The influence of feeding on the daily rhythm of mRNA expression on melatonin bio-synthesizing enzyme genes and clock associated genes in the zebrafish (Danio rerio) gut

ABSTRACT

The study aimed to investigate the presence of melatonin bio-synthesizing enzyme genes in the zebrafish gut and its daily mRNA expression profile along with core clock genes in different feeding regime under regular photoperiod. Zebrafish were randomly distributed in the laboratory condition into two feeding groups; one was regular feeding (NF), where food was supplied at light phase. Another was the altered feeding (AF), where food was provided at the dark phase for 30 days. Primarily, the presence of melatonin bio-synthesizing machinery has been demonstrated in the zebrafish gut through immunohistochemistry and End Point PCR. Subsequently, the transcript profile of the said genes was analyzed by qRT-PCR. The study reveals an opposite phage in the daily mRNA expression of tph1, aanat2, and asmt in AF, concerning the NF condition. In contrast, all core clock genes in the gut display a rhythmic expression without any change in the acrophase, irrespective of the feeding schedule, indicating melatonin production may be controlled through the feeding cycle. Still, clock genes need other influence to entrain. The change in the rhythmic expression of the bio-synthesizing enzyme genes of the chronobiotic molecule through feeding may lead to desynchronization in fish physiology.

KEYWORDS:

• Feeding
• gut
• melatonin biosynthesis
• clock
• light

Acknowledgments

The authors are grateful to the Director, IBSD, India, and CSIR-JRF Programme to GM [09/1044(0003)/2016-EMR-I(20/12/2016)] for financial support. The authors are thankful to Mr W. Rahul for the continuous support in the collection and maintenance of fish in IBSD Zebrafish Facility, Imphal, Manipur, India. We are also grateful to the security personnel/of the Institute for their support in this long experiment during the holidays. We are also grateful to the anonymous reviewers for their valuable comments to improve the manuscript. Our sincere gratitude to every Indian taxpayer for their contribution towards the funding for research. The IBSD, Imphal manuscript number is 2015059.

Disclosure statement

The author(s) has no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Author contributions

GM acquisition of data, analysis/interpretation, statistical analysis, and manuscript drafting. ZAK critical analysis of the data, organization of figures, preparation of the manuscript. SDD, TY, CR, and HSD sampling. AC, concept/design, manuscript preparation, and critical review of the definitive version.

Additional information

Funding

This work was supported by the CSIR [09/1044(0003)/2016-EMR-I(20/12/2016)].