Light history influences the response of the marine cyanobacterium Synechococcus sp. WH7803 to oxidative stress

TitleLight history influences the response of the marine cyanobacterium Synechococcus sp. WH7803 to oxidative stress
Publication TypeJournal Article
Year of Publication2011
AuthorsBlot N, Mella-Flores D, Six C, Lecorguille G, Boutte C, Peyrat A, Monnier A, Ratin M, Gourvil P, Campbell DA, Garczarek L
JournalPlant Physiology
Keywords2011, rcc, SBR$_\textrmP$hyto$_\textrmP$PM, sbr?hyto?app

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 (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 addition of 25 microM H2O2. Depending upon light conditions and H2O2 concentration, the latter oxidizing agent induced photosystem II inactivation through both direct damages to the reaction centres 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 damages 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 to LL cells, but up-regulated by oxidative stress under both growth irradiances.