Madhavi Bhatia, National Institute of Pharmaceutical Education and Research, Guwahati
Annual molt is a critical physiology event that exists in multiple phyla across the animal kingdom. The event is characterized by periodic partial or complete shedding and replacement of the organism’s outer layer. In birds and mammals, the molt is associated with a variable loss and replacement of the worn appendages that are feathers or hairs. Especially in birds, molt acts as a critical stage in the life cycle as individual fitness tightly depends on the functionality of its plumage which regulates flight, thermoregulation, and mating aptitudes.
Impact of Molt on gene expression
The Impact of molt on gene expression appears to differ based on the tissue concerned and also on the stage of molt. Molt was associated with the down-regulation of gene expression in most tissues. Except for female blood, meninges, shin and tail skins, and billiducts, an upregulation was observed. The gene expression changes that are induced by molt were highly variable from one tissue to another. Changes were observed in 5202 differential gene expression (DGE) and differential transcript usage (DTU) genes in male blood and only a few 6 differential gene expression (DGE) and differential transcript usage (DTU) genes in seminiferous ducts.
The genes that are down-regulated in males and up-regulated in females appear to be related to terms linked to chromosome structure. Molt is responsible for the renewing of appendages, which heavily conditions sexual dimorphism in birds. One hypothesis is developed that the higher impact of molt on male blood gene expression could be due to stronger sexual selection. However, sex-based gene expression highly differs from tissue-based gene expression.
Impact of Molt on tissues
Transcriptome analysis shows that the changes that occur in tissues at the transcriptome level due to molt can be observed at the phenotypic level that includes immunity, cell dynamics, dermis, and nervous system are all putatively impacted by molt. One hypothesis was developed to understand the neurobiological control of molt. There was a switch of the autonomic nervous system from the parasympathetic nervous system to the sympathetic nervous system that transduces a state of stress for the organism.
In the nervous tissue cluster composed of the cerebellum, cerebrum, hypothalamus, eyes, and meninges samples, genes as reported by the transcriptome analysis. Acetylcholine and cholinesterase activities were found altered by molt. The CRH and PTHLH genes, coding corticotropin-releasing hormone for parathyroid, were found to increase during the molt and might be related to the neuroendocrine control of the molt. There is up-regulation of β-keratin genes during the molt stage. These genes constitute a key component of a feather, scale, claw, and beak of birds, and also diversification at the origin of unique properties of feathers.
Conclusion
The transcriptome analysis will help in the future for understanding of the transcriptome of chicken and also understand the molting processes which is one of the crucial processes in the avian lifecycle.
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Reference:
- Charton, C., Youm, D.-J., Ko, B. J., Seol, D., Kim, B., Chai, H.-H., Lim, D., & Kim, H. (2021). The transcriptomic blueprint of molt in rooster using various tissues from Ginkkoridak (Korean long-tailed chicken). BMC Genomics, 22(1), 594. https://doi.org/10.1186/s12864-021-07903-9
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About the author:
Madhavi Bhatia is currently pursuing a Master of Science in Pharmaceutical Biotechnology from NIPER, Guwahati. Her area of interest lies in understanding the role of gene mutation in the development of various diseases and developing a treatment for such diseases.
Publications
1. https://bioxone.in/news/worldnews/impact-of-plastic-pollution-on-marine-turtles/
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