The golden rabbitfish, Siganus guttatus, is a reef fish exhibiting a restricted lunar-related rhythm in behavior and reproduction. Here, to understand the circadian rhythm of this lunar-synchronized spawner, a melatonin receptor subtype-Mel1c-was cloned. The full-length Mel1c melatonin receptor cDNA comprised 1747 bp with a single open reading frame (1062 bp) that encodes a 353-amino acid protein, which included 7 presumed transmembrane domains. Real-time PCR revealed high Mel1c mRNA expression in the retina and brain but not in the peripheral tissues. When the fish were reared under light/dark (LD 12:12) conditions, Mel1c mRNA in the retina and brain was expressed with daily variations and increased during nighttime. Similar variations were noted under constant conditions, suggesting that Mel1c mRNA expression is regulated by the circadian clock system. Daily variations of Mel1c mRNA expression with a peak at zeitgeber time (ZT) 12 were observed in the cultured pineal gland under LD 12:12. Exposure of the cultured pineal gland to light at ZT17 resulted in a decrease in Mel1c mRNA expression. When light was obstructed at ZT5, the opposite effect was obtained. These results suggest that light exerts certain effects on Mel1c mRNA expression directly or indirectly through melatonin actions.
|ジャーナル||Comparative Biochemistry and Physiology - A Molecular and Integrative Physiology|
|出版ステータス||Published - 2007 5|
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