The Relationship Between TOR Activity and the Circadian Clock of Neurospora crassa

Circadian cycles are 24-hour rhythms that are present in almost all eukaryotes and some prokaryotes. These rhythms are believed to be driven by a Transcription-Translation Feedback Loop (TTFL) including frq, wc-1, and wc-2 genes in our model organism, Neurospora crassa. However, evidence showed that other oscillators (FLO), can drive these rhythms in Neurospora.

Our lab previously found mutants in the TOR (Target of Rapamycin) pathway that affect the FLO. Thus, we became interested in the TOR pathway as a potential FLO. I measured 40S ribosomal protein S6 phosphorylation as an assay of TOR activity. I found that TOR activity is rhythmic with a circadian period in the wildtype and is rhythmic with different periods in TOR-mutant and clock-mutant strains. Rhythmic TOR activity correlates with conidiation (spore formation), which is under the control of the clock.