The Mg-chelatase H subunit is an abscisic acid receptor

Nature. 2006 Oct 19;443(7113):823-6. doi: 10.1038/nature05176.


Abscisic acid (ABA) is a vital phytohormone that regulates mainly stomatal aperture and seed development, but ABA receptors involved in these processes have yet to be determined. We previously identified from broad bean an ABA-binding protein (ABAR) potentially involved in stomatal signalling, the gene for which encodes the H subunit of Mg-chelatase (CHLH), which is a key component in both chlorophyll biosynthesis and plastid-to-nucleus signalling. Here we show that Arabidopsis ABAR/CHLH specifically binds ABA, and mediates ABA signalling as a positive regulator in seed germination, post-germination growth and stomatal movement, showing that ABAR/CHLH is an ABA receptor. We show also that ABAR/CHLH is a ubiquitous protein expressed in both green and non-green tissues, indicating that it might be able to perceive the ABA signal at the whole-plant level.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Abscisic Acid / metabolism*
  • Arabidopsis / enzymology
  • Arabidopsis / genetics
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / chemistry
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Gene Expression Regulation, Plant
  • Lyases / chemistry*
  • Lyases / genetics
  • Lyases / metabolism*
  • Molecular Sequence Data
  • Plants, Genetically Modified
  • Protein Binding
  • Protein Subunits / genetics
  • Protein Subunits / metabolism*
  • Signal Transduction
  • Substrate Specificity


  • Arabidopsis Proteins
  • Protein Subunits
  • Abscisic Acid
  • Lyases
  • magnesium chelatase

Associated data

  • GENBANK/DQ376081