MYCOSPORINE-LIKE AMINO ACIDS IN PHYTOPLANKTON: BIOCHEMISTRY, PHYSIOLOGY AND OPTICS
Authors: Tiffany A. Moisan, Joaquim Goes and Patrick J. Neale
Abstract: Mycosporine-like amino acids (MAAs) are colorless water-soluble compounds with a cyclohexenone chromophore conjugated to a nitrogen substituent of either an amino acid or imino alcohol. MAAs have a high molar absorptivity in the UV-A and UV-B (280 nm to 400 nm) region, with absorption maxima for individual MAAs ranging from ~308 nm to ~360 nm. When present within phytoplankton cells, MAAs are considered to be photochemically stable molecules acting as sunscreens against harmful ultraviolet (UV) radiation. At times, MAAs can function as antioxidants and also as osmolytes. On account of their low molecular weight, MAAs such as mycosporine-glycine, shinorine and porphyra-334 can be quickly synthesized in response to light, nutrients or temperature stress. High photosynthetically available radiation (PAR) and UV exposure are the strongest inducing factors. The composition of the intracellular pool of MAAs is however not steady. Due to the complex spectral light, nutrients, and species dependent inter-conversions, the composition of the MAA pool can vary significantly during phytoplankton growth. This environmentally and species-regulated production of a diverse suite of MAAs appears to be advantageous to cells, because it improves their ability to acclimate to a wider window of spectral light quality and quantity. MAA production is generally highest in phytoplankton species capable of forming large blooms at the sea surface, where the photosynthetic machinery of the cells is susceptible to the greatest damage by UV radiation or high levels of PAR. At maximum concentration, MAAs strongly reduce the effects of solar UV at the wavelengths most inhibiting to photosynthesis. Large amounts of intercellular MAAs are associated with surface phytoplankton blooms. High concentrations of extracellular MAAs that are released into the environment contribute significantly to elevated attenuation of UV light during blooms. Given that the production of MAAs is species dependent, it has been suggested that the overall suite of MAAs may be a factor in determining species composition in phytoplankton assemblage essential for carbon cycle transfer and linkages.
Open Access item.
Click below PDF icon for free download.
This is an Open Access item. Click above PDF icon for free download.