Abstract
The UV-B photoreceptor UVR8 plays a central role in plant responses to ultraviolet light, but its function in extremophilic algae remains poorly understood. In this study, we isolated and characterized a UVR8 homolog (CiUVR8) from the Antarctic ice alga Chlamydomonas sp. ICE-L. The full-length CiUVR8 gene encodes a 406-amino-acid protein highly conserved with Arabidopsis thaliana UVR8, including the key tryptophan residues essential for UV-B perception. Bioinformatics and phylogenetic analyses confirmed its structural conservation and distinct evolutionary placement among polar algae. Quantitative real-time PCR revealed that CiUVR8 expression is dynamically regulated in response to temperature (-20 °C to 15 °C), salinity (16‰ to 128‰), and varying intensities of UV-B radiation. Notably, CiUVR8 expression generally decreased with increasing UV-B intensity, suggesting a potential photoprotective mechanism. The recombinant CiUVR8 protein was successfully expressed in Escherichia coli and purified, providing a foundation for subsequent functional validation. These results highlight CiUVR8 as a functional UV-B receptor involved in stress adaptation, offering insight into algal survival strategies in extreme polar environments. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s13205-025-04627-5.