China
March 19, 2025
A research team led by Prof. CAO Xiaofeng at the Institute of Genetics and Developmental Biology (IGDB) of the Chinese Academy of Sciences (CAS) has uncovered the cooperative roles of photoreceptors, epigenetic modifiers, and transcription factors in regulating light-responsive genes in plants.
Their findings were published in PNAS on March 10.
Light is not only the primary energy source for photosynthesis but also a crucial environmental cue that shapes various plant developmental processes, including seed germination, seedling morphogenesis, leaf expansion, stem elongation, flowering time, circadian rhythms, and shade avoidance. When a seedling emerges from the soil, light signals rapidly trigger photomorphogenesis, a critical developmental transition characterized by suppressed hypocotyl elongation, expanded and greened cotyledons, and the initiation of photosynthesis.
To adapt to dynamic light environments, plants have evolved sophisticated light-signaling mechanisms. Epigenetic modifications, particularly histone covalent modifications, play a crucial role in regulating plant growth and environmental responses. Among these, histone H3 lysine 27 trimethylation (H3K27me3) is a key repressive mark that maintains gene silencing, with its dynamic regulation essential for cell fate determination and development in both plants and animals.
Prof. CAO's team had previously identified and characterized REF6/JMJ12, an H3K27me3 demethylase in Arabidopsis, revealing its targeting mechanism and role in plant development and ambient temperature responses. In their latest study, they employed chromatin profiling, transcriptomics, biochemical, and genetic approaches to systematically explore the molecular mechanisms by which REF6 mediates red light signaling.
Phenotypic analyses showed that REF6 loss-of-function mutants exhibited markedly shortened hypocotyls under light, whereas mutants of other H3K27me3 demethylases (JMJ11, JMJ13, JMJ30 and JMJ32) showed no significant phenotypic changes, indicating the dominant role for REF6 in photomorphogenesis.
Further investigations demonstrated that REF6 protein accumulation and H3K27 demethylase activity were significantly enhanced under red light compared to darkness. Red light-activated phytochrome B (phyB-Pfr) physically interacts with REF6, stabilizing REF6 protein and enhancing its chromatin-binding capacity. This interaction facilitated the expression of cell elongation-related genes in open chromatin states. Then, REF6 synergizes with the phyB-PIF4 module to finely regulate hypocotyl growth under continuous light, ensuring proper plant development.
By integrating light signaling with epigenetic regulation, this study expands the multidimensional regulatory framework of photomorphogenesis. It highlights how photoreceptors, epigenetic factors, and transcription factors collaboratively fine-tune hypocotyl growth in fluctuating light environments—a sophisticated strategy critical for plant adaptation.
This work was supported by grants from the National Natural Science Foundation of China, the Youth Talent Support Project of the China Association for Science and Technology, and the Youth Innovation Promotion Association of CAS.
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