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Ekdahl LI, Salcedo JA, Dungan MM, Mason DV, Myagmarsuren D, Murphy HA. Selection on plastic adherence leads to hyper-multicellular strains and incidental virulence in the budding yeast. eLife 2023; 12:e81056. [PMID: 37916911 PMCID: PMC10764007 DOI: 10.7554/elife.81056] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Accepted: 11/01/2023] [Indexed: 11/03/2023] Open
Abstract
Many disease-causing microbes are not obligate pathogens; rather, they are environmental microbes taking advantage of an ecological opportunity. The existence of microbes whose life cycle does not require a host and are not normally pathogenic, yet are well-suited to host exploitation, is an evolutionary puzzle. One hypothesis posits that selection in the environment may favor traits that incidentally lead to pathogenicity and virulence, or serve as pre-adaptations for survival in a host. An example of such a trait is surface adherence. To experimentally test the idea of 'accidental virulence', replicate populations of Saccharomyces cerevisiae were evolved to attach to a plastic bead for hundreds of generations. Along with plastic adherence, two multicellular phenotypes- biofilm formation and flor formation- increased; another phenotype, pseudohyphal growth, responded to the nutrient limitation. Thus, experimental selection led to the evolution of highly-adherent, hyper-multicellular strains. Wax moth larvae injected with evolved hyper-multicellular strains were significantly more likely to die than those injected with evolved non-multicellular strains. Hence, selection on plastic adherence incidentally led to the evolution of enhanced multicellularity and increased virulence. Our results support the idea that selection for a trait beneficial in the open environment can inadvertently generate opportunistic, 'accidental' pathogens.
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Affiliation(s)
- Luke I Ekdahl
- Department of Biology, College of William and MaryWilliamsburgUnited States
| | - Juliana A Salcedo
- Department of Biology, College of William and MaryWilliamsburgUnited States
| | - Matthew M Dungan
- Department of Biology, College of William and MaryWilliamsburgUnited States
| | - Despina V Mason
- Department of Biology, College of William and MaryWilliamsburgUnited States
| | | | - Helen A Murphy
- Department of Biology, College of William and MaryWilliamsburgUnited States
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2
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Le Montagner P, Guilbaud M, Miot-Sertier C, Brocard L, Albertin W, Ballestra P, Dols-Lafargue M, Renouf V, Moine V, Bellon-Fontaine MN, Masneuf-Pomarède I. High intraspecific variation of the cell surface physico-chemical and bioadhesion properties in Brettanomyces bruxellensis. Food Microbiol 2023; 112:104217. [PMID: 36906300 DOI: 10.1016/j.fm.2023.104217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 01/11/2023] [Accepted: 01/17/2023] [Indexed: 01/19/2023]
Abstract
Brettanomyces bruxellensis is the most damaging spoilage yeast in the wine industry because of its negative impact on the wine organoleptic qualities. The strain persistence in cellars over several years associated with recurrent wine contamination suggest specific properties to persist and survive in the environment through bioadhesion phenomena. In this work, the physico-chemical surface properties, morphology and ability to adhere to stainless steel were studied both on synthetic medium and on wine. More than 50 strains representative of the genetic diversity of the species were considered. Microscopy techniques made it possible to highlight a high morphological diversity of the cells with the presence of pseudohyphae forms for some genetic groups. Analysis of the physico-chemical properties of the cell surface reveals contrasting behaviors: most of the strains display a negative surface charge and hydrophilic behavior while the Beer 1 genetic group has a hydrophobic behavior. All strains showed bioadhesion abilities on stainless steel after only 3 h with differences in the concentration of bioadhered cells ranging from 2.2 × 102 cell/cm2 to 7.6 × 106 cell/cm2. Finally, our results show high variability of the bioadhesion properties, the first step in the biofilm formation, according to the genetic group with the most marked bioadhesion capacity for the beer group.
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Affiliation(s)
- Paul Le Montagner
- Univ. Bordeaux, INRAE, Bordeaux INP, Bordeaux Sciences Agro, OENO, UMR 1366, ISVV, 33140, Villenave d'Ornon, France; Laboratoire EXCELL, Floirac, France; Biolaffort, Floirac, France.
| | - Morgan Guilbaud
- Univ. Paris-Saclay, SayFood, AgroParisTech, INRAE UMR 782, 91300, Massy, France
| | - Cécile Miot-Sertier
- Univ. Bordeaux, INRAE, Bordeaux INP, Bordeaux Sciences Agro, OENO, UMR 1366, ISVV, 33140, Villenave d'Ornon, France
| | - Lysiane Brocard
- Univ. Bordeaux, Plant Imaging Platform, Bordeaux Imaging Center, UMS 3420, CNRS, 33000, Bordeaux, France
| | - Warren Albertin
- Univ. Bordeaux, INRAE, Bordeaux INP, Bordeaux Sciences Agro, OENO, UMR 1366, ISVV, 33140, Villenave d'Ornon, France; ENSCBP, Bordeaux INP, 33600, Pessac, France
| | - Patricia Ballestra
- Univ. Bordeaux, INRAE, Bordeaux INP, Bordeaux Sciences Agro, OENO, UMR 1366, ISVV, 33140, Villenave d'Ornon, France
| | - Marguerite Dols-Lafargue
- Univ. Bordeaux, INRAE, Bordeaux INP, Bordeaux Sciences Agro, OENO, UMR 1366, ISVV, 33140, Villenave d'Ornon, France; ENSCBP, Bordeaux INP, 33600, Pessac, France
| | | | | | | | - Isabelle Masneuf-Pomarède
- Univ. Bordeaux, INRAE, Bordeaux INP, Bordeaux Sciences Agro, OENO, UMR 1366, ISVV, 33140, Villenave d'Ornon, France; Bordeaux Sciences Agro, 33175, Gradignan, France
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3
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Britton SJ, Rogers LJ, White JS, Neven H, Maskell DL. Disparity in pseudohyphal morphogenic switching response to the quorum sensing molecule 2-phenylethanol in commercial brewing strains of Saccharomyces cerevisiae. FEMS MICROBES 2023; 4:xtad002. [PMID: 37333439 PMCID: PMC10117810 DOI: 10.1093/femsmc/xtad002] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 12/22/2022] [Accepted: 01/06/2023] [Indexed: 12/03/2023] Open
Abstract
Saccharomyces cerevisiae can undergo filamentous growth in response to specific environmental stressors, particularly nitrogen-limitation, whereby cells undergo pseudohyphal differentiation, a process where cells transition from a singular ellipsoidal appearance to multicellular filamentous chains from the incomplete scission of the mother-daughter cells. Previously, it was demonstrated that filamentous growth in S. cerevisiae is co-regulated by multiple signaling networks, including the glucose-sensing RAS/cAMP-PKA and SNF pathways, the nutrient-sensing TOR pathway, the filamentous growth MAPK pathway, and the Rim101 pathway, and can be induced by quorum-sensing aromatic alcohols, such as 2-phenylethanol. However, the prevalent research on the yeast-pseudohyphal transition and its induction by aromatic alcohols in S. cerevisiae has been primarily limited to the strain Σ1278b. Due to the prospective influence of quorum sensing on commercial fermentation, the native variation of yeast-to-filamentous phenotypic transition and its induction by 2-phenylethanol in commercial brewing strains was investigated. Image analysis software was exploited to enumerate the magnitude of whole colony filamentation in 16 commercial strains cultured on nitrogen-limiting SLAD medium; some supplemented with exogenous 2-phenylethanol. The results demonstrate that phenotypic switching is a generalized, highly varied response occurring only in select brewing strains. Nevertheless, strains exhibiting switching behavior altered their filamentation response to exogenous concentrations of 2-phenylethanol.
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Affiliation(s)
- Scott J Britton
- International Centre for Brewing and Distilling, Institute of Biological Chemistry, Biophysics, and Bioengineering, School of Engineering and Physical Sciences, Heriot-Watt University, EH14 4AS Edinburgh, United Kingdom
- Research & Development, Brewery Duvel Moortgat, 2870 Puurs-Sint-Amands, Belgium
| | | | - Jane S White
- International Centre for Brewing and Distilling, Institute of Biological Chemistry, Biophysics, and Bioengineering, School of Engineering and Physical Sciences, Heriot-Watt University, EH14 4AS Edinburgh, United Kingdom
| | - Hedwig Neven
- Research & Development, Brewery Duvel Moortgat, 2870 Puurs-Sint-Amands, Belgium
- Department M2S, Centre for Food and Microbial Technology (CLMT), KU Leuven, 3000 Leuven, Belgium
| | - Dawn L Maskell
- International Centre for Brewing and Distilling, Institute of Biological Chemistry, Biophysics, and Bioengineering, School of Engineering and Physical Sciences, Heriot-Watt University, EH14 4AS Edinburgh, United Kingdom
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4
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Winters M, Aru V, Howell K, Arneborg N. Saccharomyces cerevisiae does not undergo a quorum sensing-dependent switch of budding pattern. Sci Rep 2022; 12:8738. [PMID: 35610257 PMCID: PMC9130263 DOI: 10.1038/s41598-022-12308-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 02/21/2022] [Indexed: 11/29/2022] Open
Abstract
Saccharomyces cerevisiae can alter its morphology to a filamentous form associated with unipolar budding in response to environmental stressors. Induction of filamentous growth is suggested under nitrogen deficiency in response to alcoholic signalling molecules through quorum sensing. To investigate this further, we analysed the budding pattern of S. cerevisiae cells over time under low nitrogen conditions while concurrently measuring cell density and extracellular metabolite concentration. We found that the proportion of cells displaying unipolar budding increased between local cell densities of 4.8 × 106 and 5.3 × 107 cells/ml. This increase in unipolar budding was not reproduced with cells growing at the critical cell density and in conditioned media. Growth under high nitrogen conditions also resulted in increased unipolar budding between local cell densities of 5.2 × 106 and 8.2 × 107 cells/ml, but with differences in metabolite concentration compared to low nitrogen conditions. Neither cell density, metabolite concentration, nor nitrogen deficiency were therefore sufficient to increase unipolar budding. Therefore, by using the budding pattern as an early indicator of filamentous growth, our results suggest that quorum sensing may not control the switch of budding behaviour in S. cerevisiae. Only a high concentration of the putative signalling molecule, 2-phenylethanol, resulted in an increase in unipolar budding. However, this concentration was not physiologically relevant, suggesting toxicity rather than a known quorum sensing mechanism.
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Affiliation(s)
- Michela Winters
- School of Agriculture and Food, Faculty of Veterinary and Agricultural Science, University of Melbourne, Parkville, 3010, Australia
| | - Violetta Aru
- Department of Food Science, University of Copenhagen, 1958, Frederiksberg, Denmark
| | - Kate Howell
- School of Agriculture and Food, Faculty of Veterinary and Agricultural Science, University of Melbourne, Parkville, 3010, Australia.
| | - Nils Arneborg
- Department of Food Science, University of Copenhagen, 1958, Frederiksberg, Denmark
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Xiang Neik T, Ghanbarnia K, Ollivier B, Scheben A, Severn‐Ellis A, Larkan NJ, Haddadi P, Fernando DWG, Rouxel T, Batley J, Borhan HM, Balesdent M. Two independent approaches converge to the cloning of a new Leptosphaeria maculans avirulence effector gene, AvrLmS-Lep2. MOLECULAR PLANT PATHOLOGY 2022; 23:733-748. [PMID: 35239989 PMCID: PMC8995059 DOI: 10.1111/mpp.13194] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 01/24/2022] [Accepted: 02/01/2022] [Indexed: 05/10/2023]
Abstract
Brassica napus (oilseed rape, canola) seedling resistance to Leptosphaeria maculans, the causal agent of blackleg (stem canker) disease, follows a gene-for-gene relationship. The avirulence genes AvrLmS and AvrLep2 were described to be perceived by the resistance genes RlmS and LepR2, respectively, present in B. napus 'Surpass 400'. Here we report cloning of AvrLmS and AvrLep2 using two independent methods. AvrLmS was cloned using combined in vitro crossing between avirulent and virulent isolates with sequencing of DNA bulks from avirulent or virulent progeny (bulked segregant sequencing). AvrLep2 was cloned using a biparental cross of avirulent and virulent L. maculans isolates and a classical map-based cloning approach. Taking these two approaches independently, we found that AvrLmS and AvrLep2 are the same gene. Complementation of virulent isolates with this gene confirmed its role in inducing resistance on Surpass 400, Topas-LepR2, and an RlmS-line. The gene, renamed AvrLmS-Lep2, encodes a small cysteine-rich protein of unknown function with an N-terminal secretory signal peptide, which is a common feature of the majority of effectors from extracellular fungal plant pathogens. The AvrLmS-Lep2/LepR2 interaction phenotype was found to vary from a typical hypersensitive response through intermediate resistance sometimes towards susceptibility, depending on the inoculation conditions. AvrLmS-Lep2 was nevertheless sufficient to significantly slow the systemic growth of the pathogen and reduce the stem lesion size on plant genotypes with LepR2, indicating the potential efficiency of this resistance to control the disease in the field.
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Affiliation(s)
- Ting Xiang Neik
- School of Biological SciencesUniversity of Western AustraliaPerthWestern AustraliaAustralia
| | - Kaveh Ghanbarnia
- Agriculture and Agri‐Food CanadaSaskatoon Research CenterSaskatoonSaskatchewanCanada
- Department of Plant SciencesUniversity of ManitobaWinnipegManitobaCanada
| | | | - Armin Scheben
- School of Biological SciencesUniversity of Western AustraliaPerthWestern AustraliaAustralia
- Simons Center for Quantitative Biology, Cold Spring Harbor LaboratoryCold Spring HarborNew YorkUSA
| | - Anita Severn‐Ellis
- School of Biological SciencesUniversity of Western AustraliaPerthWestern AustraliaAustralia
| | - Nicholas J. Larkan
- Agriculture and Agri‐Food CanadaSaskatoon Research CenterSaskatoonSaskatchewanCanada
- Armatus Genetics Inc.SaskatoonSaskatchewanCanada
| | - Parham Haddadi
- Agriculture and Agri‐Food CanadaSaskatoon Research CenterSaskatoonSaskatchewanCanada
| | | | - Thierry Rouxel
- Université Paris‐SaclayINRAEUR BIOGERThiverval‐GrignonFrance
| | - Jacqueline Batley
- School of Biological SciencesUniversity of Western AustraliaPerthWestern AustraliaAustralia
| | - Hossein M. Borhan
- Agriculture and Agri‐Food CanadaSaskatoon Research CenterSaskatoonSaskatchewanCanada
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6
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Abstract
Quorum sensing (QS) is one of the most studied cell-cell communication mechanisms in fungi. Research in the last 20 years has explored various fungal QS systems that are involved in a wide range of biological processes, especially eukaryote- or fungus-specific behaviors, mirroring the significant contribution of QS regulation to fungal biology and evolution. Based on recent progress, we summarize in this review fungal QS regulation, with an emphasis on its functional role in behaviors unique to fungi or eukaryotes. We suggest that using fungi as genetically amenable eukaryotic model systems to address why and how QS regulation is integrated into eukaryotic reproductive strategies and molecular or cellular processes could be an important direction for QS research. Expected final online publication date for the Annual Review of Microbiology, Volume 75 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Xiuyun Tian
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; .,University of Chinese Academy of Sciences, Beijing 100039, China
| | - Hao Ding
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; .,University of Chinese Academy of Sciences, Beijing 100039, China
| | - Weixin Ke
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; .,University of Chinese Academy of Sciences, Beijing 100039, China
| | - Linqi Wang
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; .,University of Chinese Academy of Sciences, Beijing 100039, China
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7
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Kumar A. The Complex Genetic Basis and Multilayered Regulatory Control of Yeast Pseudohyphal Growth. Annu Rev Genet 2021; 55:1-21. [PMID: 34280314 DOI: 10.1146/annurev-genet-071719-020249] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Eukaryotic cells are exquisitely responsive to external and internal cues, achieving precise control of seemingly diverse growth processes through a complex interplay of regulatory mechanisms. The budding yeast Saccharomyces cerevisiae provides a fascinating model of cell growth in its stress-responsive transition from planktonic single cells to a filamentous pseudohyphal growth form. During pseudohyphal growth, yeast cells undergo changes in morphology, polarity, and adhesion to form extended and invasive multicellular filaments. This pseudohyphal transition has been studied extensively as a model of conserved signaling pathways regulating cell growth and for its relevance in understanding the pathogenicity of the related opportunistic fungus Candida albicans, wherein filamentous growth is required for virulence. This review highlights the broad gene set enabling yeast pseudohyphal growth, signaling pathways that regulate this process, the role and regulation of proteins conferring cell adhesion, and interesting regulatory mechanisms enabling the pseudohyphal transition. Expected final online publication date for the Annual Review of Genetics, Volume 55 is November 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Anuj Kumar
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109, USA;
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8
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Abstract
Most of the yeast bypasses the developmental stage from simple unicellular yeast to elongated structure like hyphae. Regulation of this transition is governed by various quorum sensing and signalling molecules produced under different conditions of growth, that differ significantly, both physiologically and chemically. The evidence of fungal quorum sensing was uncovered ten years ago after the discovery of farnesol as first eukaryotic quorum sensing molecules in Candida albicans. In addition to farnesol, tyrosol was identified as second quorum sensing molecules in C. albicans controlling physiological activities. After the discovery of farnesol and tyrosol, regulation of morphogenesis through the production of chemical signalling molecules such as isoamyl alcohol, 2-phenylethyl alcohol, 1-dodecanol, E-nerolidol, etc. is reported in C. albicans. Some of the evidence suggests that the budding yeast Saccharomyces cerevisiae exhibits this type of regulation and the signals are regulated by aromatic alcohols which are the end product of amino acid metabolism. The effects of these molecules on morphogenesis are not similar in both yeasts, making comparisons hard. It is hypothesized that these signals works in microorganisms to derive a competitive advantage. Here, we present an example for utilization of competitive strategy by C. albicans and S. cerevisiae over other microorganisms.
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Affiliation(s)
| | - S Mohan Karuppayil
- Professor and Head, Department of Stem Cell & Regenerative Medicine and Medical Biotechnology, D Y Patil Education Society, Kasaba Bawada, Kolhapur, Maharashtra 416006, India
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9
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Britton SJ, Neven H, Maskell DL. Microbial Small-Talk: Does Quorum Sensing Play a Role in Beer Fermentation? JOURNAL OF THE AMERICAN SOCIETY OF BREWING CHEMISTS 2020. [DOI: 10.1080/03610470.2020.1843928] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Scott J. Britton
- Research & Development, Duvel Moortgat, Puurs-Sint-Amands, Belgium
- International Centre for Brewing and Distilling, Institute of Biological Chemistry, Biophysics and Bioengineering, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, UK
| | - Hedwig Neven
- Research & Development, Duvel Moortgat, Puurs-Sint-Amands, Belgium
- Centre for Food and Microbial Technology (CLMT), Department M2S, KU Leuven, Leuven, Belgium
| | - Dawn L. Maskell
- International Centre for Brewing and Distilling, Institute of Biological Chemistry, Biophysics and Bioengineering, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, UK
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10
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Vandermeulen MD, Cullen PJ. New Aspects of Invasive Growth Regulation Identified by Functional Profiling of MAPK Pathway Targets in Saccharomyces cerevisiae. Genetics 2020; 216:95-116. [PMID: 32665277 PMCID: PMC7463291 DOI: 10.1534/genetics.120.303369] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2020] [Accepted: 07/07/2020] [Indexed: 12/21/2022] Open
Abstract
MAPK pathways are drivers of morphogenesis and stress responses in eukaryotes. A major function of MAPK pathways is the transcriptional induction of target genes, which produce proteins that collectively generate a cellular response. One approach to comprehensively understand how MAPK pathways regulate cellular responses is to characterize the individual functions of their transcriptional targets. Here, by examining uncharacterized targets of the MAPK pathway that positively regulates filamentous growth in Saccharomyces cerevisiae (fMAPK pathway), we identified a new role for the pathway in negatively regulating invasive growth. Specifically, four targets were identified that had an inhibitory role in invasive growth: RPI1, RGD2, TIP1, and NFG1/YLR042cNFG1 was a highly induced unknown open reading frame that negatively regulated the filamentous growth MAPK pathway. We also identified SFG1, which encodes a transcription factor, as a target of the fMAPK pathway. Sfg1p promoted cell adhesion independently from the fMAPK pathway target and major cell adhesion flocculin Flo11p, by repressing genes encoding presumptive cell-wall-degrading enzymes. Sfg1p also contributed to FLO11 expression. Sfg1p and Flo11p regulated different aspects of cell adhesion, and their roles varied based on the environment. Sfg1p also induced an elongated cell morphology, presumably through a cell-cycle delay. Thus, the fMAPK pathway coordinates positive and negative regulatory proteins to fine-tune filamentous growth resulting in a nuanced response. Functional analysis of other pathways' targets may lead to a more comprehensive understanding of how signaling cascades generate biological responses.
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Affiliation(s)
| | - Paul J Cullen
- Department of Biological Sciences, University at Buffalo, New York 14260-1300
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11
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Rowlands H, Shaban K, Foster B, Proteau Y, Yankulov K. Histone chaperones and the Rrm3p helicase regulate flocculation in S. cerevisiae. Epigenetics Chromatin 2019; 12:56. [PMID: 31547833 PMCID: PMC6757361 DOI: 10.1186/s13072-019-0303-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2019] [Accepted: 09/03/2019] [Indexed: 12/16/2022] Open
Abstract
Background Biofilm formation or flocculation is a major phenotype in wild type budding yeasts but rarely seen in laboratory yeast strains. Here, we analysed flocculation phenotypes and the expression of FLO genes in laboratory strains with various genetic backgrounds. Results We show that mutations in histone chaperones, the helicase RRM3 and the Histone Deacetylase HDA1 de-repress the FLO genes and partially reconstitute flocculation. We demonstrate that the loss of repression correlates to elevated expression of several FLO genes, to increased acetylation of histones at the promoter of FLO1 and to variegated expression of FLO11. We show that these effects are related to the activity of CAF-1 at the replication forks. We also demonstrate that nitrogen starvation or inhibition of histone deacetylases do not produce flocculation in W303 and BY4742 strains but do so in strains compromised for chromatin maintenance. Finally, we correlate the de-repression of FLO genes to the loss of silencing at the subtelomeric and mating type gene loci. Conclusions We conclude that the deregulation of chromatin maintenance and transmission is sufficient to reconstitute flocculation in laboratory yeast strains. Consequently, we propose that a gain in epigenetic silencing is a major contributing factor for the loss of flocculation phenotypes in these strains. We suggest that flocculation in yeasts provides an excellent model for addressing the challenging issue of how epigenetic mechanisms contribute to evolution.
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Affiliation(s)
- Hollie Rowlands
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Canada
| | - Kholoud Shaban
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Canada
| | - Barret Foster
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Canada
| | - Yannic Proteau
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Canada
| | - Krassimir Yankulov
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Canada.
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