Effects of elevated ultraviolet radiation on primary metabolites in selected alpine algae and cyanobacteria

Abstract

Extremophilic green algae and cyanobacteria are the most abundant species in high mountain habitats, where rough climate conditions such as temperature differences, limited water retention and high ultraviolet (UV) radiation are the cause for a restricted biological diversity in favor of a few specialized autotrophic microorganisms. In this study, we investigated four algal species from alpine habitat in a sun simulator for their defense strategies in response to UV-A radiation (315–400 nm) up to 13.4 W/m2 and UV-B radiation (280–315 nm) up to 2.8 W/m2. Besides changes in pigment composition we discovered that primary polar metabolites like aromatic amino acids, nucleic bases and nucleosides are increasingly produced when the organisms are exposed to elevated UV radiation. Respective compounds were isolated and identified, and in order to quantify them an HPLC-DAD method was developed and validated. Our results show that especially tyrosine and guanosine were found to be generally two to three times upregulated in the UV-B exposed samples compared to the non-treated control.

Arctic, Antarctic, and temperate green algae Zygnema spp. under UV-B stress: vegetative cells perform better than pre-akinetes

“…The duration of the light phase was chosen to simulate long summer days, as realistic for the temperate strain. The duration of the experiment was previously found to generate UV-induced changes in various algae exposed in the same sun simulator (Hartmann et al 2015). The samples were harvested on the 4th day, 2 h after the onset of the UV-B exposure.…”

“…In cultured Zygnema spp., we used previously a UV simulation that was described as a predominantly UV-A treatment (Pichrtová et al 2013). Therefore, the “sun-simulation system” at the Helmholtz Center in Munich is used, which creates realistic PAR to UV conditions (Remias et al 2010; Hartmann et al 2015). Hartmann et al (2015) exposed the chlorophyte green algae Pseudomuriella engadiensis and Coelastrella terrestris in the same sun-simulation device used in the present study; by exposing the cells to 13.4 W m −2 UV-A and UV-B up to 2.8 W m −2 , they found an enhancement of some primary metabolites, mainly aromatic amino acids, nucleic bases, and nucleosides (Hartmann et al 2015).…”

“…Therefore, the “sun-simulation system” at the Helmholtz Center in Munich is used, which creates realistic PAR to UV conditions (Remias et al 2010; Hartmann et al 2015). Hartmann et al (2015) exposed the chlorophyte green algae Pseudomuriella engadiensis and Coelastrella terrestris in the same sun-simulation device used in the present study; by exposing the cells to 13.4 W m −2 UV-A and UV-B up to 2.8 W m −2 , they found an enhancement of some primary metabolites, mainly aromatic amino acids, nucleic bases, and nucleosides (Hartmann et al 2015). In a study by Remias et al (2010) applying this sun simulator, the chlorophytic snow alga Chlamydomonas nivalis and a terrestrial alga from a polar habitat were investigated by relatively high PAR of 724 μmol photons m −2  s −1 that was combined with UV-A values of 15.9 W m −2 and UV-B values of up to 1.43 W m −2 (Remias et al 2010).…”

Chemical profiling of mycosporine‐like amino acids in twenty‐three red algal species

“…), and the accumulation of primary (Hartmann et al. ) or secondary metabolites such as mycosporine‐like amino acids. MAAs are composed of a cyclohexenone or cyclohexenimine chromophore conjugated with the nitrogen substituent of an amino acid or its imino alcohol (Sinha et al.…”

“…UVR is strongly affecting many benthic marine organisms in the shallow water zone such as seaweeds (Karsten 2007). Algae have developed various adaptation mechanisms to withstand the harmful effects of UV-A (315-400 nm) and UV-B (280-315 nm;Karsten 2007 and references therein), like self-shading by mat formation (Blindow and Sch€ utte 2007), dissipation of excess energy as heat (Ramanan et al 2014), development of anti-oxidative systems involving enzymatic and non-enzymatic mechanisms (Lee andShiu 2009, Ramanan et al 2014), and the accumulation of primary (Hartmann et al 2015a) or secondary metabolites such as mycosporine-like amino acids. MAAs are composed of a cyclohexenone or cyclohexenimine chromophore conjugated with the nitrogen substituent of an amino acid or its imino alcohol (Sinha et al 2007) and characterized by their small molecular weight, high solubility, and polarity (Wada et al 2015).…”