Sensitivity of Cyanobacterial Antenna, Reaction Center and CO2 Assimilation Transcripts and Proteins to Moderate UVB: Light Acclimation Potentiates Resistance to UVB †¶

MacDonald, Tara M.; Dubois, Luc; Smith, Laura C.; Campbell, Douglas A.

doi:10.1562/0031-8655(2003)0770405socarc2.0.co2

Cited by 10 publications

(12 citation statements)

References 54 publications

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“…However, the effects can be complex, being dependent not only on the exposure dose of UV‐B, but also on the PPFD to which the cells are exposed during the UV‐B treatment as well as the diatom species. Such dependencies of UV‐B effects on the PPFD during exposure to UV‐B have been previously reported in cyanobacteria (MacDonald et al . 2003), planktonic diatoms (Grzymski, Orrico & Schofield 2001) and higher plants (Warner & Caldwell 1983; Mirecki & Teramura 1984; Cen & Bornman 1990).…”

Section: Discussionsupporting

confidence: 80%

Impact of elevated UV‐B radiation on photosynthetic electron transport, primary productivity and carbon allocation in estuarine epipelic diatoms

Waring

Underwood

Baker

2005

Plant Cell & Environment

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Epipelic diatoms are important components of microphytobenthic biofilms. Cultures of four diatom species ( Amphora coffeaeformis , Cylindrotheca closterium , Navicula perminuta and Nitzschia epithemioides ) and assemblages of mixed diatom species collected from an estuary were exposed to elevated levels of ultraviolet-B (UV-B) radiation. Short exposures to UV-B resulted in decreases in photosystem II (PSII) photochemistry, photosynthetic electron transport, photosynthetic carbon assimilation and changes in the pattern of allocation of assimilated carbon into soluble colloidal, extracellular polysaccharides (EPS) and glucan pools. The magnitude of the effects of the UV-B treatments varied between species and was also dependent upon the photosynthetically active photon flux density (PPFD) to which the cells were also exposed, with effects being greater at lower light levels. Both increases in nonphotochemical quenching of excitation energy in the pigment antennae and photodamage to the D1 reaction centres contributed to decreases in PSII photochemistry. All species demonstrated a rapid ability to recover from perturbations of PSII photochemistry, with some species recovering during the UV-B exposure period. Some of the perturbations induced in carbon metabolism were independent of effects on PSII photochemistry and photosynthetic electron transport. Elevated UV-B can significantly inhibit photosynthetic performance, and modify carbon metabolism in epipelic diatoms. However, the ecological effects of UV-B at the community level are difficult to predict as large variations occur between species.

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Section: Discussionsupporting

confidence: 80%

Impact of elevated UV‐B radiation on photosynthetic electron transport, primary productivity and carbon allocation in estuarine epipelic diatoms

Waring

Underwood

Baker

2005

Plant Cell & Environment

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“…Western analysis of cellular extracts of wild type and PsbUΩ using antibodies to the PSII‐core protein, D1 (A and B) and to the large subunit of Rubisco (C). The anti‐D1 antibodies detect both form 1 and 2 of the protein [33]. Where indicated, chloramphenicol (Cm, 250 μg/mL) was added for the indicated time (h).…”

Section: Methodsmentioning

confidence: 99%

Inactivation of the extrinsic subunit of photosystem II, PsbU, in Synechococcus PCC 7942 results in elevated resistance to oxidative stress

et al. 2006

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PsbU is a subunit of the extrinsic complex attached to the core of photosystem II. A PsbU-mutant of Synechococcus PCC 7942 was isolated based on its elevated resistance to externally applied oxidative stress. PsbU-mutant exhibits fast rates of degradation of the photosystem II core protein, D1, under subsaturating as well as high-light conditions. While forward electron transfer is not affected, back electron flow is severely impaired in the mutant. We suggest that impairment of psbU results in production of reactive-oxygen-species, which trigger antioxidative mechanisms even under standard growth conditions. Accordingly, when challenged with external oxidative stress, these cells are more resistant than wild type cells.

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“…The time of residence of cells at a certain depth ( i.e. the light history of the cells [15,16]), is therefore influenced by the mixing regime prevailing in the water column. The degree of exposure as well as the balance between cell damage and repair processes will then be a function of both mixing velocity and depth (14).…”

Section: Introductionmentioning

confidence: 99%

Photoacclimation to Long‐Term Ultraviolet Radiation Exposure of Natural Sub‐Antarctic Phytoplankton Communities: Fixed Surface Incubations Versus Mixed Mesocosms

Hernando

Schloss

Roy

et al. 2006

Photochem & Photobiology

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Solar UVB radiation (280-320 nm) is known to have detrimental effects on marine phytoplankton. Associated with the seasonal ozone hole in Antarctica, stratospheric ozone depletion occasionally influences the sub-Antarctic (Beagle Channel, Argentina) region, enhancing levels of UVB. The primary objective of this work was to study the effects of several (i.e. 6-10) days of exposure to UVB on the taxonomic composition and photosynthetic inhibition of local phytoplankton communities. For different light treatments, fixed-depth incubations placed in an outdoors water tank were compared with incubations in 1900 L mesocosms, where vertical mixing was present. Phytoplankton growth was inhibited by UV radiation (UVR) in fixed-depth experiments but not in the mixed mesocosms. Under fixed and mixed conditions alike, photosynthesis was significantly inhibited by UVB at the beginning of the experiment but no longer after several days of exposure, suggesting that cells had acclimated to radiation conditions. There was a change in species composition in response to UVR exposure in both experiments, which likely explained acclimation. In the community exposed to fixed conditions this change was from a phytoflagellate-dominated assemblage to a community with high relative abundance of diatoms after 6 days of exposure. UVA was responsible for most of the observed growth inhibition; however, the reduction in photosynthesis was produced by UVB. The reasons behind this variability in responses to UVR are associated with species-specific sensitivity and acclimation, and the previous light history of cells. In the community exposed in mesocosms, an assemblage codominated by phytoflagellates and diatoms was observed at the beginning of the experiments. After 10 days of exposure, green algae (Eutreptiella sp.) had increased, and phytoflagellates were the dominant group. The synthesis of mycosporine-like amino acids (MAAs), antioxidant enzymes and photosynthetic antenna pigments, in relation to repair and protection processes, may explain the reduced inhibition of both growth and photosynthesis that was observed in the phytoplankton community after several days of exposure. For environments such as the Beagle Channel seasonally exposed to the ozone hole, the results obtained from the fixed-depth experiments show that species can cope with UVR by means of MAA synthesis, while mixing would primarily promote a change in species composition and defense strategies.

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Sensitivity of Cyanobacterial Antenna, Reaction Center and CO2 Assimilation Transcripts and Proteins to Moderate UVB: Light Acclimation Potentiates Resistance to UVB †¶

Cited by 10 publications

References 54 publications

Impact of elevated UV‐B radiation on photosynthetic electron transport, primary productivity and carbon allocation in estuarine epipelic diatoms

Impact of elevated UV‐B radiation on photosynthetic electron transport, primary productivity and carbon allocation in estuarine epipelic diatoms

Inactivation of the extrinsic subunit of photosystem II, PsbU, in Synechococcus PCC 7942 results in elevated resistance to oxidative stress

Photoacclimation to Long‐Term Ultraviolet Radiation Exposure of Natural Sub‐Antarctic Phytoplankton Communities: Fixed Surface Incubations Versus Mixed Mesocosms

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