title: UVB-induced DNA and photosystem II damage in two intertidal green macroalgae: distinct survival strategies in UV-screening and non-screening Chlorophyta.
abstract: Ultraviolet-B-induced (UVB, 280-315 nm) accumulation of cyclobutane pyrimidine dimers (CPDs) and deactivation of photosystem II (PS II) was quantified in two intertidal green macroalgae, Ulva clathrata and Rhizoclonium riparium. The species were chosen due to their shared habitats but contrasting UVB screening potentials. In the non-screening U. clathrata CPDs accumulated and PS II activity declined as a linear function of applied UVB irradiance. In R. riparium UVB-induced damage was significantly lower than in U. clathrata, demonstrating an efficient UVB protection of DNA and PS II by screening. Based on the UVB irradiance reaching the chloroplasts, both species showed an identical intrinsic sensitivity of PS II towards UVB, but DNA lesions accumulated slower in U. clathrata. While repair of CPDs was similar in both species, U. clathrata was capable of restoring its PS II function decidedly faster than R. riparium. In R. riparium efficient screening may represent an adaptation to its high light habitat, whereas in U. clathrata high repair rates of PS II appear to be important to survive natural UVB exposure. The role of shading of the nucleus by the large chloroplasts in U. clathrata is discussed.
authors.affiliation: Botanical Institute, Christian-Albrechts-University Kiel, Olshausenstr. 40, 24098 Kiel, Germany. Electronic address: fpescheck@bot.uni-kiel.de.
authors.forename: Frauke
authors.initials: F
authors.lastname: Pescheck
authors.affiliation: GEOMAR Helmholtz Centre for Ocean Research Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany.
authors.forename: Kai T
authors.initials: KT
authors.lastname: Lohbeck
authors.affiliation: Institute for Polar Ecology, Christian-Albrechts-University Kiel, Wischhofstr. 1-3, 24148 Kiel, Germany; Bioforsk Norwegian Institute for Agricultural and Environmental Research, Kudalsveien 6, 8049 Bodø, Norway.
authors.forename: Michael Y
authors.initials: MY
authors.lastname: Roleda
authors.affiliation: Botanical Institute, Christian-Albrechts-University Kiel, Olshausenstr. 40, 24098 Kiel, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Bilger
mesh_terms: D002138:Calibration; D000460:Chlorophyta / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism / Q000528:radiation effects; D004247:DNA / Q000737:chemistry; D004249:DNA Damage / Q000528:radiation effects*; D004260:DNA Repair; D007118:Immunoassay / Q000592:standards; D045332:Photosystem II Protein Complex / Q000737:chemistry / Q000378:metabolism*; D011740:Pyrimidine Dimers / Q000032:analysis / Q000592:standards; D012624:Seaweed / Q000235:genetics / Q000378:metabolism*; D014466:Ultraviolet Rays
chemical_list: D045332:Photosystem II Protein Complex; D011740:Pyrimidine Dimers; D004247:DNA
keywords: Cyclobutane pyrimidine dimers; Green alga; Photosynthesis; Repair; Rhizoclonium riparium; Screening; Ultraviolet radiation; Ulva clathrata