PPKs mediate direct signal transfer from phytochrome photoreceptors to transcription factor PIF3

5 years ago

PPKs mediate direct signal transfer from phytochrome photoreceptors to transcription factor PIF3

Shou-Ling Xu, Robert J. Chalkley, Weimin Ni, Alma L. Burlingame, Zhi-Yong Wang, Eduardo González-Grandío, Andreas F. R. Huhmer, Peter H. Quail

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.

Publisher URL: http://www.nature.com/articles/ncomms15236

DOI: 10.1038/ncomms15236