Drosophila CRY Entrains Clocks in Body Tissues to Light and Maintains Passive Membrane Properties in a Non-clock Body Tissue Independent of Light

Abstract

Circadian (∼24 hr) clocks regulate daily rhythms in physiology, metabolism, and behavior via cell-autonomous transcriptional feedback loops. In Drosophila, the blue-light photoreceptor CRYPTOCHROME (CRY) synchronizes these feedback loops to light:dark cycles by binding to and degrading TIMELESS (TIM) protein. CRY also acts independently of TIM in Drosophila to alter potassium channel conductance in arousal neurons after light exposure, and in many animals CRY acts independently of light to repress rhythmic transcription. CRY expression has been characterized in the Drosophila brain and eyes, but not in peripheral clock and non-clock tissues in the body. To investigate CRY expression and function in body tissues, we generated a GFP-tagged-cry transgene that rescues light-induced behavioral phase resetting in cry mutant flies and sensitively reports GFP-CRY expression. In bodies, CRY is detected in clock-containing tissues including Malpighian tubules, where it mediates both light-dependent TIM degradation and clock function. In larval salivary glands, which lack clock function but are amenable to electrophysiological recording, CRY prevents membrane input resistance from falling to low levels in a light-independent manner. The ability of CRY to maintain high input resistance in these non-excitable cells also requires the K channel subunits Hyperkinetic, Shaker, and ether-a-go-go. These findings for the first time define CRY expression in Drosophila peripheral tissues and reveal that CRY acts together with K channels to maintain passive membrane properties in a non-clock-containing peripheral tissue independent of light.

CLOCK stabilizes CYCLE to initiate clock function in Drosophila

“…S3 A and C), while MB neurons lack CRY expression (20,21). Since CRY mediates light entrainment in some pacemaker neurons and is necessary for light entrainment and clock function in peripheral tissues (19,22,23,(36)(37)(38)(39), our inability to generate an ectopic MB clock may be due to the lack of CRY. Indeed, expressing both Clk and cry in MB neurons resulted in robust PER cycling in LD (Fig.…”

“…The ability of 3.0cry-Gal4driven Clk, but not MB-GS-driven Clk, to generate ectopic clocks likely results from gene expression differences in these target cell populations. One obvious difference is that 3.0cry-Gal4 presumably drives expression only in CRY-positive cells, whereas no CRY is detected in MB neurons targeted by MB-GS (19)(20)(21). To confirm that CRY is expressed in DOL cells, we used a GFP-cry transgene to mark cells that endogenously express CRY with high sensitivity (19) and found that GFP-CRY is indeed expressed in DOL cells, albeit at lower levels than in pacemaker neurons ( Fig.…”

One Actor, Multiple Roles: The Performances of Cryptochrome in Drosophila

“…Furthermore, it is worth noticing that such CRY-mediated light response, involving a flavin redox-based mechanism and relying on potassium channel conductance, is independent of the circadian interaction of CRY with TIM (Fogle et al, 2011). Also, in non-neural tissues, like salivary glands, which lack a peripheral clock, CRY maintains high membrane input resistance in an Hk, Shaker, and Ether-ago-go-dependent but light-independent manner (Agrawal et al, 2017). Very interestingly, it was recently reported that lightevoked CRY membrane electrical depolarization involves W420, located in proximity to CRY FAD and important for CRYmediated depolarization in responses to not only UV and blue but also red light, at relatively low light intensity (Baik et al, 2019).…”

A Drosophila Model for Behavioral Sleep Modification

“…4M-O), indicating that a functional eye is necessary for induction of sleep restriction. CRY is a UV- and blue light-sensitive protein that communicates light information to the circadian system [56][57][58] . To test whether CRY plays a role in the response to sleep opportunity restriction, we generated cry 02 :fumin double mutants.…”