The Photoreceptor for Phototaxis in the Photosynthetic Flagellate Euglena gracilis

摘要: The unicellular flagellate Euglena gracilis shows positive phototaxis at low fluence rates (≤10 W m 2) and negative high (≥100 2). Currently, retinal or flavins/pterins are discussed as chromo-phores of the photoreceptor. When grown in presence 4 mM nicotine, a inhibitor, for several generations, cells still showed both responses, indicating that is unlikely to be chromophoric group photoreceptor responsible phototaxis. native flavin(s) can substituted by growing roseo-flavin dissolved medium. absorption spectrum roseoflavin extends well beyond action (up 600 nm). Excitation wavelengths >550 nm does not cause phototactic orientation control but causes roseoflavin-grown cells, an uptake assembly chromophore complex. white mutant strain 1224-5/1f, induced streptomycin treatment, lacks flavins indicated fluorescence spectroscopy. phototaxis-deficient pheno-type cannot complemented addition external riboflavin. Fluorescence spectra intact paraxonemal bodies (PAB) indicate pterins involved photoperception excitation energy efficiently funneled from flavins. This transfer disrupted solubilization PAB. In PAB accessible reducing oxidizing substances, they located inside structure, while accessible, so their localization assumed on surface. results described above with regard potential involvement photoperception.