Did you recognize that not only does organism’s body have a biological clock that may tell the time of the day, it could also tell the time of the 12 months? Now, researchers from Japan have found that one capable little molecule could also be behind the mechanism by which the biological clock keeps track of the seasons.
In a study that was recently published in PLOS Biology, researchers from Osaka University reveal that glutamate signaling is liable for the seasonal regulation of reproduction in bean bugs by genes involved in maintaining circadian rhythm.
The circadian rhythm is driven by a biological clock that controls body processes based on time of day. A related process is photoperiod sensitivity, or seasonal regulation, wherein body processes are regulated on a seasonal basis based on the length of the daytime and nighttime periods.
“Previous studies have shown that circadian clock genes are involved not only in regulating day by day processes, but in addition in regulating seasonal events, akin to reproduction in insects,” states Masaharu Hasebe, first writer on the study. “Nevertheless, the mechanism governing this interaction was unclear.”
To deal with this, the researchers focused on glutamate, a neurotransmitter that’s involved in transmitting a wide selection of signals within the brains of many animals, from invertebrates to mammals. Using bean bugs, a convenient model of circadian clock-related seasonal rhythms, a brain glutamate level was assessed in numerous photoperiodic conditions related to the seasonal reproductive cycle and in response to interference with circadian clock genes.
The outcomes were very clear. Extracellular glutamate levels in the entire brain were significantly higher under short-day conditions than under long-day conditions, and pulling down the clock gene period abolished this difference.”
Sakiko Shiga, senior writer of the study
Directly reducing or increasing glutamate levels in bean bug brains also decreased season-specific changes in reproductive status. As well as, reducing or increasing glutamate levels disrupted the photoperiodic responses of pars intercerebralis neurons, which generally change their neural activity seasonally and promote egg laying.
“Our results show that extracellular glutamate dynamics are regulated by clock genes and play an important role within the photoperiodic control of reproduction,” says Hasebe.
Provided that glutamate is widely used for neurotransmission in animals, from insects to mammals, the findings from this study have implications beyond bean bug biology. It is feasible that further studies investigating this newly discovered mechanistic link between the circadian clock and photoperiod regulation will advance our understanding of seasonal adaptation in a wide selection of animals.
Source:
Journal reference:
Hasebe, M & Shiga, S., (2022) Clock gene-dependent glutamate dynamics within the bean bug brain regulate photoperiodic reproduction. PLOS Biology. doi.org/10.1371/journal.pbio.3001734.