Journal of Biochemistry Advance Access published online on October 25, 2009
Journal of Biochemistry, doi:10.1093/jb/mvp160
Circadian clock in Ciona intestinalis revealed by microarray analysis and oxygen consumption
1 Clock Cell Biology Research Group, Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8566, Japan
2 Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
3 Department of Bioinformatics, Graduate School of Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8510, Japan
4 Division of Innovative Research, Creative Research Initiative ‘Sousei’ (CRIS), Hokkaido University, Kita-ku, Sapporo 001-0021, Japan
5 Department of Zoology, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
6 Department of Molecular Immunology, Institute of Development, Aging and Cancer, Tohoku University, Aoba-ku, Sendai 980-8575, Japan
7 Life Sciences and Bioengineering, Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba 305-8572, Japan
Corresponding author: Norio Ishida Address: Clock Cell Biology Research Group, Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8566, Japan Phone: +81-29-861-6053. Fax: +81-29-861-9499. E-mail: n.ishida{at}aist.go.jp
Received July 1, 2009; Accepted September 20, 2009
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Abstract |
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The molecular mechanisms of the endogenous circadian clocks that allow most animals to adapt to environmental cycles have recently been uncovered. The draft genome of the ascidian, Ciona intestinalis, a model animal that is close to vertebrates, has been described. However, the C. intestinalis genome lacks the canonical clock genes such as Per, Bmal and Clock that are shared by vertebrates and insects. Here, we found the circadian rhythms at the physiological and molecular levels. The oxygen consumption rate was lower during the light phase and higher during the dark phase during a day, and the rhythm highly damped and continued under constant darkness. From the microarray analysis, the 396 spots (1.8% of the total; corresponding to 388 clones) were extracted as candidates for circadian expression. We confirmed the circadian expression of several candidate genes by Northern blotting. Furthermore, three of four rhythmic expressed genes showed phase-shifts to prolonged light period. However, most of known clock genes did not oscillate. These data suggest that C. intestinalis have a unique molecular circadian clock and suggest that the daily environmental change is not so strong effect for sea squirt in its evolution when compared to vertebrates and insects.
Key Words: ascidian, Ciona intestinalis, circadian clock, microarray, Northern blotting