title: PHYTOCHROME-DEPENDENT LATE-FLOWERING accelerates flowering through physical interactions with phytochrome B and CONSTANS.
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.
authors.affiliation: Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Motomu
authors.initials: M
authors.lastname: Endo
authors.forename: Yoshiyasu
authors.initials: Y
authors.lastname: Tanigawa
authors.forename: Tadashi
authors.initials: T
authors.lastname: Murakami
authors.forename: Takashi
authors.initials: T
authors.lastname: Araki
authors.forename: Akira
authors.initials: A
authors.lastname: Nagatani
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D035264:Flowers / Q000502:physiology*; D047468:Immunoprecipitation; D008027:Light; D046912:Multiprotein Complexes / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D017440:Photoperiod; D055519:Photoreceptors, Plant / Q000378:metabolism / Q000502:physiology*; D051939:Phytochrome B / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C092776:CONSTANS protein, Arabidopsis; D004268:DNA-Binding Proteins; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; C585477:PHL protein, Arabidopsis; C497952:PHYB protein, Arabidopsis; D055519:Photoreceptors, Plant; D014157:Transcription Factors; D051939:Phytochrome B
keywords: FT; light signaling