Two bHLH transcription factors, bHLH48 and bHLH60, associate with phytochrome interacting factor 7 to regulate hypocotyl elongation in Arabidopsis
Chuanwei Yang,
Sha Huang,
Yue Zeng,
Chang Liu,
Qinyi Ma,
Jose Pruneda-Paz,
Steve A. Kay,
Lin Li
Affiliations
Chuanwei Yang
State Key Laboratory of Genetic Engineering and Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200438, People’s Republic of China
Sha Huang
State Key Laboratory of Genetic Engineering and Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200438, People’s Republic of China
Yue Zeng
State Key Laboratory of Genetic Engineering and Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200438, People’s Republic of China
Chang Liu
State Key Laboratory of Genetic Engineering and Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200438, People’s Republic of China
Qinyi Ma
State Key Laboratory of Genetic Engineering and Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200438, People’s Republic of China
Jose Pruneda-Paz
Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093, USA
Steve A. Kay
Department of Neurology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90098, USA
Lin Li
State Key Laboratory of Genetic Engineering and Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai 200438, People’s Republic of China; Corresponding author
Summary: The basic helix-loop-helix (bHLH) transcription factor PHYTOCHROME-INTERACTING FACTOR 7 (PIF7) is a central regulator that promotes stem growth by activating growth-related gene expression during shade-avoidance responses. Studying the co-factors of PIF7 can facilitate understanding of the mechanism of PIFs and light signal transduction. Here, we describe the identification of two bHLH transcription factors, bHLH48 and bHLH60 (bHLH48/bHLH60), as essential partners for PIF7-dependent modulation of hypocotyl elongation and function downstream of phytochrome B. These two bHLH factors display DNA binding activity and interact with PIF7. Genetic analysis indicated that bHLH48/bHLH60 and PIF7 are interdependent in promoting hypocotyl elongation. Chromatin immunoprecipitation sequencing (ChIP-seq) analysis identified the substantially overlapping downstream targets of bHLH60 and PIF7. Biochemical analysis revealed that bHLH48/bHLH60 enhance the DNA binding ability of PIF7. These results provide evidence that bHLH48/bHLH60 act as positive partners of PIF7 for mutual benefit in the regulation of hypocotyl elongation.
