Moonlight affects mRNA abundance of arylalkylamine N-acetyltransferase in the retina of a lunar-synchronized spawner, the goldlined spinefoot

Authors

  • Tomomi Kashiwagi,

    1. Department of Chemistry, Biology and Marine Science, University of the Ryukyus, Nishihara, Okinawa, Japan
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  • Yong-Ju Park,

    1. Department of Chemistry, Biology and Marine Science, University of the Ryukyus, Nishihara, Okinawa, Japan
    2. Marine and Environmental Research Institute, Jeju National University, Jocheon, Jeju Special Self-Governing Province, Republic of Korea
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  • Ji-Gweon Park,

    1. Department of Chemistry, Biology and Marine Science, University of the Ryukyus, Nishihara, Okinawa, Japan
    2. Department of Biology, Jeju National University, Jeju Special Self-Governing Province, Republic of Korea
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  • Satoshi Imamura,

    1. Department of Chemistry, Biology and Marine Science, University of the Ryukyus, Nishihara, Okinawa, Japan
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  • Yuki Takeuchi,

    1. Department of Chemistry, Biology and Marine Science, University of the Ryukyus, Nishihara, Okinawa, Japan
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  • Sung-Pyo Hur,

    1. Department of Chemistry, Biology and Marine Science, University of the Ryukyus, Nishihara, Okinawa, Japan
    2. Marine and Environmental Research Institute, Jeju National University, Jocheon, Jeju Special Self-Governing Province, Republic of Korea
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  • Akihiro Takemura

    Corresponding author
    • Department of Chemistry, Biology and Marine Science, University of the Ryukyus, Nishihara, Okinawa, Japan
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  • Conflicts of interest: None.

Correspondence to: Akihiro Takemura, Department of Chemistry, Biology and Marine Science, University of the Ryukyus, 1 Senbaru, Nishihara, Okinawa 903-0213, Japan.

E-mail: takemura@sci.u-ryukyu.ac.jp

Abstract

Melatonin synthesis in the pineal gland and retina shows a rhythmic fashion with high levels at night and is controlled by a rate-limiting enzyme, arylalkylamine N-acetyltransferase (AANAT). A previous study revealed that moonlight suppresses the plasma melatonin levels of the goldlined spinefoot (Siganus guttatus), which exhibits a lunar cycle in its reproductive activity and repeats gonadal development toward and spawning around the first quarter moon. Whether the retina of this species responds to moonlight is unknown. To clarify the photoperceptive ability of this species, we aimed to clone the full-length cDNA of Aanat1 (sgAanat1) from the retina and examine its transcriptional pattern under several daylight and moonlight regimes. The full-length sgAanat1 cDNA (1,038 bp) contained a reading frame encoding a protein of 225 amino acids, which was highly homologous to AANAT1 of other teleosts. Reverse transcription-polymerase chain reaction (PCR) analysis revealed that among the tissues tested, sgAanat1 fragments were expressed exclusively in the retina. Real-time quantitative PCR analysis revealed that sgAanat1 fluctuated with high abundance at night under light–dark cycle and at subjective night under constant darkness, but not under constant light. These results suggest that sgAanat1 is regulated by both the external light signal and internal clock system. The abundance of sgAanat1 in the retina was higher at the culmination time around new moon than full moon phase. Additionally, exposing fish to brightness around the full moon period suppressed sgAanat1 mRNA abundance. Thus, moonlight is perceived by fish and has an impact on melatonin fluctuation in the retina. J. Exp. Zool. 319A: 505–516, 2013. © 2013 Wiley Periodicals, Inc.

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