The occurrence of UV-B absorbing mycosporine-like amino acids in freshwater and terrestrial microalgae (Chlorophyta)

Abstract

The occurrence of mycosporine-like amino acids (MAAs) in freshwater and terrestrial microalgae and their accumulation in response to UV-B exposure were examined. Three UV-B-resistant species, Enallax coelastroides, Scenedesmus sp. and Scotiella chlorelloidea, and four UV-B-sensitive microalgal species: Ankistrodesmus spiralis, Chlorella minutissima, Chlorella sorokiniana and Pseudococcomyxa sp. were found to contain MAAs. However, Coelastrum microporum did not appear to contain any MAA. A total of seven MAAs was identified among the tested species. Besides five known MAAs: mycosporine-Gly ( λ max = 310 nm), palythine ( λ max = 320 nm), asterina ( λ max = 330 nm), shinorine ( λ max = 334 nm) and porphyra ( λ max = 334 nm), two novel compounds (compound I: λ max = 302 nm, Rt = 2.6 min; compound II: λ max = 292 nm, Rt = 7.3 min) were found in Ch. sorokiniana and Scenedesmus sp. The accumulation of MAAs was induced by both artificial and solar UV-B radiation, which was observed in both the UV-B-resistant and UV-B-sensitive species. No clear correlation between MAA accumulation and UV-B resistance of the photosynthetic apparatus was established. The response of MAA accumulation to UV-B exposure was species-dependent and individual MAA-specific.