PHYTOCHROME-DEPENDENT LATE-FLOWERING accelerates flowering through physical interactions with phytochrome B and CONSTANS

Proc Natl Acad Sci U S A. 2013 Oct 29;110(44):18017-22. doi: 10.1073/pnas.1310631110. Epub 2013 Oct 14.

Abstract

In flowering plants, light is one of the major environmental stimuli that determine the timing of the transition from the vegetative to reproductive phase. In Arabidopsis, phytochrome B (phyB); phyA; cryptochrome 2; and flavin-binding, KELCH repeat, F-BOX 1 are major photoreceptors that regulate flowering. Unlike phyA; cryptochrome 2; and flavin-binding, KELCH repeat, F-BOX 1, phyB delays flowering mainly by destabilizing the CONSTANS (CO) protein, whose reduction leads to decreased expression of a florigen gene, flowering locus T. However, it remains unclear how the phyB-mediated CO destabilization is mechanistically regulated. Here, we identify a unique phytochrome-dependent late-flowering (PHL) gene, which is mainly involved in the phyB-dependent regulation of flowering. Plants with mutant phl exhibited a late-flowering phenotype, especially under long-day conditions. The late-flowering phenotype of the phl mutant was completely overridden by a phyB mutation, indicating that PHL normally accelerates flowering by countering the inhibitory effect of phyB on flowering. Accordingly, PHL physically interacted with phyB both in vitro and in vivo in a red light-dependent manner. Furthermore, in the presence of phyB under red light, PHL interacted with CO as well. Taken together, we propose that PHL regulates photoperiodic flowering by forming a phyB-PHL-CO tripartite complex.

Keywords: FT; light signaling.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / genetics
  • Arabidopsis / physiology*
  • Arabidopsis Proteins / metabolism*
  • DNA-Binding Proteins / metabolism*
  • Flowers / physiology*
  • Immunoprecipitation
  • Light*
  • Multiprotein Complexes / metabolism*
  • Nuclear Proteins / metabolism*
  • Photoperiod
  • Photoreceptors, Plant / metabolism
  • Photoreceptors, Plant / physiology*
  • Phytochrome B / metabolism*
  • Transcription Factors / metabolism*

Substances

  • Arabidopsis Proteins
  • CONSTANS protein, Arabidopsis
  • DNA-Binding Proteins
  • Multiprotein Complexes
  • Nuclear Proteins
  • PHL protein, Arabidopsis
  • PHYB protein, Arabidopsis
  • Photoreceptors, Plant
  • Transcription Factors
  • Phytochrome B