Mechanism of up-regulated HO BPA-derived production and production of (poly)phenols by two seaweeds of the genus Ulva.

The present study provides information on the effects of BPA on ROS production-related phenomena in the chlorophytes Ulva rigida and U. intestinalis, and on the mechanism they establish against BPA toxicity, at environmentally relevant concentrations (0.1-3 μg L). Up-regulated HO generation seems to be a key factor causing oxidative damage. Interspecific differences, in terms of the mechanism and the temporal response to BPA toxicity were observed. BPA effects on U. rigida were more intense and appeared earlier (on 1D at 0.1 μg L) compared to U. intestinalis and mostly after 7D (LOEC: 0.3 μg L, Terminal time, Tt: 7D). In U. rigida, on 1-5D, the 'mosaic' type effect patterns ('models' 3A/3B) with 'unaffected' and 'affected' areas (dark content, positive HDCF-DA staining signal/HO production and chlorophyll autofluorescence signal loss) indicated a time-dependent manner. After 7D, only U. rigida cells with dark content formed aggregates, showing positive HO production ('model' 4) or in some cells oxidative damages triggering retrograde signaling in the neighboring 'unaffected' areas ('model' 5). HO overproduction (CTCF ratio) in U. rigida, on 1D at the lowest concentration and after 7D at 0.3-1/3 μg L, respectively, seems to stimulate (poly)phenolic production, in a dose- and time-dependent manner. U. intestinalis did not display severe BPA impact (i.e., 'models' 4, 5) at any exposures, although at a later time indicated a lower LOEC (0.1 μg L, Tt: 9D) than that in U. rigida. In U. intestinalis, HO production does not appear to stimulate high (poly)phenolic amounts.