Influence of photoperiod variations on the mRNA expression pattern of melatonin bio‐synthesizing enzyme genes in the pineal organ and retina: A study in relation to the serum melatonin profile in the tropical carp Catla catla

Abstract

Surface-dwelling C. catla were exposed to different photoperiods (8L:16D, 12L:12D, 12D:12L and 16L:8D) and the mRNA level profile of enzymes involved in melatonin synthesis was evaluated in the pineal gland and retina. Furthermore, a comparative analysis of the serum melatonin profile with the mRNA level was also performed. The results indicated diurnal variations in the transcripts of tph1, aanat and hiomt in the pineal organ and retina, and these variations change with the change in lighting regime. The serum melatonin profile showed rhythmicity in the natural photoperiod, but the serum melatonin level increased proportionally with increasing daylength. In short photoperiods, the peak value (though lower than in long photoperiods) of melatonin maintains a longer duration in serum. Moreover, the comparative analysis revealed a similar profile of mRNA of pineal aanat1 and aanat2 with serum melatonin under the same lighting conditions. This indicates that serum melatonin is produced by the pineal gland. Our results specify the importance of day length and the timing of onset or offset of the dark for maintaining the oscillating levels of serum melatonin and mRNA levels of melatonin biosynthesizing enzyme genes in the pineal organ and retina as well. The findings in this study highlight the distinctive pattern of mRNA levels in the pineal organ and retina under different photoperiods. The pineal melatonin biosynthesizing enzyme genes showed a similar pattern with serum melatonin levels while the retinal genes changed dramatically with photoperiod. We also revealed a light-dependent transcriptional regulation of pineal aanat genes in C. catla. Moreover, our results suggest that ALAN and skyglow can influence the levels of serum melatonin and its biosynthesis, resulting in desynchronization of the entire biological clock as well as the overall physiology of the animal.

A Crosstalk Between Pineal and Major Extra-Pineal Sources of Melatonin and its Role in Ovarian Growth and Maturation in Fish

“…It was also pointed out that the rhythm parameters of various melatonin biosynthesizing enzyme genes in these two organs vary and/or shift differently. Additionally, under the influence of different photoperiodic conditions, the pattern of mRNA expression of the melatonin biosynthesizing enzyme genes in the retina and pineal organ changes 36 . This investigation reveals a distinctive way of mRNA transcripts for the genes TPH1, AANAT1, AANAT2, and ASMT in the retinal and pineal organ; the pineal melatonin biosynthesizing enzyme genes exhibited a pattern similar to that of serum levels of melatonin, and the retinal genes underwent a dramatic change with photoperiod.…”

The Circadian Rhythm of the Behavior and Gut Microbiota in Dybowski’s Frogs (Rana dybowskii) during the Autumn Migration Period

“…Esculenta [ 5 ] and plasma corticosterone in Bufo americanus [ 6 ]. The circadian rhythm changes in response to environmental factors, such as light [ 7 ] and temperature [ 8 ]. In our previous studies [ 9 , 10 ], we revealed the circadian rhythm of Dybowski’s frog ( Rana dybowskii ) and the impact of photoperiod on its Melatonin.…”

Sleeping with the fishes: Looking under the bonnet of melatonin synthesis

“…Authors demonstrate that there are diurnal variation in the expression of these genes not only occurs in the pineal gland, but also occurs in the retina (Devi et al ., 2022). The expression of the melatonin production genes in the pineal gland were concordant with serum level melatonin, however, retinal mRNA levels changed dramatically with photoperiod, confirming that the pineal gland as the main melatonin producer.…”

“…However, in this issue a few more of those unknowns are answered by the work of Devi et al . (2022) who investigate the expression of three genes involved in the four stage enzymatic process of melatonin production ( tph1 , aanat and hiomt) in Indian carp ( Catla Catla ).…”

“…Despite its importance, there is still not a complete understanding of how this hormone is synthesized in response to photoperiod. However, in this issue a few more of those unknowns are answered by the work of Devi et al (2022) who investigate the expression of three genes involved in the four stage enzymatic process of melatonin production (tph1, aanat and hiomt) in Indian carp (Catla Catla).…”