular stability, so any alteration can lead to cell death.
Plants avidly absorb potassium from the soil and store the excess in an intracellular compartment called a vacuole. It is a sort of gigantic bag that plant cells have inside them to store water, mineral salts or reserve substances, such as potassium. “When potassium in the soil is low, plants recover what is stored in the vacuole. If this process does not provide the necessary levels of potassium, the plants need fertilizers,” explains Armando Albert, researcher at the Blas Cabrera Institute of Physical Chemistry.
Within the plant, this potassium flow is regulated by transport proteins found in cell and vacuolar membranes, which are activated or deactivated depending on their availability. “Our goal is to understand how plant cells detect sufficient levels of potassium to regulate these transporters in the vacuole,” explains Albert.
The exchange of hydrogen ions (H+), the concentration of which determines the pH of the plant, with potassium ions helps transport nutrients across membranes. That is, each potassium ion that enters the cytosol (aqueous substance surrounding the organelles and nucleus of cells) releases a hydrogen ion outside the cell. At the same time, each potassium ion stored in the vacuole releases a hydrogen ion into the cytosol. When there are low levels of potassium in the soil, vacuolar storage shuts down to prevent potassium depletion in the cytosol and reduce the accumulation of cytosolic hydrogen ions, i.e., pH.
Calcium, the second ionic messenger
In plants and animals, many ion balance processes are regulated indirectly by calcium (Ca²⁺), which acts as a second messenger. This function is due to specific proteins that regulate the activity of transporters in cell membranes by sensing changes in calcium levels.
“This work reveals key aspects of the regulation of potassium homeostasis in plants and demonstrates that it is pH, and not calcium, where the key information to activate the response to nutrient starvation is stored,” says José Manuel Pardo , researcher at the Institute of Plant Biochemistry and Photosynthesis (IBVF, joint center of the CSIC and the University of Seville). The results show the discovery of a calcium-binding protein, called CML18, which, unlike the vast majority of this large family of proteins, acts as a molecular sensor of hydrogen ion levels. “CML18 acts like a light switch, when the pH drops (there are more free H+ ions), CML18 interacts with hydrogen ions, at that moment it blocks the function of potassium transporters, interrupting the flow of potassium to the vacuole,” he explains Albert. “This demonstrates for the first time that it is pH, and not calcium as previously thought, that links potassium availability with transporter actions in the vacuolar membrane,” says Pardo.
The study results, together with previous research, show how pH levels control potassium transport in plants and provide fundamental knowledge for developing new biotechnological tools and improving plant performance under abiotic stress.
Alterations in potassium levels can cause plant cell death. (Photo: Amazings/NCYT)
Research to improve crop yields
This study, a collaboration between researchers Pardo and Albert, builds bridges between plant physiology and structural biology to provide a comprehensive view of the functioning of ion transporters under various environmental conditions, which is very promising for agricultural innovation.
These results are linked to a line of research, developed by Armando Albert, which seeks to understand how plants adapt to harsh environments. Proof of this is the method patented by the CSIC to develop drugs that allow mechanisms to be activated at will to improve the resistance of cultivated plants to the effects of drought.
These investigations are complemented by the work of José Manuel Pardo, focused on understanding the mechanisms that regulate the absorption and transport of nutrients under stress conditions. His research on potassium and other essential ions influences the advancement of sustainable agricultural practices aimed at improving crop resilience.
“The massive use of fertilizers brings with it contamination of water and soil. Furthermore, when potassium flows into aquifers and rivers that flow into inland seas, such as the Mar Menor or the Albufera de Valencia, it contributes to eutrophication, favoring the growth of algae that consume oxygen and damage the life of fish that they live there. there,” explains Albert.
“All this biophysical knowledge offers plant breeders valuable tools to increase plant resistance to salinity and drought stress, and thus minimize dependence on fertilizers,” the researchers conclude.
The study is titled “Vacuolar K+/H+ Exchangers and Calmodulin-Like CML18 Constitute a pH-Sensing Module Regulating K+ State in Arabidopsis.” And it was published in the academic journal Science Advances. (Source: CSIC)
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How do pH levels affect potassium availability in plants according to recent research findings?
Interview between Time.news Editor and Miguel Daniel-Mozo, Lead Researcher
Time.news Editor: Welcome, Miguel! We’re thrilled to have you here today to discuss your fascinating research on the role of pH in potassium sensing within plants. Let’s dive right in. Why is potassium so essential for plant health?
Miguel Daniel-Mozo: Thank you for having me! Potassium is crucial for plants because it directly affects their water regulation and the functionality of their stomata—the tiny openings that facilitate gas exchange with the atmosphere. A stable concentration of potassium inside plant cells is vital; any disruption can result in cell death.
Time.news Editor: That’s intriguing! I understand that plants store potassium in a vacuole. Could you explain how this storage system works and its significance?
Miguel Daniel-Mozo: Certainly! The vacuole acts as a storage unit within the plant cell, holding excess potassium along with water and mineral salts. When potassium levels in the soil drop, plants rely on this internal reserve. If the vacuole does not provide enough potassium, plants may require fertilizers, which can lead to increased agricultural input costs and environmental concerns.
Time.news Editor: Your study highlights the interaction between pH levels and potassium availability. Could you elaborate on how pH plays a role in this process?
Miguel Daniel-Mozo: Absolutely. The exchange of hydrogen ions (H+) and potassium ions is key to transporting nutrients across membranes. When potassium levels are low, vacuolar storage is limited to preserve potassium in the cytosol while managing hydrogen ion accumulation. Our research reveals that it is the pH level, influenced by these hydrogen ions, that activates or inhibits the transport proteins responsible for potassium management.
Time.news Editor: So, if I understand correctly, pH acts as a signal for potassium deficiency. What makes this discovery groundbreaking for agricultural practices?
Miguel Daniel-Mozo: This is a significant shift in our understanding. Previously, calcium was thought to be the primary messenger in potassium regulation. Our findings indicate that pH is the key factor in activating responses to nutrient starvation. This knowledge allows for the development of biotechnological tools aimed at improving plant resilience during droughts and reducing reliance on fertilizers, which is excellent for both the environment and agricultural productivity.
Time.news Editor: Fascinating! I see you also mention a specific calcium-binding protein, CML18. How does it contribute to this regulatory process?
Miguel Daniel-Mozo: CML18 acts as a molecular sensor for hydrogen ions. When the pH drops—indicating more free H+ ions—CML18 interacts with these ions and effectively signals the potassium transporters to halt potassium flow to the vacuole. This discovery underscores the importance of understanding pH deregulation in potassium homeostasis within plants.
Time.news Editor: It sounds like your research could lead to innovative strategies for crop management. What are the next steps for your team?
Miguel Daniel-Mozo: We’re focusing on validating our findings through further experiments, aiming to create more robust plant varieties that can thrive with less potassium, particularly during difficult climatic conditions. The ultimate goal is to design crops that can maintain high yields with reduced fertilizer use.
Time.news Editor: That’s an ambitious and essential goal! Before we wrap up, what message would you like to convey to our readers regarding the importance of this research?
Miguel Daniel-Mozo: I would emphasize that understanding plant nutrient management and stress responses is critical as we face climate change and the pressing need for sustainable agriculture. Each breakthrough in our understanding can pave the way for practical applications that ensure food security while protecting our environment.
Time.news Editor: Thank you, Miguel, for sharing your insights today. Your work undeniably has the potential to revolutionize agricultural methodologies and plant science.
Miguel Daniel-Mozo: Thank you for the opportunity to discuss our research! I look forward to seeing how it can impact future agricultural practices.