A recent study conducted by the University of California reveals that plants utilize a variety of thermosensory systems, with sunlight-generated sugar playing a critical and previously overlooked role in their responses to daytime temperatures.
“Textbooks traditionally assert that proteins like phytochrome B and early flowering 3 (ELF3) are primarily responsible for thermoregulation in plants,” noted Professor Chen.
“However, these theories are derived from data collected at night.”
“We aimed to explore the dynamics during the day when both light and temperature are elevated, reflecting the typical conditions most plants encounter.”
Professor Chen and his team conducted their research using Arabidopsis, a favored small flowering plant within the Institute of Genetics.
The researchers subjected the seedlings to temperatures from 12-27 degrees Celsius under varying light settings and monitored the elongation of hypocotyls, a classic indicator of growth response to warmth.
They discovered that phytochrome B, the photosensitive protein, could only sense temperature in low light. In bright conditions that mimicked midday sunlight, its ability to detect warmth was significantly inhibited.
Interestingly, plants continued to respond to heat, and their growth metrics remained elevated even when the thermosensory function of phytochrome B was curtailed.
“This highlights the existence of other sensory mechanisms,” Professor Chen remarked.
One significant observation stemmed from examining phytochrome B mutants that lacked thermosensory capabilities.
These mutants were only able to react to warmth when grown under light conditions.
In darkness, devoid of photosynthesis, they lost chloroplasts and did not exhibit increased growth in response to warmth.
However, their temperature response was restored upon reintroducing sugar to the growth medium.
“That was the point I realized that sugar does more than just promote growth; it serves as a signal indicating warmth,” Professor Chen explained.
Additional experiments demonstrated that elevated temperatures lead to the breakdown of stored starch in leaves, releasing sucrose.
This sugar stabilized a protein called PIF4, a crucial growth regulator. In the absence of sucrose, PIF4 would decompose rapidly, but its accumulation only occurred when another sensor, ELF3, became inactive and responded to heat.
“PIF4 requires two conditions: access to sugars and relief from suppression. Temperature facilitates both,” Professor Chen added.
This research unveils a complex network of systems. During daylight, when light serves as an energy source for carbon fixation, sugar-based mechanisms have evolved that enable plants to sense environmental changes.
As temperatures rise, stored starch transforms into sugar, permitting essential growth proteins to function.
The implications of these findings are noteworthy. As climate change brings about extreme temperatures, understanding the mechanisms plants use to sense heat may assist scientists in developing crops that thrive under increasingly unpredictable stress.
“This will transform our understanding of how plants perceive temperature,” Professor Chen remarked.
“It’s not merely about proteins activating or deactivating; it’s about energy, light, sugar, and more.”
“The results also emphasize the intricate sophistication found in the plant kingdom.”
“There’s a hidden intelligence in photosynthesis and the management of starch reserves.”
“When the moment arrives for them to reach for the sky, they do so with sweetness and precision.”
study published in the journal Natural Communication.
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D. Fan et al. 2025. Multi-sensor high temperature signaling framework for triggering daytime thermochemistry. Arabidopsis. Nat Commun 16, 5197; doi:10.1038/s41467-025-60498-7
Source: www.sci.news
