1
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Xia Y, Ding X, Wang S, Ren W. Circadian orchestration of host and gut microbiota in infection. Biol Rev Camb Philos Soc 2023; 98:115-131. [PMID: 36106627 DOI: 10.1111/brv.12898] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Revised: 08/15/2022] [Accepted: 08/16/2022] [Indexed: 01/12/2023]
Abstract
Circadian rhythms are present in almost every organism and regulate multiple aspects of biological and physiological processes (e.g. metabolism, immune responses, and microbial exposure). There exists a bidirectional circadian interaction between the host and its gut microbiota, and potential circadian orchestration of both host and gut microbiota in response to invading pathogens. In this review, we summarize what is known about these intestinal microbial oscillations and the relationships between host circadian clocks and various infectious agents (bacteria, fungi, parasites, and viruses), and discuss how host circadian clocks prime the immune system to fight pathogen infections as well as the direct effects of circadian clocks on viral activity (e.g. SARS-CoV-2 entry and replication). Finally, we consider strategies employed to realign normal circadian rhythmicity for host health, such as chronotherapy, dietary intervention, good sleep hygiene, and gut microbiota-targeted therapy. We propose that targeting circadian rhythmicity may provide therapeutic opportunities for the treatment of infectious diseases.
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Affiliation(s)
- Yaoyao Xia
- Key Laboratory of Veterinary Pharmaceutical Development of Ministry of Agriculture and Rural Affairs, Lanzhou Institute of Husbandry and Pharmaceutical Sciences of Chinese Academy of Agricultural Science, Lanzhou, 730050, China.,State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Laboratory of Lingnan Modern Agriculture, National Engineering Research Center for Breeding Swine Industry, Guangdong Provincial Key Laboratory of Animal Nutrition Control, College of Animal Science, South China Agricultural University, Guangzhou, 510642, China
| | - Xuezhi Ding
- Key Laboratory of Veterinary Pharmaceutical Development of Ministry of Agriculture and Rural Affairs, Lanzhou Institute of Husbandry and Pharmaceutical Sciences of Chinese Academy of Agricultural Science, Lanzhou, 730050, China
| | - Shengyi Wang
- Key Laboratory of Veterinary Pharmaceutical Development of Ministry of Agriculture and Rural Affairs, Lanzhou Institute of Husbandry and Pharmaceutical Sciences of Chinese Academy of Agricultural Science, Lanzhou, 730050, China
| | - Wenkai Ren
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Laboratory of Lingnan Modern Agriculture, National Engineering Research Center for Breeding Swine Industry, Guangdong Provincial Key Laboratory of Animal Nutrition Control, College of Animal Science, South China Agricultural University, Guangzhou, 510642, China
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2
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Muñoz-Guzmán F, Caballero V, Larrondo LF. A global search for novel transcription factors impacting the Neurospora crassa circadian clock. G3 (BETHESDA, MD.) 2021; 11:jkab100. [PMID: 33792687 PMCID: PMC8495738 DOI: 10.1093/g3journal/jkab100] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 03/16/2021] [Indexed: 01/15/2023]
Abstract
Eukaryotic circadian oscillators share a common circuit architecture, a negative feedback loop in which a positive element activates the transcription of a negative one that then represses the action of the former, inhibiting its own expression. While studies in mammals and insects have revealed additional transcriptional inputs modulating the expression of core clock components, this has been less characterized in the model Neurospora crassa, where the participation of other transcriptional components impacting circadian clock dynamics remains rather unexplored. Thus, we sought to identify additional transcriptional regulators modulating the N. crassa clock, following a reverse genetic screen based on luminescent circadian reporters and a collection of transcription factors (TFs) knockouts, successfully covering close to 60% of them. Besides the canonical core clock components WC-1 and -2, none of the tested transcriptional regulators proved to be essential for rhythmicity. Nevertheless, we identified a set of 23 TFs that when absent lead to discrete, but significant, changes in circadian period. While the current level of analysis does not provide mechanistic information about how these new players modulate circadian parameters, the results of this screen reveal that an important number of light and clock-regulated TFs, involved in a plethora of processes, are capable of modulating the clockworks. This partial reverse genetic clock screen also exemplifies how the N. crassa knockout collection continues to serve as an expedite platform to address broad biological questions.
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Affiliation(s)
- Felipe Muñoz-Guzmán
- ANID—Millennium Science Initiative Program—Millennium Institute for Integrative Biology (iBio), Santiago 8331150, Chile
- Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago 8331150, Chile
| | - Valeria Caballero
- Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago 8331150, Chile
| | - Luis F Larrondo
- ANID—Millennium Science Initiative Program—Millennium Institute for Integrative Biology (iBio), Santiago 8331150, Chile
- Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago 8331150, Chile
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3
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Jin D, Kotar J, Silvester E, Leptos KC, Croze OA. Diurnal Variations in the Motility of Populations of Biflagellate Microalgae. Biophys J 2020; 119:2055-2062. [PMID: 33091375 DOI: 10.1016/j.bpj.2020.10.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Revised: 09/29/2020] [Accepted: 10/07/2020] [Indexed: 10/23/2022] Open
Abstract
The motility of microalgae has been studied extensively, particularly in model microorganisms such as Chlamydomonas reinhardtii. For this and other microalgal species, diurnal cycles are well known to control the metabolism, growth, and cell division. Diurnal variations, however, have been largely neglected in quantitative studies of motility. Here, we demonstrate using tracking microscopy how the motility statistics of C. reinhardtii are modulated by diurnal cycles. With nine independently inoculated cultures synchronized to the light-dark cycle at the exponential growth phase, we repeatedly observed that the mean swimming speed is greater during the dark period of a diurnal cycle. From this measurement, using a hydrodynamic power balance, we infer the mean flagellar beat frequency and conjecture that its diurnal variation reflects modulation of intracellular ATP. Our measurements also quantify the diurnal variations of the orientational and gravitactic transport of C. reinhardtii. We use this to explore the population-level consequences of diurnal variations of motility statistics by evaluating a prediction for how the gravitactic steady state changes with time during a diurnal cycle. Finally, we discuss the consequences of diurnal variations of microalgal motility in soil and pelagic environments.
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Affiliation(s)
- Di Jin
- Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom.
| | - Jurij Kotar
- Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom
| | - Emma Silvester
- Clarendon Laboratory, University of Oxford, Oxford, United Kingdom
| | - Kyriacos C Leptos
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, United Kingdom
| | - Ottavio A Croze
- Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom.
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4
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Asirim EZ, Humberg TH, Maier GL, Sprecher SG. Circadian and Genetic Modulation of Visually-Guided Navigation in Drosophila Larvae. Sci Rep 2020; 10:2752. [PMID: 32066794 PMCID: PMC7026142 DOI: 10.1038/s41598-020-59614-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Accepted: 01/23/2020] [Indexed: 12/17/2022] Open
Abstract
Organisms possess an endogenous molecular clock which enables them to adapt to environmental rhythms and to synchronize their metabolism and behavior accordingly. Circadian rhythms govern daily oscillations in numerous physiological processes, and the underlying molecular components have been extensively described from fruit flies to mammals. Drosophila larvae have relatively simple nervous system compared to their adult counterparts, yet they both share a homologous molecular clock with mammals, governed by interlocking transcriptional feedback loops with highly conserved constituents. Larvae exhibit a robust light avoidance behavior, presumably enabling them to avoid predators and desiccation, and DNA-damage by exposure to ultraviolet light, hence are crucial for survival. Circadian rhythm has been shown to alter light-dark preference, however it remains unclear how distinct behavioral strategies are modulated by circadian time. To address this question, we investigate the larval visual navigation at different time-points of the day employing a computer-based tracking system, which allows detailed evaluation of distinct navigation strategies. Our results show that due to circadian modulation specific to light information processing, larvae avoid light most efficiently at dawn, and a functioning clock mechanism at both molecular and neuro-signaling level is necessary to conduct this modulation.
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Affiliation(s)
- Ece Z Asirim
- Department of Biology, Institute of Zoology, University of Fribourg, Fribourg, Switzerland
| | - Tim-Henning Humberg
- Department of Biology, Institute of Zoology, University of Fribourg, Fribourg, Switzerland
| | - G Larisa Maier
- Department of Biology, Institute of Zoology, University of Fribourg, Fribourg, Switzerland
| | - Simon G Sprecher
- Department of Biology, Institute of Zoology, University of Fribourg, Fribourg, Switzerland.
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5
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Costantini C, Renga G, Sellitto F, Borghi M, Stincardini C, Pariano M, Zelante T, Chiarotti F, Bartoli A, Mosci P, Romani L, Brancorsini S, Bellet MM. Microbes in the Era of Circadian Medicine. Front Cell Infect Microbiol 2020; 10:30. [PMID: 32117804 PMCID: PMC7013081 DOI: 10.3389/fcimb.2020.00030] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Accepted: 01/15/2020] [Indexed: 12/29/2022] Open
Abstract
The organisms of most domains of life have adapted to circadian changes of the environment and regulate their behavior and physiology accordingly. A particular case of such paradigm is represented by some types of host-pathogen interaction during infection. Indeed, not only some hosts and pathogens are each endowed with their own circadian clock, but they are also influenced by the circadian changes of the other with profound consequences on the outcome of the infection. It comes that daily fluctuations in the availability of resources and the nature of the immune response, coupled with circadian changes of the pathogen, may influence microbial virulence, level of colonization and damage to the host, and alter the equilibrium between commensal and invading microorganisms. In the present review, we discuss the potential relevance of circadian rhythms in human bacterial and fungal pathogens, and the consequences of circadian changes of the host immune system and microbiome on the onset and development of infection. By looking from the perspective of the interplay between host and microbes circadian rhythms, these concepts are expected to change the way we approach human infections, not only by predicting the outcome of the host-pathogen interaction, but also by indicating the best time for intervention to potentiate the anti-microbial activities of the immune system and to weaken the pathogen when its susceptibility is higher.
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Affiliation(s)
- Claudio Costantini
- Department of Experimental Medicine, University of Perugia, Perugia, Italy
| | - Giorgia Renga
- Department of Experimental Medicine, University of Perugia, Perugia, Italy
| | - Federica Sellitto
- Department of Experimental Medicine, University of Perugia, Perugia, Italy
| | - Monica Borghi
- Department of Experimental Medicine, University of Perugia, Perugia, Italy
| | | | - Marilena Pariano
- Department of Experimental Medicine, University of Perugia, Perugia, Italy
| | - Teresa Zelante
- Department of Experimental Medicine, University of Perugia, Perugia, Italy
| | - Flavia Chiarotti
- Reference Centre for Behavioural Sciences and Mental Health, Istituto Superiore di Sanità, Rome, Italy
| | - Andrea Bartoli
- Department of Experimental Medicine, University of Perugia, Perugia, Italy
| | - Paolo Mosci
- Department of Veterinary Medicine, University of Perugia, Perugia, Italy
| | - Luigina Romani
- Department of Experimental Medicine, University of Perugia, Perugia, Italy
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6
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Abstract
Circadian oscillators are networks of biochemical feedback loops that generate 24-hour rhythms in organisms from bacteria to animals. These periodic rhythms result from a complex interplay among clock components that are specific to the organism, but share molecular mechanisms across kingdoms. A full understanding of these processes requires detailed knowledge, not only of the biochemical properties of clock proteins and their interactions, but also of the three-dimensional structure of clockwork components. Posttranslational modifications and protein–protein interactions have become a recent focus, in particular the complex interactions mediated by the phosphorylation of clock proteins and the formation of multimeric protein complexes that regulate clock genes at transcriptional and translational levels. This review covers the structural aspects of circadian oscillators, and serves as a primer for this exciting realm of structural biology.
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Affiliation(s)
- Reena Saini
- Center for Biocrystallographic Research, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland.,Max-Planck-Institut für Pflanzenzüchtungsforschung, Cologne, Germany
| | - Mariusz Jaskolski
- Center for Biocrystallographic Research, Institute of Bioorganic Chemistry, Polish Academy of Sciences, Poznan, Poland.,Department of Crystallography, Faculty of Chemistry, A. Mickiewicz University, Poznan, Poland
| | - Seth J Davis
- Max-Planck-Institut für Pflanzenzüchtungsforschung, Cologne, Germany. .,Department of Biology, University of York, York, UK.
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7
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Gooch VD, Freeman L, Lakin-Thomas PL. Time-Lapse Analysis of the Circadian Rhythms of Conidiation and Growth Rate in Neurospora. J Biol Rhythms 2016; 19:493-503. [PMID: 15523111 DOI: 10.1177/0748730404270391] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The filamentous fungus Neurospora crassa has frequently served as a model organism for the study of circadian rhythms through its ability to form conidial spores on a daily basis. This phenomenon leaves a spatial pattern of conidiation bands along a solid surface of agar after several days of growth. Using time-lapse video, the authors have quantified the rate of conidiation. They have found that conidia do not form at a specified lag time after the growth front is laid down, but rather the band region tends to simultaneously develop over a short time frame. This produces a sharp peak when the conidiation rate is plotted against time. In addition, the authors used time-lapse video to assay growth rate with greater accuracy than previously reported. It is usually assumed that Neurospora’s rate of growth is constant, and this assumption of linear growth has been used extensively to determine period and phase of the conidiation circadian rhythm. The authors have confirmed an earlier report of nonlinear growth rate and have shown that the growth rate varies by a factor of about 2 with each circadian cycle. They have demonstrated that the errors in calculating times of conidiation peaks are maximally 1 to 2 h if linearity is assumed. The conidiation rate and growth rate rhythms are not apparent under conditions (using mutants or high or low temperatures) where the spatial banding rhythm is not observed. In light/dark entraining conditions, the conidiation rate and growth rate rhythms maintain the same phase relationship in different T-cycles. These data are consistent with the hypothesis that the growth rate rhythm is a consequence of the conidiation rate rhythm.
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Affiliation(s)
- Van D Gooch
- Division of Science and Mathematics, University of Minnesota-Morris, Morris, Minnesota, USA
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8
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de Paula RM, Lewis ZA, Greene AV, Seo KS, Morgan LW, Vitalini MW, Bennett L, Gomer RH, Bell-Pedersen D. Two Circadian Timing Circuits in Neurospora crassa Cells Share Components and Regulate Distinct Rhythmic Processes. J Biol Rhythms 2016; 21:159-68. [PMID: 16731655 DOI: 10.1177/0748730406288338] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
In Neurospora crassa, FRQ, WC-1, and WC-2 proteins comprise the core circadian FRQ-based oscillator that is directly responsive to light and drives daily rhythms in spore development and gene expression. However, physiological and biochemical studies have demonstrated the existence of additional oscillators in the cell that function in the absence of FRQ (collectively termed FRQ-less oscillators [FLOs]). Whether or not these represent temperature-compensated, entrainable circadian oscillators is not known. The authors previously identified an evening-peaking gene, W06H2 (now called clock-controlled gene 16 [ ccg-16]), which is expressed with a robust daily rhythm in cells that lack FRQ protein, suggesting that ccg-16 is regulated by a FLO. In this study, the authors provide evidence that the FLO driving ccg-16 rhythmicity is a circadian oscillator. They find that ccg-16 rhythms are generated by a temperature-responsive, temperature-compensated circadian FLO that, similar to the FRQ-based oscillator, requires functional WC-1 and WC-2 proteins for activity. They also find that FRQ is not essential for rhythmic WC-1 protein levels, raising the possibility that this WCFLO is involved in the generation of WC-1 rhythms. The results are consistent with the presence of 2 circadian oscillators within Neurospora cells, which the authors speculate may interact with each other through the shared WC proteins.
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Affiliation(s)
- Renato M de Paula
- Department of Biology, Center for Research on Biological Clocks, Texas A&M University, College Station, TX 77843, USA
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9
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Assessing the relevance of light for fungi: Implications and insights into the network of signal transmission. ADVANCES IN APPLIED MICROBIOLOGY 2016; 76:27-78. [PMID: 21924971 DOI: 10.1016/b978-0-12-387048-3.00002-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Light represents an important environmental cue, which provides information enabling fungi to prepare and react to the different ambient conditions between day and night. This adaptation requires both anticipation of the changing conditions, which is accomplished by daily rhythmicity of gene expression brought about by the circadian clock, and reaction to sudden illumination. Besides perception of the light signal, also integration of this signal with other environmental cues, most importantly nutrient availability, necessitates light-dependent regulation of signal transduction pathways and metabolic pathways. An influence of light and/or the circadian clock is known for the cAMP pathway, heterotrimeric G-protein signaling, mitogen-activated protein kinases, two-component phosphorelays, and Ca(2+) signaling. Moreover, also the target of rapamycin signaling pathway and reactive oxygen species as signal transducing elements are assumed to be connected to the light-response pathway. The interplay of the light-response pathway with signaling cascades results in light-dependent regulation of primary and secondary metabolism, morphology, development, biocontrol activity, and virulence. The frequent use of fungi in biotechnology as well as analysis of fungi in the artificial environment of a laboratory therefore requires careful consideration of still operative evolutionary heritage of these organisms. This review summarizes the diverse effects of light on fungi and the mechanisms they apply to deal both with the information content and with the harmful properties of light. Additionally, the implications of the reaction of fungi to light in a laboratory environment for experimental work and industrial applications are discussed.
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10
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Bratsun DA, Merkuriev DV, Zakharov AP, Pismen LM. Multiscale modeling of tumor growth induced by circadian rhythm disruption in epithelial tissue. J Biol Phys 2016; 42:107-32. [PMID: 26293211 PMCID: PMC4713406 DOI: 10.1007/s10867-015-9395-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 07/17/2015] [Indexed: 12/17/2022] Open
Abstract
We propose a multiscale chemo-mechanical model of cancer tumor development in epithelial tissue. The model is based on the transformation of normal cells into a cancerous state triggered by a local failure of spatial synchronization of the circadian rhythm. The model includes mechanical interactions and a chemical signal exchange between neighboring cells, as well as a division of cells and intercalation that allows for modification of the respective parameters following transformation into the cancerous state. The numerical simulations reproduce different dephasing patterns--spiral waves and quasistationary clustering, with the latter being conducive to cancer formation. Modification of mechanical properties reproduces a distinct behavior of invasive and localized carcinoma.
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Affiliation(s)
- D A Bratsun
- Theoretical Physics Department, Perm State Humanitarian Pedagogical University, 614990, Perm, Russia
| | - D V Merkuriev
- Department of Hospital Pediatrics, Perm State Medical Academy, 614990, Perm, Russia
| | - A P Zakharov
- Department of Chemical Engineering, Technion-Israel Institute of Technology, 32000, Haifa, Israel.
| | - L M Pismen
- Department of Chemical Engineering, Technion-Israel Institute of Technology, 32000, Haifa, Israel.
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11
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Ruiz-Mirazo K, Briones C, de la Escosura A. Prebiotic Systems Chemistry: New Perspectives for the Origins of Life. Chem Rev 2013; 114:285-366. [DOI: 10.1021/cr2004844] [Citation(s) in RCA: 563] [Impact Index Per Article: 51.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Kepa Ruiz-Mirazo
- Biophysics
Unit (CSIC-UPV/EHU), Leioa, and Department of Logic and Philosophy
of Science, University of the Basque Country, Avenida de Tolosa 70, 20080 Donostia−San Sebastián, Spain
| | - Carlos Briones
- Department
of Molecular Evolution, Centro de Astrobiología (CSIC−INTA, associated to the NASA Astrobiology Institute), Carretera de Ajalvir, Km 4, 28850 Torrejón de Ardoz, Madrid, Spain
| | - Andrés de la Escosura
- Organic
Chemistry Department, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid, Spain
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12
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Edgar RS, Green EW, Zhao Y, van Ooijen G, Olmedo M, Qin X, Xu Y, Pan M, Valekunja UK, Feeney KA, Maywood ES, Hastings MH, Baliga NS, Merrow M, Millar AJ, Johnson CH, Kyriacou CP, O’Neill JS, Reddy AB. Peroxiredoxins are conserved markers of circadian rhythms. Nature 2012; 485:459-64. [PMID: 22622569 PMCID: PMC3398137 DOI: 10.1038/nature11088] [Citation(s) in RCA: 617] [Impact Index Per Article: 51.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2011] [Accepted: 03/26/2012] [Indexed: 11/16/2022]
Abstract
Cellular life emerged ∼3.7 billion years ago. With scant exception, terrestrial organisms have evolved under predictable daily cycles owing to the Earth's rotation. The advantage conferred on organisms that anticipate such environmental cycles has driven the evolution of endogenous circadian rhythms that tune internal physiology to external conditions. The molecular phylogeny of mechanisms driving these rhythms has been difficult to dissect because identified clock genes and proteins are not conserved across the domains of life: Bacteria, Archaea and Eukaryota. Here we show that oxidation-reduction cycles of peroxiredoxin proteins constitute a universal marker for circadian rhythms in all domains of life, by characterizing their oscillations in a variety of model organisms. Furthermore, we explore the interconnectivity between these metabolic cycles and transcription-translation feedback loops of the clockwork in each system. Our results suggest an intimate co-evolution of cellular timekeeping with redox homeostatic mechanisms after the Great Oxidation Event ∼2.5 billion years ago.
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Affiliation(s)
- Rachel S. Edgar
- Department of Clinical Neurosciences, University of Cambridge Metabolic Research Laboratories, NIHR Biomedical Research Centre, Institute of Metabolic Science, University of Cambridge, Addenbrooke’s Hospital, Cambridge CB2 0QQ,UK
| | - Edward W. Green
- Department of Genetics, University of Leicester, Leicester LE1 7RH, UK
| | - Yuwei Zhao
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, USA
| | - Gerben van Ooijen
- Synthetic and Systems Biology (SynthSys), Mayfield Road, EH9 3JD, Edinburgh, UK
| | - Maria Olmedo
- Department of Molecular Chronobiology, Center for Life Sciences, University of Groningen, The Netherlands
| | - Ximing Qin
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, USA
| | - Yao Xu
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, USA
| | - Min Pan
- Institute for Systems Biology, 401 Terry Ave N, Seattle, WA 98109, USA
| | - Utham K. Valekunja
- Department of Clinical Neurosciences, University of Cambridge Metabolic Research Laboratories, NIHR Biomedical Research Centre, Institute of Metabolic Science, University of Cambridge, Addenbrooke’s Hospital, Cambridge CB2 0QQ,UK
| | - Kevin A. Feeney
- Department of Clinical Neurosciences, University of Cambridge Metabolic Research Laboratories, NIHR Biomedical Research Centre, Institute of Metabolic Science, University of Cambridge, Addenbrooke’s Hospital, Cambridge CB2 0QQ,UK
| | | | | | - Nitin S. Baliga
- Institute for Systems Biology, 401 Terry Ave N, Seattle, WA 98109, USA
| | - Martha Merrow
- Department of Molecular Chronobiology, Center for Life Sciences, University of Groningen, The Netherlands
| | - Andrew J. Millar
- Synthetic and Systems Biology (SynthSys), Mayfield Road, EH9 3JD, Edinburgh, UK
- School of Biological Sciences, University of Edinburgh, Mayfield Road, EH9 3JR, Edinburgh, UK
| | - Carl H. Johnson
- Department of Biological Sciences, Vanderbilt University, Nashville, Tennessee, USA
| | | | - John S. O’Neill
- Department of Clinical Neurosciences, University of Cambridge Metabolic Research Laboratories, NIHR Biomedical Research Centre, Institute of Metabolic Science, University of Cambridge, Addenbrooke’s Hospital, Cambridge CB2 0QQ,UK
| | - Akhilesh B. Reddy
- Department of Clinical Neurosciences, University of Cambridge Metabolic Research Laboratories, NIHR Biomedical Research Centre, Institute of Metabolic Science, University of Cambridge, Addenbrooke’s Hospital, Cambridge CB2 0QQ,UK
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13
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Freddolino PL, Tavazoie S. Beyond homeostasis: a predictive-dynamic framework for understanding cellular behavior. Annu Rev Cell Dev Biol 2012; 28:363-84. [PMID: 22559263 DOI: 10.1146/annurev-cellbio-092910-154129] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Microbial regulatory strategies have long been understood in terms of the homeostatic framework, in which a response is interpreted as a restoring force counteracting the immediate intracellular consequences of a change in the environment. In this review, we summarize the breadth of recent discoveries of cellular behavior extending beyond the homeostatic framework. We argue that the nonrandom structure of native habitats makes environmental fluctuations inherently multidimensional. Beyond its utility for accurate perception of immediate events, the temporal regularity of this multidimensional correlation structure allows microbes to make predictions about the trajectory of their sensory environment. We describe recently discovered examples of such predictive behavior, their physiological benefits, and the underlying evolutionary forces shaping them. These observations compel us to go beyond homeostasis and consider a predictive-dynamic framework in which cellular behavior is orchestrated in response to the meaning of an environmental perturbation, not only its direct and immediate fitness consequences.
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Affiliation(s)
- Peter L Freddolino
- Joint Centers for Systems Biology, Columbia University, New York, New York 10032, USA.
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14
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Hunt S, Elvin M, Heintzen C. Temperature-sensitive and circadian oscillators of Neurospora crassa share components. Genetics 2012; 191:119-31. [PMID: 22367035 PMCID: PMC3338254 DOI: 10.1534/genetics.111.137976] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Accepted: 02/06/2012] [Indexed: 11/18/2022] Open
Abstract
In Neurospora crassa, the interactions between products of the frequency (frq), frequency-interacting RNA helicase (frh), white collar-1 (wc-1), and white collar-2 (wc-2) genes establish a molecular circadian clockwork, called the FRQ-WC-Oscillator (FWO), which is required for the generation of molecular and overt circadian rhythmicity. In strains carrying nonfunctional frq alleles, circadian rhythms in asexual spore development (conidiation) are abolished in constant conditions, yet conidiation remains rhythmic in temperature cycles. Certain characteristics of these temperature-synchronized rhythms have been attributed to the activity of a FRQ-less oscillator (FLO). The molecular components of this FLO are as yet unknown. To test whether the FLO depends on other circadian clock components, we created a strain that carries deletions in the frq, wc-1, wc-2, and vivid (vvd) genes. Conidiation in this ΔFWO strain was still synchronized to cyclic temperature programs, but temperature-induced rhythmicity was distinct from that seen in single frq knockout strains. These results and other evidence presented indicate that components of the FWO are part of the temperature-induced FLO.
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Affiliation(s)
- Suzanne Hunt
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Mark Elvin
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
| | - Christian Heintzen
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, United Kingdom
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15
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Yoshida Y, Iigusa H, Wang N, Hasunuma K. Cross-talk between the cellular redox state and the circadian system in Neurospora. PLoS One 2011; 6:e28227. [PMID: 22164247 PMCID: PMC3229512 DOI: 10.1371/journal.pone.0028227] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Accepted: 11/03/2011] [Indexed: 01/03/2023] Open
Abstract
The circadian system is composed of a number of feedback loops, and multiple feedback loops in the form of oscillators help to maintain stable rhythms. The filamentous fungus Neurospora crassa exhibits a circadian rhythm during asexual spore formation (conidiation banding) and has a major feedback loop that includes the FREQUENCY (FRQ)/WHITE COLLAR (WC) -1 and -2 oscillator (FWO). A mutation in superoxide dismutase (sod)-1, an antioxidant gene, causes a robust and stable circadian rhythm compared with that of wild-type (Wt). However, the mechanisms underlying the functions of reactive oxygen species (ROS) remain unknown. Here, we show that cellular ROS concentrations change in a circadian manner (ROS oscillation), and the amplitudes of ROS oscillation increase with each cycle and then become steady (ROS homeostasis). The ROS oscillation and homeostasis are produced by the ROS-destroying catalases (CATs) and ROS-generating NADPH oxidase (NOX). cat-1 is also induced by illumination, and it reduces ROS levels. Although ROS oscillation persists in the absence of frq, wc-1 or wc-2, its homeostasis is altered. Furthermore, genetic and biochemical evidence reveals that ROS concentration regulates the transcriptional function of WCC and a higher ROS concentration enhances conidiation banding. These findings suggest that the circadian system engages in cross-talk with the cellular redox state via ROS-regulatory factors.
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Affiliation(s)
- Yusuke Yoshida
- Kihara Institute for Biological Research, Graduate School of Integrated Science, Yokohama City University, Totsuka-ku, Yokohama, Japan.
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16
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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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Steyaert JM, Weld RJ, Mendoza-Mendoza A, Stewart A. Reproduction without sex: conidiation in the filamentous fungus Trichoderma. Microbiology (Reading) 2010; 156:2887-2900. [DOI: 10.1099/mic.0.041715-0] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Trichoderma spp. have served as models for asexual reproduction in filamentous fungi for over 50 years. Physical stimuli, such as light exposure and mechanical injury to the mycelium, trigger conidiation; however, conidiogenesis itself is a holistic response determined by the cell's metabolic state, as influenced by the environment and endogenous biological rhythms. Key environmental parameters are the carbon and nitrogen status and the C : N ratio, the ambient pH and the level of calcium ions. Recent advances in our understanding of the molecular biology of this fungus have revealed a conserved mechanism of environmental perception through the White Collar orthologues BLR-1 and BLR-2. Also implicated in the molecular regulation are the PacC pathways and the conidial regulator VELVET. Signal transduction cascades which link environmental signals to physiological outputs have also been revealed.
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Affiliation(s)
- Johanna M. Steyaert
- Bio-Protection Research Centre, PO Box 84, Lincoln University, Lincoln 7647, New Zealand
| | - Richard J. Weld
- Lincoln Ventures Limited, PO Box 133, Lincoln University, Lincoln 7647, New Zealand
| | | | - Alison Stewart
- Bio-Protection Research Centre, PO Box 84, Lincoln University, Lincoln 7647, New Zealand
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18
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Stamatakis M, Mantzaris NV. Intrinsic noise and division cycle effects on an abstract biological oscillator. CHAOS (WOODBURY, N.Y.) 2010; 20:033118. [PMID: 20887058 PMCID: PMC2955726 DOI: 10.1063/1.3484868] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Accepted: 08/11/2010] [Indexed: 05/29/2023]
Abstract
Oscillatory dynamics are common in biological pathways, emerging from the coupling of positive and negative feedback loops. Due to the small numbers of molecules typically contained in cellular volumes, stochastic effects may play an important role in system behavior. Thus, for moderate noise strengths, stochasticity has been shown to enhance signal-to-noise ratios or even induce oscillations in a class of phenomena referred to as "stochastic resonance" and "coherence resonance," respectively. Furthermore, the biological oscillators are subject to influences from the division cycle of the cell. In this paper we consider a biologically relevant oscillator and investigate the effect of intrinsic noise as well as division cycle which encompasses the processes of growth, DNA duplication, and cell division. We first construct a minimal reaction network which can oscillate in the presence of large or negligible timescale separation. We then derive corresponding deterministic and stochastic models and compare their dynamical behaviors with respect to (i) the extent of the parameter space where each model can exhibit oscillatory behavior and (ii) the oscillation characteristics, namely, the amplitude and the period. We further incorporate division cycle effects on both models and investigate the effect of growth rate on system behavior. Our results show that in the presence but not in the absence of large timescale separation, coherence resonance effects result in extending the oscillatory region and lowering the period for the stochastic model. When the division cycle is taken into account, the oscillatory region of the deterministic model is shown to extend or shrink for moderate or high growth rates, respectively. Further, under the influence of the division cycle, the stochastic model can oscillate for parameter sets for which the deterministic model does not. The division cycle is also found to be able to resonate with the oscillator, thereby enhancing oscillation robustness. The results of this study can give valuable insight into the complex interplay between oscillatory intracellular dynamics and various noise sources, stemming from gene expression, cell growth, and division.
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Affiliation(s)
- Michail Stamatakis
- Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, USA.
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19
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Bluhm BH, Burnham AM, Dunkle LD. A circadian rhythm regulating hyphal melanization in Cercospora kikuchii. Mycologia 2010; 102:1221-8. [PMID: 20943572 DOI: 10.3852/09-041] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Many metabolic and developmental processes in fungi are controlled by biological rhythms. Circadian rhythms approximate a daily (24 h) cycle and have been thoroughly studied in the model fungus, Neurospora crassa. However relatively few examples of true circadian rhythms have been documented among other filamentous fungi. In this study we describe a circadian rhythm underlying hyphal melanization in Cercospora kikuchii, an important pathogen of soybean. After growth in light or light : dark cycles, colonies transferred to darkness produced zonate bands of melanized hyphae interspersed with bands of hyaline hyphae. Rhythmic production of bands was remarkably persistent in the absence of external cues, lasting at least 7 d after transfer to darkness, and was compensated over a range of temperatures. As in N. crassa, blue light but not red light was sufficient to entrain the circadian rhythm in C. kikuchii, and a putative ortholog of white collar-1, one of the genes required for light responses in N. crassa, was identified in C. kikuchii. Circadian regulation of melanization is conserved in other members of the genus: Similar rhythms were identified in another field isolate of C. kikuchii as well as field isolates of C. beticola and C. sorghi, but not in wild-type strains of C. zeae-maydis or C. zeina. This report represents the first documented circadian rhythm among Dothideomycete fungi and provides a new opportunity to dissect the molecular basis of circadian rhythms among filamentous fungi.
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Affiliation(s)
- Burton H Bluhm
- Department of Plant Pathology, University of Arkansas Division of Agriculture, Fayetteville, Arkansas 72701, USA
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20
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Salichos L, Rokas A. The diversity and evolution of circadian clock proteins in fungi. Mycologia 2010; 102:269-78. [PMID: 20361495 DOI: 10.3852/09-073] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Circadian rhythms are endogenous cellular patterns that associate multiple physiological and molecular functions with time. The Neurospora circadian system contains at least three oscillators: the FRQ/WC-dependent circadian oscillator (FWO), whose core components are the FRQ, WC-1, WC-2, FRH, and FWD-1 proteins; the WC-dependent circadian oscillator (WC-FLO); and one or more FRQ/ WC-independent oscillators (FLO). Little is known about the distribution of homologs of the Neurospora clock proteins or about the molecular foundations of circadian rhythms across fungi. Here, we examined 64 diverse fungal proteomes for homologs of all five Neurospora clock proteins and retraced their evolutionary history. The FRH and FWD-1 proteins were likely present in the fungal ancestor. WC-1 and WC-2 homologs are absent from the early diverging chytrids and Microsporidia but are present in all other major clades. In contrast to the deep origins of these four clock proteins FRQ homologs are taxonomically restricted within Sordariomycetes, Leotiomycetes and Dothideomycetes. The large number of FRH and FWD-1 homologs identified and their lack of concordance with the fungal species phylogeny indicate that they likely underwent multiple rounds of duplications and losses. In contrast, the FRQ, WC-1 and WC-2 proteins exhibit relatively few duplications and losses. A notable exception is the 10 FRQ-like proteins in Fusarium oxysporum, which resulted from nine duplication events. Our results suggest that the machinery required for FWO oscillator function is taxonomically restricted within Ascomycetes. Although the WC proteins are widely distributed, the functional diversity of the few non-Neurospora circadian oscillators suggests that a WC-FLO oscillator is unlikely to fully explain the observed rhythms. The contrast between the diversity of circadian oscillators and the conservation of most of their machinery is likely best explained by considering the centrality of noncircadian functions in which RNA helicase (FRH), F-box (FWD-1), WC-1 and WC-2 (light-sensing) proteins participate in fungi and eukaryotes.
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Affiliation(s)
- Leonidas Salichos
- Department of Biological Sciences, Vanderbilt University, VU Station B 35-1634, Nashville, Tennessee 37235, USA
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21
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Li N, McMurry T, Berg A, Wang Z, Berceli SA, Wu R. Functional clustering of periodic transcriptional profiles through ARMA(p,q). PLoS One 2010; 5:e9894. [PMID: 20419127 PMCID: PMC2855703 DOI: 10.1371/journal.pone.0009894] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Accepted: 02/24/2010] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Gene clustering of periodic transcriptional profiles provides an opportunity to shed light on a variety of biological processes, but this technique relies critically upon the robust modeling of longitudinal covariance structure over time. METHODOLOGY We propose a statistical method for functional clustering of periodic gene expression by modeling the covariance matrix of serial measurements through a general autoregressive moving-average process of order (p,q), the so-called ARMA(p,q). We derive a sophisticated EM algorithm to estimate the proportions of each gene cluster, the Fourier series parameters that define gene-specific differences in periodic expression trajectories, and the ARMA parameters that model the covariance structure within a mixture model framework. The orders and of the ARMA process that provide the best fit are identified by model selection criteria. CONCLUSIONS Through simulated data we show that whenever it is necessary, employment of sophisticated covariance structures such as ARMA is crucial in order to obtain unbiased estimates of the mean structure parameters and increased precision of estimation. The methods were implemented on recently published time-course gene expression data in yeast and the procedure was shown to effectively identify interesting periodic clusters in the dataset. The new approach will provide a powerful tool for understanding biological functions on a genomic scale.
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Affiliation(s)
- Ning Li
- Department of Epidemiology and Biostatistics, University of Florida, Gainesville, Florida, United States of America
| | - Timothy McMurry
- Department of Mathematical Sciences, DePaul University, Chicago, Illinois, United States of America
| | - Arthur Berg
- Division of Biostatistics, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
- Center for Computational Biology, Beijing Forestry University, Beijing, People's Republic of China
| | - Zhong Wang
- Division of Biostatistics, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
| | - Scott A. Berceli
- Department of Surgery, University of Florida, Gainesville, Florida, United States of America
| | - Rongling Wu
- Division of Biostatistics, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
- Center for Computational Biology, Beijing Forestry University, Beijing, People's Republic of China
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22
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Abstract
The engineering of genetic circuits with predictive functionality in living cells represents a defining focus of the expanding field of synthetic biology. This focus was elegantly set in motion a decade ago with the design and construction of a genetic toggle switch and an oscillator, with subsequent highlights that have included circuits capable of pattern generation, noise shaping, edge detection and event counting. Here we describe an engineered gene network with global intercellular coupling that is capable of generating synchronized oscillations in a growing population of cells. Using microfluidic devices tailored for cellular populations at differing length scales, we investigate the collective synchronization properties along with spatiotemporal waves occurring at millimetre scales. We use computational modelling to describe quantitatively the observed dependence of the period and amplitude of the bulk oscillations on the flow rate. The synchronized genetic clock sets the stage for the use of microbes in the creation of a macroscopic biosensor with an oscillatory output. Furthermore, it provides a specific model system for the generation of a mechanistic description of emergent coordinated behaviour at the colony level.
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23
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Cheng Z, Liu F, Zhang XP, Wang W. Reversible phosphorylation subserves robust circadian rhythms by creating a switch in inactivating the positive element. Biophys J 2010; 97:2867-75. [PMID: 19948115 DOI: 10.1016/j.bpj.2009.09.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Revised: 09/02/2009] [Accepted: 09/03/2009] [Indexed: 11/28/2022] Open
Abstract
Reversible phosphorylation of proteins is ubiquitous in circadian systems, but the role it plays in generating rhythmicity is not completely understood. A common mechanism for most circadian rhythms involves a negative feedback loop between the positive and negative elements. Here, we built a minimal model for the Neurospora crassa circadian clock based on the core negative feedback loop and the protein FREQUENCY (FRQ)-dependent phosphorylation of the White Collar Complex (WCC). The model can reproduce basic features of the clock, such as the period length, phase relationship, and entrainment to light/dark cycles. We found that the activity of WCC can be controlled by FRQ in a switchlike manner owing to zero-order ultrasensitivity. WCC is inactivated when FRQ level crosses a threshold from below. As a result, low cooperativity in transcriptional activation is sufficient for circadian rhythms, and the level of active WCC exhibits spiky oscillations. Such oscillations are robust to molecular noise and may subserve controlling circadian output. Therefore, the core negative feedback together with phosphorylation of the positive element can ensure robust circadian rhythms. Our work provides insights into the critical roles of posttranslational modification in circadian clocks.
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Affiliation(s)
- Zhang Cheng
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing, China
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24
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Steyaert JM, Weld RJ, Loguercio LL, Stewart A. Rhythmic conidiation in the blue-light fungus Trichoderma pleuroticola. Fungal Biol 2010; 114:219-23. [PMID: 20943132 DOI: 10.1016/j.funbio.2010.01.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Revised: 12/11/2009] [Accepted: 01/04/2010] [Indexed: 02/05/2023]
Abstract
Trichoderma species conidiate in response to blue light, however, unlike in the blue-light model fungus Neurospora crassa, conidiation in Trichoderma spp. has been considered to be non-circadian. In this study we uncovered evidence for circadian conidiation in Trichoderma pleuroticola and identified orthologues of the key N. crassa clock components, wc-1 (blr-1) and frq.
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Affiliation(s)
- Johanna M Steyaert
- Bio-Protection Research Centre, PO Box 84, Lincoln University, Lincoln 7647, New Zealand.
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25
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The pedestrian watchmaker: genetic clocks from engineered oscillators. FEBS Lett 2010; 583:3931-7. [PMID: 19903483 DOI: 10.1016/j.febslet.2009.10.089] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Accepted: 10/26/2009] [Indexed: 01/29/2023]
Abstract
The crucial role of time-keeping has required organisms to develop sophisticated regulatory networks to ensure the reliable propagation of periodic behavior. These biological clocks have long been a focus of research; however, a clear understanding of how they maintain oscillations in the face of unpredictable environments and the inherent noise of biological systems remains elusive. Here, we review the current understanding of circadian oscillations using Drosophila melanogaster as a typical example and discuss the utility of an alternative synthetic biology approach to studying these highly intricate systems.
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26
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Circadian rhythms in Neurospora crassa: dynamics of the clock component frequency visualized using a fluorescent reporter. Fungal Genet Biol 2010; 47:332-41. [PMID: 20051268 DOI: 10.1016/j.fgb.2009.12.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2009] [Revised: 12/13/2009] [Accepted: 12/30/2009] [Indexed: 11/29/2022]
Abstract
The frequency (frq) gene of Neurospora crassa has long been considered essential to the function of this organism's circadian rhythm. Increasingly, deciphering the coupling of core oscillator genes such as frq to the output pathways of the circadian rhythm has become a major focus of circadian research. To address this coupling it is critical to have a reporter of circadian activity that can deliver high resolution spatial and temporal information about the dynamics of core oscillatory proteins such as FRQ. However, due to the difficulty of studying the expression of circadian rhythm genes in aerobic N. crassa cultures, little is known about the dynamics of this gene under physiologically realistic conditions. To address these issues we report a fluorescent fusion to the frq gene using a codon optimized version of the mCherry gene. To trace the expression and accumulation of FRQ-mCherryNC (FRQ-mCh) during the circadian rhythm, growing vegetative hyphae were scanned every hour under confocal microscopy (100x). Fluorescence of FRQ-mCh was detected only at the growing edge of the colony, and located in the cytoplasm and nuclei of vegetative hyphae for a distance of approximately 150-200microm from the apices of leading hyphae. When driven by the frq promoter, apparently there was also a second FRQ entrance into the nucleus during the circadian cycle; however the second entrance had a lower accumulation level than the first entrance. Thus this fluorescent fusion protein has proven useful in tracking the spatial dynamics of the frq protein and has indicated that the dynamics of the FRQ protein's nuclear trafficking may be more complex than previously realized.
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27
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Martín O, Peñate L, Alvaré A, Cárdenas R, Horvath JE. Some possible dynamical constraints for life's origin. ORIGINS LIFE EVOL B 2009; 39:533-44. [PMID: 19554472 DOI: 10.1007/s11084-009-9170-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2009] [Accepted: 05/01/2009] [Indexed: 10/20/2022]
Abstract
Oscillating biochemical reactions are common in cell dynamics and could be closely related to the emergence of the life phenomenon itself. In this work, we study the dynamical features of some classical chemical or biochemical oscillators where the effect of cell volume changes is explicitly considered. Such analysis enables us to find some general conditions about the cell membrane to preserve such oscillatory patterns, of possible relevance to hypothetical primitive cells in which these structures first appeared.
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Affiliation(s)
- Osmel Martín
- Physics Department, Universidad Central de las Villas, Santa Clara, Cuba.
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28
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Brody S, Oelhafen K, Schneider K, Perrino S, Goetz A, Wang C, English C. Circadian rhythms in Neurospora crassa: Downstream effectors. Fungal Genet Biol 2009; 47:159-68. [PMID: 19800017 DOI: 10.1016/j.fgb.2009.09.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Revised: 09/23/2009] [Accepted: 09/23/2009] [Indexed: 10/20/2022]
Abstract
The circadian rhythm in Neurospora crassa is exhibited as alternating areas of conidiating and non-conidiating mycelia growth. A significant role in this circadian rhythm is played by the frq (frequency) and wc (white-collar) genes, comprising the "FWC" oscillator. Strains lacking the FWC can be restored to rhythmicity, which has been attributed to a second oscillator, called the FLO (frq-less oscillator). This study reports additional conditions that allow this rhythmicity to occur. Rhythmicity was restored to mutants lacking either the frq, or wc-1, or wc-2 genes in D/D (constant darkness) or L/L (constant light) by the addition of low levels of menadione, a known stimulator of ROS (reactive oxygen species). Additional studies are reported on the rhythm effects from caffeine, a known cAMP phospho-diesterase inhibitor as well as the effects from mutations in the csp-1 gene, the rco-1 gene, and other genes. A theme ties all of these "downstream effects" together, i.e., they affect either components thought to be part of the conidiation process itself, or the RAS-cAMP-protein kinase pathway. Since mutations in these components unexpectedly had rhythm effects, this suggests that these components may be good candidates for some part of the frq-less oscillator.
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Affiliation(s)
- Stuart Brody
- Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093-0116, USA.
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29
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30
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Abstract
In Neurospora crassa, a circadian rhythm of conidiation (asexual spore formation) can be seen on the surface of agar media. This rhythm has a period of 22 hr in constant darkness (D/D). Under constant illumination (L/L), no rhythm is visible and cultures show constant conidiation. However, here we report that strains with a mutation in the vivid (vvd) gene, previously shown to code for the photoreceptor involved in photo-adaptation, exhibit conidiation rhythms in L/L as well as in D/D. The period of the rhythm of vvd strains ranges between 6 and 21 hr in L/L, depending upon the intensity of the light, the carbon source, and the presence of other mutations. Temperature compensation of the period also depends on light intensity. Dark pulses given in L/L shift the phase of the rhythm. Shifts from L/L to D/D show unexpected after effects; i.e., the short period of a vvd strain in L/L gradually lengthens over 2-3 days in D/D. The rhythm in L/L requires the white collar (wc-1) gene, but not the frequency (frq) gene. FRQ protein shows no rhythm in L/L in a vvd strain. The conidiation rhythm in L/L in vvd is therefore driven by a FRQ-less oscillator (FLO).
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31
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A computational approach to the functional clustering of periodic gene-expression profiles. Genetics 2008; 180:821-34. [PMID: 18780724 DOI: 10.1534/genetics.108.093690] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
DNA microarray analysis has emerged as a leading technology to enhance our understanding of gene regulation and function in cellular mechanism controls on a genomic scale. This technology has advanced to unravel the genetic machinery of biological rhythms by collecting massive gene-expression data in a time course. Here, we present a statistical model for clustering periodic patterns of gene expression in terms of different transcriptional profiles. The model incorporates biologically meaningful Fourier series approximations of gene periodic expression into a mixture-model-based likelihood function, thus producing results that are likely to be closer to biological relevance, as compared to those from existing models. Also because the structures of the time-dependent means and covariance matrix are modeled, the new approach displays increased statistical power and precision of parameter estimation. The approach was used to reanalyze a real example with 800 periodically expressed transcriptional genes in yeast, leading to the identification of 13 distinct patterns of gene-expression cycles. The model proposed can be useful for characterizing the complex biological effects of gene expression and generate testable hypotheses about the workings of developmental systems in a more precise quantitative way.
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33
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Koharudin LMI, Viscomi AR, Jee JG, Ottonello S, Gronenborn AM. The evolutionarily conserved family of cyanovirin-N homologs: structures and carbohydrate specificity. Structure 2008; 16:570-84. [PMID: 18400178 DOI: 10.1016/j.str.2008.01.015] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2007] [Revised: 01/09/2008] [Accepted: 01/11/2008] [Indexed: 11/28/2022]
Abstract
Solution structures for three members of the recently discovered cyanovirin-N (CV-N) homolog family of lectins have been determined. Cyanovirin-N homologs (CVNHs) from Tuber borchii, Ceratopteris richardii, and Neurospora crassa, representing each of the three phylogenetic groups, were selected. All proteins exhibit the same fold, and the overall structures resemble that of the founding member of the family, CV-N, albeit with noteworthy differences in loop conformation and detailed local structure. Since no data are available regarding the proteins' function or their natural ligands, extensive carbohydrate-binding studies were conducted. We delineated ligand-binding sites on all three proteins by nuclear magnetic resonance and identified which sugars interact by array screening. The number and location of binding sites vary for the three proteins, and different ligand specificities exist. Potential physiological roles for two family members, TbCVNH and NcCVNH, were probed in nutrition deprivation experiments that suggest a possible involvement of these proteins in lifestyle-related responses.
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Affiliation(s)
- Leonardus M I Koharudin
- Department of Structural Biology, School of Medicine, University of Pittsburgh, Biomedical Science Tower 3, 3501 Fifth Avenue, Pittsburgh, PA 15260, USA
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34
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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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35
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Villagrá A, Althaus RL, Lainez M, Martinez AB, Torres AG. Modelling of daily rhythms of behavioural patterns in growing pigs on two commercial farms. BIOL RHYTHM RES 2007. [DOI: 10.1080/09291010600950131] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Affiliation(s)
- Aránzazu Villagrá
- a Instituto Valenciano de Investigaciones Agrarias - CITA , Polígono La Esperanza n°100, 12400, Segorbe, Castellón, Spain
- c Department of Animal Science , Universidad Politécnica de Valencia , Camino de Vera s/n, 46022, Valencia, Spain
| | - Rafael L. Althaus
- b Cátedra de Biofísica, Departamento de Ciencias Básicas , Facultad de Ciencias Veterinarias, Universidad Nacional del Litoral , R. P. L. Kreder, 2805 (3080), Esperanza, Santa Fe, Argentina
| | - Manuel Lainez
- a Instituto Valenciano de Investigaciones Agrarias - CITA , Polígono La Esperanza n°100, 12400, Segorbe, Castellón, Spain
| | - Ana Belén Martinez
- c Department of Animal Science , Universidad Politécnica de Valencia , Camino de Vera s/n, 46022, Valencia, Spain
| | - Antonio G. Torres
- c Department of Animal Science , Universidad Politécnica de Valencia , Camino de Vera s/n, 46022, Valencia, Spain
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Michael TP, Park S, Kim TS, Booth J, Byer A, Sun Q, Chory J, Lee K. Simple sequence repeats provide a substrate for phenotypic variation in the Neurospora crassa circadian clock. PLoS One 2007; 2:e795. [PMID: 17726525 PMCID: PMC1949147 DOI: 10.1371/journal.pone.0000795] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2007] [Accepted: 07/25/2007] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND WHITE COLLAR-1 (WC-1) mediates interactions between the circadian clock and the environment by acting as both a core clock component and as a blue light photoreceptor in Neurospora crassa. Loss of the amino-terminal polyglutamine (NpolyQ) domain in WC-1 results in an arrhythmic circadian clock; this data is consistent with this simple sequence repeat (SSR) being essential for clock function. METHODOLOGY/PRINCIPAL FINDINGS Since SSRs are often polymorphic in length across natural populations, we reasoned that investigating natural variation of the WC-1 NpolyQ may provide insight into its role in the circadian clock. We observed significant phenotypic variation in the period, phase and temperature compensation of circadian regulated asexual conidiation across 143 N. crassa accessions. In addition to the NpolyQ, we identified two other simple sequence repeats in WC-1. The sizes of all three WC-1 SSRs correlated with polymorphisms in other clock genes, latitude and circadian period length. Furthermore, in a cross between two N. crassa accessions, the WC-1 NpolyQ co-segregated with period length. CONCLUSIONS/SIGNIFICANCE Natural variation of the WC-1 NpolyQ suggests a mechanism by which period length can be varied and selected for by the local environment that does not deleteriously affect WC-1 activity. Understanding natural variation in the N.crassa circadian clock will facilitate an understanding of how fungi exploit their environments.
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Affiliation(s)
- Todd P. Michael
- Department of Plant Pathology, Cornell University, Ithaca, New York, United States of America
- Plant Biology Laboratory, The Salk Institute, La Jolla, California, United States of America
| | - Sohyun Park
- Department of Plant Pathology, Cornell University, Ithaca, New York, United States of America
| | - Tae-Sung Kim
- Department of Plant Pathology, Cornell University, Ithaca, New York, United States of America
| | - Jim Booth
- Department of Biological Statistics and Computational Biology, Cornell University, Ithaca, New York, United States of America
| | - Amanda Byer
- Plant Biology Laboratory, The Salk Institute, La Jolla, California, United States of America
| | - Qi Sun
- Cornell Theory Center, Cornell University, Ithaca, New York, United States of America
| | - Joanne Chory
- Plant Biology Laboratory, The Salk Institute, La Jolla, California, United States of America
- Howard Hughes Medical Institute, The Salk Institute for Biological Studies, La Jolla, California, United States of America
| | - Kwangwon Lee
- Department of Plant Pathology, Cornell University, Ithaca, New York, United States of America
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Harrington ED, Singh AH, Doerks T, Letunic I, von Mering C, Jensen LJ, Raes J, Bork P. Quantitative assessment of protein function prediction from metagenomics shotgun sequences. Proc Natl Acad Sci U S A 2007; 104:13913-8. [PMID: 17717083 PMCID: PMC1955820 DOI: 10.1073/pnas.0702636104] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To assess the potential of protein function prediction in environmental genomics data, we analyzed shotgun sequences from four diverse and complex habitats. Using homology searches as well as customized gene neighborhood methods that incorporate intergenic and evolutionary distances, we inferred specific functions for 76% of the 1.4 million predicted ORFs in these samples (83% when nonspecific functions are considered). Surprisingly, these fractions are only slightly smaller than the corresponding ones in completely sequenced genomes (83% and 86%, respectively, by using the same methodology) and considerably higher than previously thought. For as many as 75,448 ORFs (5% of the total), only neighborhood methods can assign functions, illustrated here by a previously undescribed gene associated with the well characterized heme biosynthesis operon and a potential transcription factor that might regulate a coupling between fatty acid biosynthesis and degradation. Our results further suggest that, although functions can be inferred for most proteins on earth, many functions remain to be discovered in numerous small, rare protein families.
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Affiliation(s)
- E. D. Harrington
- *Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany; and
| | - A. H. Singh
- *Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany; and
| | - T. Doerks
- *Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany; and
| | - I. Letunic
- *Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany; and
| | - C. von Mering
- *Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany; and
| | - L. J. Jensen
- *Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany; and
| | - J. Raes
- *Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany; and
| | - P. Bork
- *Structural and Computational Biology Unit, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany; and
- Max Delbrück Centre for Molecular Medicine, D-13092 Berlin, Germany
- To whom correspondence should be addressed. E-mail:
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38
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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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Abstract
This review examines the connections between circadian and metabolic rhythms. Examples from a wide variety of well-studied organisms are used to illustrate some of the genetic and molecular pathways linking circadian timekeeping to metabolism. The principles underlying biological timekeeping by intrinsic circadian clocks are discussed briefly. Genetic and molecular studies have unambiguously identified the importance of gene expression feedback circuits to the generation of overt circadian rhythms. This is illustrated particularly well by the results of genome-wide expression studies, which have uncovered hundreds of clock-controlled genes in cyanobacteria, fungi, plants, and animals. The potential connections between circadian oscillations in gene expression and circadian oscillations in metabolic activity are a major focus of this review.
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Affiliation(s)
- Herman Wijnen
- Department of Biology, University of Virginia, Charlottesville, Virginia 22904-4328, USA.
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40
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Wang C, St Leger RJ. The MAD1 adhesin of Metarhizium anisopliae links adhesion with blastospore production and virulence to insects, and the MAD2 adhesin enables attachment to plants. EUKARYOTIC CELL 2007; 6:808-16. [PMID: 17337634 PMCID: PMC1899246 DOI: 10.1128/ec.00409-06] [Citation(s) in RCA: 205] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Metarhizium anisopliae is a fungus of considerable metabolic and ecological versatility, being a potent insect pathogen that can also colonize plant roots. The mechanistic details of these interactions are unresolved. We provide evidence that M. anisopliae adheres to insects and plants using two different proteins, MAD1 and MAD2, that are differentially induced in insect hemolymph and plant root exudates, respectively, and produce regional localization of adhesive conidial surfaces. Expression of Mad1 in Saccharomyces cerevisiae allowed this yeast to adhere to insect cuticle. Expression of Mad2 caused yeast cells to adhere to a plant surface. Our study demonstrated that as well as allowing adhesion to insects, MAD1 at the surface of M. anisopliae conidia or blastospores is required to orientate the cytoskeleton and stimulate the expression of genes involved in the cell cycle. Consequently, the disruption of Mad1 in M. anisopliae delayed germination, suppressed blastospore formation, and greatly reduced virulence to caterpillars. The disruption of Mad2 blocked the adhesion of M. anisopliae to plant epidermis but had no effects on fungal differentiation and entomopathogenicity. Thus, regulation, localization, and specificity control the functional distinction between Mad1 and Mad2 and enable M. anisopliae cells to adapt their adhesive properties to different habitats.
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Affiliation(s)
- Chengshu Wang
- Department of Entomology, 4112 Plant Science Building, University of Maryland, College Park, MD 20742-4454, USA
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41
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Liu Y, Bell-Pedersen D. Circadian rhythms in Neurospora crassa and other filamentous fungi. EUKARYOTIC CELL 2007; 5:1184-93. [PMID: 16896204 PMCID: PMC1539135 DOI: 10.1128/ec.00133-06] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Yi Liu
- Department of Physiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9040, USA.
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42
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Vitalini MW, de Paula RM, Park WD, Bell-Pedersen D. The rhythms of life: circadian output pathways in Neurospora. J Biol Rhythms 2007; 21:432-44. [PMID: 17107934 DOI: 10.1177/0748730406294396] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Research in Neurospora crassa pioneered the isolation of clock-controlled genes (ccgs), and more than 180 ccgs have been identified that function in various aspects of the fungal life cycle. Many clock-controlled genes are associated with damage repair, stress responses, intermediary metabolism, protein synthesis, and development. The expression of most of these genes peaks just before dawn and appears to prepare the cells for the desiccation, mutagenesis, and stress caused by sunlight. Progress on characterization of the output signaling pathways from the circadian oscillator mechanism to the ccgs is discussed. The authors also review evidence suggesting that, similar to other clock model organisms, a connection exists between the redox state of the cell and the Neurospora clock. The authors speculate that the clock system may sense not only light but also the redox potential of the cell through one of the PAS domains of the core clock components WC-1 or WC-2.
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Affiliation(s)
- Michael W Vitalini
- Center for Biological Clocks Research, Department of Biology, Texas A&M University, College Station, TX 77843, USA
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43
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Lombardi L, Schneider K, Tsukamoto M, Brody S. Circadian rhythms in Neurospora crassa: clock mutant effects in the absence of a frq-based oscillator. Genetics 2007; 175:1175-83. [PMID: 17237512 PMCID: PMC1840085 DOI: 10.1534/genetics.106.068270] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In Neurospora, the circadian rhythm is expressed as rhythmic conidiation driven by a feedback loop involving the protein products of frq (frequency), wc-1 (white collar-1), and wc-2, known as the frq/wc (FWC) oscillator. Although strains carrying null mutations such as frq(10) or wc-2Delta lack a functional FWC oscillator and do not show a rhythm under most conditions, a rhythm can be observed in them by the addition of geraniol or farnesol to the media. Employing this altered media as an assay, the effect of other clock mutations in a frq(10)- or wc-2Delta-null background can be measured. It was found that the existing clock mutations fall into three classes: (1) those, such as prd-3 or prd-4 or frq(1), that showed no effect in a clock null background; (2) those, such as prd-1 or prd-2 or prd-6, that did have a measurable effect in the frq(10) background; and (3) those, such as the new mutation ult, that suppressed the frq(10) or wc-2Delta effect, i.e., geraniol/farnesol was not required for a visible rhythm. This classification suggests that some of the known clock mutations are part of a broader multioscillator system.
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Affiliation(s)
- Laura Lombardi
- Division of Biological Sciences, University of California, San Diego, California 92093-0116, USA
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44
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Castro-Longoria E, Brody S, Bartnicki-García S. Kinetics of circadian band development in Neurospora crassa. Fungal Genet Biol 2007; 44:672-81. [PMID: 17329132 DOI: 10.1016/j.fgb.2007.01.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Revised: 01/10/2007] [Accepted: 01/12/2007] [Indexed: 11/21/2022]
Abstract
The circadian rhythm of Neurospora crassa can be seen as a conidiation rhythm that produces concentric rings of bands (conidiating regions) alternating with interbands (non-conidiating regions) on the surface of an agar medium. To follow quantitatively this rhythm, densitometric analysis, gravimetric procedures, and video microscopy were employed. The circadian behavior of N. crassa is commonly monitored by cultivation in race tubes; in this work we report different growth kinetics during cultivation in conventional Petri dish cultures. Two different growth parameters were measured: total colony mass (true growth rate) and distance (colony radial expansion or hyphal elongation). Determinations of cellular mass revealed a dramatic circadian oscillation with a marked drop in growth rate during new interband formation followed by a sharp increase during the development of a new conidiation band. On the other hand, we found that the radial expansion of the colony previously reported to decrease periodically seemed unaffected by the circadian clock. Densitometric analysis showed no initial difference in the expanding margin of the colony, independent of whether that area was destined to be a band or an interband. The band areas increased rapidly in density for about 15 h whereas the interband areas maintained an equally rapid rate of increase for only 6h. The density of band areas kept increasing slowly for almost 40 h, along with an increase in the amount of conidia. Video microscopy showed the importance of cytoplasmic flow in colony development with continuous forward flow to support hyphal morphogenesis and reverse flow to support an extended period of conidiogenesis. Our results indicate that the circadian system of Neurospora can be expressed at the level of cellular mass formation, not just as the developmental conidiation rhythm.
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Affiliation(s)
- E Castro-Longoria
- Department of Microbiology, Center for Scientific Research and Higher Education of Ensenada (CICESE), Km. 107 Carretera Tijuana-Ensenada, 22860 Ensenada, Baja California, Mexico.
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45
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Tralau T, Lanthaler K, Robson GD, Crosthwaite SK. Circadian rhythmicity during prolonged chemostat cultivation of Neurospora crassa. Fungal Genet Biol 2006; 44:754-63. [PMID: 17196855 DOI: 10.1016/j.fgb.2006.11.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2006] [Revised: 11/06/2006] [Accepted: 11/07/2006] [Indexed: 10/23/2022]
Abstract
Following exposure to light and attainment of steady-state in the chemostat, Neurospora was grown in constant conditions of darkness at 25 degrees C for 6 days. Biomass samples were taken every 4h for the extraction of RNA and protein, and the state of the circadian clock was assessed by assaying the levels of three rhythmically expressed mRNAs; frequency (frq), antisense frq (qrf) and clock-controlled gene-14 (ccg-14), and by monitoring the clock-controlled rhythm of sporulation. Our results indicate that the Neurospora clock continued to run in the chemostat. This is the longest reported time that Neurospora has been grown in a chemostat in filamentous form and opens up the possibility of studying the response of Neurospora to a range of stimuli in the absence of confounding effects due to; alterations in growth rate, aging, and changing conditions of the growth medium.
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Affiliation(s)
- Tewes Tralau
- Faculty of Life Sciences, The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
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46
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Abstract
The accepted dogma in circadian biology is that the transcription factor CLOCK lies at the heart of the molecular clock that drives behavioral and molecular rhythms. In this issue of Neuron, the generation of CLOCK-deficient mice with only subtle clock defects by DeBruyne et al. shakes up this view of the mammalian clock.
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Affiliation(s)
- Ben Collins
- Biology Department, New York University, 100 Washington Square East, New York, New York 10003, USA
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47
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Abstract
Microorganisms provide important model systems for studying circadian rhythms, and they are overturning established ideas about the molecular mechanisms of rhythmicity. The transcription/translation feedback model that has been accepted as the basis of circadian clock mechanisms in eukaryotes does not account for old data from the alga Acetabularia demonstrating that transcription is not required for rhythmicity. Moreover, new results showing in vitro rhythmicity of KaiC protein phosphorylation in the cyanobacterium Synechococcus, and rhythmicity in strains of the fungus Neurospora carrying clock gene null mutations, require new ways of looking at circadian systems.
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48
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Abstract
The molecular mechanism of circadian rhythmicity is usually modeled by a transcription/translation feedback oscillator in which clock proteins negatively feed back on their own transcription to produce rhythmic levels of clock protein mRNAs, which in turn cause the production of rhythmic levels of clock proteins. This mechanism has been applied to all model organisms for which molecular data are available. This review summarizes the increasing number of anomalous observations that do not fit the standard molecular mechanism for the model organisms Acetabularia, Synechococcus, Drosophila, Neurospora, and mouse. The anomalies fall into 2 classes: observations of rhythmicity in the organism when transcription of clock genes is held constant, and rhythmicity in the organism when clock gene function is missing in knockout mutants. It is concluded that the weight of anomalies is now so large that the standard transcription/translation mechanism is no longer an adequate model for circadian oscillators. Rhythmic transcription may have other functions in the circadian system, such as participating in input and output pathways and providing robustness to the oscillations. It may be most useful to think in terms of a circadian system that uses a noncircadian oscillator consisting of metabolic feedback loops, which acquires its circadian properties from additional regulatory molecules such as the products of canonical clock genes.
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49
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Lakin-Thomas PL. Circadian clock genes frequency and white collar-1 are not essential for entrainment to temperature cycles in Neurospora crassa. Proc Natl Acad Sci U S A 2006; 103:4469-74. [PMID: 16537415 PMCID: PMC1450195 DOI: 10.1073/pnas.0510404103] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The fungus Neurospora crassa is a model system for investigating the mechanism of circadian rhythmicity, and the core of its circadian oscillator is thought to be a transcription/translation feedback loop involving the products of the frq (frequency), wc-1 (white-collar-1) and wc-2 (white-collar-2) genes. Several reports of rhythmicity in frq and wc null mutants have raised questions about how central the FRQ/WC loop is to the circadian system of Neurospora. Several research groups have attempted to answer this question by looking for entrainment of the conidiation banding rhythm in frq null mutants. Because the frq mutants are blind to light and cannot be entrained to light/dark cycles, these groups have used symmetric temperature cycles of equal-duration cool and warm phases to entrain the rhythm. Under these conditions, the direct effects of temperature on conidiation (masking effects) can compromise observations of the endogenous rhythm. I have reexamined this question by using short heat pulses to clearly separate masking from endogenous rhythms, and I have assayed entrainment in both frq and wc-1 null mutants. I found similar patterns of entrainment in the wild type and both mutant strains. Strong masking effects were found in the frq mutant but not in the wc-1 mutant. I conclude that a rapidly damping temperature-entrainable oscillator is present in the null mutants. A single temperature-entrainable oscillator may drive the conidiation rhythm in all strains, and additional properties such as light sensitivity and temperature compensation may be conferred by the intact FRQ/WC loop in the WT strain.
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50
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Merrow M, Spoelstra K, Roenneberg T. The circadian cycle: daily rhythms from behaviour to genes. EMBO Rep 2006; 6:930-5. [PMID: 16222241 PMCID: PMC1369194 DOI: 10.1038/sj.embor.7400541] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2005] [Accepted: 08/23/2005] [Indexed: 11/09/2022] Open
Abstract
The daily recurrence of activity and rest are so common as to seem trivial. However, they reflect a ubiquitous temporal programme called the circadian clock. In the absence of either anatomical clock structures or clock genes, the timing of sleep and wakefulness is disrupted. The complex nature of circadian behaviour is evident in the fact that phasing of the cycle during the day varies widely for individuals, resulting in extremes colloquially called 'larks' and 'owls'. These behavioural oscillations are mirrored in the levels of physiology and gene expression. Deciphering the underlying mechanisms will provide important insights into how the circadian clock affects health and disease.
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Affiliation(s)
- Martha Merrow
- Biologisch Centrum, University of Groningen, PO Box 14, 9750AA Haren, The Netherlands.
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