Induction of sunscreen compounds in Antarctic macroalgae by different radiation conditions

Abstract

The formation of UV-absorbing mycosporine-like amino acids (MAAs) as a photoprotective strategy against biologically harmful ultraviolet radiation was studied in Antarctic red macroalgae. After exposure to three different radiation treatments (PAR: 400–700 nm, PAR+UVA: 320–700 nm, PAR+UVA+UVB: 295–700 nm), using artificial irradiance sources under controlled conditions, the physiological capability to stimulate MAA synthesis was investigated. While 8 out of 18 species showed an induction of MAA formation and accumulation, the remaining ten, mainly deep water species, did not exhibit any traces of MAAs. The MAA-containing samples were divided into three physiological response types based on their MAA accumulation versus different radiation treatments. The first response type included Kallymenia antarctica, Gymnogongrus antarcticus, Palmaria decipiens and Porphyra plocamiestris, and exhibited additionally increasing MAA concentrations under the different radiation treatments, i.e. highest total MAA values were measured under the full radiation spectrum. The second response type included Porphyra endiviifolium and Gymnogongrus turquetii, showing highest MAA concentrations already under PAR+UVA. In contrast, Neuroglossum ligulatum and Plocamium cartilagineum exhibited a strong MAA decrease under PAR+UVR and were grouped in the third response type. No consistent MAA induction patterns could be found, even for individual MAAs, indicating that induction, formation and accumulation of individual MAAs is a very flexible and species-specific mechanism.