Latin American Journal of Aquatic Research, 39 (3) November 2011
Non-enzymatic antioxidant photoprotection against potential UVBR-induced damage in an Antarctic diatom (Thalassiosira sp.)
In January 1999, unialgal cultures of the diatom Thalassiosira sp., solate from natural phytoplankton assemblages from Potter Cove, Antarctica, were exposed to solar ultraviolet radiation (UVR, 280-400 nm) in order to study the long-term acclimation of this species. Ultraviolet radiation B (UVBR, 280-315nm) inhibited the growth rate during the first and second days of exposure. No UVBR inhibition was observed on the third day. The initial content of α-tocopherol (13 pmol (104 cell)-1) showed a marked decrease during the exponential growth phase (4 pmol (104 cell-1) by day 3). The initial content of β-carotene (3 pmol (104cell)-1) did not show significant differences over time in cells exposed to UVBR. Two mycosporine-like amino acids (MAAs) were identified: porphyra-334 and shinorine. Cellular concentrations of MAAs increased significantly on days 2 and 3, and exposure of the algae to UVBR significantly enhanced this value. The relative importance of MAAs concentration was significant (P < 0.05) in relation to the α-tocopherol content. A positive correlation was shown between cellular MAAs concentration and growth rate. Our results suggest that photoprotection against UV-induced damage is characterized by short-term consumption of α-tocopherol and longer-term synthesis of MAAs. The UVBR damage/repair ratio during long-term exposure involves the combined action of several endogenous factors within the cell, with MAAs synthesis being the most effective factor related to photoprotection.
Author: Marcelo Hernando, Gabriela Malanga, Susana Puntarulo & Gustavo Ferreyra

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