Complexity of the<i>Neurospora crassa</i>Circadian Clock System: Multiple Loops and Oscillators

Paula, Renato M. de; Vitalini, Michael W.; Gomer, Richard H.; Bell-Pedersen, Deborah

doi:10.1101/sqb.2007.72.002

Cited by 20 publications

(25 citation statements)

References 68 publications

(83 reference statements)

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“…In addition, rhythms in the expression of the ccg-16 gene in N. crassa are controlled by a FLO that requires WC-1, but not FRQ, for activity. This FLO, called the WC-FLO, that appears to be both temperature-compensated and entrained to environmental cycles independently of WCC and FRQ (de Paula et al , 2007.…”

Section: Discussionmentioning

confidence: 99%

A Novel Cryptochrome-Dependent Oscillator inNeurospora crassa

et al. 2014

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Several lines of evidence suggest that the circadian clock is constructed of multiple molecular feedback oscillators that function to generate robust rhythms in organisms. However, while core oscillator mechanisms driving specific behaviors are well described in several model systems, the nature of other potential circadian oscillators is not understood. Using genetic approaches in the fungus Neurospora crassa, we uncovered an oscillator mechanism that drives rhythmic spore development in the absence of the well-characterized FRQ/WCC oscillator (FWO) and in constant light, conditions under which the FWO is not functional. While this novel oscillator does not require the FWO for activity, it does require the blue-light photoreceptor CRYPTOCHROME (CRY); thus, we call it the CRY-dependent oscillator (CDO). The CDO was uncovered in a strain carrying a mutation in cog-1 (cry-dependent oscillator gate-1), has a period of 1 day in constant light, and is temperature-compensated. In addition, cog-1 cells lacking the circadian blue-light photoreceptor WC-1 respond to blue light, suggesting that alternate light inputs function in cog-1 mutant cells. We show that the blue-light photoreceptors VIVID and CRY compensate for each other and for WC-1 in CRY-dependent oscillator light responses, but that WC-1 is necessary for circadian light entrainment.

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Section: Discussionmentioning

confidence: 99%

A Novel Cryptochrome-Dependent Oscillator inNeurospora crassa

et al. 2014

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“…FLOs might represent more than a dozen metabolic oscillators, which are not connected to the circadian system. Or, according to de Paula et al (2007), there are multiple FLOs, which together with the FRQ/WCC oscillator form a network of coupled oscillators. But individual FLOs may drive a particular output.…”

Section: The Circadian System Of Neurospora and Modelsmentioning

confidence: 99%

How Light Resets Circadian Clocks

2014

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The daily revolutions of the earth around its axis are responsible for day and night and its annual orbit around the sun for the seasons with their fluctuations in day length. Most organisms have adapted to these diurnal and annual cycles. The strategies and mechanisms used are quite delicate and complicated.It came as a surprise that photosynthesis and many other processes are, however, additionally controlled by internal clocks. Thus, photosynthesis fluctuates not only during the daily light-dark cycle (=LD; see the List of Abbreviations and http://www.circadian.org/dictionary.html) but also when the plants are kept under LL and constant temperature (Hennessey and Field 1991). However, the period length (period for short) of this rhythmic event then deviates from exactly 24 h and is therefore called circadian (from Latin circa, about, and dies, day). If in the absence of LD and temperature cycles other 24 h time cues (also called zeitgeber, German for time giver) would control the rhythm, it should show an exact 24 h rhythm. This is not the case, demonstrating the endogenous nature of a clock that is locked to light signals (see Fig. 18.1). Spectrum of RhythmsEndogenous rhythms of organisms are not only tuned to the daily cycle of 24 h. The range of rhythms found in organisms covers ultradian (with periods of several hours to very short ones), circadian, and annual (with periods of about a year) rhythms. Other rhythms such as tidal, 14-day, and monthly ones cope with influences of the moon on the earth, mainly on the water movements of the oceans, and they are therefore found in organisms at the coasts and in the sea. Annual rhythms interact with the day-length changes during the year (see below). There are furthermore rhythms with periods covering several years. The following discussion of a "biological clock" is restricted to circadian rhythms. Even they are often not just composed of one clock type but form a "circadian system" consisting of two or more clocks with different prop- Function of Circadian ClocksThe term "clock" usually implies a time-measuring device or function. For instance, the day length (or night length) can be determined by an organism. Since day length is a function of the time of the year (long days in summer, short days in winter), it can be used to time certain events such as flowering or tuber formation of a plant or breeding of birds and mammals during the most appropriate season. These processes are denoted photoperiodism (see Chap. 19).However, a clock can also be used to set a certain temporal order. For instance, the circadian control of our sleepwake cycle ensures that we rise in the morning and fall asleep in the evening at a preferred time. Food intake and digestion are likewise controlled by this clock and gated to certain times of the day (Silver et al. 2011;Duguay and Cermakian 2009;Forsgren 1935). The circadian clock will time these events also under constant conditions. Furthermore, circadian clocks can serve as alarm clocks.

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“…One view (Shi et al ., 2007) describes FLOs as “metabolic oscillators” and proposes that there are different FLOs driving the observed rhythms for every reported condition; these multiple metabolic oscillators (of which there would need to be more than a dozen at the latest count) are not considered to be connected to the circadian system (Shi et al ., 2007). Another view proposes multiple FLOs that, under normal circumstances, interact with one another and with the FRQ/WCC to produce a network of coupled oscillators, but that individual FLOs may act independently to drive a particular output (de Paula et al ., 2007). If there are multiple oscillators, there is a formal possibility that they may function either “upstream” or “downstream” of FRQ/WCC; in either case, they would need to bypass FRQ/WCC to provide output to the conidiation pathway and biochemical rhythms when FRQ/ WCC is disabled.…”

Section: Frq-less Rhythmsmentioning

confidence: 99%

“…In support for a role of the clock in providing a mechanism for anticipating stress responses, the highly conserved Neurospora osmosensing p-38 MAPK pathway (the OS pathway), essential for osmotic stress responses, functions as a circadian output pathway that regulates daily rhythms in expression of several downstream target genes of the pathway (de Paula et al ., 2007; Vitalini et al ., 2007). In this pathway, a circadian signal is relayed to the MAPK OS-2, resulting in rhythmic phosphorylation and activation of the MAPK.…”

Section: Clock-controlled Genesmentioning

confidence: 99%

The Genetics of Circadian Rhythms in Neurospora

Lakin-Thomas¹,

Bell-Pedersen²,

Brody³

2011

The Genetics of Circadian Rhythms

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This chapter describes our current understanding of the genetics of the Neurospora clock and summarizes the important findings in this area in the past decade. Neurospora is the most intensively studied clock system, and the reasons for this are listed. A discussion of the genetic interactions between clock mutants is included, highlighting the utility of dissecting complex mechanisms by genetic means. The molecular details of the Neurospora circadian clock mechanism are described, as well as the mutations that affect the key clock proteins, FRQ, WC-1, and WC-2, with an emphasis on the roles of protein phosphorylation. Studies on additional genes affecting clock properties are described and place these genes into two categories: those that affect the FRQ/WCC oscillator and those that do not. A discussion of temperature compensation and the mutants affecting this property is included. A section is devoted to the observations pertinent to the existence of other oscillators in this organism with respect to their properties, their effects, and their preliminary characterization. The output of the clock and the control of clock-controlled genes are discussed, emphasizing the phasing of these genes and the layers of control. In conclusion, the authors provide an outlook summarizing their suggestions for areas that would be fruitful for further exploration.

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Complexity of theNeurospora crassaCircadian Clock System: Multiple Loops and Oscillators

Cited by 20 publications

References 68 publications

A Novel Cryptochrome-Dependent Oscillator inNeurospora crassa

A Novel Cryptochrome-Dependent Oscillator inNeurospora crassa

How Light Resets Circadian Clocks

The Genetics of Circadian Rhythms in Neurospora

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