title: A molecular framework for light and gibberellin control of cell elongation.
abstract: Cell elongation during seedling development is antagonistically regulated by light and gibberellins (GAs). Light induces photomorphogenesis, leading to inhibition of hypocotyl growth, whereas GAs promote etiolated growth, characterized by increased hypocotyl elongation. The mechanism underlying this antagonistic interaction remains unclear. Here we report on the central role of the Arabidopsis thaliana nuclear transcription factor PIF4 (encoded by PHYTOCHROME INTERACTING FACTOR 4) in the positive control of genes mediating cell elongation and show that this factor is negatively regulated by the light photoreceptor phyB (ref. 4) and by DELLA proteins that have a key repressor function in GA signalling. Our results demonstrate that PIF4 is destabilized by phyB in the light and that DELLAs block PIF4 transcriptional activity by binding the DNA-recognition domain of this factor. We show that GAs abrogate such repression by promoting DELLA destabilization, and therefore cause a concomitant accumulation of free PIF4 in the nucleus. Consistent with this model, intermediate hypocotyl lengths were observed in transgenic plants over-accumulating both DELLAs and PIF4. Destabilization of this factor by phyB, together with its inactivation by DELLAs, constitutes a protein interaction framework that explains how plants integrate both light and GA signals to optimize growth and development in response to changing environments.
authors.affiliation: Departamento de Genética Molecular de Plantas, Centro Nacional de Biotecnología-CSIC, Campus Univ. Autónoma de Madrid, Cantoblanco. c/ Darwin 3, 28049 Madrid, Spain.
authors.forename: Miguel
authors.initials: M
authors.lastname: de Lucas
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Davière
authors.forename: Mariana
authors.initials: M
authors.lastname: Rodríguez-Falcón
authors.forename: Mariela
authors.initials: M
authors.lastname: Pontin
authors.forename: Juan Manuel
authors.initials: JM
authors.lastname: Iglesias-Pedraz
authors.forename: Séverine
authors.initials: S
authors.lastname: Lorrain
authors.forename: Christian
authors.initials: C
authors.lastname: Fankhauser
authors.forename: Miguel Angel
authors.initials: MA
authors.lastname: Blázquez
authors.forename: Elena
authors.initials: E
authors.lastname: Titarenko
authors.forename: Salomé
authors.initials: S
authors.lastname: Prat
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051792:Basic Helix-Loop-Helix Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D048430:Cell Shape / Q000187:drug effects* / Q000528:radiation effects*; D048429:Cell Size / Q000187:drug effects / Q000528:radiation effects; D018744:DNA, Plant / Q000378:metabolism; D005875:Gibberellins / Q000494:pharmacology*; D018546:Hypocotyl / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D008027:Light; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051939:Phytochrome B / Q000235:genetics / Q000378:metabolism; D018515:Plant Leaves / Q000378:metabolism; D011485:Protein Binding; D036226:Seedlings / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014026:Nicotiana / Q000378:metabolism; D014230:Triazoles / Q000494:pharmacology; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D018744:DNA, Plant; D005875:Gibberellins; D009687:Nuclear Proteins; D051939:Phytochrome B; D014230:Triazoles; C497952:PHYB protein, Arabidopsis; C459466:PIF4 protein, Arabidopsis; C053370:paclobutrazol