Influence of light and temperature cycles on the expression of circadian clock genes in the mussel Mytilus edulis

Abstract

Clock genes and environmental cues regulate essential biological rhythms. The blue mussel, Mytilus edulis, is an ecologically and economically important intertidal bivalve undergoing seasonal reproductive rhythms. We previously identified seasonal expression differences in M. edulis clock genes. Herein, the effects of light/dark cycles, constant darkness, and daily temperature cycles on the circadian expression patterns of such genes are characterised. Clock genes Clk, Cry1, ROR/HR3, Per and Rev-erb/NR1D1, and Timeout-like, show significant mRNA expression variation, persisting in darkness indicating endogenous control. Rhythmic expression was apparent under diurnal temperature cycles in darkness for all except Reverb. Temperature cycles induced a significant expression difference in the non-circadian clock-associated gene aaNAT. Furthermore, Suppression Subtractive Hybridisation (SSH) was used to identify seasonal genes with potential links to molecular clock function revealed numerous genes meriting further investigation. Understanding the relationship between environmental cues and molecular clocks is crucial in predicting the outcomes of environmental change on fundamental rhythmic processes.

Step in Time: Biomineralisation of Bivalve’s Shell

“…The outputs of this conserved structure are circadian (Dunlap, 1999). Homologous clock genes (clock and bmal as activators and cryptochrome 1 and 2, period and timeless as repressors) have been described for bivalves, such as the oyster Magallana gigas (Perrigault and Tran, 2017), the mussels M. edulis (Chapman et al, 2020) and M. californianus (Connor and Gracey, 2011), the scallops Argopecten irradians (Pairett and Serb, 2013) and Chlamys islandica (Perrigault et al, 2020) and even in the deep-sea [i.e., Bathymodiolus azoricus (Mat et al, 2020)]. The main periods associated with biological clocks in bivalves are daily and tidal, but others with lower (several days to a year) or higher frequencies (hours to minutes) have also been reported (Figure 6B).…”

“…NR1D1) oscillate with a different amplitude when bivalves are placed in complete darkness (DD-Dark/Dark condition) with a 24 hours temperature cycle of 3.6 ± 0.2°C compared to those placed in DD and constant temperature (Chapman et al, 2020). It should be noted that the clock system responds to a periodical variation of the temperature and not to the temperature as a calorific energy.…”

Circadian Rhythm and Neurotransmitters Are Potential Pathways through Which Ocean Acidification and Warming Affect the Metabolism of Thick-Shell Mussels

“…Although both circadian rhythm and neurotransmitters of marine species are susceptible to environmental factors, − little is known about the impacts of ocean acidification and warming on these important regulatory processes of metabolism. Therefore, to improve the present understanding of the impacts and interaction of ocean acidification and warming, the effects of these two environmental factors on metabolism (clearance rate, oxygen consumption rate, ammonia excretion rate, oxygen: nitrogen ratio (O:N), ATP content, activity of pyruvate kinase (PK), and expression of metabolism-related genes), circadian rhythm (heart rate, interval between maximum and minimum heart rates, and expression of Per2 , Cry , and BMAL1 ), and neurotransmitters (activity of acetyl cholinesterase (AChE) and in vivo contents of ACh, GABA, and DA) were investigated in economically and ecologically important bivalve species, the thick-shell mussel M.…”

Benthic macrofauna under extremes

“…For example, the hormone serotonin (5-hydroxytryptamine) can decrease oysters' mortality during air exposure by modulating the physiological redox process (Dong et al, 2017). Additionally, the hormone melatonin has been found to play a role in the circadian rhythm of certain shellfish species, such as the blue mussel (Chapman et al, 2020). Other hormones, such as dopamine and octopamine, have also been found to regulate various behaviors in shellfish, such as movement and aggression (Aiello et al, 1981;Jones, 1983).…”