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Updated: May 25, 2026

Investigating Interactions Between Histone Modifying Enzymes and Transcription Factors in vivo by Fluorescence Resonance Energy Transfer
Published on: October 14, 2022
Interactions between HLH and bHLH factors modulate light-regulated plant development
Yaqi Hao1, Eunkyoo Oh, Giltsu Choi
1College of Life Science, Northwest A&F University, Yangling, Shaanxi 712100, China.
Light signaling regulates plant growth. PAR1 protein interacts with PIF4, inhibiting its activity and controlling shade-avoidance syndrome. This reveals a complex network regulating plant development.
Area of Science:
- Plant Biology
- Molecular Biology
- Genetics
Background:
- Phytochromes (Phy) and phytochrome-interacting factors (PIFs) regulate plant development based on light signals.
- Shade-avoidance syndrome (SAS), triggered by low red:far-red light ratios, promotes cell elongation.
- PAR1 and PAR2 are HLH transcription factors that negatively regulate SAS but lack DNA-binding domains.
Purpose of the Study:
- To investigate the mechanism by which PAR1 regulates plant development and SAS.
- To identify the DNA-binding partners of PAR1.
- To elucidate the role of PAR1 in light and hormone signaling pathways.
Main Methods:
- Protein stabilization assays.
- Yeast two-hybrid and co-immunoprecipitation for protein interactions.
- DNA pull-down and chromatin immunoprecipitation (ChIP) assays.
- Analysis of transgenic plants overexpressing PAR1 (PAR1OX).
Main Results:
- Light signal stabilizes PAR1 protein.
- PAR1 directly interacts with PIF4 and inhibits PIF4-mediated gene activation.
- PAR1 inhibits PIF4 DNA binding both in vitro and in vivo.
- PAR1 overexpression confers insensitivity to gibberellin (GA) and high temperature in hypocotyl elongation.
- PAR1 also interacts with PRE1, another HLH transcription factor.
- Overexpression of PRE1 rescues the dwarf phenotype of PAR1OX plants.
Conclusions:
- PAR1 acts as a negative regulator of SAS by inhibiting PIF4 DNA binding.
- PAR1 forms heterodimers with PIF4 and PRE1, creating a complex HLH/bHLH network.
- This network integrates light and hormonal signals (GA, BR) to control plant cell elongation and development.
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