title: Light history influences the response of the marine cyanobacterium Synechococcus sp. WH7803 to oxidative stress.
abstract: Marine Synechococcus undergo a wide range of environmental stressors, especially high and variable irradiance, which may induce oxidative stress through the generation of reactive oxygen species (ROS). While light and ROS could act synergistically on the impairment of photosynthesis, inducing photodamage and inhibiting photosystem II repair, acclimation to high irradiance is also thought to confer resistance to other stressors. To identify the respective roles of light and ROS in the photoinhibition process and detect a possible light-driven tolerance to oxidative stress, we compared the photophysiological and transcriptomic responses of Synechococcus sp. WH7803 acclimated to low light (LL) or high light (HL) to oxidative stress, induced by hydrogen peroxide (H₂O₂) or methylviologen. While photosynthetic activity was much more affected in HL than in LL cells, only HL cells were able to recover growth and photosynthesis after the addition of 25 μM H₂O₂. Depending upon light conditions and H₂O₂ concentration, the latter oxidizing agent induced photosystem II inactivation through both direct damage to the reaction centers and inhibition of its repair cycle. Although the global transcriptome response appeared similar in LL and HL cells, some processes were specifically induced in HL cells that seemingly helped them withstand oxidative stress, including enhancement of photoprotection and ROS detoxification, repair of ROS-driven damage, and regulation of redox state. Detection of putative LexA binding sites allowed the identification of the putative LexA regulon, which was down-regulated in HL compared with LL cells but up-regulated by oxidative stress under both growth irradiances.
authors.affiliation: UPMC-Université Paris 06, Station Biologique, 29680 Roscoff, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Blot
authors.forename: Daniella
authors.initials: D
authors.lastname: Mella-Flores
authors.forename: Christophe
authors.initials: C
authors.lastname: Six
authors.forename: Gildas
authors.initials: G
authors.lastname: Le Corguillé
authors.forename: Christophe
authors.initials: C
authors.lastname: Boutte
authors.forename: Anne
authors.initials: A
authors.lastname: Peyrat
authors.forename: Annabelle
authors.initials: A
authors.lastname: Monnier
authors.forename: Morgane
authors.initials: M
authors.lastname: Ratin
authors.forename: Priscillia
authors.initials: P
authors.lastname: Gourvil
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Campbell
authors.forename: Laurence
authors.initials: L
authors.lastname: Garczarek
mesh_terms: D000064:Acclimatization / Q000187:drug effects / Q000528:radiation effects; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D016000:Cluster Analysis; D004579:Electron Transport / Q000187:drug effects / Q000528:radiation effects; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects / Q000528:radiation effects; D005798:Genes, Bacterial / Q000235:genetics; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008027:Light; D008969:Molecular Sequence Data; D015999:Multivariate Analysis; D020411:Oligonucleotide Array Sequence Analysis; D018384:Oxidative Stress / Q000187:drug effects / Q000528:radiation effects*; D010269:Paraquat / Q000494:pharmacology; D010788:Photosynthesis / Q000187:drug effects / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000378:metabolism; D018085:Regulon / Q000235:genetics; D012623:Seawater / Q000382:microbiology*; D046940:Synechococcus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects*; D059467:Transcriptome
chemical_list: D001426:Bacterial Proteins; D045332:Photosystem II Protein Complex; D006861:Hydrogen Peroxide; D010269:Paraquat