title: Photoisomerization of retinal at 13-ene is important for phototaxis of Chlamydomonas reinhardtii: simultaneous measurements of phototactic and photophobic responses.
abstract: 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.
authors.affiliation: Suntory Institute for Bioorganic Research, Osaka, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Takahashi
authors.forename: K
authors.initials: K
authors.lastname: Yoshihara
authors.forename: M
authors.initials: M
authors.lastname: Watanabe
authors.forename: M
authors.initials: M
authors.lastname: Kubota
authors.forename: R
authors.initials: R
authors.lastname: Johnson
authors.forename: F
authors.initials: F
authors.lastname: Derguini
authors.forename: K
authors.initials: K
authors.lastname: Nakanishi
mesh_terms: D002465:Cell Movement / Q000187:drug effects / Q000528:radiation effects; D002696:Chlamydomonas / Q000187:drug effects / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D003624:Darkness; D007536:Isomerism; D008027:Light; D012172:Retinaldehyde / Q000031:analogs & derivatives* / Q000494:pharmacology* / Q000528:radiation effects; D013329:Structure-Activity Relationship
chemical_list: D012172:Retinaldehyde