Molecular Mechanism Regulating Seasonality

Seasonal Reproduction in Vertebrates: Melatonin Synthesis, Binding, and Functionality Using Tinbergen’s Four Questions

“…Chronic exposure (16 h) to melatonin in mediobasal hypothalamic explants including the pars tuberalis showed lower melatonin binding in the pars tuberalis in mink ( Mustela vison ) at all times of the year the tissue was harvested [ 225 ]. For further reading on the molecular mechanism of Dio2 see [ 226 ].…”

Revealing the profound influence of diapause on gene expression: Insights from the annual transcriptome of the copepod Calanus finmarchicus

“…Despite the apparent fitness and ecological importance of annual rhythms, the endogenous circannual clock mechanism underlying phenology is still poorly understood, probably since studying biological processes over such a long time period is logistically challenging (Baumgartner & Tarrant, 2017; Denlinger, 2022a; Helm & Lincoln, 2017; Ikegami & Yoshimura, 2017). Nevertheless, the necessity of circadian clock genes for photoperiodic responses is well described in many groups (Denlinger, 2022a; Helm & Lincoln, 2017; Schwarzenberger et al., 2020).…”

“…However, while EYA and PDF promote, respectively, ‘winter’ and ‘summer’ physiology in Drosophila (Hidalgo et al., 2023), the seasonal patterns would be the opposites in Calanus . Finally, melatonin has been reported in several of invertebrates and vertebrates, as well as plants and bacteria, and shown to be involved in temporal signalling for daily, lunar, and annual rhythms (Denlinger, 2022a; Ikegami & Yoshimura, 2017; Reiter, 1993), including in zooplankton species (Schwarzenberger et al., 2023; Tosches et al., 2014). It is synthesized from serotonin by the enzymes arylalkylamine‐N‐acetyltransferase (AA‐NAT) and hydroxyindole‐O‐methyltransferase (HIOMT), two outputs of the circadian clock.…”

“…The annual rotation of the Earth around the Sun is the cause of periodic, predictable changes in risks and opportunities for living organisms. Thus, numerous species have evolved annual rhythms (Denlinger, 2022a; Helm & Lincoln, 2017; Ikegami & Yoshimura, 2017) conceptualized mechanistically by the endogenous circannual clock, synchronized by reliable external cues. This clock enables organisms to anticipate seasonal events and initiate biological processes accordingly.…”

“…This clock enables organisms to anticipate seasonal events and initiate biological processes accordingly. While external cues such as food availability, predator presence, or temperature can fine‐tune the timing of annual rhythms, change in day length (photoperiod) is the most reliable and thus the most important external factor synchronizing the endogenous circannual timing mechanism (Baumgartner & Tarrant, 2017; Denlinger, 2022a; Helm & Lincoln, 2017; Ikegami & Yoshimura, 2017). Perhaps the most profound annual biological rhythms in organisms include those which involve long periods of dormancy, hibernation, or diapause (i.e.…”