Cyanidiales Transcriptomics in Acidic Geothermal Environments

Ultra-violet (UV) and high-intensity visible (VIS) radiation are environmental stressors known to harm photosynthetic organisms through the generation of reactive intermediates that damage photosynthetic machinery. This study shows the potential of using a thermoacidophilic red alga of the order Cyanidiales to model in situ algal gene expression dynamics as a function of UV exposure and seasonal shifts in UV-VIS intensity. These algae exhibit a dynamic seasonal biomass fluctuation referred to as 'mat decline' where viability drastically decreases as seasonal UV-VIS irradiance intensity increases. In Yellowstone National Park (YNP), temporal experiments coupling UV irradiance manipulations (filtering) with whole-community transcription profiling revealed significant cyanidial gene expression changes occurring as a result of exposure to UV, and that patterns of response adjust across low and high irradiance time periods. Separate analyses examined genes responding to either increasing seasonal UV or VIS intensity, or by the combined effects of both irradiance wavelengths (UV and VIS). Results not only corroborated known physiological changes to solar irradiance, but also suggested the strategies employed to deal with excess VIS and UV intensity may be highly integrated. Finally, a suite of comparative analyses determined the relative utility of environmental transcriptomics technologies in studying ecologically-relevant expression patterns. Results suggest in situ expression profiles will improve understanding of how photosynthetic organisms are responding to environmental stressors as they are observed in nature. 16 samples with 3 biological replicates each.