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Liang M, Dong L, Deng YZ. Circadian Redox Rhythm in Plant-Fungal Pathogen Interactions. Antioxid Redox Signal 2022; 37:726-738. [PMID: 35044223 DOI: 10.1089/ars.2021.0281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Significance: Circadian-controlled cellular growth, differentiation, and metabolism are mainly achieved by a classical transcriptional-translational feedback loop (TTFL), as revealed by investigations in animals, plants, and fungi. Recent Advances: Recently, reactive oxygen species (ROS) have been reported as part of a cellular network synchronizing nontranscriptional oscillators with established TTFL components, adding complexity to regulatory mechanisms of circadian rhythm. Both circadian rhythm and ROS homeostasis have a great impact on plant immunity as well as fungal pathogenicity, therefore interconnections of these two factors are implicit in plant-fungus interactions. Critical Issues: In this review, we aim to summarize the recent advances in circadian-controlled ROS homeostasis, or ROS-modulated circadian clock, in plant-fungus pathosystems, particularly using the rice (Oryza sativa) blast fungus (Magnaporthe oryzae) pathosystem as an example. Understanding of such bidirectional interaction between the circadian timekeeping machinery and ROS homeostasis/signaling would provide a theoretical basis for developing disease control strategies for important plants/crops. Future Directions: Questions remain unanswered about the detailed mechanisms underlying circadian regulation of redox homeostasis in M. oryzae, and the consequent fungal differentiation and death in a time-of-day manner. We believe that the rice-M. oryzae pathobiosystem would provide an excellent platform for investigating such issues in circadian-ROS interconnections in a plant-fungus interaction context. Antioxid. Redox Signal. 37, 726-738.
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Affiliation(s)
- Meiling Liang
- Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, China.,State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
| | - Lihong Dong
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
| | - Yi Zhen Deng
- Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, China.,State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Centre, South China Agricultural University, Guangzhou, China
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Highly Sensitive Tryptophan Fluorescence Probe for detecting Rhythmic Conformational changes of KaiC in the Cyanobacterial Circadian Clock System. Biochem J 2022; 479:1505-1515. [PMID: 35771042 PMCID: PMC9342895 DOI: 10.1042/bcj20210544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 06/27/2022] [Accepted: 06/30/2022] [Indexed: 11/17/2022]
Abstract
KaiC, a core protein of the cyanobacterial circadian clock, consists of an N-terminal CI domain and a C-terminal CII domain, and assembles into a double-ring hexamer upon binding with ATP. KaiC rhythmically phosphorylates and dephosphorylates its own two adjacent residues Ser431 and Thr432 at the CII domain with a period of approximately 24h through assembly and disassembly with the other clock proteins, KaiA and/or KaiB. In this study, to understand how KaiC alters its conformation as the source of circadian rhythm, we investigated structural changes of an inner-radius side of the CII ring using time-resolved Trp fluorescence spectroscopy. A KaiC mutant harboring a Trp fluorescence probe at a position of 419 exhibited a robust circadian rhythm with little temperature sensitivity in the presence of KaiA and KaiB. Our fluorescence observations show a remarkable environmental change at the inner-radius side of the CII ring during circadian oscillation. Crystallographic analysis revealed that a side chain of Trp at the position of 419 was oriented toward a region undergoing a helix-coil transition, which is considered to be a key event to allosterically regulate the CI ring that plays a crucial role in determining the cycle period. The present study provides a dynamical insight into how KaiC generates circadian oscillation.
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Nelson RJ, Bumgarner JR, Liu JA, Love JA, Meléndez-Fernández OH, Becker-Krail DD, Walker WH, Walton JC, DeVries AC, Prendergast BJ. Time of day as a critical variable in biology. BMC Biol 2022; 20:142. [PMID: 35705939 PMCID: PMC9202143 DOI: 10.1186/s12915-022-01333-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 05/17/2022] [Indexed: 01/16/2023] Open
Abstract
BACKGROUND Circadian rhythms are important for all aspects of biology; virtually every aspect of biological function varies according to time of day. Although this is well known, variation across the day is also often ignored in the design and reporting of research. For this review, we analyzed the top 50 cited papers across 10 major domains of the biological sciences in the calendar year 2015. We repeated this analysis for the year 2019, hypothesizing that the awarding of a Nobel Prize in 2017 for achievements in the field of circadian biology would highlight the importance of circadian rhythms for scientists across many disciplines, and improve time-of-day reporting. RESULTS Our analyses of these 1000 empirical papers, however, revealed that most failed to include sufficient temporal details when describing experimental methods and that few systematic differences in time-of-day reporting existed between 2015 and 2019. Overall, only 6.1% of reports included time-of-day information about experimental measures and manipulations sufficient to permit replication. CONCLUSIONS Circadian rhythms are a defining feature of biological systems, and knowing when in the circadian day these systems are evaluated is fundamentally important information. Failing to account for time of day hampers reproducibility across laboratories, complicates interpretation of results, and reduces the value of data based predominantly on nocturnal animals when extrapolating to diurnal humans.
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Affiliation(s)
- Randy J Nelson
- Department of Neuroscience, Rockefeller Neuroscience Institute, West Virginia University, Morgantown, WV, 26505, USA.
| | - Jacob R Bumgarner
- Department of Neuroscience, Rockefeller Neuroscience Institute, West Virginia University, Morgantown, WV, 26505, USA
| | - Jennifer A Liu
- Department of Neuroscience, Rockefeller Neuroscience Institute, West Virginia University, Morgantown, WV, 26505, USA
| | - Jharnae A Love
- Department of Psychology, University of Chicago and Institute for Mind and Biology, IL, 60637, Chicago, USA
| | - O Hecmarie Meléndez-Fernández
- Department of Neuroscience, Rockefeller Neuroscience Institute, West Virginia University, Morgantown, WV, 26505, USA
| | - Darius D Becker-Krail
- Department of Neuroscience, Rockefeller Neuroscience Institute, West Virginia University, Morgantown, WV, 26505, USA
| | - William H Walker
- Department of Neuroscience, Rockefeller Neuroscience Institute, West Virginia University, Morgantown, WV, 26505, USA
| | - James C Walton
- Department of Neuroscience, Rockefeller Neuroscience Institute, West Virginia University, Morgantown, WV, 26505, USA
| | - A Courtney DeVries
- Department of Neuroscience, Rockefeller Neuroscience Institute, West Virginia University, Morgantown, WV, 26505, USA
- Department of Medicine, Rockefeller Neuroscience Institute, West Virginia University, Morgantown, WV, 26505, USA
| | - Brian J Prendergast
- Department of Psychology, University of Chicago and Institute for Mind and Biology, IL, 60637, Chicago, USA
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Buhr ED. Molecular circadian rhythms in mammals: From angstroms to organisms. Semin Cell Dev Biol 2021; 126:1-2. [PMID: 34607770 DOI: 10.1016/j.semcdb.2021.09.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Affiliation(s)
- Ethan D Buhr
- Department of Ophthalmology, University of Washington School of Medicine, Seattle, Washington.
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5
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Genome-wide circadian regulation: A unique system for computational biology. Comput Struct Biotechnol J 2020; 18:1914-1924. [PMID: 32774786 PMCID: PMC7385043 DOI: 10.1016/j.csbj.2020.07.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2019] [Revised: 06/30/2020] [Accepted: 07/02/2020] [Indexed: 01/20/2023] Open
Abstract
Circadian rhythms are 24-hour oscillations affecting an organism at multiple levels from gene expression all the way to tissues and organs. They have been observed in organisms across the kingdom of life, spanning from cyanobacteria to humans. In mammals, the master circadian pacemaker is located in the hypothalamic suprachiasmatic nuclei (SCN) in the brain where it synchronizes the peripheral oscillators that exist in other tissues. This system regulates the circadian activity of a large part of the transcriptome and recent findings indicate that almost every cell in the body has this clock at the molecular level. In this review, we briefly summarize the different factors that can influence the circadian transcriptome, including light, temperature, and food intake. We then summarize recently identified general principles governing genome-scale circadian regulation, as well as future lines of research. Genome-scale circadian activity represents a fascinating study model for computational biology. For this purpose, systems biology methods are promising exploratory tools to decode the global regulatory principles of circadian regulation.
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Key Words
- ABSR, Autoregressive Bayesian spectral regression
- AMPK, AMP-activated protein kinase
- AR, Arrhythmic feeding
- ARSER, Harmonic regression based on autoregressive spectral estimation
- BMAL1, The aryl hydrocarbon receptor nuclear translocator-like (ARNTL)
- CCD, Cortical collecting duct
- CR, Calorie-restricted diet
- CRY, Cryptochrome
- Circadian regulatory network
- Circadian rhythms
- Circadian transcriptome
- Cycling genes
- DCT/CNT, Distal convoluted tubule and connecting tubule
- DD, Dark: dark
- Energetic cost
- HF, High fat diet
- JTK_CYCLE, Jonckheere-Terpstra-Kendall (JTK) cycle
- KD, Ketogenic diet
- LB, Ad libitum
- LD, Light:dark
- LS, Lomb-Scargle
- Liver-RE, Liver clock reconstituted BMAL1-deficient mice
- NAD, Nicotinamide adenine dinucleotides
- ND, Normal diet
- NR, Night-restricted feeding
- PAS, PER-ARNT-SIM
- PER, Period
- RAIN, Rhythmicity Analysis Incorporating Nonparametric methods
- RF, Restricted feeding
- SCN, Suprachiasmatic nucleus
- SREBP, The sterol regulatory element binding protein
- TTFL, Transcriptional-translational feedback loop
- WT, Wild type
- eJTK_CYCLE, Empirical JTK_CYCLE
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Díaz RD, Larrondo LF. A circadian clock in Neurospora crassa functions during plant cell wall deconstruction. Fungal Biol 2020; 124:501-508. [PMID: 32389313 DOI: 10.1016/j.funbio.2020.03.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 03/05/2020] [Accepted: 03/07/2020] [Indexed: 01/24/2023]
Abstract
Circadian clocks are autonomous timers that are believed to confer organisms a selective advantage by enabling processes to occur at appropriate times of the day. In the model fungus Neurospora crassa, 20-40 % of its genes are reported to be under circadian regulation, as assayed in simple sugar media. Although it has been well-described that Neurospora efficiently deconstructs plant cell wall components, little is known regarding the status of the clock when Neurospora grows on cellulosic material, or whether such a clock has an impact on any of the genes involved in this process. Through luciferase-based reporters and fluorescent detection assays, we show that a clock is functioning when Neurospora grows on cellulose-containing wheat straw as the only carbon and nitrogen source. Additionally, we found that the major cellobiohydrolase encoding gene involved in plant cell wall deconstruction, cbh-1, is rhythmically regulated by the Neurospora clock, in a manner that depends on cellulose concentration and on the transcription factor CRE-1, known as a key player in carbon-catabolite repression in this fungus. Our findings are a step towards a more comprehensive understanding on how clock regulation modulates cellulose degradation, and thus Neurospora's physiology.
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Affiliation(s)
- Rodrigo D Díaz
- Millennium Institute for Integrative Biology, Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile
| | - Luis F Larrondo
- Millennium Institute for Integrative Biology, Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile.
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Abstract
In Neurospora and other fungi, the protein frequency (FRQ) is an integral part and a negative element in the fungal circadian oscillator. In Drosophila and many other higher organisms, the protein period (PER) is an integral part and a negative element of their circadian oscillator. Employing bioinformatic techniques, such as BLAST, CLUSTAL, and MEME (Multiple Em for Motif Elicitation), 11 regions (sequences) of potential similarity were found between the fungal FRQ and the Drosophila PER. Many of these FRQ regions are conserved in many fungal FRQ(s). Many of these PER regions are conserved in many insects. In addition, these regions are also of biological significance since mutations in these regions lead to changes in the circadian clock of Neurospora and Drosophila. Many of these regions of similarity between FRQ and PER are also conserved between the Drosophila PER and the mouse PER (mPER2). This suggests conserved and important regions for all 3 proteins and a common ancestor, possibly in those amoeba, such as Capsaspora, that sits at the base of the phylogenetic tree where fungi and animals diverged. Two additional examples of a possible common ancestor between Neurospora and Drosophila were found. One, the white collar (WC-1) protein of Neurospora and the Drosophila PER, shows significant similarity in its Per/Arnt/Sim (PAS) motifs to the PAS motif of an ARNT-like protein found in the amoeba, Capsaspora. Two, both of the positive elements in each system (i.e., WC-1 in Neurospora and cycle [CYC] in Drosophila), show significant similarity to this Capsaspora ARNT protein. A discussion of these findings centers on the long-time debate about the origins of the many different clock systems (i.e., independent evolution or common ancestor as well as to the question of how new genes are formed).
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Affiliation(s)
- Stuart Brody
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, and Center for Circadian Biology, UCSD, La Jolla, California
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Evolution Shapes the Gene Expression Response to Oxidative Stress. Int J Mol Sci 2019; 20:ijms20123040. [PMID: 31234431 PMCID: PMC6627103 DOI: 10.3390/ijms20123040] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2019] [Revised: 06/14/2019] [Accepted: 06/18/2019] [Indexed: 12/12/2022] Open
Abstract
Reactive oxygen species (ROS) play a key role in cell physiology and function. ROS represents a potential source of damage for many macromolecules including DNA. It is thought that daily changes in oxidative stress levels were an important early factor driving evolution of the circadian clock which enables organisms to predict changes in ROS levels before they actually occur and thereby optimally coordinate survival strategies. It is clear that ROS, at relatively low levels, can serve as an important signaling molecule and also serves as a key regulator of gene expression. Therefore, the mechanisms that have evolved to survive or harness these effects of ROS are ancient evolutionary adaptations that are tightly interconnected with most aspects of cellular physiology. Our understanding of these mechanisms has been mainly based on studies using a relatively small group of genetic models. However, we know comparatively little about how these mechanisms are conserved or have adapted during evolution under different environmental conditions. In this review, we describe recent work that has revealed significant species-specific differences in the gene expression response to ROS by exploring diverse organisms. This evidence supports the notion that during evolution, rather than being highly conserved, there is inherent plasticity in the molecular mechanisms responding to oxidative stress.
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Dunlap JC, Loros JJ. Making Time: Conservation of Biological Clocks from Fungi to Animals. Microbiol Spectr 2017; 5:10.1128/microbiolspec.FUNK-0039-2016. [PMID: 28527179 PMCID: PMC5446046 DOI: 10.1128/microbiolspec.funk-0039-2016] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2016] [Indexed: 01/03/2023] Open
Abstract
The capacity for biological timekeeping arose at least three times through evolution, in prokaryotic cyanobacteria, in cells that evolved into higher plants, and within the group of organisms that eventually became the fungi and the animals. Neurospora is a tractable model system for understanding the molecular bases of circadian rhythms in the last of these groups, and is perhaps the most intensively studied circadian cell type. Rhythmic processes described in fungi include growth rate, stress responses, developmental capacity, and sporulation, as well as much of metabolism; fungi use clocks to anticipate daily environmental changes. A negative feedback loop comprises the core of the circadian system in fungi and animals. In Neurospora, the best studied fungal model, it is driven by two transcription factors, WC-1 and WC-2, that form the White Collar Complex (WCC). WCC elicits expression of the frq gene. FRQ complexes with other proteins, physically interacts with the WCC, and reduces its activity; the kinetics of these processes is strongly influenced by progressive phosphorylation of FRQ. When FRQ becomes sufficiently phosphorylated that it loses the ability to influence WCC activity, the circadian cycle starts again. Environmental cycles of light and temperature influence frq and FRQ expression and thereby reset the internal circadian clocks. The molecular basis of circadian output is also becoming understood. Taken together, molecular explanations are emerging for all the canonical circadian properties, providing a molecular and regulatory framework that may be extended to many members of the fungal and animal kingdoms, including humans.
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Affiliation(s)
- Jay C Dunlap
- Department of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
| | - Jennifer J Loros
- Department of Molecular and Systems Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, NH 03755
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Kelliher CM, Haase SB. Connecting virulence pathways to cell-cycle progression in the fungal pathogen Cryptococcus neoformans. Curr Genet 2017; 63:803-811. [PMID: 28265742 PMCID: PMC5605583 DOI: 10.1007/s00294-017-0688-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Revised: 02/22/2017] [Accepted: 02/22/2017] [Indexed: 11/01/2022]
Abstract
Proliferation and host evasion are critical processes to understand at a basic biological level for improving infectious disease treatment options. The human fungal pathogen Cryptococcus neoformans causes fungal meningitis in immunocompromised individuals by proliferating in cerebrospinal fluid. Current antifungal drugs target "virulence factors" for disease, such as components of the cell wall and polysaccharide capsule in C. neoformans. However, mechanistic links between virulence pathways and the cell cycle are not as well studied. Recently, cell-cycle synchronized C. neoformans cells were profiled over time to identify gene expression dynamics (Kelliher et al., PLoS Genet 12(12):e1006453, 2016). Almost 20% of all genes in the C. neoformans genome were periodically activated during the cell cycle in rich media, including 40 genes that have previously been implicated in virulence pathways. Here, we review important findings about cell-cycle-regulated genes in C. neoformans and provide two examples of virulence pathways-chitin synthesis and G-protein coupled receptor signaling-with their putative connections to cell division. We propose that a "comparative functional genomics" approach, leveraging gene expression timing during the cell cycle, orthology to genes in other fungal species, and previous experimental findings, can lead to mechanistic hypotheses connecting the cell cycle to fungal virulence.
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Affiliation(s)
- Christina M Kelliher
- Department of Biology, Duke University, Box 90338, 130 Science Drive, Durham, NC, 27708-0338, USA
| | - Steven B Haase
- Department of Biology, Duke University, Box 90338, 130 Science Drive, Durham, NC, 27708-0338, USA.
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11
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Deng Z, Arsenault S, Caranica C, Griffith J, Zhu T, Al-Omari A, Schüttler HB, Arnold J, Mao L. Synchronizing stochastic circadian oscillators in single cells of Neurospora crassa. Sci Rep 2016; 6:35828. [PMID: 27786253 PMCID: PMC5082370 DOI: 10.1038/srep35828] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Accepted: 10/05/2016] [Indexed: 11/09/2022] Open
Abstract
The synchronization of stochastic coupled oscillators is a central problem in physics and an emerging problem in biology, particularly in the context of circadian rhythms. Most measurements on the biological clock are made at the macroscopic level of millions of cells. Here measurements are made on the oscillators in single cells of the model fungal system, Neurospora crassa, with droplet microfluidics and the use of a fluorescent recorder hooked up to a promoter on a clock controlled gene-2 (ccg-2). The oscillators of individual cells are stochastic with a period near 21 hours (h), and using a stochastic clock network ensemble fitted by Markov Chain Monte Carlo implemented on general-purpose graphical processing units (or GPGPUs) we estimated that >94% of the variation in ccg-2 expression was stochastic (as opposed to experimental error). To overcome this stochasticity at the macroscopic level, cells must synchronize their oscillators. Using a classic measure of similarity in cell trajectories within droplets, the intraclass correlation (ICC), the synchronization surface ICC is measured on >25,000 cells as a function of the number of neighboring cells within a droplet and of time. The synchronization surface provides evidence that cells communicate, and synchronization varies with genotype.
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Affiliation(s)
- Zhaojie Deng
- College of Engineering, University of Georgia, Athens, GA 30602, USA
| | - Sam Arsenault
- Department of Entomology, University of Georgia, Athens, GA 30602, USA
| | - Cristian Caranica
- Department of Statistics, University of Georgia, Athens, GA 30602, USA
| | - James Griffith
- Genetics Department, University of Georgia, Athens, GA 30602, USA.,College of Agricultural and Environmental Sciences, University of Georgia, Athens, GA 30602, USA
| | - Taotao Zhu
- College of Engineering, University of Georgia, Athens, GA 30602, USA
| | - Ahmad Al-Omari
- Department of Biomedical Systems and Informatics Engineering, Yarmouk University, Irbid, 21163, Jordan
| | | | - Jonathan Arnold
- Genetics Department, University of Georgia, Athens, GA 30602, USA
| | - Leidong Mao
- College of Engineering, University of Georgia, Athens, GA 30602, USA
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Ibata Y, Tanaka M, Tamada Y, Hayashi S, Kawakami F, Takamatsu T, Hisa Y, Okamura H. REVIEW ■ : The Suprachiasmatic Nucleus: A Circadian Oscillator. Neuroscientist 2016. [DOI: 10.1177/107385849700300409] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The suprachiasmatic nucleus (SCN) is considered to be a circadian oscillator that regulates a set of phys iological aspects of behavior, including sleep-wakefulness and hormone release in mammalian species. In this review, we describe recent research that has begun to reveal the functional organization of the SCN. The SCN, which consists of a bilateral pair of tiny nuclei located just above the optic chiasm, contains several kinds of peptidergic neurons, but vasoactive intestinal peptide (VIP), arginine vasopressin (AVP), and somatostatin (SOM) neurons are the main components. VIP neurons and AVP neurons show distinctly different locations in the SCN; the former are found in the ventrolateral portion, whereas the latter are localized in the dorsomedial portion. VIP neurons receive all neuronal inputs from other regions of the CNS, such as those evoked by photic stimulation via the retinal ganglion cells and those relayed by 5HT inner vation from the raphe nuclei. VIP neurons relay their information to other kinds of neurons in the SCN, such as AVP and SOM neurons. VIP neurons, thus, may play a significant role in entrainment of circadian rhythm. VIP, AVP, SOM, and their mRNAs show rhythmic fluctuations that are predicted by this model; VIP and its mRNA show diurnal variation under the influence of photic stimulation, whereas AVP, SOM, and their mRNAs show endogenous rhythms. Immediate early genes (lEGs), such as c-fos mRNA, are also expressed in VIP neurons in the SCN, and IEG expression in the cells appears to be modified by photic stimuli. Together with transplantation studies showing that exogenous SCN tissue tends to restore circadian rhythm in arrhythmic animals, these results are beginning to clarify the function of the SCN in setting, maintaining, and resetting the biological clock. NEUROSCIENTIST 3:215-225, 1997
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Affiliation(s)
| | | | | | | | | | | | | | - Hitoshi Okamura
- Department of Anatomy & Brain Science (HO) Kobe University School of Medicine Kusunokicho, Chuoku, Kobe
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14
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Choi J, Chung H, Lee GW, Koh SK, Chae SK, Lee YH. Genome-Wide Analysis of Hypoxia-Responsive Genes in the Rice Blast Fungus, Magnaporthe oryzae. PLoS One 2015; 10:e0134939. [PMID: 26241858 PMCID: PMC4524601 DOI: 10.1371/journal.pone.0134939] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Accepted: 07/16/2015] [Indexed: 01/09/2023] Open
Abstract
Rice blast fungus, Magnaporthe oryzae, is the most destructive pathogen in the rice-growing area. This fungus has a biotrophic phase early in infection and later switches to a necrotrophic lifestyle. During the biotrophic phase, the fungus competes with its host for nutrients and oxygen. Continuous uptake of oxygen is essential for successful establishment of blast disease of this pathogen. Here, we report transcriptional responses of the fungus to oxygen limitation. Transcriptome analysis using RNA-Seq identified that 1,047 genes were up-regulated in response to hypoxia. Those genes are involved in mycelial development, sterol biosynthesis, and metal ion transport based on hierarchical GO terms, and are well-conserved among three fungal species. In addition, null mutants of two hypoxia-responsive genes were generated and their roles in fungal development and pathogenicity tested. The mutant for the sterol regulatory element-binding protein gene, MoSRE1, exhibited increased sensitivity to a hypoxia-mimicking agent, increased conidiation, and delayed invasive growth within host cells, which is suggestive of important roles in fungal development. However, such defects did not cause any significant decrease in disease severity. The other null mutant, for the alcohol dehydrogenase gene MoADH1, showed no defect in the hypoxia-mimicking condition (using cobalt chloride) and fungal development. Taken together, this comprehensive transcriptional profiling in response to a hypoxic condition with experimental validations would provide new insights into fungal development and pathogenicity in plant pathogenic fungi.
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Affiliation(s)
- Jaehyuk Choi
- Division of Life Sciences, College of Life Sciences and Bioengineering, Incheon National University, Incheon 406–772, Korea
| | - Hyunjung Chung
- Department of Agricultural Biotechnology, Seoul National University, Seoul 151–921, Korea
| | - Gir-Won Lee
- Fungal Bioinformatics Laboratory, Seoul National University, Seoul 151–921, Korea
| | - Sun-Ki Koh
- Department of Biochemistry, Paichai University, Daejeon 302–735, Korea
| | - Suhn-Kee Chae
- Department of Biochemistry, Paichai University, Daejeon 302–735, Korea
| | - Yong-Hwan Lee
- Department of Agricultural Biotechnology, Seoul National University, Seoul 151–921, Korea
- Fungal Bioinformatics Laboratory, Seoul National University, Seoul 151–921, Korea
- Center for Fungal Pathogenesis, Seoul National University, Seoul 151–921, Korea
- Center for Fungal Genetic Resources, Seoul National University, Seoul 151–921, Korea
- Plant Genomics and Breeding Institute, Seoul National University, Seoul 151–921, Korea
- Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151–921, Korea
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A circadian oscillator in the fungus Botrytis cinerea regulates virulence when infecting Arabidopsis thaliana. Proc Natl Acad Sci U S A 2015; 112:8744-9. [PMID: 26124115 DOI: 10.1073/pnas.1508432112] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The circadian clock of the plant model Arabidopsis thaliana modulates defense mechanisms impacting plant-pathogen interactions. Nevertheless, the effect of clock regulation on pathogenic traits has not been explored in detail. Moreover, molecular description of clocks in pathogenic fungi--or fungi in general other than the model ascomycete Neurospora crassa--has been neglected, leaving this type of question largely unaddressed. We sought to characterize, therefore, the circadian system of the plant pathogen Botrytis cinerea to assess if such oscillatory machinery can modulate its virulence potential. Herein, we show the existence of a functional clock in B. cinerea, which shares similar components and circuitry with the Neurospora circadian system, although we found that its core negative clock element FREQUENCY (BcFRQ1) serves additional roles, suggesting extracircadian functions for this protein. We observe that the lesions produced by this necrotrophic fungus on Arabidopsis leaves are smaller when the interaction between these two organisms occurs at dawn. Remarkably, this effect does not depend solely on the plant clock, but instead largely relies on the pathogen circadian system. Genetic disruption of the B. cinerea oscillator by mutation, overexpression of BcFRQ1, or by suppression of its rhythmicity by constant light, abrogates circadian regulation of fungal virulence. By conducting experiments with out-of-phase light:dark cycles, we confirm that indeed, it is the fungal clock that plays the main role in defining the outcome of the Arabidopsis-Botrytis interaction, providing to our knowledge the first evidence of a microbial clock modulating pathogenic traits at specific times of the day.
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Montenegro-Montero A, Canessa P, Larrondo LF. Around the Fungal Clock. ADVANCES IN GENETICS 2015; 92:107-84. [DOI: 10.1016/bs.adgen.2015.09.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Abstract
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Circadian clocks are self-sustaining
timekeepers found in almost
all organisms on earth. The filamentous fungus Neurospora
crassa is a preeminent model for eukaryotic circadian clocks.
Investigations of the Neurospora circadian clock
system have led to elucidation of circadian clock regulatory mechanisms
that are common to all eukaryotes. In this work, we will focus on
the Neurospora circadian oscillator mechanism with
an emphasis on the regulation of the core clock component FREQUENCY.
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Affiliation(s)
- Joonseok Cha
- Department of Physiology, University of Texas Southwestern Medical Center , 5323 Harry Hines Boulevard, Dallas, Texas 75390-9040, United States
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Abstract
The circadian clock exists to synchronize inner physiology with the external world, allowing life to anticipate and adapt to the continual changes that occur in an organism's environment. The clock architecture is highly conserved, present in almost all major branches of life. Within eukaryotes, the filamentous fungus Neurospora crassa has consistently been used as an excellent model organism to uncover the basic circadian physiology and molecular biology. The Neurospora model has elucidated our fundamental understanding of the clock as nested positive and negative feedback loop, regulated by transcriptional and posttranscriptional processes. This review will examine the basics of circadian rhythms in the model filamentous fungus N. crassa as well as highlight the output of the clock in Neurospora and the reasons that N. crassa has continued to be a strong model for the study of circadian rhythms. It will also synopsize classical and emerging methods in the study of the circadian clock.
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Affiliation(s)
- Jennifer Hurley
- Department of Genetics, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
| | - Jennifer J Loros
- Department of Genetics, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA; Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
| | - Jay C Dunlap
- Department of Genetics, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.
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PDF and cAMP enhance PER stability in Drosophila clock neurons. Proc Natl Acad Sci U S A 2014; 111:E1284-90. [PMID: 24707054 DOI: 10.1073/pnas.1402562111] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
The neuropeptide PDF is important for Drosophila circadian rhythms: pdf(01) (pdf-null) animals are mostly arrhythmic or short period in constant darkness and have an advanced activity peak in light-dark conditions. PDF contributes to the amplitude, synchrony, as well as the pace of circadian rhythms within clock neurons. PDF is known to increase cAMP levels in PDR receptor (PDFR)-containing neurons. However, there is no known connection of PDF or of cAMP with the Drosophila molecular clockworks. We discovered that the mutant period gene per(S) ameliorates the phenotypes of pdf-null flies. The period protein (PER) is a well-studied repressor of clock gene transcription, and the per(S) protein (PERS) has a markedly short half-life. The result therefore suggests that the PDF-mediated increase in cAMP might lengthen circadian period by directly enhancing PER stability. Indeed, increasing cAMP levels and cAMP-mediated protein kinase A (PKA) activity stabilizes PER, in S2 tissue culture cells and in fly circadian neurons. Adding PDF to fly brains in vitro has a similar effect. Consistent with these relationships, a light pulse causes more prominent PER degradation in pdf(01) circadian neurons than in wild-type neurons. The results indicate that PDF contributes to clock neuron synchrony by increasing cAMP and PKA, which enhance PER stability and decrease clock speed in intrinsically fast-paced PDFR-containing clock neurons. We further suggest that the more rapid degradation of PERS bypasses PKA regulation and makes the pace of clock neurons more uniform, allowing them to avoid much of the asynchrony caused by the absence of PDF.
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Bidirectional-genetics platform, a dual-purpose mutagenesis strategy for filamentous fungi. EUKARYOTIC CELL 2013; 12:1547-53. [PMID: 24058171 DOI: 10.1128/ec.00234-13] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Rapidly increasing fungal genome sequences call for efficient ways of generating mutants to translate quickly gene sequences into their functions. A reverse genetic strategy via targeted gene replacement (TGR) has been inefficient for many filamentous fungi due to dominant production of undesirable ectopic transformants. Although large-scale random insertional mutagenesis via transformation (i.e., forward genetics) facilitates high-throughput uncovering of novel genes of interest, generating a huge number of transformants, which is necessary to ensure the likelihood of mutagenizing most genes, is time-consuming. We propose a new strategy, entitled the Bidirectional-Genetics (BiG) platform, which combines both forward and reverse genetic strategies by recycling ectopic transformants derived from TGR as a source for random insertional mutants. The BiG platform was evaluated using the rice blast fungus Magnaporthe oryzae as a model. Over 10% of >1,000 M. oryzae ectopic transformants, generated during disruption of specific genes, displayed abnormality in vegetative growth, pigmentation, and/or asexual reproduction. In this pool of putative mutants, we isolated insertional mutants with mutations in three genes involved in histidine biosynthesis (MoHIS5), vegetative growth (MoVPS74), or conidiophore formation (MoFRQ) (where "Mo" indicates "M. oryzae"), supporting the utility of this platform for systematic gene function studies.
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Querfurth C, Diernfellner ACR, Gin E, Malzahn E, Höfer T, Brunner M. Circadian conformational change of the Neurospora clock protein FREQUENCY triggered by clustered hyperphosphorylation of a basic domain. Mol Cell 2011; 43:713-22. [PMID: 21884974 DOI: 10.1016/j.molcel.2011.06.033] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Revised: 01/31/2011] [Accepted: 06/26/2011] [Indexed: 10/17/2022]
Abstract
In the course of a day, the Neurospora clock protein FREQUENCY (FRQ) is progressively phosphorylated at up to 113 sites and eventually degraded. Phosphorylation and degradation are crucial for circadian time keeping, but it is not known how phosphorylation of a large number of sites correlates with circadian degradation of FRQ. We show that two amphipathic motifs in FRQ interact over a long distance, bringing the positively charged N-terminal portion in spatial proximity to the negatively charged middle and C-terminal portion of FRQ. The interaction is essential for the recruitment of casein kinase 1a (CK1a) into a stable complex with FRQ. FRQ-bound CK1a progressively phosphorylates the positively charged N-terminal domain of FRQ at up to 46 nonconsensus sites, triggering a conformational change, presumably by electrostatic repulsion, that commits the protein for degradation via the PEST1 signal in the negatively charged central portion of FRQ.
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Affiliation(s)
- Christina Querfurth
- University of Heidelberg Biochemistry Center, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany
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Abstract
Circadian clocks organize our inner physiology with respect to the external world, providing life with the ability to anticipate and thereby better prepare for major fluctuations in its environment. Circadian systems are widely represented in nearly all major branches of life, except archaebacteria, and within the eukaryotes, the filamentous fungus Neurospora crassa has served for nearly half a century as a durable model organism for uncovering the basic circadian physiology and molecular biology. Studies using Neurospora have clarified our fundamental understanding of the clock as nested positive and negative feedback loops regulated through transcriptional and post-transcriptional processes. These feedback loops are centered on a limited number of proteins that form molecular complexes, and their regulation provides a physical explanation for nearly all clock properties. This review will introduce the basics of circadian rhythms, the model filamentous fungus N. crassa, and provide an overview of the molecular components and regulation of the circadian clock.
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Population genomics and local adaptation in wild isolates of a model microbial eukaryote. Proc Natl Acad Sci U S A 2011; 108:2831-6. [PMID: 21282627 DOI: 10.1073/pnas.1014971108] [Citation(s) in RCA: 181] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Elucidating the connection between genotype, phenotype, and adaptation in wild populations is fundamental to the study of evolutionary biology, yet it remains an elusive goal, particularly for microscopic taxa, which comprise the majority of life. Even for microbes that can be reliably found in the wild, defining the boundaries of their populations and discovering ecologically relevant phenotypes has proved extremely difficult. Here, we have circumvented these issues in the microbial eukaryote Neurospora crassa by using a "reverse-ecology" population genomic approach that is free of a priori assumptions about candidate adaptive alleles. We performed Illumina whole-transcriptome sequencing of 48 individuals to identify single nucleotide polymorphisms. From these data, we discovered two cryptic and recently diverged populations, one in the tropical Caribbean basin and the other endemic to subtropical Louisiana. We conducted high-resolution scans for chromosomal regions of extreme divergence between these populations and found two such genomic "islands." Through growth-rate assays, we found that the subtropical Louisiana population has a higher fitness at low temperature (10 °C) and that several of the genes within these distinct regions have functions related to the response to cold temperature. These results suggest the divergence islands may be the result of local adaptation to the 9 °C difference in average yearly minimum temperature between these two populations. Remarkably, another of the genes identified using this unbiased, whole-genome approach is the well-known circadian oscillator frequency, suggesting that the 2.4°-10.6° difference in latitude between the populations may be another important environmental parameter.
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Lakin-Thomas PL, Bell-Pedersen D, Brody S. The genetics of circadian rhythms in Neurospora. ADVANCES IN GENETICS 2011; 74:55-103. [PMID: 21924975 DOI: 10.1016/b978-0-12-387690-4.00003-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
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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FRQ-interacting RNA helicase mediates negative and positive feedback in the Neurospora circadian clock. Genetics 2009; 184:351-61. [PMID: 19948888 DOI: 10.1534/genetics.109.111393] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Neurospora circadian oscillator comprises FREQUENCY (FRQ) and its transcription activator, the White Collar Complex (WCC). Repression of WCC's transcriptional activity by FRQ via negative feedback is indispensable for clock function. An unbiased genetic screen that targeted mutants with defects in negative feedback regulation yielded a fully viable arrhythmic strain bearing a novel allele of FRQ-interacting RNA helicase (frh), an essential gene that encodes a putative exosome component protein. In the allele, frh(R806H), clock function is completely disturbed, while roles of FRQ-interacting RNA helicase (FRH) essential for viability are left intact. FRH(R806H) still interacts with FRQ, but interaction between the FRQ-FRH(R806H) complex (FFC) and WCC is severely affected. Phosphorylation of WC-1 is reduced in the mutant leading to constantly elevated WCC activity, which breaks the negative feedback loop. WCC levels are considerably reduced in the mutant, especially those of WC-1, consistent both with loss of positive feedback (FRQ-dependent WC-1 stabilization) and with a reduced level of the FRQ-mediated WCC phosphorylation that leads to high WCC activity accompanied by rapid transcription-associated turnover. FRH overexpression promotes WC-1 accumulation, confirming that FRH together with FRQ plays a role in WC-1 stabilization. Identification of a viable allele of frh, displaying virtually complete loss of both negative and positive circadian feedback, positions FRH as a core component of the central oscillator that is permissive for rhythmicity but appears not to modulate periodicity. Moreover, the results suggest that there are clock-specific roles for FRH that are distinct from the predicted essential exosome-associated functions for the protein.
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Merrow M, Boesl C, Ricken J, Messerschmitt M, Goedel M, Roenneberg T. Entrainment of theNeurosporaCircadian Clock. Chronobiol Int 2009; 23:71-80. [PMID: 16687281 DOI: 10.1080/07420520500545888] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Neurospora crassa has been systematically investigated for circadian entrainment behavior. Many aspects of synchronization can be investigated in this simple, cellular system, ranging from systematic entrainment and drivenness to masking. Clock gene expression during entrainment and entrainment without clock genes suggest that the known transcription/translation feedback loop is not alone responsible for entrainment in Neurospora.
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Affiliation(s)
- Martha Merrow
- Biologisch Centrum, University of Groningen, Haren, The Netherlands.
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Abstract
We report the discovery and validation of a set of single nucleotide polymorphisms (SNPs) between the reference Neurospora crassa strain Oak Ridge and the Mauriceville strain (FGSC 2555), of sufficient density to allow fine mapping of most loci. Sequencing of Mauriceville cDNAs and alignment to the completed genomic sequence of the Oak Ridge strain identified 19,087 putative SNPs. Of these, a subset was validated by cleaved amplified polymorphic sequence (CAPS), a simple and robust PCR-based assay that reliably distinguishes between SNP alleles. Experimental confirmation resulted in the development of 250 CAPS markers distributed evenly over the genome. To demonstrate the applicability of this map, we used bulked segregant analysis followed by interval mapping to locate the csp-1 mutation to a narrow region on LGI. Subsequently, we refined mapping resolution to 74 kbp by developing additional markers, resequenced the candidate gene, NCU02713.3, in the mutant background, and phenocopied the mutation by gene replacement in the WT strain. Together, these techniques demonstrate a generally applicable and straightforward approach for the isolation of novel genes from existing mutants. Data on both putative and validated SNPs are deposited in a customized public database at the Broad Institute, which encourages augmentation by community users.
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Dunlap JC, Loros JJ, Colot HV, Mehra A, Belden WJ, Shi M, Hong CI, Larrondo LF, Baker CL, Chen CH, Schwerdtfeger C, Collopy PD, Gamsby JJ, Lambreghts R. A circadian clock in Neurospora: how genes and proteins cooperate to produce a sustained, entrainable, and compensated biological oscillator with a period of about a day. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2008; 72:57-68. [PMID: 18522516 DOI: 10.1101/sqb.2007.72.072] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Neurospora has proven to be a tractable model system for understanding the molecular bases of circadian rhythms in eukaryotes. At the core of the circadian oscillatory system is a negative feedback loop in which two transcription factors, WC-1 and WC-2, act together to drive expression of the frq gene. WC-2 enters the promoter region of frq coincident with increases in frq expression and then exits when the cycle of transcription is over, whereas WC-1 can always be found there. FRQ promotes the phosphorylation of the WCs, thereby decreasing their activity, and phosphorylation of FRQ then leads to its turnover, allowing the cycle to reinitiate. By understanding the action of light and temperature on frq and FRQ expression, the molecular basis of circadian entrainment to environmental light and temperature cues can be understood, and recently a specific role for casein kinase 2 has been found in the mechanism underlying circadian temperature-compensation. These data promise molecular explanations for all of the canonical circadian properties of this model system, providing biochemical answers and regulatory logic that may be extended to more complex eukaryotes including humans.
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Affiliation(s)
- J C Dunlap
- Department of Genetics, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
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Merrow M, Roenneberg T. Circadian entrainment of Neurospora crassa. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2008; 72:279-85. [PMID: 18419284 DOI: 10.1101/sqb.2007.72.032] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The circadian clock evolved under entraining conditions, yet most circadian experiments and much circadian theory are built around free-running rhythms. The interpretation of entrainment experiments is certainly more complex than that of free-running rhythms due to the relationship between exogenous and endogenous cycles. Here, we systematically describe entrainment in the simplest of the traditional eukaryotic model systems in circadian research, Neurospora crassa. This fungus forms a mass of spores (bands of conidia) each day. Over a wide range of photoperiods, these bands begin to appear at midnight, suggesting integration of neither dawn nor dusk signals alone. However, when symmetrical light/dark cycles (T cycles, each with 50% light) are applied, dusk determines the time of conidiation with a uniform, period-dependent delay in phase. This "forced" synchronization appears to be specific for the zeitgeber light because similar experiments, but using temperature, result in systematic entrainment, with bands appearing relatively later in shorter cycles and earlier in longer cycles. We find that the molecular mechanism of entrainment primarily concerns posttranscriptional regulation. Finally, we have used Neurospora to investigate acute effects of zeitgeber stimuli known as "masking."
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Affiliation(s)
- M Merrow
- The Biological Center, University of Groningen, 9750AA Haren, The Netherlands
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A developmental cycle masks output from the circadian oscillator under conditions of choline deficiency in Neurospora. Proc Natl Acad Sci U S A 2007; 104:20102-7. [PMID: 18056807 DOI: 10.1073/pnas.0706631104] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In Neurospora, metabolic oscillators coexist with the circadian transcriptional/translational feedback loop governed by the FRQ (Frequency) and WC (White Collar) proteins. One of these, a choline deficiency oscillator (CDO) observed in chol-1 mutants grown under choline starvation, drives an uncompensated long-period developmental cycle ( approximately 60-120 h). To assess possible contributions of this metabolic oscillator to the circadian system, molecular and physiological rhythms were followed in liquid culture under choline starvation, but these only confirmed that an oscillator with a normal circadian period length can run under choline starvation. This finding suggested that long-period developmental cycles elicited by nutritional stress could be masking output from the circadian system, although a caveat was that the CDO sometimes requires several days to become consolidated. To circumvent this and observe both oscillators simultaneously, we used an assay using a codon-optimized luciferase to follow the circadian oscillator. Under conditions where the long-period, uncompensated, CDO-driven developmental rhythm was expressed for weeks in growth tubes, the luciferase rhythm in the same cultures continued in a typical compensated manner with a circadian period length dependent on the allelic state of frq. Periodograms revealed no influence of the CDO on the circadian oscillator. Instead, the CDO appears as a cryptic metabolic oscillator that can, under appropriate conditions, assume control of growth and development, thereby masking output from the circadian system. frq-driven luciferase as a reporter of the circadian oscillator may in this way provide a means for assessing prospective role(s) of metabolic and/or ancillary oscillators within cellular circadian systems.
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Rensing L, Kallies A, Gebauer G, Mohsenzadeh S. The effects of temperature change on the circadian clock of Neurospora. CIBA FOUNDATION SYMPOSIUM 2007; 183:26-41; discussion 41-50. [PMID: 7656690 DOI: 10.1002/9780470514597.ch3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The phase resetting of the circadian oscillatory system by pulses of increased temperature (zeitgebers) and the temperature compensation of its period length during longer exposures are major features of the system, but are not well understood in molecular terms. In Neurospora crassa, the effects of pulses of increased temperature on the circadian rhythm of conidiation were determined and possible inputs to the oscillatory system tested, including changes in cyclic 3',5'-adenosine monophosphate (cAMP), inositol 1,4,5-trisphosphate and H+ concentrations, as well as changes of phosphorylation, synthesis and degradation of proteins. Following the kinetics of these parameters during exposure to increased temperature showed transient changes. Experimental manipulation of cAMP, Ca2+ and H+ levels, and of the synthesis and, possibly, degradation of proteins, resulted in phase shifts of the oscillatory system. It is assumed that the temperature signal affects the oscillator(s) by multiple pathways and shifts the whole state of the oscillatory system. Second messenger levels, protein synthesis and protein degradation show adaptation to longer exposures to elevated temperature which may be involved in the temperature compensation of the period length. The temperature compensation is also proposed to involve a shift in the state of all or most oscillator variables.
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Affiliation(s)
- L Rensing
- Department of Biology, University of Bremen, Germany
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Dunlap JC, Loros JJ, Aronson BD, Merrow M, Crosthwaite S, Bell-Pedersen D, Johnson K, Lindgren K, Garceau NY. The genetic basis of the circadian clock: identification of frq and FRQ as clock components in Neurospora. CIBA FOUNDATION SYMPOSIUM 2007; 183:3-17; discussion 17-25. [PMID: 7656691 DOI: 10.1002/9780470514597.ch2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Genetic approaches to the identification of clock components have succeeded in two model systems, Neurospora and Drosophila. In each organism, genes identified through screens for clock-affecting mutations (frq in Neurospora, per in Drosophila) have subsequently been shown to have characteristics of central clock components: (1) mutations in each gene can affect period length and temperature compensation, two canonical characteristics of circadian systems; (2) each gene regulates the timing of its own transcription in a circadian manner; and (3) in the case of frq, constitutively elevated expression will set the phase of the clock on release into normal conditions. Despite clear genetic and molecular similarities, however, the two genes are neither molecular nor temporal homologues. The timing of peak expression is distinct in the two genes, frq expression peaking after dawn and per expression peaking near midnight. Also, although expression of per from a constitutive promoter can rescue rhythmicity in a fly lacking the gene, constitutive expression of frq will not rescue rhythmicity in Neurospora frq-null strains, and in fact causes arrhythmicity when expressed in a wild-type strain. These data suggest that frq is and/or encodes a state variable of the circadian oscillator. Recent molecular genetic analyses of frq have shed light on the origin of temperature compensation and strongly suggest that this property is built into the oscillatory feedback loop rather than appended to it. It seems plausible that clocks are adjusted and reset through adjustments in central clock components such as frq, and, by extension, per.
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Affiliation(s)
- J C Dunlap
- Department of Biochemistry, Dartmouth Medical School, Hanover, NH 03755-3844, USA
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Mertens I, Husson SJ, Janssen T, Lindemans M, Schoofs L. PACAP and PDF signaling in the regulation of mammalian and insect circadian rhythms. Peptides 2007; 28:1775-83. [PMID: 17586087 DOI: 10.1016/j.peptides.2007.05.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2007] [Revised: 04/11/2007] [Accepted: 05/09/2007] [Indexed: 12/27/2022]
Abstract
Endogenous circadian clocks are inherent to all living organisms. They are needed to guarantee successful life since they regulate very important biological processes such as behavior and reproduction. Secretin-like G-protein coupled receptors are very important factors in the signal transduction pathways of circadian clocks. In this review, we will focus on the role of two secretin-like signaling pathways that play an important role in the regulation of the mammalian and the insect clock, respectively: the pituitary adenylate cyclase-activating polypeptide (PACAP) and pigment dispersing factor (PDF) signaling pathways. Both pathways are most likely related although their function in the biological clock differs.
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Affiliation(s)
- Inge Mertens
- Animal Physiology and Neurobiology, Katholieke Universiteit Leuven, Naamsestraat 59, 3000 Leuven, Belgium
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Abstract
The filamentous fungus Neurospora crassa is one of a handful of model organisms that has proven tractable for dissecting the molecular basis of a eukaryotic circadian clock. Work on Neurospora and other eukaryotic and prokaryotic organisms has revealed that a limited set of clock genes and clock proteins are required for generating robust circadian rhythmicity. This molecular clockwork is tuned to the daily rhythms in the environment via light- and temperature-sensitive pathways that adjust its periodicity and phase. The circadian clockwork in turn transduces temporal information to a large number of clock-controlled genes that ultimately control circadian rhythms in physiology and behavior. In summarizing our current understanding of the molecular basis of the Neurospora circadian system, this chapter aims to elucidate the basic building blocks of model eukaryotic clocks as we understand them today.
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Affiliation(s)
- Christian Heintzen
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
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Dunlap JC, Borkovich KA, Henn MR, Turner GE, Sachs MS, Glass NL, McCluskey K, Plamann M, Galagan JE, Birren BW, Weiss RL, Townsend JP, Loros JJ, Nelson MA, Lambreghts R, Colot HV, Park G, Collopy P, Ringelberg C, Crew C, Litvinkova L, DeCaprio D, Hood HM, Curilla S, Shi M, Crawford M, Koerhsen M, Montgomery P, Larson L, Pearson M, Kasuga T, Tian C, Baştürkmen M, Altamirano L, Xu J. Enabling a community to dissect an organism: overview of the Neurospora functional genomics project. ADVANCES IN GENETICS 2007; 57:49-96. [PMID: 17352902 PMCID: PMC3673015 DOI: 10.1016/s0065-2660(06)57002-6] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
A consortium of investigators is engaged in a functional genomics project centered on the filamentous fungus Neurospora, with an eye to opening up the functional genomic analysis of all the filamentous fungi. The overall goal of the four interdependent projects in this effort is to accomplish functional genomics, annotation, and expression analyses of Neurospora crassa, a filamentous fungus that is an established model for the assemblage of over 250,000 species of non yeast fungi. Building from the completely sequenced 43-Mb Neurospora genome, Project 1 is pursuing the systematic disruption of genes through targeted gene replacements, phenotypic analysis of mutant strains, and their distribution to the scientific community at large. Project 2, through a primary focus in Annotation and Bioinformatics, has developed a platform for electronically capturing community feedback and data about the existing annotation, while building and maintaining a database to capture and display information about phenotypes. Oligonucleotide-based microarrays created in Project 3 are being used to collect baseline expression data for the nearly 11,000 distinguishable transcripts in Neurospora under various conditions of growth and development, and eventually to begin to analyze the global effects of loss of novel genes in strains created by Project 1. cDNA libraries generated in Project 4 document the overall complexity of expressed sequences in Neurospora, including alternative splicing alternative promoters and antisense transcripts. In addition, these studies have driven the assembly of an SNP map presently populated by nearly 300 markers that will greatly accelerate the positional cloning of genes.
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Affiliation(s)
- Jay C Dunlap
- Department of Genetics, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
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41
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Kramer C, Crosthwaite SK. Northern analysis of sense and antisense frequency RNA in Neurospora crassa. Methods Mol Biol 2007; 362:329-42. [PMID: 17417020 DOI: 10.1007/978-1-59745-257-1_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
In Northern analysis the presence of specific RNA transcripts is detected and their quantity can be estimated. RNA is separated using denaturing agarose gel electrophoresis and is subsequently transferred and fixed to a solid support, such as a nitrocellulose filter. When labeled probes are hybridized to these immobilized RNA molecules, their presence can be visualized by autoradiography. Here we describe Northern hybridization using radioactively labeled riboprobes to show circadian expression of endogenous sense and antisense frequency RNA in the filamentous fungus Neurospora crassa.
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Affiliation(s)
- Cas Kramer
- Department of Genetics, University of Leicester, UK
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42
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Dunlap JC, Loros JJ. How fungi keep time: circadian system in Neurospora and other fungi. Curr Opin Microbiol 2006; 9:579-87. [PMID: 17064954 DOI: 10.1016/j.mib.2006.10.008] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2006] [Accepted: 10/11/2006] [Indexed: 02/07/2023]
Abstract
The circadian system in Neurospora remains a premier model system for understanding circadian rhythms, and evidence has now begun to accumulate suggesting broad conservation of rhythmicity amongst the filamentous fungi. A well-described transcription-translation-based negative feedback loop involving the FREQUENCY, WHITE COLLAR-1 and WHITE COLLAR-2 proteins is integral to the Neurospora system. Recent advances include descriptions of the surprisingly complex frequency transcription unit, an enhanced appreciation of the roles of kinases and their regulation in the generation of the circadian rhythm and their links to the cell cycle, and strong evidence for an additional WHITE COLLAR-associated feedback loop. Documentation of sequence homologs of integral circadian and photoresponsive proteins amongst the 42 available sequenced fungal genomes suggests unexpected roles for circadian timing among both pathogens and saprophytes.
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Affiliation(s)
- Jay C Dunlap
- Department of Genetics, Dartmouth Medical School, Hanover, NH 03755, USA.
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Iida Y, Ohara T, Tsuge T. Identification of genes up-regulated during conidiation of Fusarium oxysporum through expressed sequence tag analysis. Fungal Genet Biol 2006; 43:179-89. [PMID: 16480905 DOI: 10.1016/j.fgb.2005.11.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2005] [Revised: 11/10/2005] [Accepted: 11/30/2005] [Indexed: 11/19/2022]
Abstract
Fusarium oxysporum produces three kinds of asexual spores, microconidia, macroconidia, and chlamydospores. F. oxysporum produces microconidia and macroconidia in carboxymethyl cellulose-added liquid medium (CMCLM) and exhibits vegetative growth without conidiation in complete liquid medium (CLM). The cDNA libraries were constructed using mRNAs from CLM and CMCLM cultures. A total of 1288 and 1353 clones from CLM (vegetative growth) and CMCLM (conidiation) libraries, respectively, were sequenced, and 641 and 626 unique genes were identified. Of these unique genes, only 130 ( approximately 20%) were common in the two libraries, indicating different patterns of gene expression during vegetative growth and conidiation. The expression levels of 496 CMCLM-specific genes were compared during vegetative growth and conidiation by cDNA dot-blot differential hybridization and real-time quantitative PCR analyses, and 42 genes were identified to display >5-fold increases in mRNA abundance during conidiation. These genes provide ideal candidates for further studies directed at understanding fungal conidiogenesis and its molecular regulation.
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Affiliation(s)
- Yuichiro Iida
- Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Japan
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44
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Diernfellner ACR, Schafmeier T, Merrow MW, Brunner M. Molecular mechanism of temperature sensing by the circadian clock of Neurospora crassa. Genes Dev 2005; 19:1968-73. [PMID: 16107616 PMCID: PMC1199567 DOI: 10.1101/gad.345905] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Expression levels and ratios of the long (l) and short (s) isoforms of the Neurospora circadian clock protein FREQUENCY (FRQ) are crucial for temperature compensation of circadian rhythms. We show that the ratio of l-FRQ versus s-FRQ is regulated by thermosensitive splicing of intron 6 of frq, a process removing the translation initiation site of l-FRQ. Thermosensitivity is due to inefficient recognition of nonconsensus splice sites at elevated temperature. The temperature-dependent accumulation of FRQ relative to bulk protein is controlled at the level of translation. The 5'-UTR of frq RNA contains six upstream open reading frames (uORFs) that are in nonconsensus context for translation initiation. Thermosensitive trapping of scanning ribosomes at the uORFs leads to reduced translation of the main ORF and allows adjustment of FRQ levels according to ambient temperature.
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45
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Hasegawa K, Saigusa T, Tamai Y. Caenorhabditis elegans opens up new insights into circadian clock mechanisms. Chronobiol Int 2005; 22:1-19. [PMID: 15865318 DOI: 10.1081/cbi-200038149] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The roundworm, Caenorhabditis elegans, is known to carry homologues of clock genes such as per (=period) and tim (=timeless), which constitute the core of the circadian clock in Drosophila and mammals: lin-42 and tim-1. Analyses using WormBase (C. elegans gene database) have identified with relatively high identity analogous of the clock genes recognized in Drosophila and mammals, with the notable exception of cry (=cryptochrome), which is lacking in C. elegans. All of these C. elegans cognates of the clock genes appear to belong to members of the PAS-superfamily and to participate in development or responsiveness to the environment but apparently are not involved in the C. elegans circadian clock. Nevertheless, C. elegans exhibits convincing circadian rhythms in locomotor behavior in the adult stage and in resistance to hyperosmotic stress in starved larvae (L1) after hatching, indicating that it has a circadian clock with a core design entirely different from that of Drosophila and mammals. Here two possibilities are considered. First, the core of the C. elegans circadian clock includes transcriptional/translational feedback loops between genes and their protein products that are entirely different from those of Drosophila and mammals. Second, a more basic principle such as homeostasis governs the circadian cellular physiology, and was established primarily to minimize the accumulation of DNA damage in response to an environment cycling at 24 h intervals.
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Affiliation(s)
- Kenji Hasegawa
- Division of Brain Science, Graduate School of Medicine, Kitasato University, Sagamihara, Kanagawa 228-8555, Japan.
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46
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Kritsky MS, Belozerskaya TA, Sokolovsky VY, Filippovich SY. Photoreceptor Apparatus of the Fungus Neurospora crassa. Mol Biol 2005. [DOI: 10.1007/s11008-005-0068-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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47
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Abstract
A combination of forward and reverse genetic approaches together with transcriptome-scale gene expression analyses have allowed the elaboration of a model for the Arabidopsis thaliana circadian clock. The working model largely conforms to the expected negative feedback loop model that has emerged from studies in other model systems. Although a core loop has emerged, it is clear that additional components remain to be identified and that the workings of the Arabidopsis clock have been established only in outline. Similarly, the details of resetting by light and temperature are only incompletely known. In contrast, the mechanism of photoperiodic induction of flowering is known in considerable detail and is consistent with the external coincidence model.
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Affiliation(s)
- Patrice A Salomé
- Department of Biological Sciences, 6044 Gilman Laboratories, Dartmouth College, Hanover, NH 03755-3576, USA
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48
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Abstract
The molecular mechanism of circadian clocks has been unraveled primarily by the use of phenotype-driven (forward) genetic analysis in a number of model systems. We are now in a position to consider what constitutes a clock component, whether we can establish criteria for clock components, and whether we have found most of the primary clock components. This perspective discusses clock genes and how genetics, molecular biology, and biochemistry have been used to find clock genes in the past and how they will be used in the future.
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Affiliation(s)
- Joseph S Takahashi
- Howard Hughes Medical Institute, Department of Neurobiology & Physiology, Northwestern University, Evanston, IL 60208-3520, USA.
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Vitalini MW, Morgan LW, March IJ, Bell-Pedersen D. A genetic selection for circadian output pathway mutations in Neurospora crassa. Genetics 2005; 167:119-29. [PMID: 15166141 PMCID: PMC1470853 DOI: 10.1534/genetics.167.1.119] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In most organisms, circadian oscillators regulate the daily rhythmic expression of clock-controlled genes (ccgs). However, little is known about the pathways between the circadian oscillator(s) and the ccgs. In Neurospora crassa, the frq, wc-1, and wc-2 genes encode components of the frq-oscillator. A functional frq-oscillator is required for rhythmic expression of the morning-specific ccg-1 and ccg-2 genes. In frq-null or wc-1 mutant strains, ccg-1 mRNA levels fluctuate near peak levels over the course of the day, whereas ccg-2 mRNA remains at trough levels. The simplest model that fits the above observations is that the frq-oscillator regulates a repressor of ccg-1 and an activator of ccg-2. We utilized a genetic selection for mutations that affect the regulation of ccg-1 and ccg-2 by the frq-oscillator. We find that there is at least one mutant strain, COP1-1 (circadian output pathway derived from ccg-1), that has altered expression of ccg-1 mRNA, but normal ccg-2 expression levels. However, the clock does not appear to simply regulate a repressor of ccg-1 and an activator of ccg-2 in two independent pathways, since in our selection we identified three mutant strains, COP1-2, COP1-3, and COP1-4, in which a single mutation in each strain affects the expression levels and rhythmicity of both ccg-1 and ccg-2.
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Affiliation(s)
- Michael W Vitalini
- Center for Biological Clocks Research and Program for the Biology of Filamentous Fungi, Department of Biology, Texas A&M University, College Station, Texas 77843, USA
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50
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Dunlap JC, Loros JJ. Analysis of circadian rhythms in Neurospora: overview of assays and genetic and molecular biological manipulation. Methods Enzymol 2005; 393:3-22. [PMID: 15817284 DOI: 10.1016/s0076-6879(05)93001-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The eukaryotic filamentous fungus Neurospora crassa is a tractable model system that has provided numerous insights into the molecular basis of circadian rhythms. In the core circadian clock feedback loop, WC-1 and WC-2 interact via PAS domains to heterodimerize, and this complex acts both as the circadian photoreceptor and, in the dark, as a transcription factor that promotes the expression of the frq gene. In the negative step of the loop, dimers of FRQ feed back to block the activity of the WC-1/WC-2 complex (WCC) and, in a positive step, to promote the synthesis of WC-1. Several kinases phosphorylate FRQ, leading to its ubiquitination and turnover, releasing the WC-1/WC-2 dimer to reactivate frq expression and restart the circadian cycle. Light and temperature entrainment of the clock arise from rapid light induction of frq expression and from the effect of elevated temperatures in driving higher levels of FRQ. Noncircadian candidate slave oscillators, termed FRQ-less oscillators (FLOs), have been described, each of which appears to regulate aspects of Neurospora growth or development. Overall, the core FRQ/WCC feedback loop coordinates the circadian system by regulating downstream clock-controlled genes either directly or via regulation of driven FLOs. This article provides a brief synopsis of the system and describes current assays for the Neurospora clock. Methods for genetic and molecular manipulation of the core clock are summarized, and accompanying chapters address more specifically aspects of photobiology and output.
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Affiliation(s)
- Jay C Dunlap
- Department of Genetics, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
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