Mycosporines and mycosporine-like amino acids: UV protectants or multipurpose secondary metabolites?

Abstract

Mycosporines and mycosporine-like amino acids (MAAs) are low-molecular-weight water-soluble molecules absorbing UV radiation in the wavelength range 310-365 nm. They are accumulated by a wide range of microorganisms, prokaryotic (cyanobacteria) as well as eukaryotic (microalgae, yeasts, and fungi), and a variety of marine macroalgae, corals, and other marine life forms. The role that MAAs play as sunscreen compounds to protect against damage by harmful levels of UV radiation is well established. However, evidence is accumulating that MAAs may have additional functions: they may serve as antioxidant molecules scavenging toxic oxygen radicals, they can be accumulated as compatible solutes following salt stress, their formation is induced by desiccation or by thermal stress in certain organisms, they have been suggested to function as an accessory light-harvesting pigment in photosynthesis or as an intracellular nitrogen reservoir, and they are involved in fungal reproduction. Here, the evidence for these additional roles of MAAs as 'multipurpose' secondary metabolites is reviewed, with special emphasis on their functions in the microbial world.

Marine CDOM accumulation during a coastal Arctic mesocosm experiment: No response to elevated pCO2 levels

“…By analyzing the MAA index, we found a distinct difference between CDOM properties in the fjord and in the mesocosms. MAA signatures in the mesocosms were produced in the absence of UV exposure (blocked by mesocosm walls), providing another indication that MAAs act not only as photo protective compounds, but are multipurpose metabolites [Oren and Gunde-Cimerman, 2007].…”

“…They are most likely related to a presence of mycosporine-like amino acids (MAAs) [Řezanka et al, 2004;Oren and Gunde-Cimerman, 2007]. To our knowledge, no thorough method has been proposed to date to quantify MAAs peaks present in CDOM absorption spectra.…”

“…However, while absorption peaks at 330 nm and 360 nm are most common among MAAs, their magnitude and wavelength location depend on overall MAAs' composition, superposition, and optical properties [Řezanka et al, 2004;Oren and Gunde-Cimerman, 2007], so this approach might not be ideal when samples with different MAA composition are considered.…”

Osmotic adaptation of the halophilic fungus Hortaea werneckii: role of osmolytes and melanization

“…Mycosporines, substances with an aminocyclohexenone unit bound to an amino acid or amino alcohol group, were initially known as morphogenetic factors in fungal sporulation and as UV-protecting compounds (Bandaranayake, 1998). Recently, it has been hypothesized that in certain micro-organisms, mycosporines or MAAs play a role as complementary compatible solutes (Kogej et al, 2006b;Oren, 1997;Oren & Gunde-Cimerman, 2007). In an earlier study, a higher amount of mycosporine-glutaminol-glucoside was measured in H. werneckii and in the cells of other black yeasts from a hypersaline environment (Phaeotheca triangularis and Aureobasidium pullulans) grown at 10 % NaCl than on non-saline growth medium (Kogej et al, 2006b), with a marked increase of mycosporines in the stationary-phase cells of H. werneckii.…”

Mycosporine-Like Compounds in Chlorolichens: Isolation from Dermatocarpon luridum and Dermatocarpon miniatum, and their Photoprotective Properties

“…Mycosporine-like compounds comprising mycosporines and MAAs have received much attention for their putative role in UV photoprotection as antioxidants and osmoprotectants [1][2][3][4]. Mycosporine-like compounds are small water-soluble molecules composed of cyclohexenone (oxo-mycosporine) or cyclohexenimine (imino-mycosporine) ring structures conjugated to an amino acid or an amino alcohol subunit.…”