Adaptation to glucose starvation is associated with molecular reorganization of the circadian clock in Neurospora crassa

The circadian clock governs rhythmic cellular functions by driving the expression of a substantial fraction of the genome and thereby significantly contributes to the adaptation to changing environmental conditions. Using the circadian model organism Neurospora crassa, we show that molecular timekeeping is robust even under severe limitation of carbon sources, however, stoichiometry, phosphorylation and subcellular distribution of the key clock components display drastic alterations. Protein kinase A, protein phosphatase 2 A and glycogen synthase kinase are involved in the molecular reorganization of the clock. RNA-seq analysis reveals that the transcriptomic response of metabolism to starvation is highly dependent on the positive clock component WC-1. Moreover, our molecular and phenotypic data indicate that a functional clock facilitates recovery from starvation. We suggest that the molecular clock is a flexible network that allows the organism to maintain rhythmic physiology and preserve fitness even under long-term nutritional stress.

Automated summary

Using the circadian model organism Neurospora crassa, this study demonstrates that the molecular timekeeping of the circadian clock remains robust even under severe carbon source limitation. However, the stoichiometry, phosphorylation, and subcellular distribution of key clock components undergo drastic alterations. Protein kinase A, protein phosphatase 2 A, and glycogen synthase kinase are identified as regulators of clock reorganization. It is suggested that a functional clock facilitates recovery from starvation and allows the organism to maintain rhythmic physiology under long-term nutritional stress.