New Study Reveals Sugar's Role in Plant Temperature Regulation

Recent research conducted by a team at the University of California, Riverside, has unveiled a significant shift in the understanding of how plants sense temperature. For over a decade, scientists have predominantly attributed temperature sensing in plants to specialized proteins, particularly during cooler night hours. However, the new findings indicate that sugar, produced through photosynthesis during the day, plays a crucial role in this process, allowing plants to detect heat and regulate growth more effectively.

The study, led by Professor Meng Chen, published in *Nature Communications* on July 2, 2025, challenges long-standing theories that focused mainly on proteins such as phytochrome B and early flowering 3 (ELF3) as the primary thermosensors in plants. "Our textbooks have traditionally indicated that these proteins are the main thermosensors, but those conclusions were primarily based on nighttime data. We aimed to explore the plant's response to temperature during the day, when both light and heat are present," stated Professor Chen.

To investigate these dynamics, the research team used *Arabidopsis thaliana*, a small flowering plant commonly used in genetic studies. The researchers exposed seedlings to varying temperatures ranging from 12 to 27 degrees Celsius under different light conditions, carefully monitoring their hypocotyl elongation—an established indicator of growth response to warmth.

The results showed that phytochrome B, a light-sensitive protein, lost its ability to detect heat under bright light conditions, which mimic midday sunlight. Despite the diminished function of phytochrome B in these conditions, the plants continued to respond to heat, suggesting the involvement of other sensing mechanisms. Notably, when studying a mutant strain of phytochrome B that lacked its thermosensing capabilities, researchers found that these plants only exhibited growth responses to warmth when grown in light. Conversely, in darkness, without photosynthesis, the plants did not show growth in response to heat.

This led the researchers to a pivotal discovery: when the growing medium was supplemented with sugar, the temperature response in the mutant plants was restored. "This was a key moment for us. It became clear that sugar is not merely an energy source for growth; it acts as a signaling molecule that informs the plant about temperature changes," Chen explained.

Further exploration revealed that elevated temperatures triggered the breakdown of starch stored in leaves, which released sucrose. This sugar was found to stabilize a protein known as PIF4, a critical regulator of growth. Without sucrose present, PIF4 degraded rapidly, but with sucrose, the protein accumulated and became active only when another sensor, ELF3, responded to the heat by releasing its repression.

The study illustrates a complex system wherein, during daylight hours, plants utilize sugar as a mechanism to sense environmental changes in conjunction with traditional protein-based sensing. As temperatures increase, the conversion of starch to sugar enables key growth proteins to function effectively.

The implications of these findings are profound, particularly in the context of climate change. Understanding the mechanisms through which plants sense temperature can inform agricultural practices and help develop crops that are more resilient to fluctuating environmental conditions. Professor Chen emphasized, "This research fundamentally alters our understanding of thermosensing in plants. It's not just about proteins toggling on and off; it's about the intricate interplay between energy, light, and sugar."

As climate change exacerbates temperature extremes, the insights from this study could guide scientists in breeding crops that exhibit more predictable and resilient growth patterns under stress. The research underscores the sophisticated capabilities of plants and their nuanced responses to environmental stimuli, revealing a hidden intelligence that determines their growth strategies in an ever-changing climate.