The JA-pathway MYC transcription factors regulate photomorphogenic responses by targeting HY5 gene expression

Plant J. 2020 Apr;102(1):138-152. doi: 10.1111/tpj.14618. Epub 2020 Jan 4.


Jasmonates are key regulators of the balance between defence and growth in plants. However, the molecular mechanisms by which activation of defence reduces growth are not yet fully understood. Here, we analyze the role of MYC transcription factors (TFs) and jasmonic acid (JA) in photomorphogenic growth. We found that multiple myc mutants share light-associated phenotypes with mutants of the phytochrome B photoreceptor, such as delayed seed germination in the dark and long hypocotyl growth. Overexpression of MYC2 in a phyB background partially suppressed its long hypocotyl phenotype. Transcriptomic analysis of multiple myc mutants confirmed that MYCs are required for full expression of red (R) light-regulated genes, including the master regulator HY5. ChIP-seq analyses revealed that MYC2 and MYC3 bind directly to the promoter of HY5 and that HY5 gene expression and protein levels are compromised in multiple myc mutants. Altogether, our results pinpoint MYCs as photomorphogenic TFs that control phytochrome responses by activating HY5 expression. This has important implications in understanding the trade-off between growth and defence as the same TFs that activate defence responses are photomorphogenic growth regulators.

Keywords: Arabidopsis; HY5; MYC; defence; jasmonate; light signalling; trade-off.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Arabidopsis / growth & development
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / genetics*
  • Arabidopsis Proteins / metabolism
  • Arabidopsis Proteins / physiology*
  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / genetics*
  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / physiology
  • Basic-Leucine Zipper Transcription Factors / metabolism
  • Basic-Leucine Zipper Transcription Factors / physiology*
  • Cyclopentanes / metabolism*
  • Gene Expression Regulation, Plant
  • Genes, myc
  • Oxylipins / metabolism*
  • Phototropism* / genetics
  • Phototropism* / physiology
  • Plant Growth Regulators / metabolism*
  • Signal Transduction*


  • Arabidopsis Proteins
  • Basic Helix-Loop-Helix Leucine Zipper Transcription Factors
  • Basic-Leucine Zipper Transcription Factors
  • Cyclopentanes
  • HY5 protein, Arabidopsis
  • MYC2 protein, Arabidopsis
  • Oxylipins
  • Plant Growth Regulators
  • jasmonic acid