Class I TCP Transcription Factors Target the Gibberellin Biosynthesis Gene GA20ox1 and the Growth-Promoting Genes HBI1 and PRE6 during Thermomorphogenic Growth in Arabidopsis

Plant Cell Physiol. 2019 Aug 1;60(8):1633-1645. doi: 10.1093/pcp/pcz137.


Plants respond to a rise in ambient temperature by increasing the growth of petioles and hypocotyls. In this work, we show that Arabidopsis thaliana class I TEOSINTE BRANCHED 1, CYCLOIDEA, PCF (TCP) transcription factors TCP14 and TCP15 are required for optimal petiole and hypocotyl elongation under high ambient temperature. These TCPs influence the levels of the DELLA protein RGA and the expression of growth-related genes, which are induced in response to an increase in temperature. However, the class I TCPs are not required for the induction of the auxin biosynthesis gene YUCCA8 or for auxin-dependent gene expression responses. TCP15 directly targets the gibberellin biosynthesis gene GA20ox1 and the growth regulatory genes HBI1 and PRE6. Several of the genes regulated by TCP15 are also targets of the growth regulator PIF4 and show an enrichment of PIF4- and TCP-binding motifs in their promoters. PIF4 binding to GA20ox1 and HBI1 is enhanced in the presence of the TCPs, indicating that TCP14 and TCP15 directly participate in the induction of genes involved in gibberellin biosynthesis and cell expansion by high temperature functionally interacting with PIF4. In addition, overexpression of HBI1 rescues the growth defects of tcp14 tcp15 double mutants, suggesting that this gene is a major outcome of regulation by both class I TCPs during thermomorphogenesis.

Keywords: Ambient temperature; Gibberellin; PIF4; Plant growth; TCP transcription factor.

MeSH terms

  • Arabidopsis / genetics
  • Arabidopsis / growth & development*
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Basic Helix-Loop-Helix Transcription Factors / genetics
  • Basic Helix-Loop-Helix Transcription Factors / metabolism*
  • Gene Expression Regulation, Plant
  • Gibberellins / metabolism*
  • Mixed Function Oxygenases / genetics
  • Mixed Function Oxygenases / metabolism
  • Proteasome Endopeptidase Complex / genetics
  • Proteasome Endopeptidase Complex / metabolism*
  • Temperature
  • Transcription Factors / genetics
  • Transcription Factors / metabolism


  • Arabidopsis Proteins
  • Basic Helix-Loop-Helix Transcription Factors
  • Gibberellins
  • HBI1 protein, Arabidopsis
  • TCP14 protein, Arabidopsis
  • TCP15 protein, Arabidopsis
  • Transcription Factors
  • Mixed Function Oxygenases
  • YUCCA8 protein, Arabidopsis
  • Proteasome Endopeptidase Complex