The reciprocal switching of two thyroid hormone-activating and -inactivating enzyme genes is involved in the photoperiodic gonadal response of Japanese quail.
The molecular mechanisms underlying photoperiodic time measurement are not well understood in any organism. Relatively recently, however, it has become clear that thyroid hormones play an important role in photoperiodism, and in a previous study we reported that long daylengths in Japanese quail increase hypothalamic levels of T(3) and of the thyroid hormone-activating enzyme, type 2 iodothyronine deiodinase. The present study extends these observations to measure gene levels of the thyroid hormone-inactivating enzyme, type 3 deiodinase. Levels decreased after exposure to long days, but increased under short days. Changes in the two genes were then analyzed during the precisely timed photoinduction that occurs in quail exposed to a single long day. The two gene switches are the earliest events yet recorded in the photoinduction process, and overall, these reciprocal changes offer the potential to regulate active brain thyroid hormone concentrations rather precisely at the site in the brain where photoinduction is triggered.
Yasuo
Shinobu
S
Division of Biomodeling, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan.
Watanabe
Miwa
M
Nakao
Nobuhiro
N
Takagi
Tsuyoshi
T
Follett
Brian K
BK
Ebihara
Shizufumi
S
Yoshimura
Takashi
T
D000818:Animals; D003370:Coturnix / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D006066:Gonads / Q000502:physiology; D007031:Hypothalamus / Q000502:physiology*; D007453:Iodide Peroxidase / Q000235:genetics* / Q000378:metabolism; D008297:Male; D017440:Photoperiod; D012098:Reproduction / Q000502:physiology*; D012621:Seasons; D013974:Thyroxine / Q000378:metabolism; D014284:Triiodothyronine / Q000378:metabolism; D000097564:Iodothyronine Deiodinase Type II
D007453:Iodide Peroxidase; D013974:Thyroxine; D014284:Triiodothyronine; D000097564:Iodothyronine Deiodinase Type II; C117274:iodothyronine deiodinase type III