Non-enzymatic antioxidant photoprotection against potential UVBR-induced damage in an Antarctic Diatom (Thalasiosira sp)

HERNANDO M. ; MALANGA G; PUNTARULO S.; FERREYRA G.

LATIN AMERICAN JOURNAL OF AQUATIC RESEARCH

UNIV CATOLICA DE VALPARAISO

Año: 2011 vol. 39 p. 397 - 408

0718-560X

During January 1999, unialgal cultures of the diatom Thalassiosira sp, isolated from natural phytoplankton assemblages from Potter Cove (62°14´S, 58°38´W, 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, 280-315 nm) inhibited the growth rate during the first and second days of exposure. No UVBR inhibition was observed on the 3rd day. The initial content of á-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 â-carotene (3 pmol (104 cell)-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 concentration of MAAs showed significant increases by day 2 and 3, and UVBR exposure of the algae significantly enhanced this value. The relative importance of MAAs concentration was significant (p < 0.05) in relation to á-tocopherol content. A positive correlation between cellular MAAs concentration and growth rate was shown. Our results suggest that photoprotection against UV-induced damage is characterized by a short-term consumption of á-tocopherol and a longer-term synthesis of MAAs. 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.