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Differential effect of ultraviolet exposure (UVR) in the stress response of the Dinophycea Gymnodinium sp. and the Chlorophyta Dunaliella tertiolecta: mortality versus survival

Differential effect of ultraviolet exposure (UVR) in the stress response of the Dinophycea Gymnodinium sp. and the Chlorophyta Dunaliella tertiolecta: mortality versus survival
Differential effect of ultraviolet exposure (UVR) in the stress response of the Dinophycea Gymnodinium sp. and the Chlorophyta Dunaliella tertiolecta: mortality versus survival
Dunaliella tertiolecta (Chlorophyta) and Gymnodinium sp. (Dinophyceae) cells were exposed to ultraviolet radiation (UVR) (PAR, UVA and UVB: PAB) for 6 days either continuously or during a photoperiod. Both UVR treatments were harmful to Gymnodinium but exposure to continuous PAB had the most dramatic effects. Although a number of lesions/damage could have happened during the first few hours of exposure to UVR, in less than 24 h, Gymnodinium lost its ability to detoxify ROS efficiently, photoinhibition occurred, thymine dimers formed in the DNA, caspase-like enzymatic activities DEVDase sharply increased and cells died as determined by SYTOX-green staining. Superoxide dismutase activity did not significantly change with time, and although the catalase activity augmented in both treatments, cells still suffered from the UVR stress. Clearly, UVR was fatal to the dinoflagellate. For the chlorophyte, however, cell numbers increased regardless of the UVR treatment and mortality remained low (<20 %). F v/F m showed an initial decrease but then remained constant for both light treatments. After 6 days of continuous PAB exposure, however, signs of stress (thymine dimers, oxidative stress) paralleled a drop in catalase activity. Results obtained here demonstrate that the dinoflagellate Gymnodinium was much more sensitive and was harmed more rapidly by UVR exposure than the chlorophyte D. tertiolecta. The increased tolerance to UVR exposure of the chlorophyte may provide advantages over other more sensitive phytoplankton species within the photic zone. We provide strong support in the present study for repair being an important component of UV resistance in this species.
0025-3162
2547-2560
Bouchard, Josée Nina
a41e7786-de08-47a5-a464-e5941e83237b
García-Gómez, Candela
aeeacb68-90b4-47bd-8eac-125538cf4bd5
Lorenzo, M. Rosario
c15c768d-c5aa-4f97-8e17-c62b2f3bdac6
Segovia, María
5ed9d659-cb14-444f-8a29-33f34b1f2daf
Bouchard, Josée Nina
a41e7786-de08-47a5-a464-e5941e83237b
García-Gómez, Candela
aeeacb68-90b4-47bd-8eac-125538cf4bd5
Lorenzo, M. Rosario
c15c768d-c5aa-4f97-8e17-c62b2f3bdac6
Segovia, María
5ed9d659-cb14-444f-8a29-33f34b1f2daf

Bouchard, Josée Nina, García-Gómez, Candela, Lorenzo, M. Rosario and Segovia, María (2013) Differential effect of ultraviolet exposure (UVR) in the stress response of the Dinophycea Gymnodinium sp. and the Chlorophyta Dunaliella tertiolecta: mortality versus survival. Marine Biology, 160 (10), 2547-2560. (doi:10.1007/s00227-013-2247-z).

Record type: Article

Abstract

Dunaliella tertiolecta (Chlorophyta) and Gymnodinium sp. (Dinophyceae) cells were exposed to ultraviolet radiation (UVR) (PAR, UVA and UVB: PAB) for 6 days either continuously or during a photoperiod. Both UVR treatments were harmful to Gymnodinium but exposure to continuous PAB had the most dramatic effects. Although a number of lesions/damage could have happened during the first few hours of exposure to UVR, in less than 24 h, Gymnodinium lost its ability to detoxify ROS efficiently, photoinhibition occurred, thymine dimers formed in the DNA, caspase-like enzymatic activities DEVDase sharply increased and cells died as determined by SYTOX-green staining. Superoxide dismutase activity did not significantly change with time, and although the catalase activity augmented in both treatments, cells still suffered from the UVR stress. Clearly, UVR was fatal to the dinoflagellate. For the chlorophyte, however, cell numbers increased regardless of the UVR treatment and mortality remained low (<20 %). F v/F m showed an initial decrease but then remained constant for both light treatments. After 6 days of continuous PAB exposure, however, signs of stress (thymine dimers, oxidative stress) paralleled a drop in catalase activity. Results obtained here demonstrate that the dinoflagellate Gymnodinium was much more sensitive and was harmed more rapidly by UVR exposure than the chlorophyte D. tertiolecta. The increased tolerance to UVR exposure of the chlorophyte may provide advantages over other more sensitive phytoplankton species within the photic zone. We provide strong support in the present study for repair being an important component of UV resistance in this species.

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Published date: October 2013
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 359544
URI: https://eprints.soton.ac.uk/id/eprint/359544
ISSN: 0025-3162
PURE UUID: 36c99875-5c84-4e19-bf76-a54da919f845

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Date deposited: 04 Nov 2013 10:50
Last modified: 16 Jul 2019 21:18

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