Stomata are distributed across the surfaces of leaves and are controlled by pairs of specialised guard cells. When these cells take up ions and water, they become more pressurised and bend apart, opening the pore between them. This opening allows carbon dioxide to enter the leaf for photosynthesis, but it also permits water to escape through transpiration. Under hot conditions, that water loss can have a cooling effect: as water evaporates from internal leaf surfaces, it carries heat away, much as evaporation of sweat cools the human body. The process is useful but potentially costly, because excessive transpiration can deplete the plant’s water supply. Plants therefore need precise molecular control over when stomata open and close.

The new study identifies UBP24 as an important part of that control system. According to the researchers, high temperature triggers a molecular change that stabilises UBP24. In its more stable state, UBP24 helps preserve other proteins involved in maintaining stomatal opening, allowing the plant’s evaporative cooling system to remain active during heat stress. The findings add a previously unrecognised layer to the signalling network that connects temperature sensing with stomatal behaviour. Rather than functioning only as a passive response to water status, stomata can therefore be actively regulated to help leaves avoid overheating.

UBP24 belongs to a class of proteins associated with the removal or processing of ubiquitin-related molecular signals. Ubiquitin is a small protein that can be attached to other proteins to influence their stability, activity or fate inside the cell. By altering these molecular tags, cells can rapidly remodel their protein landscape in response to changing conditions. The researchers’ results indicate that the heat-responsive behaviour of UBP24 is linked to its molecular charge state, a property shaped by changes in the protein’s amino-acid chemistry. This charge-sensitive switch appears to influence how UBP24 behaves under high temperatures and how effectively it supports the stability of proteins controlling stomata.

The work was carried out by researchers led by Prof. Ive De Smet of VIB and Ghent University, with contributions from the laboratory of Prof. Kevin Verstrepen at the VIB-KU Leuven Center for Microbiology and the group of Prof. Kris Gevaert at the VIB-UGent Center for Medical Biotechnology. By combining plant physiology, molecular biology, biochemical analysis and evolutionary comparisons, the teams examined how UBP24 responds to heat and how that response affects the plant’s ability to regulate leaf pores. The experimental findings connected changes in the protein with the behaviour of stomata, providing evidence that the pathway is not merely correlated with heat tolerance but contributes directly to the plant’s cooling response.

The researchers then placed the mechanism in an evolutionary context by comparing UBP24-related proteins across dozens of plant species. Their analysis suggests that the molecular switch allowing UBP24 to respond to high temperature emerged in vascular plants around the same period that actively controlled stomatal opening and closing evolved. Vascular plants possess specialised tissues for transporting water and nutrients, and their emergence was accompanied by increasingly sophisticated ways of managing water movement and gas exchange. The appearance of this charge-sensitive feature may have provided an additional means of tuning stomata as plants expanded into environments where temperature, water availability and atmospheric conditions could fluctuate sharply.

This evolutionary timing is significant because stomata are more than simple openings in a leaf. They represent a central point of control between the plant and its environment. Opening them can improve carbon dioxide uptake and promote cooling, while closing them limits dehydration but may increase the risk of overheating and restrict photosynthesis. A regulatory mechanism that adjusts the stability and activity of key stomatal proteins could help plants make these trade-offs more precisely. The study suggests that the UBP24 switch became part of this sophisticated control architecture, helping plants coordinate cellular protein regulation with the physical demands imposed by heat.

The researchers also found that the underlying principle may extend beyond the plant kingdom. A related protein in yeast appears to rely on a similar molecular feature when cells experience elevated temperatures. Plants and yeast are separated by hundreds of millions of years of evolution and have very different lifestyles, yet both must protect proteins and cellular processes from heat-induced disruption. The parallel suggests that regulating protein behaviour through changes in molecular charge may represent an ancient cellular strategy for coping with thermal stress. In plants, that strategy has been integrated into the control of stomata; in yeast, it may support other aspects of cellular survival.

The discovery arrives as heat waves become more frequent and intense in many parts of the world. High temperatures can damage cellular membranes, destabilise proteins, disrupt photosynthesis and accelerate water loss, reducing plant growth and agricultural productivity. Crops exposed to prolonged heat may close their stomata to conserve water, but this can also limit carbon dioxide uptake and reduce photosynthetic performance. Understanding how plants naturally keep stomata open enough to cool their leaves could eventually help researchers identify targets for improving heat resilience. Any agricultural application would need to preserve the balance between cooling and water conservation, since a plant that transpires too freely could become vulnerable to drought.

The findings remain fundamental rather than immediately agricultural, and the researchers emphasise that much work is still required before the mechanism could be translated into crop improvement. Future studies will need to determine how UBP24 interacts with the full network of temperature, humidity, light and water signals that govern stomatal activity, and whether altering the pathway improves performance under realistic combinations of heat and drought. Nevertheless, the work provides a new molecular entry point for studying plant adaptation. By showing how an evolutionary change in a protein’s charge state can connect heat perception to stomatal regulation, the study offers a detailed example of how plants have developed cellular solutions to survive a warming world.

Subject of Research: Experimental study

Article Title: Evolutionary tuning of molecular charge state of UBP24 shapes responses to high temperature

News Publication Date: 26 August 2026

Web References: https://doi.org/10.1038/s41477-026-02345-1

References: Nature Plants, DOI: 10.1038/s41477-026-02345-1

Keywords: Plant heat stress, UBP24, stomata, transpiration, plant cooling, heat resilience, molecular charge state, protein stability, plant evolution, vascular plants, yeast, climate change, crop resilience, photosynthesis, cellular stress response

Groundbreaking research out of the Salk Institute has unveiled a fascinating mechanism within plants that acts as an internal “thermostat,” directly linking temperature sensing to growth regulation through a sophisticated interplay of proteins associated with the plant hormone auxin. Auxin, a cornerstone of plant development, orchestrates diverse processes ranging from cell elongation to the formation of roots and shoots. While previous studies emphasized the hormone’s levels as drivers of growth at varying temperatures, this new work shifts the paradigm. It identifies the Auxin Response Factor transcription factors (ARFs), previously known only as gene expression regulators, as direct sensors of temperature changes, thus adding a new dimension to our understanding of plant thermosensitivity.

What emerged from this research is a model in which ARFs accumulate in inactive, clustered forms within the cytoplasm of plant cells when temperatures are low. These protein aggregates serve as a readily mobilizable reservoir, conserving ARFs in a dormant state. As environmental temperatures rise, the physicochemical properties of the ARFs shift—the proteins become increasingly soluble and dissociate from their clusters. Freed from these aggregates, the ARFs translocate into the nucleus where they activate gene networks responsible for promoting root growth. This dynamic redistribution, rather than de novo protein synthesis, enables plants to mount an immediate response to fluctuating temperatures—an elegant and energy-efficient solution to rapid environmental adaptation.

The discovery resolves a longstanding paradox in plant biology. Historically, elevated temperatures have been correlated with increased auxin levels and enhanced root growth. Paradoxically, excessively high auxin concentrations are known to inhibit root elongation. The identification of ARFs as thermal sensors explains how plants circumvent the potentially inhibitory effects of high auxin by modifying the activity and localization of ARFs in response to temperature, rather than merely altering hormone concentration. This nuanced control mechanism ensures that auxin signaling remains “just right”—precisely calibrated for optimal growth in a given thermal environment.

This research exemplifies a remarkable coalescence of protein biochemistry, molecular genetics, and environmental physiology. By characterizing the temperature-dependent solubility properties of ARFs, the researchers revealed that thermal cues directly influence the biophysical state of these transcription factors—shifting them between inactive aggregated reservoirs and active, soluble forms. This intrinsic thermostability within ARFs forms the molecular basis of the plant’s internal thermostat, linking environmental variability to gene expression programs. In practical terms, it enables plants to rapidly adjust root development without the metabolic cost and temporal delay of producing new proteins from scratch.

At a broader scale, such thermosensory adaptations have profound implications for agricultural sustainability. Climate change forecasts predict more frequent and intense heatwaves, threatening crop yields globally. Understanding the molecular architecture through which plants perceive and respond to temperature paves the way for engineering crops with enhanced resilience. By manipulating ARF thermostability or modulating their temperature-triggered solubility dynamics, scientists could develop cultivars capable of maintaining root growth–and thus efficient water and nutrient uptake–under elevated temperature conditions. This innovation holds promise for securing food production in hotter, drier climates.

This work also exemplifies the strength of international scientific collaboration. The Salk Institute team, led by Dr. Lucia Strader, coordinated efforts with Dr. Jorge Casal’s lab at the University of Buenos Aires. Despite distinct experimental approaches, both groups converged on the theme of plant temperature sensing, advancing the field concurrently and synergistically. Such cooperative models not only optimize resource use but foster scientific culture that transcends geographic and institutional boundaries, accelerating discovery.

The insights presented in this study redefine established concepts of hormone-driven growth regulation by positioning ARFs as primary thermal sensors embedded within the auxin signaling cascade. The temperature-dependent phase behavior of ARFs—their reversible clustering and dispersal—effectively translates external thermal conditions into quantifiable intracellular signals, thereby modulating developmental outcomes. This biophysical phenomenon of protein phase separation connected to environmental sensing is an emerging theme across biology, and its revelation in plants opens exciting new avenues for research across kingdoms.

From a methodological perspective, the study employed sophisticated biochemical assays, live-cell imaging, and gene expression analyses to characterize ARF behavior under varying temperatures. Structural investigation of ARF domains revealed the molecular determinants governing their phase partitioning and solubility. These findings underscore the importance of protein structure-function relationships in environmental responsiveness, demonstrating that plants harness intrinsic physicochemical properties of regulatory proteins to overcome challenges posed by fluctuating temperatures.

While auxin levels have long been considered proxies for growth potential, this research delineates a subtler regulatory layer. The presence of a pre-existing pool of ARFs poised for activation provides a rapid response mechanism that decouples immediate regulatory outputs from slower hormone biosynthesis pathways. This layered control enhances phenotypic plasticity by ensuring that growth modulation can occur on timescales aligned with environmental fluctuations, from minutes to hours.

Furthermore, the discovery invites speculation into whether similar temperature-sensing reservoirs exist for other plant hormones or signaling pathways, suggesting a broader paradigm where phase-separated protein assemblies act as environmental sensors within cells. This possibility sets the stage for a new understanding of plant biology wherein dynamic intracellular condensates serve as key nodes for integrating multifactorial stimuli.

The identification of ARF thermostability as a molecular switch enhances our comprehension of the origins of growth plasticity and environmental integration in plants. It advances the conceptual framework for hormone-mediated development, demonstrating that thermosensory capacity is not solely a factor of hormone concentration but also of protein state and context. This knowledge enriches our biological toolkit and could inspire innovative strategies in synthetic biology aimed at optimizing plant growth resilience.

In summary, the innovation presented by Strader and colleagues shifts the frontier of plant environmental sensing, revealing an inherent cellular thermostat mechanism that balances growth with changing temperatures through protein reservoir dynamics. As humanity faces escalating climatic challenges, decoding such molecular strategies is indispensable for safeguarding agricultural productivity and understanding the fundamental principles of life on Earth.

Subject of Research: Molecular mechanisms of temperature sensing in plants and regulation of root growth through auxin response factor thermostability.

Article Title: AUXIN RESPONSE FACTOR thermostability

News Publication Date: 27-Mar-2026

Web References:

• Original study: https://www.nature.com/articles/s41467-026-71012-y
• Complementary study by Jorge Casal’s lab: https://www.nature.com/articles/s41467-026-71011-z

Image Credits: Salk Institute

Keywords: Plant thermosensing, Auxin Response Factors, ARF thermostability, root growth regulation, auxin signaling, temperature adaptation, plant hormones, protein phase separation, plant development, environmental plasticity, agricultural resilience, molecular plant biology