The blue-light (BL) receptor, aureochrome was found and isolated from xanthophycean macro alga Vaucheria in 2007. Aureochrome is a BL receptor only in photosynthetic stramenopiles, such as diatoms, raphidophycean and brown algae. Aureochrome is composed of a bZIP (basic leucine Zipper) transcription factor domain at the N terminus and a LOV (Light-Oxygen-Voltage) domain at the C terminus. FMN (flavin mononucleotide) binds to LOV domain of aureochrome to function as a BL receptor. After BL irradiation, bZIP binds to cis elements (specific DNA binding sequence) with conformational change of LOV domain and regulates gene expression. These results suggest that various BL responses of photosynthetic stramenopiles are induced via the aureochrome. In this review, we introduce the function of aureochrome and future perspective.