title: Elevated CO2 alleviates high PAR and UV stress in the unicellular chlorophyte Dunaliella tertiolecta.
abstract: The effects of increased CO2 and irradiance on the physiological performance of the chlorophyte Dunaliella tertiolecta were studied at different PAR and UVR (UVA + UVB) irradiances, simulating the solar radiation at different depths, at present (390 ppmv, LC) and predicted CO2 levels for the year 2100 (1000 ppmv, HC). Elevated CO2 resulted in higher optimum and effective quantum yields (F(v)/F(m) and ϕPSII, respectively), electron transport rates (ETR) and specific growth rates (μ). Cell stress was alleviated in HC with respect to LC as evidenced by a decrease in reactive oxygen species (ROS) accumulation. DNA damage showed a 42-fold increase in cyclobutane-pyrimidine dimer (CPD) formation under the highest irradiance (1100 μmol quanta m(-2) s(-1)) in LC with respect to the lowest irradiance (200 μmol quanta m(-2) s(-1)). Photolyase (CII-PCD-PL) gene expression was upregulated under HC resulting in a drastic decrease in CPD accumulation to only 25% with respect to LC. Proliferating cell nuclear antigen (PCNA) accumulation was always higher in HC and the accumulation pattern indicated its involvement in repair or growth depending on the irradiance dose. The repressor of silencing (ROS1) was only marginally involved in the response, suggesting that photoreactivation was the most relevant mechanism to overcome UVR damage. Our results demonstrate that future scenarios of global change result in alleviation of irradiance stress by CO2-induced photoprotection in D. tertiolecta.
authors.affiliation: Department of Ecology, Faculty of Sciences, University of Málaga, Bvd. Louis Pasteur s/n, 29010 Málaga, Spain. candelagg@uma.es.
authors.forename: Candela
authors.initials: C
authors.lastname: García-Gómez
authors.forename: Francisco J L
authors.initials: FJ
authors.lastname: Gordillo
authors.forename: Armando
authors.initials: A
authors.lastname: Palma
authors.forename: M Rosario
authors.initials: MR
authors.lastname: Lorenzo
authors.forename: María
authors.initials: M
authors.lastname: Segovia
mesh_terms: D002245:Carbon Dioxide / Q000737:chemistry*; D000460:Chlorophyta / Q000378:metabolism / Q000528:radiation effects*; D004249:DNA Damage / Q000528:radiation effects*; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000235:genetics / Q000378:metabolism; D004579:Electron Transport / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000378:metabolism; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D011740:Pyrimidine Dimers / Q000737:chemistry / Q000378:metabolism; D011789:Quantum Theory; D016601:RNA-Binding Proteins / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D014466:Ultraviolet Rays; D015854:Up-Regulation / Q000528:radiation effects
chemical_list: D045332:Photosystem II Protein Complex; D018809:Proliferating Cell Nuclear Antigen; D011740:Pyrimidine Dimers; D016601:RNA-Binding Proteins; D017382:Reactive Oxygen Species; D002245:Carbon Dioxide; D004255:Deoxyribodipyrimidine Photo-Lyase