title: Hypothalamic gene switches control transitions between seasonal life history states in a night-migratory photoperiodic songbird.
abstract: This study investigated photoperiodic plasticity in hypothalamic expression of genes implicated in the photoperiodic light perception (rhodopsin, melanopsin, neuropsin and peropsin), transduction (pax6, bmal1, clock, per2 and casr), induction (eya3, tshβ, dio2 and dio3, gnrh and gnih) and metabolism (NPY, sirtuin1, foxO1, hmgcr, citrate synthase and dehydrogenases) in photosensitive and photorefractory redheaded buntings. There was a significant increase in eya3, tsh β, dio2, pax6 and rhodopsin and decrease in dio3 mRNA expression at hour 15 and/or 19 on the day photosensitive buntings were subjected to a 13- or 16 h, but not to 8- and 11 h light exposure. Downstream reproductive and metabolic gene expression was not altered, except for an increase in those genes coding for succinate and malate dehydrogenase enzymes involved in lipogenesis. Photorefractory buntings had high dio3 mRNA expression which significantly declined after 1 short day exposure, suggesting possible involvement of dio3 in the maintenance of photorefractoriness. Positive correlation of rhodopsin on eya 3 and tshβ indicates its role in photoperiodic timing, perhaps involving the peropsin and pax6 genes. These results suggest that rapid switching of hypothalamic gene expression underlies photoperiod-induced seasonal plasticity and regulates transitions from photosensitive to photostimulated and from photorefractory to photosensitive states in migratory songbirds.
authors.affiliation: DST-IRHPA Center for Excellence in Biological Rhythms Research, Department of Zoology, University of Delhi, Delhi 110 007, India.
authors.forename: Gaurav
authors.initials: G
authors.lastname: Majumdar
authors.affiliation: DST-IRHPA Center for Excellence in Biological Rhythms Research, Department of Zoology, University of Lucknow, Lucknow 226 007, India.
authors.forename: Sangeeta
authors.initials: S
authors.lastname: Rani
authors.affiliation: DST-IRHPA Center for Excellence in Biological Rhythms Research, Department of Zoology, University of Delhi, Delhi 110 007, India. Electronic address: drvkumar11@yahoo.com.
authors.forename: Vinod
authors.initials: V
authors.lastname: Kumar
mesh_terms: D025041:Animal Migration; D000818:Animals; D030161:Avian Proteins / Q000096:biosynthesis* / Q000235:genetics; D005786:Gene Expression Regulation / Q000502:physiology*; D007031:Hypothalamus / Q000378:metabolism*; D012621:Seasons; D020308:Songbirds / Q000235:genetics / Q000378:metabolism*
chemical_list: D030161:Avian Proteins
keywords: Bunting; Circadian; Critical day length; Genes; Metabolism; Opsins