4 July 2022 Constant Light, Pdp1, and Tim Exert Influence on Free-Running Period of Locomotor Rhythms in the Cricket Gryllus bimaculatus
Yoshiyuki Moriyama, Kazuki Takeuchi, Kenji Tomioka
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Most insects show circadian rhythms of which the free-running period changes in a light-dependent manner and is generally longer under constant light (LL) than under constant dark conditions in nocturnal animals. However, the mechanism underlying this LL-dependent period change remains unclear. Here, using the cricket Gryllus bimaculatus, we examined the effects of long-term LL exposure on the free-running period of locomotor rhythms. Initially, the free-running period was considerably longer than 24 h but it gradually became shorter during long-term exposure to LL. The initial lengthening and ensuing gradual shortening under long-term LL exposure were observed even after unilateral removal of the optic lobe. Thus, these changes in the free-running period could be attributable to a single optic lobe clock. RNA interference (RNAi)-mediated silencing of the clock genes Par domain protein 1 (Pdp1) and timeless (tim) revealed that the treatments eliminated the initial period lengthening by LL without reducing circadian photoreceptor gene expression. However, they did not affect the period shortening during long-term LL exposure. The slopes of the regression line for the period change during long-term LL for Pdp1RNAi-treated and timRNAi-treated crickets were not different from that of the dsDsRed2-treated control. These results suggest that the initial period lengthening after transfer to LL requires tim and Pdp1, while the ensuing period shortening during long-term LL exposure is caused by a mechanism independent of tim and Pdp1.

© 2022 Zoological Society of Japan
Yoshiyuki Moriyama, Kazuki Takeuchi, and Kenji Tomioka "Constant Light, Pdp1, and Tim Exert Influence on Free-Running Period of Locomotor Rhythms in the Cricket Gryllus bimaculatus," Zoological Science 39(5), 459-467, (4 July 2022). https://doi.org/10.2108/zs220014
Received: 6 February 2022; Accepted: 5 May 2022; Published: 4 July 2022
circadian rhythm
clock gene
constant light
free-running period
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