Transcriptional and nontranscriptional events are involved in photic entrainment of the circadian clock in the cricket Gryllus bimaculatus

Most insects show daily activity rhythms that are controlled by endogenous circadian clocks. A basic property of the clock is entrainment to daily environmental cycles to run with an exact 24‐h period. The entrainment is achieved mainly through resetting by light. The present study analyses the ligh...

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Bibliographic Details
Published in:Physiological entomology 2016-12, Vol.41 (4), p.358-368
Main Authors: Kutaragi, Yuki, Miki, Taiki, Bando, Tetsuya, Tomioka, Kenji
Format: Article
Language:English
Subjects:
Circadian clock
clock genes
Gryllidae
Gryllus bimaculatus
light entrainment
locomotor rhythm
mRNA
phase shifts
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Summary:Most insects show daily activity rhythms that are controlled by endogenous circadian clocks. A basic property of the clock is entrainment to daily environmental cycles to run with an exact 24‐h period. The entrainment is achieved mainly through resetting by light. The present study analyses the light resetting mechanism of the clock in first‐instar nymphal and adult crickets Gryllus bimaculatus (De Geer). A 3‐h light pulse given at early subjective night and late subjective night causes a phase delay and an advance, respectively, of adult locomotor rhythms. The magnitude of the shift caused by the light pulse at circadian time 12 h in constant darkness is significantly smaller than that caused by a 3‐h extension of light phase. Measurement of mRNA levels during the light‐induced phase shifts yielded basically similar results for nymphs and adults. When a 3‐h light pulse is given at early night by light phase extension, an increase of Pdp1 occurs, which is followed by upregulation of the genes Clk and subsequently by per and tim. These changes are eliminated by RNA interference of opsin‐long wavelength, which is expressed in the compound eye and encodes a green‐sensitive opsin, the major photoreceptor for photic entrainment of the clock. No clear changes in mRNA levels are observed for light pulses given at late subjective night or at early subjective night after 24 h of constant darkness. These results suggest that the photic entrainment mechanism of the clock may be shared by nymphal and adult crickets, including transcriptional and nontranscriptional events.
ISSN:0307-6962
1365-3032
DOI:10.1111/phen.12162