TY - JOUR
T1 - Temporal expression of genes coding for aryl-alkamine-N-acetyltransferase and melatonin receptors in circadian clock tissues
T2 - Circadian rhythm dependent role of melatonin in seasonal responses
AU - Trivedi, Amit Kumar
AU - Mishra, Ila
AU - Kumar, Vinod
N1 - Publisher Copyright:
© 2019 Elsevier Inc.
PY - 2019/8/1
Y1 - 2019/8/1
N2 - We investigated at the transcriptional level the role of daily rhythm in melatonin secretion in seasonal responses in the migratory blackheaded bunting (Emberiza melanocephala), which when exposed to short (SP) and long (LP) photoperiods exhibits distinct seasonal life-history states (LHSs). We reproduced the seasonal LHS by subjecting buntings to SP (8 h light: 16 h darkness, 8 L:16D), which maintained the nonmigratory/ nonbreeding phenotype, and to LP (16 L:8D), which induced the premigratory/ prebreeding, migratory/ breeding and nonmigratory/ postbreeding phenotypes. Plasma melatonin measured at 4 h intervals showed loss of the daily rhythm in the LP-induced premigratory/ prebreeding and migratory/ breeding LHSs. Subsequently, mRNA expression of genes coding for the aryl-alkamine-N-acetyltransferase (AANAT; the rate-liming enzyme of melatonin biosynthesis) and for the receptors for melatonin (Mel1A, Mel1B and Mel1C) was examined in the retina, pineal and hypothalamus; the interacting independent circadian clocks comprising the songbird circadian timing system. Except AANAT that was not amplified in the hypothalamus, we found significant alterations in both, the level and persistence of 24 h rhythm in mRNA expression of all genes, albeit with photoperiod and seasonal differences between three circadian clock tissues. Particularly, 24 h mRNA expression pattern of all genes, except retinal Mel1A, lacked a significant daily rhythm in the LP-induced migratory/ breeding LHS. These results underscore the overall importance of the circadian rhythm in the role of melatonin in photoperiodically-controlled seasonal responses in migratory songbirds.
AB - We investigated at the transcriptional level the role of daily rhythm in melatonin secretion in seasonal responses in the migratory blackheaded bunting (Emberiza melanocephala), which when exposed to short (SP) and long (LP) photoperiods exhibits distinct seasonal life-history states (LHSs). We reproduced the seasonal LHS by subjecting buntings to SP (8 h light: 16 h darkness, 8 L:16D), which maintained the nonmigratory/ nonbreeding phenotype, and to LP (16 L:8D), which induced the premigratory/ prebreeding, migratory/ breeding and nonmigratory/ postbreeding phenotypes. Plasma melatonin measured at 4 h intervals showed loss of the daily rhythm in the LP-induced premigratory/ prebreeding and migratory/ breeding LHSs. Subsequently, mRNA expression of genes coding for the aryl-alkamine-N-acetyltransferase (AANAT; the rate-liming enzyme of melatonin biosynthesis) and for the receptors for melatonin (Mel1A, Mel1B and Mel1C) was examined in the retina, pineal and hypothalamus; the interacting independent circadian clocks comprising the songbird circadian timing system. Except AANAT that was not amplified in the hypothalamus, we found significant alterations in both, the level and persistence of 24 h rhythm in mRNA expression of all genes, albeit with photoperiod and seasonal differences between three circadian clock tissues. Particularly, 24 h mRNA expression pattern of all genes, except retinal Mel1A, lacked a significant daily rhythm in the LP-induced migratory/ breeding LHS. These results underscore the overall importance of the circadian rhythm in the role of melatonin in photoperiodically-controlled seasonal responses in migratory songbirds.
KW - Gene expression
KW - Life-history state
KW - Melatonin
KW - Migration
KW - Photoperiod
KW - Receptors
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U2 - 10.1016/j.physbeh.2019.05.009
DO - 10.1016/j.physbeh.2019.05.009
M3 - Article
C2 - 31082443
AN - SCOPUS:85065978439
SN - 0031-9384
VL - 207
SP - 167
EP - 178
JO - Physiology and Behavior
JF - Physiology and Behavior
ER -