Unveiling of a novel bifunctional photoreceptor, Dualchrome1, isolated from a cosmopolitan green alga

Abstract Photoreceptors are conserved in green algae to land plants, and regulate various developmental stages. In the ocean, blue light penetrates deeper than red light, and blue-light sensing is key to adapting to marine environments. A search for blue-light photoreceptors in the marine metagenome uncovered a novel chimeric gene composed of a phytochrome and a cryptochrome (Dualchrome1, DUC1) in a prasinophyte, Pycnococcus provasolii. DUC1 detects light within the orange/far-red and blue spectra, and acts as a dual photoreceptor. Its complete genome revealed that P. provasolii facilitates light adaptation mechanisms via pheophorbide a oxygenase (Pao) and prasinoxanthin. Genes for the light-harvesting complex (LHC) are duplicated and transcriptionally regulated under monochromatic orange/blue light, suggesting P. provasolii has acquired environmental adaptability to a wide range of light spectra and intensities.