Photoisomerization of retinal at 13-ene is important for phototaxis of Chlamydomonas reinhardtii: simultaneous measurements of phototactic and photophobic responses.
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.
Takahashi
T
T
Suntory Institute for Bioorganic Research, Osaka, Japan.
Yoshihara
K
K
Watanabe
M
M
Kubota
M
M
Johnson
R
R
Derguini
F
F
Nakanishi
K
K
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
D012172:Retinaldehyde