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Pseudo Response Regulators regulate photoperiodic hypocotyl growth by repressing PIF4/5 transcription.

  • Li, Na1
  • Zhang, Yuanyuan1
  • He, Yuqing1
  • Wang, Yan1
  • Wang, Lei2
  • 1 Institute of Botany, Chinese Academy of Sciences CITY: Beijing STATE: Beijing China [CN]. , (China)
  • 2 Institute of Botany, Chinese Academy of Sciences CITY: Beijing STATE: Beijing POSTAL_CODE: 100093 China [CN] [email protected] , (China)
Published Article
Plant physiology
Publication Date
Mar 12, 2020
DOI: 10.1104/pp.19.01599
PMID: 32165445


The circadian clock measures and conveys daylength information to control rhythmic hypocotyl growth in photoperiodic conditions to achieve optimal fitness, but it operates through largely unknown mechanisms. Here, we show that Pseudo Response Regulators (PRRs) coordinate with the Evening Complex (EC), a transcriptional repressor complex within clock core oscillator, to specifically regulate photoperiodic hypocotyl growth in Arabidopsis thaliana. Intriguingly, a distinct daylength could shift the expression phase and extend the expression duration of PRRs. Multiple lines of evidence further demonstrated that PRRs directly bound the promoters of PHYTOCHROME-INTERACTING FACTOR4 (PIF4) and PIF5 to repress their expression, hence PRRs act as transcriptional repressors of the positive growth regulatorss PIF4 and PIF5. Importantly, mutation or truncation of the TIMING OF CAB EXPRESSION 1 (TOC1) DNA binding domain, without compromising its physical interaction with PIFs, still caused long hypocotyl growth under short days, highlighting the essential role of the PRRs-PIFs transcriptional module in photoperiodic hypocotyl growth. Finally, genetic analyses demonstrated that PIF4 and PIF5 are epistatic to PRRs in the regulation of photoperiodic hypocotyl growth. Collectively, we propose that, upon perceiving daylength information, PRRs cooperate with EC to directly repress PIF4 and PIF5 transcription together with their post-translational regulation on PIFs activities, thus forming a complex regulatory network to mediate circadian clock-regulated photoperiodic growth. {copyright, serif} 2020 American Society of Plant Biologists. All rights reserved.

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