NSF Study Aims to Reveal How Plants Sense, Respond to Heat

Yongjian Qiu, associate professor of biology, has received funding from the National Science Foundation through the EPSCoR Research Fellows program. The two-year project will examine how calcium channels contribute to temperature sensing and signaling in plants.

Whereas Qiu's previous research explored how plants adjust their growth under warmer conditions, his new project will move closer to the beginning of that process by asking how a plant cell first detects a temperature change and communicates that information.

"Plants have dedicated photoreceptors for light and receptors for many hormones," Qiu said. "Temperature sensing is more complex because temperature affects the physical and biochemical behavior of many components in a cell.

"Plants may therefore rely on several sensing mechanisms rather than one universal temperature receptor."

The project addresses a fundamental problem in plant biology: how heat, a physical condition that affects nearly every molecule in a cell, is converted into a signal that plants can respond to, the researchers said. The results could clarify how plants balance growth with protection as temperatures fluctuate.

Qiu and Sampada Timilsina, an Ole Miss doctoral student in molecular biology, will collaborate with Sheng Luan, a professor in the Department of Plant and Microbial Biology at the University of California at Berkeley. The researchers will investigate how specific calcium channels respond as temperatures rise and how channel activity shapes cellular responses.

"Plants do not have a brain, but they are constantly monitoring changes in their environment, including temperature, drought, salinity and pathogens," Timilsina said. "Calcium signaling is one of the ways their cells translate those changes into a response."

Calcium channels are proteins embedded in plant cell membranes that form small passageways through which calcium ions move. When these channels open, free calcium in the cytoplasm can rise and fall in patterns that differ in timing, magnitude and location.

These calcium signatures can carry information about a stimulus. Calcium sensor proteins decode that information and activate downstream changes in gene expression, metabolism and cell activity.

"Calcium is both an essential nutrient and a signaling molecule," Qiu said. "A temperature change can produce a characteristic calcium signature. We want to determine which channels help generate that signature and how the cell interprets it."

Plants do not respond to every increase in temperature in the same way, the researchers said. Moderately warm, nondamaging conditions can trigger a set of developmental changes that often includes altered cell elongation and growth. More intense or prolonged heat can threaten cellular function and activate protective heat-stress responses.

The boundary between warmth and heat stress depends on the plant species, tissue, developmental stage, exposure duration and other environmental conditions.

"Warm-temperature growth responses and heat-stress responses lead to very different biological outcomes," Qiu said. "We want to learn whether they begin with shared or distinct calcium-channel activities and how those early signals lead to different response pathways."

Over the next two years, Qiu and his team will combine live-cell imaging, genetic analyses and electrophysiological studies to identify the calcium channels involved in warm-temperature and heat stress responses and connect their activity to downstream growth or protective responses.

"The key is understanding the behavior of those channels and transporters in the cell, but we don't have the technique and instrument facility to study that right now," Qiu said. "In the plant field, it's not easy to do this type of research and it's not easy to find a collaborator that can help us with this.

"Dr. Luan is an expert in this field, and the U.C. Berkeley RCNR Biological Imaging Facility is very well-established. They have the facilities, the support and the expertise in electrophysiological response that we can learn from and take back to our lab."

This material is based on work supported by the National Science Foundation under award No. 2624036.

Top: Biology professor Yongijan Qiu is studying several plants, including Arabidopsis thaliana, a flowering weed commonly known as thale cress, to understand how plants detect changes in heat and respond to them. Photo by Hunt Mercier/Ole Miss Digital Imaging Services