The Role of Vitamin D in Emiliania huxleyi: A Microalgal Perspective on UV-B Exposure

An essential interaction between sunlight and eukaryotes involves the production of vitamin D through exposure to ultraviolet (UV) radiation. While extensively studied in vertebrates, the role of vitamin D in non-animal eukaryotes like microalgae remains unclear. To investigate the potential involvement of vitamin D in the response of microalgae to UV, we focus on Emiliania huxleyi, a microalga found in shallow ocean depths that are exposed to UV radiation. Our results show that E. huxleyi algae produce vitamin D2 and D3 in response to UV irradiation. We further demonstrate that E. huxleyi algae respond to external administration of vitamin D at the transcriptional level, regulating the expression of protective mechanisms that are also regulated in response to UV. Our data reveal that addition of vitamin D enhances the algal photosynthetic performance while reducing harmful reactive oxygen species buildup. This study contributes to understanding the function of vitamin D in E. huxleyi and sheds light on its role in non-animal eukaryotes, as well as its potential importance in marine ecosystems. In order to investigate the effect of weak UV radiation on the transcriptomic landscape of the algae E. huxleyi. Transcriptomic analysis was conducted using RNA extracted from E. huxleyi cultures grown in artificial sea water supplemented with L1-Si nutrients, under weak UV radiation or under regular growing light as control, using triplicates.