Bacteriophytochrome controls photosystem synthesis in anoxygenic bacteria

• Published in: Nature (London) 2002-05, Vol.417 (6885), p.202-205
• Main Authors: Verméglio, André, Giraud, Eric, Fardoux, Joël, Fourrier, Nicolas, Hannibal, Laure, Genty, Bernard, Bouyer, Pierre, Dreyfus, Bernard
• Format: Article
• Language: English
• Subjects: Absorption - radiation effects; Aeschynomene; Amino Acid Sequence; Anaerobiosis; anoxygenic bacteria; Bacteria; Bacterial Proteins - chemistry; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Bacteriophytochrome; Biological and medical sciences; Bradyrhizobium; Bradyrhizobium - genetics; Bradyrhizobium - metabolism; Bradyrhizobium - radiation effects; Ecological adaptation; Fundamental and applied biological sciences. Psychology; Genes; Genes, Bacterial - genetics; Light; Metabolism. Enzymes; Microbiology; Molecular Sequence Data; Multigene Family - genetics; Mutation - genetics; Open Reading Frames - genetics; Oxygen - metabolism; Photosynthesis; Photosynthesis - genetics; Photosynthesis - radiation effects; Photosynthetic Reaction Center Complex Proteins - radiation effects; Pigmentation; Pigments, Biological - chemistry; Pigments, Biological - genetics; Pigments, Biological - metabolism; Proteins
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/417202a

Plants use a set of light sensors to control their growth and development in response to changes in ambient light. In particular, phytochromes exert their regulatory activity by switching between a biologically inactive red-light-absorbing form (Pr) and an active far-red-light absorbing form (Pfr). Recently, biochemical and genetic studies have demonstrated the occurrence of phytochrome-like proteins in photosynthetic and non-photosynthetic bacteria-but little is known about their functions. Here we report the discovery of a bacteriophytochrome located downstream from the photosynthesis gene cluster in a Bradyrhizobium strain symbiont of Aeschynomene. The synthesis of the complete photosynthetic apparatus is totally under the control of this bacteriophytochrome. A similar behaviour is observed for the closely related species Rhodopseudomonas palustris, but not for the more distant anoxygenic photosynthetic bacteria of the genus Rhodobacter, Rubrivivax or Rhodospirillum. Unlike other (bacterio)phytochromes, the carboxy-terminal domain of this bacteriophytochrome contains no histidine kinase features. This suggests a light signalling pathway involving direct protein-protein interaction with no phosphorelay cascade. This specific mechanism of regulation may represent an important ecological adaptation to optimize the plant-bacteria interaction.