Dec 6 2018
Both humans and animals enjoy the privilege of seeking shelter in the shade or cool, air-conditioned buildings when it gets hot outside. Plants, on the other hand, have no such choice.
Meng Chen (Image credit: University of California, Riverside)
While not exempt from changing climate, plants react to the rising mercury in different ways. Temperature impacts the distribution of plants across the globe. It also influences the flowering time, crop yield, and even resistance to disease.
“It is important to understand how plants respond to temperature to predict not only future food availability but also develop new technologies to help plants cope with increasing temperature,” said Meng Chen, Ph.D., associate professor of cell biology at the University of California, Riverside.
Researchers are extremely interested in discovering how plants experience temperature during the day, but until recently this mechanism has been quite elusive. Chen is leading a team to investigate the role of phytochrome B, a molecular signaling pathway that may play a key role in how plants react to temperature.
In a paper published in Nature Communications, Chen and colleagues at UCR describe the genetic stimulants that prepare plants for growth under various temperature conditions using the model plant, Arabidopsis.
Plants grow based on the circadian clock, which is regulated by the seasons. All of a plant’s physiological processes are partitioned to take place at particular times of day.
As stated by Chen, the age-old theory held that Arabidopsis detects an increase in temperature during the evening. In a natural setting, Arabidopsis, a winter plant, would most likely never see higher temperature at night.
“This has always been puzzling to us,” said Chen, senior author on the paper. “Our understanding of the phytochrome signaling pathway is that it should also sense temperature during the daytime, when the plant would actually encounter higher temperature.”
Actually, Arabidopsis grows at various times of day as the seasons vary. The plant grows during the day in the summer, and at night during the winter. Earlier experiments that imitated winter conditions presented a dramatic response in phytochrome B, but experiments that imitated summer conditions were less strong.
Chen and his team decided to scrutinize the role of phytochrome B in Arabidopsis at 21 °C and 27 °C under red light. The monochromatic wavelength enabled the team to examine how this particular plant sensor works without the disturbance of other wavelengths of light.
Under these conditions, we see a robust response. The work shows that phytochrome B is a temperature sensor during the day in the summer. Without this photoreceptor, the response in plants is significantly reduced.
Meng Chen, Ph.D., Associate Professor of Cell Biology, University of California, Riverside.
Apart from identifying the purpose of phytochrome B, Chen’s work also highlights the role of HEMERA, a transcription activator that switches on the temperature-responsive genes that regulate plant growth.
“We found the master control for temperature sensing in plants,” Chen said. “HEMERA is conserved in all plants, from moss to flowering plants.”
Essentially, Chen and his team identified the genetic mechanism employed by all plants as they react to daylight situations as well as the ability to sense temperature.
Chen accepts that not all plants may react in the same way as Arabidopsis in this research. Before this research could be functional, it may be essential to comprehend how this temperature-signaling pathway acts in various plant systems. Chen is convinced the pathway is perhaps similar for all plants and may only require slight modifications.
The study team plan to expand on this research by incorporating more complexity to future experimental designs, such as analyzing the response of the signaling pathway under white light or diurnal settings. Chen would also like to observe how other plant systems use HEMERA to experience temperature.
To cope with rapid temperature changes associated with global warming, we may have to help nature to evolve crops to adapt to the new environment. This will require a molecular understanding of how plants sense and respond to temperature.
Meng Chen, Ph.D., Associate Professor of Cell Biology, University of California, Riverside.
The paper, titled “Daytime temperature is sensed by phytochrome B in Arabidopsis through a transcriptional activator HEMERA,” was published in the December issue of Nature Communications. Besides Chen, collaborators at UC Riverside include: Yongjian Qiu, Meina Li, Ruth Jean-Ae Kim, and Carisha M. Moore. The research was sponsored by the National Institute of General Medical Sciences.