PPKs Mediate Direct Signal Transfer From Phytochrome Photoreceptors to Transcription Factor PIF3

Nat Commun. 2017 May 11;8:15236. doi: 10.1038/ncomms15236.

Abstract

Upon light-induced nuclear translocation, phytochrome (phy) sensory photoreceptors interact with, and induce rapid phosphorylation and consequent ubiquitin-mediated degradation of, transcription factors, called PIFs, thereby regulating target gene expression and plant development. Nevertheless, the biochemical mechanism of phy-induced PIF phosphorylation has remained ill-defined. Here we identify a family of nuclear protein kinases, designated Photoregulatory Protein Kinases (PPK1-4; formerly called MUT9-Like Kinases (MLKs)), that interact with PIF3 and phyB in a light-induced manner in vivo. Genetic analyses demonstrate that the PPKs are collectively necessary for the normal light-induced phosphorylation and degradation of PIF3. PPK1 directly phosphorylates PIF3 in vitro, with a phosphosite pattern that strongly mimics the light-induced pattern in vivo. These data establish that the PPKs are directly involved in catalysing the photoactivated-phy-induced phosphorylation of PIF3 in vivo, and thereby are critical components of a transcriptionally centred signalling hub that pleiotropically regulates plant growth and development in response to multiple signalling pathways.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Arabidopsis / genetics
  • Arabidopsis / metabolism
  • Arabidopsis / radiation effects*
  • Arabidopsis Proteins / genetics*
  • Arabidopsis Proteins / metabolism
  • Basic Helix-Loop-Helix Transcription Factors / genetics*
  • Basic Helix-Loop-Helix Transcription Factors / metabolism
  • Gene Expression Regulation, Plant*
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Light
  • Light Signal Transduction
  • Phosphorylation / radiation effects
  • Phytochrome B / genetics
  • Phytochrome B / metabolism
  • Protein Processing, Post-Translational*
  • Protein-Serine-Threonine Kinases / genetics*
  • Protein-Serine-Threonine Kinases / metabolism
  • Proteolysis
  • Ubiquitination

Substances

  • Arabidopsis Proteins
  • Basic Helix-Loop-Helix Transcription Factors
  • Isoenzymes
  • PHYB protein, Arabidopsis
  • PIF3 protein, Arabidopsis
  • Phytochrome B
  • MLK1 protein, Arabidopsis
  • Protein-Serine-Threonine Kinases