Enhanced ethylene responsiveness in the Arabidopsis eer1 mutant results from a loss-of-function mutation in the protein phosphatase 2A A regulatory subunit, RCN1

Plant J. 2003 Jun;34(5):709-18. doi: 10.1046/j.1365-313x.2003.01762.x.


Ethylene signaling in Arabidopsis begins with a family of five ethylene receptors that regulate the activity of the Raf-like kinase, CTR1. Recent work to identify novel factors required for modulating ethylene signaling resulted in the isolation of enhanced ethylene response 1 (eer1), a mutant that displays both increased sensitivity and increased amplitude of response to ethylene. Molecular cloning of eer1 reveals that its mutant phenotype results from a loss-of-function mutation in the previously characterized RCN1, one of three PP2A A regulatory subunits in Arabidopsis. Our analysis shows that neither RCN1 expression nor PP2A activity is regulated by ethylene. Instead, we found that Arabidopsis PP2A-1C, a PP2A catalytic subunit previously characterized as interacting with RCN1, associates strongly with the kinase domain of CTR1 in vitro. This likely represents a role for PP2A in modulation of CTR1 activity because an in vitro kinase assay did not reveal phosphorylation of either RCN1 or PP2A-1C by CTR1, indicating that neither of them is a substrate for CTR1. PP2A activity is required for Ras-dependent activation of mammalian Raf, with reductions in PP2A activity significantly compromising the effectiveness of this mechanism. Our genetic and biochemical results suggest that a similar requirement for PP2A activity exists for ethylene signaling, with loss-of-function mutations affecting PP2A activity possibly reducing the effectiveness of CTR1 activation, thus lowering the threshold required for manifestation of ethylene response.

MeSH terms

  • Arabidopsis / drug effects*
  • Arabidopsis / genetics
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / antagonists & inhibitors
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Base Sequence
  • Cloning, Molecular
  • Ethylenes / pharmacology*
  • Gene Expression Regulation, Plant / drug effects
  • Genes, Plant / genetics
  • Mutation / genetics*
  • Phenotype
  • Phosphoprotein Phosphatases / antagonists & inhibitors
  • Phosphoprotein Phosphatases / genetics
  • Phosphoprotein Phosphatases / metabolism*
  • Phosphorylation
  • Protein Binding
  • Protein Kinases / chemistry
  • Protein Kinases / genetics
  • Protein Kinases / metabolism
  • Protein Phosphatase 2
  • Protein Structure, Tertiary
  • Seedlings / drug effects
  • Signal Transduction / drug effects
  • Substrate Specificity


  • Arabidopsis Proteins
  • Ethylenes
  • ethylene
  • Protein Kinases
  • CTR1 protein, Arabidopsis
  • Phosphoprotein Phosphatases
  • Protein Phosphatase 2
  • RCN1 protein, Arabidopsis