Slow growth is key to long-term cold detection

Plants need to interpret temperature fluctuations over a timescale of hours to months in order to coordinate growth and development with the seasons.

Although it is well known how plants respond to temperature, the mechanisms that enable plants to measure temperature signals are poorly understood.

In this study Nature, Yusheng Zhao and Rea Antoniou-Kourounioti, researchers in the group of Professors Dame Caroline Dean and Martin Howard at the John Innes Center, Slow growth It is used as a signal to detect long-term changes in temperature.

“We have discovered a new temperature-sensing mechanism that retains long-term memory of cold and integrates fluctuating temperatures to measure the duration of cold. This is a new type of physical mechanism for temperature sensing. And can guide further research in this area,” explains lead author Dr. Yusheng Zhao.

A forward genetic screen was used to examine the genetics of plants with specific characteristics and found a dysfunctional response. These plants showed a high level of protein called VIN3 at warm temperatures. This protein is well known to be upregulated during the cold months and interacts with the epigenetic molecular memory system that allows plants to remember the cold.

Dr. Yusheng Zhao discovered that these plants have one of two versions of mutant NTL8, a transcription factor or regulator protein that activates VIN3 even in the absence of cold.

To understand the role of NTL8, they tagged it Fluorescent protein (GFP) And with the help of the John Innes Center’s Bioimaging platform, we showed where this protein resides compared to VIN3. This indicates that variants were found everywhere in the plant, with wild-type proteins predominantly observed at the root growth tips. It also showed that it slowly accumulates with time in the cold.

Using Theoretical approach To investigate the problem further, the team infers that understanding how fast the NTL8 protein degrades can provide insights into how the slow dynamics of NTL8 and VIN3 work. did. They found that the NTL8 protein is long-lasting, as predicted by theory.

Mathematical modeling has shown that the major factor determining the amount of NTL8 protein is growth-dependent dilution. When the weather gets warmer, the plants grow faster and the amount of NTL8 gets diluted as the cells grow. In contrast, lower temperatures slow plant growth and NTL8 is more concentrated and can accumulate over time. The mathematical model can reproduce the NTL8 protein level observations seen in warm and cold weather.

To further test the model, they added chemicals and hormones to alter the growth of plants and see if the levels of NTL8 predicted by the model were altered. They added the plant growth hormone gibberellin to their roots. This caused the plants to grow faster and reduced NTL8 levels as expected. NTL8 when they added growth inhibitors protein The level was high in the whole plant. The team conducted similar experiments on roots and confirmed these predictions.

Co-lead author Rea Antoniou-Kourounioti adds: “I was amazed at the simplicity of the new temperature mechanism we discovered that reuses temperature information from one process [growth] Create another temperature sensing mechanism [vernalization—the acceleration of flowering by cold].. By simply changing the growth rate between warm and cold, the model was able to reproduce most of the temperature-dependent changes in the results. “

“This study has revolutionized our understanding of how plants sense temperature, especially how fluctuating long-term environmental conditions integrate,” says Martin Howard.

“This study shows a great synergistic effect of combining approaches and computational models. We couldn’t understand this mechanism by doing either separately,” Caroline Dean said. I am.

The findings will help us understand how plants and other organisms can sense long-term fluctuating environmental signals and apply them to crops.