A Comparative Physiological Perspective on UV RESISTANCE LOCUS 8 Signalling in Green Plants

Abstract

The ability for photosynthetic organisms to protect themselves from high levels of ultraviolet (UV) radiation has been a critical for their survival and evolution. To overcome this problem, some of these organisms either occupy habitats where low levels of UV radiation occur or have acquired various receptor mechanisms that protect their nucleic acids, photosynthetic machineries, and their epidermis. In green plants (Viridiplantae), photoprotective responses are predominantly mediated via photoreceptors. Initially discovered and isolated in the cress Arabidopsis thaliana, UV RESISTANCE LOCUS 8 (UVR8) is a photoreceptor that is specific to UV-B light and is mainly involved in switching on the UV-B-specific photoprotective and photomorphogenic responses in green plants. Here, I review biochemical, physiological and phylogenomic data to examine the evolution and diversity of the UVR8-mediated signalling response from algae to angiosperms. I speculate that UVR8 was necessary to act as an enabler for major transitions in green plant evolution – from chlorophyte freshwater adaptations to streptophyte terrestrialization – and discuss causal links that could motivate further research.