A molecular framework of light-controlled phytohormone action in Arabidopsis

Curr Biol. 2012 Aug 21;22(16):1530-5. doi: 10.1016/j.cub.2012.06.039. Epub 2012 Jul 19.


Environmental changes strongly affect plant growth and development. Phytohormones, endogenous plant-made small molecules such as ethylene, regulate a wide range of processes throughout the lifetime of plants. The ability of plants to integrate external signals with endogenous regulatory pathways is vital for their survival. Ethylene has been found to suppress hypocotyl elongation in darkness while promoting it in light. How ethylene regulates hypocotyl elongation in such opposite ways is largely unknown. In particular, how light modulates and even reverses the function of ethylene has yet to be characterized. Here we show that the basic-helix-loop-helix transcription factor phytochrome-interacting factor 3 (PIF3) is directly activated by ETHYLENE-INSENSITIVE 3 (EIN3) and is indispensible for ethylene-induced hypocotyl elongation in light. Ethylene via EIN3 concomitantly activates two contrasting pathways: the PIF3-dependent growth-promoting pathway and an ethylene response factor 1 (ERF1)-mediated growth-inhibiting pathway. In the light, growth-promoting PIFs are limiting due to light-dependent destabilization, and thus ethylene stimulates growth under these conditions. In contrast, ERF1 is destabilized, and thus limiting, under dark conditions, explaining why ethylene inhibits growth in the dark. Our findings provide a mechanistic insight into how light modulates internal hormone-regulated plant growth.

Publication types

  • Research Support, N.I.H., Extramural
  • 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 / metabolism*
  • Basic Helix-Loop-Helix Transcription Factors / metabolism*
  • DNA-Binding Proteins / metabolism
  • Ethylenes / metabolism*
  • Gene Expression
  • Hypocotyl / growth & development
  • Light*
  • Nuclear Proteins / metabolism*
  • Plant Growth Regulators / metabolism
  • Plant Proteins / metabolism
  • Promoter Regions, Genetic
  • Transcription Factors / metabolism*


  • Arabidopsis Proteins
  • Basic Helix-Loop-Helix Transcription Factors
  • DNA-Binding Proteins
  • EIN3 protein, Arabidopsis
  • Ethylenes
  • Nuclear Proteins
  • PIF3 protein, Arabidopsis
  • Plant Growth Regulators
  • Plant Proteins
  • Transcription Factors
  • ethylene-responsive element binding protein
  • ethylene