Grant-in-Aid for Overseas Scientific Survey.
|Research Institution||Obihiro University of Agriculture & Veterinary Medicine|
GOTO Ken Obihiro Univ of Agric/Vet Medicine, Assoc Prof, 畜産学部, 助教授 (30186887)
桑山 秀人 帯広畜産大学, 畜産学部, 助教授 (40125399)
JOHNSON Carl バンダービルト大学, 生物学部, 助教授
CARRE/ISABEL ニューヨーク州立大学, 解剖学部, ポスドク
LAVALーMARTIN アンジェ大学, 植物分子生物学部, 教授
CARRE Isabel ニューヨーク州立大学, 解剖学部, ポスドク
LAVAL Martin アンジェ大学, 植物分子生物学部, 教授
CARRE' Isabelle State Univ New York at Stony Brook, Postdoc
KUWAYAMA Hideto Obihiro Univ of Agric/Vet Medicine, Assoc Prof
JOHNSON Carl H. Vanderbilt Univ, Assist Prof
LAVAL-MARTIN Danielle L. Univ Anger, Prof
|Project Fiscal Year
1990 – 1991
Completed(Fiscal Year 1991)
|Budget Amount *help
¥5,900,000 (Direct Cost : ¥5,900,000)
Fiscal Year 1991 : ¥3,000,000 (Direct Cost : ¥3,000,000)
Fiscal Year 1990 : ¥2,900,000 (Direct Cost : ¥2,900,000)
|Keywords||Chlamydomonas reinhardtii / Euglena gracilis / Circadian rhythm / NAD^+ kinase / Ca^<2+> / calmodulin / Cell division cycle / Phototaxis / Vitamin C / 概日リズム / NAD^+キナ-ゼ / カルモジュリン / 細胞分裂周期 / 光走性 / ビタミンC / Chiamydomonas rheinhardtti / Cell cycle / Phaseーshift|
The molecular mechanism of circadian rhythms was studied in the green algae, Chlamydomonas reinhardtii and in the algal flagellate, Euglena gracilis. The activities of NAD kinase in both organisms were found to change in a circadian manner. The circadian rhythm of cell division cycle (CDC) was not responsible for the generation of that of NAD kinase. All of the efforts to detect the stimulatory effect of Ca/calmodulin on NAD kinase were unsuccessful. However., we found the existence of at least two isozymes distinguished by the enzyme kinetics study and that of an unidentified factor that inhibited the isozymes in different ways.
The pulsing with a specific calmodulin inhibitor, W7, phase-shifted the circadian CDC rhythm in Euglena both in a phase-dependent manner and in a dose-dependent manner, while the inactive analog, W5, had little effect. We therefore conclude that Ca^<2+>/calmodulin may be involved in the circadian time-keeping that regulates CDC in Euglena. This also held for the circadian time-keeping that regulates the phototaxis rhythm in Chlamydomonas.
The CDC in Chlamydomonas was found to display the major characteristics of circadian rhythms, in contrast with the prevailing belief. Furthermore, the CDC speed was found to be completely unrelated to the speed of the circadian CDC rhythm, indicating that the CDC is not involved in the circadian time-keeping and that, instead, the circadian rhythm controls the CDC. In addition, the activity of p34-cdc2 kinase was suggested to change in a circadian manner with a peak at the G1/S transition in Euglena, while the activity in Chlamydomonas could not be detected.
Finally, we found the circadian rhythm in the vitamin C content in Euglena and the rhythm was independent of both the circadian photosynthesis rhythm and the circadian CDC rhythm.