A blue-light-activated adenylyl cyclase mediates photoavoidance in Euglena gracilis

• Published in: Nature (London) Vol. 415; no. 6875; pp. 1047 - 1051
• Main Authors: Watanabe, Masakatsu, Iseki, Mineo, Matsunaga, Shigeru, Murakami, Akio, Ohno, Kaoru, Shiga, Kiyoshi, Yoshida, Kazuichi, Sugai, Michizo, Takahashi, Tetsuo, Hori, Terumitsu
• Format: Journal Article
• Language: English
• Published: London Nature Publishing 28.02.2002; Nature Publishing Group
• Subjects: Adenylyl Cyclases - genetics; Adenylyl Cyclases - metabolism; Adenylyl Cyclases - radiation effects; Amino Acid Sequence; Animals; Biological and medical sciences; Circadian rhythms; Enzyme Activation - radiation effects; Euglena gracilis; flavoproteins; Flavoproteins - genetics; Flavoproteins - metabolism; Flavoproteins - radiation effects; Freshwater; Fundamental and applied biological sciences. Psychology; Gene Expression; Light; Light intensity; Microorganisms; Molecular Sequence Data; Molecules; Movements; Organelles - metabolism; Photoreceptor Cells, Invertebrate - enzymology; Photoreceptor Cells, Invertebrate - radiation effects; Plant physiology and development; Proteins; Sequence Alignment; Swimming; Tropism; Euglenophyta; Light effect; Enzyme; Photoactivation; Algae; Photoreceptor; Phototropism; Phosphorus-oxygen lyases; Lyases; Flavoprotein; Characterization; Adenylate cyclase; Regulation(control); Enzymatic activity; Euglena gracilis; Development; Blue light; Thallophyta
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/4151047a

Blue light regulates processes such as the development of plants and fungi and the behaviour of microbes. Two types of blue-light receptor flavoprotein have been identified: cryptochromes, which have partial similarity to photolyases, and phototropins, which are photoregulated protein kinases. The former have also been found in animals with evidence of essential roles in circadian rhythms. Euglena gracilis, a unicellular flagellate, abruptly changes its swimming direction after a sudden increase or decrease in incident blue light intensity, that is, step-up or step-down photophobic responses, resulting in photoavoidance or photoaccumulation, respectively. Although these photobehaviours of Euglena have been studied for a century, the photoreceptor molecules mediating them have remained unknown. Here we report the discovery and biochemical characterization of a new type of blue-light receptor flavoprotein, photoactivated adenylyl cyclase, in the photoreceptor organelle of Euglena gracilis, with molecular genetic evidence that it mediates the step-up photophobic response.