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| Bolige, Aoen; Hagiwara, Shin-ya; Zhang, Yulan; Goto, Ken; 後藤, 健. |
| Cell population growth is gated to occur in particular circadian phases, which has been known for over four decades in various organisms including cyanobacteria and human. However, little is known as to which cell cycle phases from G(1) to M are primarily regulated by the circadian rhythm or when in a circadian cycle this primary regulation takes place. We report here that in the flagellate alga Euglena gracilis grown photoautotrophically, the circadian rhythm primarily prevented developmentally matured G(2) cells from progressing to mitosis, such that cell population growth occurred only during subjective night. In addition, we found that the circadian rhythm also arrests G(1)-to-S and S-to-G(2) transitions at particular circadian phases. |
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Palavras-chave: Cell cycle; Circadian rhythms; Englena gracilis; G2-arrest; Mitosis. |
| Ano: 2005 |
URL: http://ir.obihiro.ac.jp/dspace/handle/10322/717 |
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| Bolige, Aoen; Kiyota, Maki; Goto, Ken; 後藤, 健. |
| Radiation-induced stress, either from visible or UV light, is strongest at midday. We found that, in the absence of stress or time cues, Euglena gracilis Z was the most resistant to UV-C and UV-B at subjective midday, whether judged from immediate or reproductive survival. The circadian UV-resistance rhythms were free-running in stationary cultures under 1-h light/1-h dark cycles or continuous darkness, indicating that cell-cycle dependent DNA susceptibility to UV was not involved. We moreover examined what was the primary cause of the circadian U-V resistance, estimated as the immediate cell survival. The half-maximal lethal dose (LD50) of UV-C at subjective midday (the most resistant phase) was 156 J/m(2), which is similar to 3-fold that at subjective... |
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Palavras-chave: Antioxidant; L-ascorbic acid; Circadian rhythms; Dimethylsulfoxide; Euglena gracilis; Photo-oxidation; UV-sensitivity. |
| Ano: 2005 |
URL: http://ir.obihiro.ac.jp/dspace/handle/10322/718 |
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| Bolige, Aoen; Goto, Ken. |
| Little is known about the photoreceptors involved in the photoperiodism of unicellular organisms, which we elucidated by deriving their action spectra. The flagellated alga Euglena gracilis exhibits photoperiodism, with a long-day response in cell reproduction. The underlying clock is a circadian rhythm with photoinductive capability, peaking at subjective dusk and occurring at the 26th hour in continuous darkness (DD) when transferred from continuous light (LL); it regulates photoinduction, a high-irradiance response (HIR), of a dark-capability of progressing through cell division. We derived the action spectra by irradiating E. gracilis with monochromatic light for 3 h at around the 26th hour; the action maxima occurred at 380, 450–460, 480, 610, 640,... |
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Palavras-chave: Cell division cycle; Complementary chromatic adaptation; Circadian; Euglena; End-of-day; Photoperiodism; Phytochrome; Shade avoidance. |
| Ano: 2007 |
URL: http://ir.obihiro.ac.jp/dspace/handle/10322/719 |
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| Bolige, Aoen; Goto, Ken. |
| Irradiance spectra change spatiotemporally, and angiosperms adapt accordingly, mainly through phytochromes. This study challenges the long-held belief that the flagellated alga Euglena gracilis lacks phytochromes and is therefore unaffected by spectral changes. We photoautotrophically cultured the alga under continuous light (LL), then transferred it to darkness. After about 26 h in darkness, different irradiations for 3 h enabled cell division in dark-arrested G2 cells evoking a high-irradiance response (HIR). The spectral characteristics of the irradiation during the LL period (pre-irradiation) defined the spectral sensitivity in the subsequent dark period. LL with light rich in the red spectrum led to a HIR to the red spectrum (R-HIR), whereas light... |
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Palavras-chave: Cell division; Circadian rhythms; End-of-day; Euglena; Photoperiodism; Phytochrome; Shade avoidance. |
| Ano: 2007 |
URL: http://ir.obihiro.ac.jp/dspace/handle/10322/720 |
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