Plants have evolved to adapt to their natural habitat, rather than fleeing unfavorable conditions. One of the dynamic factors in the environment that significantly impacts plant life is the pH of the soil. Soil pH profoundly impacts plant fitness by regulating nutrient availability and the levels of toxic ions. Acidic soils elevate the concentrations of certain essential minerals such as iron and manganese, while decreasing the levels of others such as nitrate, and also pose challenges to the plants due to high aluminum ion content. Conversely, alkaline soils, often rich in bicarbonate, counteract root-mediated acidification and thus growth, yet limit the availability of crucial nutrients like iron and phosphorus. Soil pH impacts plant health and growth diversely in acidic and alkaline conditions, with certain species being specifically adapted to certain pH ranges. Low pH promotes growth by relaxing cell walls, aiding cell elongation. However, excessive growth can be detrimental in acid soils due to excess levels of ammonium or aluminum ions. By contrast, alkaline pH impedes growth by limiting cell wall flexibility. Slow growth may benefit plants in alkaline soils by preventing nutrient depletion, which is challenging due to limited mineral mobility. Therefore, adaptation to varying environmental pH is crucial for optimizing plant fitness and performance.
Using the reference plant Arabidopsis thaliana, Wolfgang Schmidt, and his colleague Dharmesh Jain, both from Academia Sinica and National Chung-Hsing University, conducted a detailed study on how plants respond to rapid changes in the pH of their environment. Their aim was to investigate the mechanisms underlying the recalibration of intracellular pH when exposed to acidic or alkaline conditions and to assess how these conditions affect plant fitness and growth. Arabidopsis plants were grown under sterile conditions on media with either alkaline or acidic pH, followed by subsequent morphological as well as proteomic and phosphoproteomic analysis after specific treatment periods. Their work is published in the renowned journal Molecular & Cellular Proteomics.
The analysis revealed that “growth of (mildly calcifuge) Arabidopsis plants was optimal at moderately acidic pH.” Alkaline soil significantly reduced plant fitness and shoot growth but had minimal impact on root length, while growth in strongly acidic soil stunted root growth without affecting shoot growth. Surprisingly, while soil pH strongly affects nutrient availability, the study found only subtle changes in mineral nutrient uptake and homeostasis.
Conspicuously, the analysis uncovered previously unknown pH-dependent protein phosphorylation sites. “Our study shows that changes in pHe lead to extensive alterations in protein phosphorylation, indicating that a large part of the acclimation to environmental pH depends on post-translational signaling events,” concluded the authors. These alterations affected processes such as proton pumping and ion transport across membranes, influencing nutrient uptake, root growth, plant fitness and the control of internal pH. These adjustments, especially in phosphopeptides, suggest intense signaling in response to short-term pH changes. Mutant plants lacking specific transporters exhibited altered responses to changes in pH, highlighting the importance of these proteins in the regulation of pH inside and outside of the cell. Central themes in this adaptation include balancing growth and defense and the regulation of proton transport across cell membranes. In conclusion, the research sheds light on how plants, exemplified by Arabidopsis thaliana, navigate the intricate dance of soil pH for their survival. Their findings underscore the pivotal role of pH in shaping plant growth and fitness, revealing how plants adapt to acidic and alkaline environments. From altered protein phosphorylation to nuanced shifts in nutrient uptake, their study uncovers the sophisticated mechanisms by which plants sense and respond to changes in soil pH. By understanding these processes, we gain valuable insights into how plants thrive in diverse environmental conditions, offering potential avenues for enhancing crop resilience and productivity in the face of changing climates.
JOURNAL REFERENCE
Dharmesh Jain, Wolfgang Schmidt. “Protein Phosphorylation Orchestrates Acclimations of Arabidopsis Plants to Environmental pH.” Molecular & Cellular Proteomics, 2024.
DOI: https://doi.org/10.1016/j.mcpro.2023.100685.
ABOUT THE AUTHORS
Wolfgang Schmidt is a plant biologist with a keen interest in how plants perceive and respond to environmental signals. In particular, research in his laboratory is interested how plants acquire essential minerals that appear to play ‘hard to get’ due to unfavourable soil pH. Originally from Berlin, Germany, Wolfgang is working since 2005 as a Research Fellow at Academia Sinica (Taipei) and as an adjunct professor at National Chung Hsing University (Tainan) in the island of Taiwan.
Dharmesh Jain, originating from the picturesque town Barwaha in India, is currently pursuing his PhD in Biotechnology in the Schmidt lab within the frame of the Taiwan International Graduate Program, in partnership with the National Chung Hsing University. His doctoral investigation centers on unraveling the effects of pH on plant performance and the plasticity of plant development amidst challenging conditions.
