title: The Pkn22 Ser/Thr kinase in Nostoc PCC 7120: role of FurA and NtcA regulators and transcript profiling under nitrogen starvation and oxidative stress.
abstract: BACKGROUND
  The filamentous cyanobacterium Nostoc sp. strain PCC 7120 can fix N2 when combined nitrogen is not available. Furthermore, it has to cope with reactive oxygen species generated as byproducts of photosynthesis and respiration. We have previously demonstrated the synthesis of Ser/Thr kinase Pkn22 as an important survival response of Nostoc to oxidative damage. In this study we wished to investigate the possible involvement of this kinase in signalling peroxide stress and nitrogen deprivation.
  
  
  RESULTS
  Quantitative RT-PCR experiments revealed that the pkn22 gene is induced in response to peroxide stress and to combined nitrogen starvation. Electrophoretic motility assays indicated that the pkn22 promoter is recognized by the global transcriptional regulators FurA and NtcA. Transcriptomic analysis comparing a pkn22-insertion mutant and the wild type strain indicated that this kinase regulates genes involved in important cellular functions such as photosynthesis, carbon metabolism and iron acquisition. Since metabolic changes may lead to oxidative stress, we investigated whether this is the case with nitrogen starvation. Our results rather invalidate this hypothesis thereby suggesting that the function of Pkn22 under nitrogen starvation is independent of its role in response to peroxide stress.
  
  
  CONCLUSIONS
  Our analyses have permitted a more complete functional description of Ser/Thr kinase in Nostoc. We have decrypted the transcriptional regulation of the pkn22 gene, and analysed the whole set of genes under the control of this kinase in response to the two environmental changes often encountered by cyanobacteria in their natural habitat: oxidative stress and nitrogen deprivation.
authors.affiliation: Aix-Marseille University and CNRS, Laboratoire de Chimie Bactérienne - UMR7283, IMM, 31 Chemin Joseph Aiguier, 13402, Marseille cedex 20, France. fanyingping@gmail.com.
authors.forename: Fan
authors.initials: F
authors.lastname: Yingping
authors.affiliation: Department of Microbiology and Molecular Medicine, CMU, Medical Faculty, University of Geneva, Genève, 1211, Switzerland. sylvain.lemeille@hotmail.fr.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Lemeille
authors.affiliation: Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, 50009, Zaragoza, Spain. andresglez2005@gmail.com.
authors.forename: Andrés
authors.initials: A
authors.lastname: González
authors.affiliation: Aix-Marseille University and CNRS, Laboratoire de Chimie Bactérienne - UMR7283, IMM, 31 Chemin Joseph Aiguier, 13402, Marseille cedex 20, France. vrisoul@imm.cnrs.fr.
authors.forename: Véronique
authors.initials: V
authors.lastname: Risoul
authors.affiliation: Plate-forme Transcriptome FR3479, IMM-CNRS, Marseille, France. ydenis@imm.cnrs.fr.
authors.forename: Yann
authors.initials: Y
authors.lastname: Denis
authors.affiliation: CEA, DSV, IBEB, SBVME, Saint-Paul-lez-Durance, F-13108, France. pierre.richaud@cea.fr.|CNRS, UMR 7265 Biol Veget & Microbiol Environ, Saint-Paul-lez-Durance, F-13108, France. pierre.richaud@cea.fr.|Aix Marseille Université, BVME UMR7265, Marseille, F-13284, France. pierre.richaud@cea.fr.
authors.forename: Pierre
authors.initials: P
authors.lastname: Richaud
authors.affiliation: Aix-Marseille University and CNRS, Laboratoire de Chimie Bactérienne - UMR7283, IMM, 31 Chemin Joseph Aiguier, 13402, Marseille cedex 20, France. otmanelamrabet@gmail.com.
authors.forename: Otmane
authors.initials: O
authors.lastname: Lamrabet
authors.affiliation: Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, 50009, Zaragoza, Spain. fillat@unizar.es.
authors.forename: Maria F
authors.initials: MF
authors.lastname: Fillat
authors.affiliation: Aix-Marseille University and CNRS, Laboratoire de Chimie Bactérienne - UMR7283, IMM, 31 Chemin Joseph Aiguier, 13402, Marseille cedex 20, France. cczhang@imm.cnrs.fr.
authors.forename: Cheng-Cai
authors.initials: CC
authors.lastname: Zhang
authors.affiliation: Aix-Marseille University and CNRS, Laboratoire de Chimie Bactérienne - UMR7283, IMM, 31 Chemin Joseph Aiguier, 13402, Marseille cedex 20, France. latifi@imm.cnrs.fr.
authors.forename: Amel
authors.initials: A
authors.lastname: Latifi
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002244:Carbon / Q000378:metabolism; D020869:Gene Expression Profiling; D006861:Hydrogen Peroxide / Q000633:toxicity; D007501:Iron / Q000378:metabolism; D008969:Molecular Sequence Data; D009584:Nitrogen / Q000378:metabolism*; D046937:Nostoc / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D018384:Oxidative Stress / Q000187:drug effects / Q000235:genetics*; D010788:Photosynthesis / Q000235:genetics; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D059467:Transcriptome / Q000187:drug effects
chemical_list: D001426:Bacterial Proteins; D014157:Transcription Factors; D002244:Carbon; D006861:Hydrogen Peroxide; D007501:Iron; D017346:Protein Serine-Threonine Kinases; D009584:Nitrogen