title: Cross-talk between the cellular redox state and the circadian system in Neurospora.
abstract: The circadian system is composed of a number of feedback loops, and multiple feedback loops in the form of oscillators help to maintain stable rhythms. The filamentous fungus Neurospora crassa exhibits a circadian rhythm during asexual spore formation (conidiation banding) and has a major feedback loop that includes the FREQUENCY (FRQ)/WHITE COLLAR (WC) -1 and -2 oscillator (FWO). A mutation in superoxide dismutase (sod)-1, an antioxidant gene, causes a robust and stable circadian rhythm compared with that of wild-type (Wt). However, the mechanisms underlying the functions of reactive oxygen species (ROS) remain unknown. Here, we show that cellular ROS concentrations change in a circadian manner (ROS oscillation), and the amplitudes of ROS oscillation increase with each cycle and then become steady (ROS homeostasis). The ROS oscillation and homeostasis are produced by the ROS-destroying catalases (CATs) and ROS-generating NADPH oxidase (NOX). cat-1 is also induced by illumination, and it reduces ROS levels. Although ROS oscillation persists in the absence of frq, wc-1 or wc-2, its homeostasis is altered. Furthermore, genetic and biochemical evidence reveals that ROS concentration regulates the transcriptional function of WCC and a higher ROS concentration enhances conidiation banding. These findings suggest that the circadian system engages in cross-talk with the cellular redox state via ROS-regulatory factors.
authors.affiliation: Kihara Institute for Biological Research, Graduate School of Integrated Science, Yokohama City University, Totsuka-ku, Yokohama, Japan. yyoshida@yokohama-cu.ac.jp
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Yoshida
authors.forename: Hideo
authors.initials: H
authors.lastname: Iigusa
authors.forename: Niyan
authors.initials: N
authors.lastname: Wang
authors.forename: Kohji
authors.initials: K
authors.lastname: Hasunuma
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D002940:Circadian Rhythm; D025461:Feedback, Physiological; D015966:Gene Expression Regulation, Fungal; D008027:Light; D008954:Models, Biological; D009154:Mutation; D009492:Neurospora crassa / Q000235:genetics* / Q000502:physiology; D009991:Oscillometry / Q000379:methods*; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D011994:Recombinant Proteins / Q000378:metabolism; D013482:Superoxide Dismutase / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D000975:Antioxidants; D017382:Reactive Oxygen Species; D011994:Recombinant Proteins; D002374:Catalase; D013482:Superoxide Dismutase