title: Control of peripheral light-harvesting complex synthesis by a bacteriophytochrome in the aerobic photosynthetic bacterium Bradyrhizobium strain BTAi1.
abstract: The recent sequence analysis of the photosynthetic and plant-symbiotic Bradyrhizobium sp. strain BTAi1 revealed the unexpected presence of a pucBA operon encoding the apoproteins of peripheral light-harvesting (LH) complexes. This pucBA operon is found close to a bacteriophytochrome gene (BphP3(B BTAi1)) and a two-component transcriptional regulator gene (TF(BTAi1) gene). In this study, we show that BphP3(B BTAi1) acts as a bona fide bacteriophytochrome and controls, according to light conditions, the expression of the pucBA operon found in its vicinity. This light regulatory pathway is very similar to the one previously described for chromo-BphP4(Rp) in Rhodopseudomonas palustris and conducts the synthesis of a peripheral LH complex. This LH complex presents a single absorption band at low temperature, centered at 803 nm. Fluorescence emission analysis of intact cells indicates that this peripheral LH complex does not act as an efficient light antenna. One putative function of this LH complex could be to evacuate excess light energy in order to protect Bradyrhizobium strain BTAi1, an aerobic anoxygenic photosynthetic bacterium, against photooxidative damage during photosynthesis.
authors.affiliation: Laboratoire des Symbioses Tropicales et Méditerranéennes, IRD, CIRAD, AGRO-M, INRA, UM2, TA A-82/J, Campus de Baillarguet, 34398 Montpellier Cedex 5, France.
authors.forename: Marianne
authors.initials: M
authors.lastname: Jaubert
authors.forename: Laurie
authors.initials: L
authors.lastname: Vuillet
authors.forename: Laure
authors.initials: L
authors.lastname: Hannibal
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Adriano
authors.forename: Joël
authors.initials: J
authors.lastname: Fardoux
authors.forename: Pierre
authors.initials: P
authors.lastname: Bouyer
authors.forename: Katia
authors.initials: K
authors.lastname: Bonaldi
authors.forename: Darrell
authors.initials: D
authors.lastname: Fleischman
authors.forename: Eric
authors.initials: E
authors.lastname: Giraud
authors.forename: André
authors.initials: A
authors.lastname: Verméglio
mesh_terms: D000332:Aerobiosis; D001426:Bacterial Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D020369:Bradyrhizobium / Q000235:genetics / Q000378:metabolism*; D000071677:Histidine Kinase; D045342:Light-Harvesting Protein Complexes / Q000235:genetics / Q000378:metabolism*; D009876:Operon / Q000235:genetics; D010641:Phenotype; D010788:Photosynthesis / Q000235:genetics / Q000502:physiology*; D010802:Phylogeny; D011494:Protein Kinases / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D011494:Protein Kinases; D000071677:Histidine Kinase