title: Concurrent hypothalamic gene expression under acute and chronic long days: Implications for initiation and maintenance of photoperiodic response in migratory songbirds.
abstract: Hypothalamic expression of the thyroid hormone (TH) responsive gonadostimulatory (eya3, cga, tshβ, dio2, dio3, gnrh, gnih) and neurosteroid pathway genes (androgen receptor [ar], aromatase [cyp19], estrogen receptor [er] α and β) was examined in photosensitive redheaded buntings exposed to 2 (acute, experiment 1) or 12 (chronic, experiment 2) long days (16L:8D). Experiment 2 also included a photorefractory group. Acute long days caused a significant increase in eya3, cga, tshβ, dio2 and gnrh and decrease in dio3 mRNA levels. eya3, cga and tshβ expressions were unchanged after the chronic long days. We also found increased cyp19, erα and erβ mRNA levels after acute, and increased cyp19 and decreased erβ levels after the chronic long-day exposure. Photorefractory buntings showed expression patterns similar to that in the photosensitive state, except for high gnrh and gnih and low dio3 mRNA levels. Consistent with gene expression patterns, there were changes in fat deposition, body mass, testis size, and plasma levels of testosterone, tri-iodothyronine and thyroxine. These results show concurrent photostimulation of the TH-signalling and neurosteroid pathways, and extend the idea, based on differences in gene expression, that transitions in seasonal photoperiodic states are accomplished at the transcriptional levels in absolute photorefractory species.
authors: IndoUS Center for Biological Timing, Department of Zoology, University of Delhi, Delhi 110 007, India.
authors: Ila
authors: I
authors: Mishra
authors: Department of Zoology, CCS University, Meerut 250 004, India.
authors: Sanjay K
authors: SK
authors: Bhardwaj
authors: Department of Zoology, University of Lucknow, Lucknow 226 007, India.
authors: Shalie
authors: S
authors: Malik
authors: IndoUS Center for Biological Timing, Department of Zoology, University of Delhi, Delhi 110 007, India. Electronic address: drvkumar11@yahoo.com.
authors: Vinod
authors: V
authors: Kumar
mesh_terms: D025041:Animal Migration / Q000502:physiology*; D000818:Animals; D005786:Gene Expression Regulation; D006066:Gonads / Q000378:metabolism; D006728:Hormones / Q000097:blood; D007031:Hypothalamus / Q000378:metabolism*; D008954:Models, Biological; D017440:Photoperiod; D015398:Signal Transduction / Q000235:genetics; D020308:Songbirds / Q000235:genetics* / Q000502:physiology*; D013256:Steroids / Q000378:metabolism
chemical_list: D006728:Hormones; D013256:Steroids
keywords: Bird; Bunting; Gene expression; Neurosteroid; Photoperiod; Thyroid hormone