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.