Light reception and circadian behavior in 'blind' and 'clock-less' mutants of Neurospora crassa

Dragovic, Zdravko; Tan, Ying; Görl, Margit; Roenneberg, Till; Merrow, Martha

doi:10.1093/emboj/cdf377

Cited by 49 publications

(40 citation statements)

References 58 publications

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“…But what are appropriate zeitgebers for the frq NULL residual Neurospora clock? Light apparently is not useful because frq NULL strains are partially blind (11,18,25,26).…”

Section: Resultsmentioning

confidence: 99%

Demasking biological oscillators: Properties and principles of entrainment exemplified by the Neurospora circadian clock

Roenneberg

Dragovic

Merrow

2005

Proc. Natl. Acad. Sci. U.S.A.

102

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Oscillations are found throughout the physical and biological worlds. Their interactions can result in a systematic process of synchronization called entrainment, which is distinct from a simple stimulus-response pattern. Oscillators respond to stimuli at some times in their cycle and may not respond at others. Oscillators can also be driven if the stimulus is strong (or if the oscillator is weak); i.e., they restart their cycle every time they receive a stimulus. Stimuli can also directly affect rhythms without entraining the underlying oscillator (masking): Drivenness and masking are often difficult to distinguish. Here we use the circadian biological clock to explore properties of entrainment. We confirm previous results showing that the residual circadian system in Neurospora can be entrained in a mutant of the clock gene frequency (frq 9 , a strain deficient in producing a functional FRQ protein). This finding has implications for understanding the evolution of circadian programs. By comparing data sets from independent studies, we develop a template for analyzing, modeling, and dissecting the interactions of entrained and masked components. These insights can be applied to oscillators of all periodicities.clock gene ͉ light ͉ masking ͉ model ͉ temperature

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“…But what are appropriate zeitgebers for the frq NULL residual Neurospora clock? Light apparently is not useful because frq NULL strains are partially blind (11,18,25,26).…”

Section: Resultsmentioning

confidence: 99%

Demasking biological oscillators: Properties and principles of entrainment exemplified by the Neurospora circadian clock

Roenneberg

Dragovic

Merrow

2005

Proc. Natl. Acad. Sci. U.S.A.

102

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“…Oscillators other than the FWC oscillator, sometimes referred to as frq-less oscillators, or FLOs (Iwasaki and Dunlap 2000), have been proposed on the basis of the observation of residual rhythmicity in the frq null strains frq 9 (Loros and Feldman 1986) and frq 10 (Aronson et al 1 1994) in wc mutants (Dragovic et al 2002) and in the csn-2 mutants defective in FRQ degradation (He et al 2005). Strains carrying null mutations of frq or wc-1 show oscillator-like behavior when entrained to cycles of temperature pulses (Merrow et al 1999;Lakin-Thomas 2006a).…”

Section: Ircadian Rhythms Are Biological Rhythms Withmentioning

confidence: 99%

Rhythmic Conidiation in Constant Light inVividMutants ofNeurospora crassa

et al. 2009

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“…FRQ also affects transcription of wc-1, which is to some extent dependent on WCC Káldi et al 2006). Yet, neither gene is transcribed in rhythmic fashion, and feedback of FRQ on wc-1 and wc-2 transcription is neither necessary nor sufficient for the support of WCC accumulation Cheng et al 2001b;Dragovic et al 2002;Káldi et al 2006;Schafmeier et al 2006). In particular, levels of WCC are dependent on FRQ even when wc-1 and wc-2 are efficiently transcribed under control of a heterologous promoter (Cheng et al 2001b;Schafmeier et al 2006).…”

Section: Positive Feedback Loopmentioning

confidence: 99%

Transcriptional and post-transcriptional regulation of the circadian clock of cyanobacteria and Neurospora

Brunner¹,

Schafmeier²

2006

Genes Dev.

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Circadian clocks are self-sustained oscillators modulating rhythmic transcription of large numbers of genes. Clock-controlled gene expression manifests in circadian rhythmicity of many physiological and behavioral functions. In eukaryotes, expression of core clock components is organized in a network of interconnected positive and negative feedback loops. This network is thought to constitute the pacemaker that generates circadian rhythmicity. The network of interconnected loops is embedded in a supra-net via a large number of interacting factors that affect expression and function of core clock components on transcriptional and post-transcriptional levels. In particular, phosphorylation and dephosphorylation of clock components are critical processes ensuring robust self-sustained circadian rhythmicity and entrainment of clocks to external cues. In cyanobacteria, three clock proteins have the capacity to generate a self-sustained circadian rhythm of autophosphorylation and dephosphorylation independent of transcription and translation. This phosphorylation rhythm regulates the function of these clock components, which then facilitate rhythmic gene transcription, including negative feedback on their own genes. In this article, we briefly present the mechanism of clock function in cyanobacteria. We then discuss in detail the contribution of transcriptional feedback and protein phosphorylation to various functional aspects of the circadian clock of Neurospora crassa.Circadian rhythms are found in numerous light-perceiving organisms including cyanobacteria, algae, fungi, plants, insects, and vertebrates. The rhythms are supported by cell-autonomous circadian clocks, which regulate expression of a large number of genes on the level of transcription (for review, see Transcriptional/translational feedback loops are hallmarks of circadian clocks in all organisms. In eukaryotes, expression of core clock components is organized in a complex network of interconnected positive and negative feedback loops (for review, see Dunlap and Loros 2004;Gachon et al. 2004;Hardin 2005). This network of gene expression is assumed to generate circadian rhythmicity. Elimination of key components of these interconnected loops disrupts many, if not all, rhythmic outputs, depending on the organism. Expression, subcellular localization, assembly, function, and turnover of clock components are crucial for circadian rhythmicity, and thus, the core clock is embedded in a supra-net of cellular machinery regulating various aspects of clock function. Protein phosphorylation and dephosphorylation are important regulatory mechanisms that are critical for self-sustained circadian rhythmicity and entrainment of clocks to external cues. It is unclear to what extent reversible phosphorylations are mechanistically instrumental for generation of rhythmicity in eukaryotic clocks.Recent findings have shown that clock proteins in cyanobacteria generate a self-sustained circadian rhythm of autophosphorylation and dephosphorylation, which is independent of tra...

show abstract

Light reception and circadian behavior in 'blind' and 'clock-less' mutants of Neurospora crassa

Cited by 49 publications

References 58 publications

Demasking biological oscillators: Properties and principles of entrainment exemplified by the Neurospora circadian clock

Demasking biological oscillators: Properties and principles of entrainment exemplified by the Neurospora circadian clock

Rhythmic Conidiation in Constant Light inVividMutants ofNeurospora crassa

Transcriptional and post-transcriptional regulation of the circadian clock of cyanobacteria and Neurospora

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