Synchronization of circadian locomotor activity behavior in Caernorhabditis elegans: Interactions between light and temperature

Circadian rhythms are driven by an endogenous clock which is synchronized by daily environmental cycles (known as zeitgebers). Although the circadian responses of C. elegans to light have been recently reported, the mechanisms and pathways involved in their synchronization are still unknown. Here we present, by means of a novel behavioral approach, a complete characterization of C. elegans circadian synchronization to light and temperature cycles. Moreover, we screened mutant strains in search of defects of photic and thermal responses in order to study their putative pathways. We show that the wild-type strain is able to synchronize to combined cycles of light and temperature, with the best performance achieved under an optimal combination and phase-relationship of zeitgebers (high temperature in the dark phase and low temperature in the light phase). A lower responsiveness for the mutant strains MT21793 (lite-1/gur3 ko) and IK597 (gcy 8, 18 and 23 ko) was found in response to light and temperature, respectively. However, both mutants were still able to synchronize to a combined cycle of both stimuli. Our results shed light on the response of C. elegans to different zeitgebers as well as their possible synchronization pathways, the molecular components involved in these pathways, and their relative strength.