title: Phytochrome and retrograde signalling pathways converge to antagonistically regulate a light-induced transcriptional network.
abstract: Plastid-to-nucleus retrograde signals emitted by dysfunctional chloroplasts impact photomorphogenic development, but the molecular link between retrograde- and photosensory-receptor signalling has remained unclear. Here, we show that the phytochrome and retrograde signalling (RS) pathways converge antagonistically to regulate the expression of the nuclear-encoded transcription factor GLK1, a key regulator of a light-induced transcriptional network central to photomorphogenesis. GLK1 gene transcription is directly repressed by PHYTOCHROME-INTERACTING FACTOR (PIF)-class bHLH transcription factors in darkness, but light-activated phytochrome reverses this activity, thereby inducing expression. Conversely, we show that retrograde signals repress this induction by a mechanism independent of PIF mediation. Collectively, our data indicate that light at moderate levels acts through the plant's nuclear-localized sensory-photoreceptor system to induce appropriate photomorphogenic development, but at excessive levels, sensed through the separate plastid-localized RS system, acts to suppress such development, thus providing a mechanism for protection against photo-oxidative damage by minimizing the tissue exposure to deleterious radiation.
authors.affiliation: Department of Molecular Genetics, Center for Research in Agricultural Genomics (CRAG), CSIC-IRTA-UAB-UB, Barcelona 08193, Spain.
authors.forename: Guiomar
authors.initials: G
authors.lastname: Martín
authors.affiliation: Department of Molecular Genetics, Center for Research in Agricultural Genomics (CRAG), CSIC-IRTA-UAB-UB, Barcelona 08193, Spain.|Department of Bioengineering, IQS School of Engineering, Barcelona 08017, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Leivar
authors.affiliation: Department of Molecular Genetics, Center for Research in Agricultural Genomics (CRAG), CSIC-IRTA-UAB-UB, Barcelona 08193, Spain.
authors.forename: Dolores
authors.initials: D
authors.lastname: Ludevid
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, California 94720, USA.|Plant Gene Expression Center, Agriculture Research Service (ARS), US Department of Agriculture (USDA), Albany, California 94710, USA.
authors.forename: James M
authors.initials: JM
authors.lastname: Tepperman
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, California 94720, USA.|Plant Gene Expression Center, Agriculture Research Service (ARS), US Department of Agriculture (USDA), Albany, California 94710, USA.
authors.forename: Peter H
authors.initials: PH
authors.lastname: Quail
authors.affiliation: Department of Molecular Genetics, Center for Research in Agricultural Genomics (CRAG), CSIC-IRTA-UAB-UB, Barcelona 08193, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Monte
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D003624:Darkness; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects*; D053263:Gene Regulatory Networks / Q000528:radiation effects; D008027:Light; D009024:Morphogenesis / Q000528:radiation effects; D010834:Phytochrome / Q000378:metabolism*; D018087:Plastids / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D015398:Signal Transduction / Q000528:radiation effects*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D010834:Phytochrome; D014157:Transcription Factors; C468867:GLK1 protein, Arabidopsis