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Aquatic Microbial Ecology

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AME 70:87-92 (2013)  -  DOI:

Photoinhibition in benthic diatom assemblages under light stress

P. Cartaxana1,*, N. Domingues1,2, S. Cruz3, B. Jesus2,4, M. Laviale3, J. Serôdio3, J. Marques da Silva

1Centro de Oceanografia, Faculdade de Ciências da Universidade de Lisboa, 1749-016 Lisboa, Portugal
2Departamento de Biologia Vegetal and Centro de Biodiversidade, Genómica Integrativa e Funcional (BioFIG), Faculdade de Ciências da Universidade de Lisboa, 1749-016 Lisboa, Portugal
3Departamento de Biologia and CESAM – Centro de Estudos do Ambiente e do Mar, Universidade de Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal
4LUNAM université, Université de Nantes, Mer Molécules Santé EA 2160, Faculté des Sciences et des Techniques, BP 92208, 44322 Nantes cedex 3, France

ABSTRACT: Microphytobenthos are frequently subjected to light intensities higher than those required to saturate photosynthesis, which consequently can cause photoinhibition. Photosystem II (PSII) protein D1 (the main target of photoinhibition) and xanthophyll cycle pigments were quantified in epipelic benthic diatom assemblages under high irradiance, in the presence of inhibitors and promoters of photoprotection mechanisms. Levels of D1 protein were significantly lower under high irradiance (1 h, 1500 µmol photons m–2 s–1) than under low light (80 µmol photons m–2 s–1), corresponding to a photoinhibition of 22 to 29%. Photoinhibition increased to 44 and 80% in the presence of lincomycin (inhibitor of chloroplast-protein synthesis) and dithiothreitol (inhibitor of the xanthophyll cycle), respectively. High light treatment had no significant effect on D1 protein concentrations in the presence of added glutathione and ascorbate, scavengers of reactive oxygen species (ROS). In contrast, the ROS promoter methylviologen increased photoinhibition to 63%. Under light stress, the functional stability of PSII reaction centres of the studied epipelic benthic diatoms was more dependent on xanthophyll cycle activation than on D1 protein recycling mechanisms, and our results substantiate the role of antioxidants in photoprotection via ROS scavenging.

KEY WORDS: Microphytobenthos · Xanthophyll cycle · D1 protein · Reactive oxygen species · Photoprotection · Antioxidants

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Cite this article as: Cartaxana P, Domingues N, Cruz S, Jesus B, Laviale M, Serôdio J, Marques da Silva J (2013) Photoinhibition in benthic diatom assemblages under light stress. Aquat Microb Ecol 70:87-92.

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