We hypothesized differences in molecular strategies for similar journeys that migrants undertake to reproduce in spring and to overwinter in autumn. We tested this in redheaded buntings (Emberiza bruniceps) photoinduced into spring and autumn migratory states, with winter and summer non-migratory states as controls. Compared with controls, buntings fattened, gained weight and showed Zugunruhe (nocturnal migratory restlessness) in the migratory state. Spring migration was associated with greater fat and body mass, and higher intensity of Zugunruhe, compared with autumn migration. Circulating corticosterone levels were higher in spring, while T3 levels were higher in autumn. Hypothalamic expression of thyroid hormone- responsive (dio2, dio3), light-responsive ( per2, cry1, adcyap1) and th (tyrosine hydroxylase, involved in dopamine biosynthesis) genes showed significant changes with transition from non-migratory to the migratory state. There were significantly higher mRNA expressions in autumn, except for higher th levels in the spring. Furthermore, the expression patterns of dnmt3a (not dnmt3b) and tet2 genes suggested an epigenetic difference between the non-migrant and migrant periods, and the spring and autumn migrant periods. These results demonstrate for the first time seasonal transition in hypothalamic gene expressions, and suggest differences in regulatory strategies at the transcriptional level for spring and autumn migrations in songbirds.
|Journal||Proceedings of the Royal Society B: Biological Sciences|
|State||Published - 2018|
Bibliographical noteFunding Information:
Ethics. All procedures were approved and carried out in accordance with guidelines of the Institutional Animal Ethics Committee (IAEC) of Department of Zoology, University of Delhi, India (Institutional Ethical Approval number: DU/ZOOL/IAECR/ 2015/04). Data accessibility. The mRNA sequences with their partial CDS can be accessed using GenBank accession numbers as provided in electronic supplementary material, table S1. Authors’ contribution. V.K. conceived the idea. V.K., D.S., N.J.G. and S.R. designed the study. D.S., A.S. and S.M. performed experiments and carried out sampling. D.S. and A.S. performed hormone assays. A.S. and D.S. performed gene expression assays. A.S. analysed data and prepared final figures. V.K. and A.S. wrote the manuscript and carried out extensive revision. N.J.G. and S.R. provided the animal resources; V.K. provided all chemical and other laboratory resources. All authors gave final approval for publication. Competing interests. Authors have no competing interests. Funding. The funds were provided by the Department of Biotechnology, New Delhi through a research grant (BT/PR4984/MED/30/ 752/2012) to V.K. A.S. received a Junior Research Fellowship from the Council of Scientific and Industrial Research, New Delhi. The experimental facility used for experiments was built with the support from the Science and Engineering Research Board, New Delhi under IRHPA grant to V.K.
© 2019 The Authors.
- Gene expression
ASJC Scopus subject areas
- Immunology and Microbiology (all)
- Biochemistry, Genetics and Molecular Biology (all)
- Environmental Science (all)
- Agricultural and Biological Sciences (all)