Light and ambient temperature are two of the most prominent cues affecting plant growth and development. Acting as both a growth and a stress hormone, ethylene is vital for plant adaptation to the environment. The interactions between the light and ethylene signaling pathways have been studied extensively. However, few studies have explored the role of ethylene in the response to ambient temperature change.

On February 2, Chair Professor Hongwei Guo from the Department of Biology at the Southern University of Science and Technology (SUSTech) led his research team to publish a paper in the prestigious scientific journal PNAS. Their article, entitled “The RING E3 ligase SDIR1 destabilizes EBF1/EBF2 and modulates the ethylene response to ambient temperature fluctuations in Arabidopsis”, showed a novel mechanism underlying the ambient temperature control of ethylene signaling.

The gaseous phytohormone ethylene mediates numerous aspects of plant growth and development as well as stress responses. The F-box proteins EIN3-binding F-box protein 1 (EBF1) and EBF2 are key components that ubiquitinate and degrade the master transcription factors ethylene insensitive 3 (EIN3) and EIN3-like 1 (EIL1) in the ethylene response pathway. Notably, EBF1 and EBF2 themselves undergo the 26S proteasome-mediated proteolysis induced by ethylene and other stress signals. However, despite their importance, little is known about the mechanisms regulating the degradation of these proteins.

The researchers in this study found that a really interesting new gene (RING)-type E3 ligase, salt- and drought-induced ring finger 1 (SDIR1), positively regulates the ethylene response and promotes the accumulation of EIN3. Further analyses indicate that SDIR1 directly interacts with EBF1/EBF2 and targets them for ubiquitination and proteasome-dependent degradation. Moreover, the transcript levels of SDIR1 are gradually up-regulated as the ambient temperature increases, enabling SDIR1 to mediate the temperature-induced degradation of EBF1/EBF2 and promote EIN3 accumulation to modulate the ethylene response at different ambient temperatures. Overall, SDIR1 may function as an important modulator coordinating the response to ethylene and temperature signals by directly destabilizing EBF1/EBF2. Their work provides another layer for ethylene signal transduction and insights into the communication between plants and their surrounding environments.

A working model depicting the SDIR1-modulated ethylene signaling through degradation of EBF1/EBF2

Dr. Dongdong Hao, a postdoctoral, and Dr. Lian Jin, a senior research scholar from the Institute of Plant and Food Science at the Department of Biology, are the co-first authors. Professor Hongwei Guo is the corresponding author. SUSTech engineer Dr. Xing Wen from the Institute of Plant and Food Science, Dr. Feifei Yu, and researcher Dr. Qi Xie from the Institute of Genetics and Developmental Biology at the Chinese Academy of Sciences, are the co-authors.

This work was funded by the National Natural Science Foundation of China (NSFC), Shenzhen Science and Technology Program, and Key Laboratory of Molecular Design for Plant Cell Factory of Guangdong Higher Education Institutes (SUSTech).