Photoisomerization of retinal at 13-ene is important for phototaxis of Chlamydomonas reinhardtii: Simultaneous measurements of phototactic and photophobic responses

• Published in: Biochemical and biophysical research communications Vol. 178; no. 3; pp. 1273 - 1279
• Main Authors: Takahashi, Tetsuo, Yoshihara, Kazuo, Watanabe, Masakatsu, Kubota, Mamoru, Johnson, Randy, Derguini, Fadila, Nakanishi, Koji
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 15.08.1991; Elsevier
• Subjects: Biological and medical sciences; Cell Movement - drug effects; Cell Movement - radiation effects; Cell physiology; Chlamydomonas - drug effects; Chlamydomonas - genetics; Chlamydomonas - physiology; Chlamydomonas - radiation effects; Chlamydomonas reinhardtii; CHLOROPHYCEAE; Darkness; Fundamental and applied biological sciences. Psychology; ISOMERISATION; Isomerism; ISOMERIZACION; Light; LUMIERE; LUZ; MEDICION; MESURE; Molecular and cellular biology; MOUVEMENT; MOVIMIENTO; MUTANT; MUTANTES; ORGANE DES SENS; ORGANOS SENSORIALES; Retinaldehyde - analogs & derivatives; Retinaldehyde - pharmacology; Retinaldehyde - radiation effects; RETINOL; Structure-Activity Relationship; Vision, photoreception; Configuration; Photoisomerization; Algae; Deficiency; Chlorophycophyta; Photoreceptor; Signal transduction; Phototaxis; Chlamydomonas reinhardtii; Photophobia; Microorganism culture; Carotenoid; Retinal; Computer aid; Thallophyta
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/0006-291X(91)91031-7

A real-time automated method was developed for simultaneous measurements of phototactic orientation (phototaxis) and step-up photophobic response of flagellated microorganisms. Addition of all- trans retinal restored both photoresponses in a carotenoid-deficient mutant strain of Chlamydomonas reinhardtii in a dose-dependent manner. The phototactic orientation was biphasic with respect to both the light intensity and the concentration of retinal. All- trans retinal was more effective than 11- cis retinal to regenerate both photobehavioral responses. Analogs having locked 11- cis configurations and a phenyl ring in the side chain also induced photoresponses, although at concentrations more than two orders of magnitude higher than all- trans retinal. According to the present assay method, the responses were hardly detectable in cells incubated with retinal analogs in which the 13-ene was locked in either its trans or cis configuration. The results strongly suggest that the isomerization of the 13–14 double bond is important for photobehavioral signal transduction and that a single retinal-dependent photoreceptor controls both phototactic and photophobic responses.