title: Photon flux density-dependent gene expression in Synechocystis sp. PCC 6803 is regulated by a small, redox-responsive, LuxR-type regulator.
abstract: The expression of many cyanobacterial genes is regulated by the redox state of the photosynthetic electron transport chain. However, factors involved in this regulation have not been identified. In this study, we demonstrate that a small LuxR-type regulator in Synechocystis sp. PCC 6803, PedR (Ssl0564), senses the activity of photosynthetic electron transport to achieve the photon flux density-dependent transcriptional regulation. PedR is constitutively expressed in Synechocystis cells and exists as a dimer bridged by intermolecular disulfide bond(s). It activates the expression of chlL, chlN, chlB, and slr1957 and represses that of ndhD2, rpe, and the pedR (ssl0564)-sll0296 operon under conditions where the activity of photosynthetic electron transport is low. When the supply of reducing equivalents from photosynthetic electron transport chain increases upon the elevation of photon flux density, PedR is inactivated through its conformational change within 5 min. This mechanism enables transient induction or repression of the target genes in response to sudden changes in light environment. The fact that orthologs of PedR are conserved among all the cyanobacterial genomes sequenced so far indicates that this type of transcriptional regulation is essential for cyanobacteria to acclimate to changing environments.
authors.affiliation: Department of Biochemistry and Molecular Biology, Faculty of Science, Saitama University, Saitama 338-8570, Japan.
authors.forename: Kinu
authors.initials: K
authors.lastname: Nakamura
authors.forename: Yukako
authors.initials: Y
authors.lastname: Hihara
mesh_terms: D000595:Amino Acid Sequence; D004220:Disulfides / Q000737:chemistry; D004579:Electron Transport; D005786:Gene Expression Regulation; D005947:Glucose / Q000737:chemistry; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D010084:Oxidation-Reduction; D017785:Photons; D010788:Photosynthesis; D010802:Phylogeny; D012313:RNA / Q000737:chemistry; D012097:Repressor Proteins / Q000235:genetics* / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D046939:Synechocystis / Q000737:chemistry*; D015534:Trans-Activators / Q000235:genetics* / Q000502:physiology*
chemical_list: D004220:Disulfides; D012097:Repressor Proteins; D015534:Trans-Activators; C064778:LuxR autoinducer binding proteins; D012313:RNA; D005947:Glucose