Dissecting the daily feeding pattern: peripheral CLOCK/CYCLE generate the feeding/fasting episodes and neuronal molecular clocks synchronize them
Description
A 24-hour rhythm of feeding behavior, or synchronized feeding/fasting episodes during the day, is crucial for survival and maintenance of energy homeostasis. Internal clocks and light input regulate rhythmic behaviors, but how they generate feeding rhythms is not fully understood. Here we aimed to dissect the molecular pathways and components that generate daily feeding patterns. To evaluate the feeding rhythm of Drosophila melanogaster , the CAFE assay was used to measure food intake every 12 hours for 2 days. By measuring the semidiurnal amount of food ingested by single flies, we demonstrate that feeding rhythms under light:dark conditions were generated without molecular clocks, and the knockdown of quasimodo (qsm) was sufficient to disrupt it. Interestingly, rhythmic feeding patterns in constant dark conditions consist of two components: CLOCK protein (CLK) in digestive/metabolic tissues generating feeding/fasting episodes, and the molecular clock in neurons that synchronizes them to subjective daytime. Although CLK is a part of the molecular clock, the generation of feeding/fasting episodes by CLK in metabolic tissues was independent of molecular clock machinery. Our results revealed the novel function of CLK in the metabolic tissues and the critical role of qsm in feeding rhythms in Drosophila.