Mycosporine-like amino acids (MAAs) protect against UV-B-induced damage in Gyrodinium dorsum Kofoid

The protective effect of mycosporine-like amino acids (MAAs) against ultraviolet-B (UV-B; 280-315 nm) radiation has been studied in the marine dinoflagellate Gyrodinium dorsum. Cultures were irradiated with artificial (simulated) solar radiation with 320-nm (UV-A + PAR) and 395-nm (PAR only) cut-off filters for a period of up to 48 h in order to stimulate the synthesis of MAAs in the cells. A pronounced rise in the amount of MAAs was detected in the cells that were exposed to UV-A + PAR, while cells that were exposed to PAR induced only a marginal increase in their MAAs content. HPLC analyses of the samples revealed the presence of five MAAs, i.e shinorine (lambda (max) 334 nm), porphyra-334 (lambda (max) 334 nm), palythine (lambda (max) 320 nm), and two unidentified MAAs having lambda (max) at 310 and 331 nm. Both cultures (one having high MAAs and another having low MAAs content) were subjected to high UV-B (8 W m(-2)) irradiation from a trans illuminator, and motility and velocity were analyzed at regular time intervals. Cells with low MAAs content suffered a complete loss of motility within 3 h, while the cells with high MAAs content survived at least 2 times longer. The results provide further evidence that MAAs function as a UV-B absorbing/screening compound in G. dorsum and help them survive in high UV-B radiation regimes.