This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (6) Citing Articles via Google Scholar Citing Articles via Scopus Google Scholar Articles by Chen, W.-F. Articles by Edery, I. Search for Related Content PubMed PubMed Citation Articles by Chen, W.-F. Articles by Edery, I. Social Bookmarking                         What's this?

Clock-Gated Photic Stimulation of Timeless Expression at Cold Temperatures and Seasonal Adaptation in Drosophila

Rutgers University, Center for Advanced Biotechnology and Medicine, Piscataway, NJ 08854

John Majercak

Rutgers University, Center for Advanced Biotechnology and Medicine, Piscataway, NJ 08854

Isaac Edery

Rutgers University, Center for Advanced Biotechnology and Medicine, Piscataway, NJ 08854, edery{at}cabm.rutgers.edu

Numerous lines of evidence indicate that the initial photoresponse of the circadian clock in Drosophila melanogaster is the light-induced degradation of TIMELESS (TIM). This posttranslational mechanism is in sharp contrast to the well-characterized pacemakers in mammals and Neurospora, where light evokes rapid changes in the transcriptional profiles of 1 or more clock genes. The authors show that light has novel effects on D. melanogaster circadian pacemakers, acutely stimulating the expression of tim at cold but not warm temperatures. This photoinduction occurs in flies defective for the classic visual phototransduction pathway or the circadian-relevant photoreceptor CRYPTOCHROME (CRY). Cold-specific stimulation of tim RNA abundance is regulated at the transcriptional level, and although numerous lines of evidence indicate that period (per) and tim expression are activated by the same mechanism, light has no measurable acute effect on per mRNA abundance. Moreover, light-induced increases in the levels of tim RNA are abolished or greatly reduced in the absence of functional CLOCK (CLK) or CYCLE (CYC) but not PER or TIM. These findings add to a growing number of examples where molecular and behavioral photoresponses in Drosophila are differentially influenced by "positive" (e.g., CLK and CYC) and "negative" (e.g., PER and TIM) core clock elements. The acute effects of light on tim expression are temporally gated, essentially restricted to the daily rising phase in tim mRNA levels. Because the start of the daily upswing in tim expression begins several hours after dawn in long photoperiods (day length), this gating mechanism likely ensures that sunrise does not prematurely stimulate tim expression during unseasonally cold spring/summer days. The results suggest that the photic stimulation of tim expression at low temperatures is part of a seasonal adaptive response that helps advance the phase of the clock on cold days, enabling flies to exhibit preferential daytime activity despite the (usually) earlier onset of dusk. Taken together with prior findings, the ability of temperature and photoperiod to adjust trajectories in the rising phases of 1 or more clock RNAs constitutes a major mechanism contributing to seasonal adaptation of clock function.

Key Words: Drosophila • circadian rhythms • tim expression • photoperiod • temperature • seasonal adaptation

Journal of Biological Rhythms, Vol. 21, No. 4, 256-271 (2006)
DOI: 10.1177/0748730406289306


CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				T. Yoshii, S. Vanin, R. Costa, and C. Helfrich-Forster Synergic Entrainment of Drosophila's Circadian Clock by Light and Temperature J Biol Rhythms, December 1, 2009; 24(6): 452 - 464. [Abstract] [PDF]

				T. Yoshii, K. Fujii, and K. Tomioka Induction of Drosophila Behavioral and Molecular Circadian Rhythms by Temperature Steps in Constant Light J Biol Rhythms, April 1, 2007; 22(2): 103 - 114. [Abstract] [PDF]

				Y. Miyasako, Y. Umezaki, and K. Tomioka Separate Sets of Cerebral Clock Neurons Are Responsible for Light and Temperature Entrainment of Drosophila Circadian Locomotor Rhythms J Biol Rhythms, April 1, 2007; 22(2): 115 - 126. [Abstract] [PDF]

				W.-F. Chen, K. H. Low, C. Lim, and I. Edery Thermosensitive Splicing of a Clock Gene and Seasonal Adaptation Cold Spring Harb Symp Quant Biol, January 1, 2007; 72(0): 599 - 606. [Abstract] [PDF]