Sunscreen Effect Exerted by Secondary Carotenoids and Mycosporine-like Amino Acids in the Aeroterrestrial Chlorophyte Coelastrella rubescens under High Light and UV-A Irradiation

Abstract

The microalga Coelastrella rubescens dwells in habitats with excessive solar irradiation; consequently, it must accumulate diverse compounds to protect itself. We characterized the array of photoprotective compounds in C. rubescens. Toward this goal, we exposed the cells to high fluxes of visible light and UV-A and analyzed the ability of hydrophilic and hydrophobic extracts from the cells to absorb radiation. Potential light-screening compounds were profiled by thin layer chromatography and UPLC-MS. Coelastrella accumulated diverse carotenoids that absorbed visible light in the blue–green part of the spectrum and mycosporine-like amino acids (MAA) that absorbed the UV-A. It is the first report on the occurrence of MAA in Coelastrella. Two new MAA, named coelastrin A and coelastrin B, were identified. Transmission electron microscopy revealed the development of hydrophobic subcompartments under the high light and UV-A exposition. We also evaluate and discuss sporopollenin-like compounds in the cell wall and autophagy-like processes as the possible reason for the decrease in sunlight absorption by cells, in addition to inducible sunscreen accumulation. The results suggested that C. rubescens NAMSU R1 accumulates a broad range of valuable photoprotective compounds in response to UV-A and visible light irradiation, which indicates this strain as a potential producer for biotechnology.

A Fast-Growing Oleaginous Strain of Coelastrella Capable of Astaxanthin and Canthaxanthin Accumulation in Phototrophy and Heterotrophy

“…Some strains/species with biotechnological relevant properties, such as the presence of astaxanthin and canthaxanthin, have been described, mainly selected in Asia or East Europe (e.g., [ 8 , 13 , 19 , 20 ]. Others also accumulate other photoprotective compounds, such as mycosporine-like amino acids which are effective against UV-A [ 21 ]. Amongst them, a few simultaneously accumulate both carotenoids and fatty acids [ 20 ].…”

Coelastrella terrestris for Adonixanthin Production: Physiological Characterization and Evaluation of Secondary Carotenoid Productivity

“…F50 grown in glass bottles [ 24 ]; Minhas et al (2016) identified five Coelastrella sp. isolates and conducted Erlenmeyer flask cultures for pigment and lipid measurements [ 25 ]; Wang et al (2019) did phylogenetic studies and described a new species of the genus Coelastrella [ 26 ]; Goecke et al (2020) published the FA pattern and qualitative pigment composition of their strain grown in a 250 mL tubular PBR [ 27 ]; and Zaytseva et al (2021) reported on their new strain C. rubescens NAMSU R1 and identified the carotenoids present after Erlenmeyer flask cultivations [ 28 ]. However, the only report on adonixanthin accumulation of Coelastrella was published by Minyuk et al (2017) [ 29 ].…”

Differential Responses to UV-A Stress Recorded in Carotenogenic Microalgae Haematococcus rubicundus, Bracteacoccus aggregatus, and Deasonia sp.

“…Some works were carried out on the cultures of unicellular algae. Changes in their pigment composition were evaluated by common approaches of absorbance spectroscopy in the visible range [ 2 , 6 , 10 , 11 , 12 , 14 , 19 , 22 , 23 , 24 ]. Valuable information on primary photochemistry was obtained by the analysis of chlorophyll fluorescence kinetics, O 2 emission and CO 2 assimilation rates [ 1 , 9 , 10 , 11 , 13 , 14 , 15 , 19 , 21 , 22 , 23 , 24 , 25 ].…”

“…Changes in their pigment composition were evaluated by common approaches of absorbance spectroscopy in the visible range [ 2 , 6 , 10 , 11 , 12 , 14 , 19 , 22 , 23 , 24 ]. Valuable information on primary photochemistry was obtained by the analysis of chlorophyll fluorescence kinetics, O 2 emission and CO 2 assimilation rates [ 1 , 9 , 10 , 11 , 13 , 14 , 15 , 19 , 21 , 22 , 23 , 24 , 25 ]. Some data were obtained with the help of studies of thermoluminescence [ 9 ] and low-temperature fluorescence spectra [ 10 ], electron paramagnetic resonance spectroscopy [ 14 ], D1 protein immunoblotting [ 14 ], analysis of expression of genes of UV response [ 21 , 25 ], etc.…”

“…Some data were obtained with the help of studies of thermoluminescence [ 9 ] and low-temperature fluorescence spectra [ 10 ], electron paramagnetic resonance spectroscopy [ 14 ], D1 protein immunoblotting [ 14 ], analysis of expression of genes of UV response [ 21 , 25 ], etc. HPLC or HPLC-MS are applied for separation and identification of secondary metabolites and phytohormones in response to UV [ 2 , 4 , 6 , 11 , 22 , 25 ]. Electron microscopy provides some important data on UV response of cell fine structure [ 2 , 3 , 15 , 22 ].…”