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Hackley RK, Hwang S, Herb JT, Bhanap P, Lam K, Vreugdenhil A, Darnell CL, Pastor MM, Martin JH, Maupin-Furlow JA, Schmid AK. TbsP and TrmB jointly regulate gapII to influence cell development phenotypes in the archaeon Haloferax volcanii. Mol Microbiol 2024; 121:742-766. [PMID: 38204420 PMCID: PMC11023807 DOI: 10.1111/mmi.15225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 12/09/2023] [Accepted: 12/22/2023] [Indexed: 01/12/2024]
Abstract
Microbial cells must continually adapt their physiology in the face of changing environmental conditions. Archaea living in extreme conditions, such as saturated salinity, represent important examples of such resilience. The model salt-loving organism Haloferax volcanii exhibits remarkable plasticity in its morphology, biofilm formation, and motility in response to variations in nutrients and cell density. However, the mechanisms regulating these lifestyle transitions remain unclear. In prior research, we showed that the transcriptional regulator, TrmB, maintains the rod shape in the related species Halobacterium salinarum by activating the expression of enzyme-coding genes in the gluconeogenesis metabolic pathway. In Hbt. salinarum, TrmB-dependent production of glucose moieties is required for cell surface glycoprotein biogenesis. Here, we use a combination of genetics and quantitative phenotyping assays to demonstrate that TrmB is essential for growth under gluconeogenic conditions in Hfx. volcanii. The ∆trmB strain rapidly accumulated suppressor mutations in a gene encoding a novel transcriptional regulator, which we name trmB suppressor, or TbsP (a.k.a. "tablespoon"). TbsP is required for adhesion to abiotic surfaces (i.e., biofilm formation) and maintains wild-type cell morphology and motility. We use functional genomics and promoter fusion assays to characterize the regulons controlled by each of TrmB and TbsP, including joint regulation of the glucose-dependent transcription of gapII, which encodes an important gluconeogenic enzyme. We conclude that TrmB and TbsP coregulate gluconeogenesis, with downstream impacts on lifestyle transitions in response to nutrients in Hfx. volcanii.
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Affiliation(s)
- Rylee K. Hackley
- Biology Department, Duke University, Durham, North Carolina, USA
- University Program in Genetics and Genomics, Duke University, Durham, North Carolina, USA
| | - Sungmin Hwang
- Biology Department, Duke University, Durham, North Carolina, USA
| | - Jake T. Herb
- Biology Department, Duke University, Durham, North Carolina, USA
| | - Preeti Bhanap
- Biology Department, Duke University, Durham, North Carolina, USA
| | - Katie Lam
- Biology Department, Duke University, Durham, North Carolina, USA
| | | | | | | | - Johnathan H. Martin
- Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, Florida, USA
| | - Julie A. Maupin-Furlow
- Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, Florida, USA
- Genetics Institute, University of Florida, Gainesville, Florida, USA
| | - Amy K. Schmid
- Biology Department, Duke University, Durham, North Carolina, USA
- University Program in Genetics and Genomics, Duke University, Durham, North Carolina, USA
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Martinez Pastor M, Sakrikar S, Hwang S, Hackley R, Soborowski A, Maupin-Furlow J, Schmid A. TroR is the primary regulator of the iron homeostasis transcription network in the halophilic archaeon Haloferax volcanii. Nucleic Acids Res 2024; 52:125-140. [PMID: 37994787 PMCID: PMC10783522 DOI: 10.1093/nar/gkad997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Revised: 10/10/2023] [Accepted: 10/23/2023] [Indexed: 11/24/2023] Open
Abstract
Maintaining the intracellular iron concentration within the homeostatic range is vital to meet cellular metabolic needs and reduce oxidative stress. Previous research revealed that the haloarchaeon Halobacterium salinarum encodes four diphtheria toxin repressor (DtxR) family transcription factors (TFs) that together regulate the iron response through an interconnected transcriptional regulatory network (TRN). However, the conservation of the TRN and the metal specificity of DtxR TFs remained poorly understood. Here we identified and characterized the TRN of Haloferax volcanii for comparison. Genetic analysis demonstrated that Hfx. volcanii relies on three DtxR transcriptional regulators (Idr, SirR, and TroR), with TroR as the primary regulator of iron homeostasis. Bioinformatics and molecular approaches revealed that TroR binds a conserved cis-regulatory motif located ∼100 nt upstream of the start codon of iron-related target genes. Transcriptomics analysis demonstrated that, under conditions of iron sufficiency, TroR repressed iron uptake and induced iron storage mechanisms. TroR repressed the expression of one other DtxR TF, Idr. This reduced DtxR TRN complexity relative to that of Hbt. salinarum appeared correlated with natural variations in iron availability. Based on these data, we hypothesize that variable environmental conditions such as iron availability appear to select for increasing TRN complexity.
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Affiliation(s)
| | - Saaz Sakrikar
- Center for Genomics and System Biology at NYU Department of Biology, New York University, NY, NY 10003, USA
| | - Sungmin Hwang
- Division of Practical Research, Honam National Institute of Biological Resources, Jeollanam-do, Mokpo-si 58762, Republic of Korea
| | - Rylee K Hackley
- Department of Biology, Duke University, Durham, NC 27708, USA
- University Program in Genetics and Genomics, Duke University, Durham, NC 27708, USA
| | - Andrew L Soborowski
- Department of Biology, Duke University, Durham, NC 27708, USA
- Computational Biology and Bioinformatics graduate program, Duke University, Durham, NC 27708, USA
| | - Julie A Maupin-Furlow
- Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611, USA
- Genetics Institute, University of Florida, Gainesville, FL 32611, USA
| | - Amy K Schmid
- Department of Biology, Duke University, Durham, NC 27708, USA
- University Program in Genetics and Genomics, Duke University, Durham, NC 27708, USA
- Computational Biology and Bioinformatics graduate program, Duke University, Durham, NC 27708, USA
- Center for Genomics and Computational Biology, Duke University, Durham, NC 27708, USA
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Hackley RK, Vreugdenhil-Hayslette A, Darnell CL, Schmid AK. A conserved transcription factor controls gluconeogenesis via distinct targets in hypersaline-adapted archaea with diverse metabolic capabilities. PLoS Genet 2024; 20:e1011115. [PMID: 38227606 PMCID: PMC10817205 DOI: 10.1371/journal.pgen.1011115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Revised: 01/26/2024] [Accepted: 12/22/2023] [Indexed: 01/18/2024] Open
Abstract
Timely regulation of carbon metabolic pathways is essential for cellular processes and to prevent futile cycling of intracellular metabolites. In Halobacterium salinarum, a hypersaline adapted archaeon, a sugar-sensing TrmB family protein controls gluconeogenesis and other biosynthetic pathways. Notably, Hbt. salinarum does not utilize carbohydrates for energy, uncommon among Haloarchaea. We characterized a TrmB-family transcriptional regulator in a saccharolytic generalist, Haloarcula hispanica, to investigate whether the targets and function of TrmB, or its regulon, is conserved in related species with distinct metabolic capabilities. In Har. hispanica, TrmB binds to 15 sites in the genome and induces the expression of genes primarily involved in gluconeogenesis and tryptophan biosynthesis. An important regulatory control point in Hbt. salinarum, activation of ppsA and repression of pykA, is absent in Har. hispanica. Contrary to its role in Hbt. salinarum and saccharolytic hyperthermophiles, TrmB does not act as a global regulator: it does not directly repress the expression of glycolytic enzymes, peripheral pathways such as cofactor biosynthesis, or catabolism of other carbon sources in Har. hispanica. Cumulatively, these findings suggest rewiring of the TrmB regulon alongside metabolic network evolution in Haloarchaea.
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Affiliation(s)
- Rylee K. Hackley
- Department of Biology, Duke University, Durham, North Carolina, United States of America
- University Program in Genetics and Genomics, Duke University, Durham, North Carolina, United States of America
| | | | - Cynthia L. Darnell
- Department of Biology, Duke University, Durham, North Carolina, United States of America
| | - Amy K. Schmid
- Department of Biology, Duke University, Durham, North Carolina, United States of America
- University Program in Genetics and Genomics, Duke University, Durham, North Carolina, United States of America
- Center for Genomics and Computational Biology, Duke University, Durham, North Carolina, United States of America
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4
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Marinov GK, Bagdatli ST, Wu T, He C, Kundaje A, Greenleaf WJ. The chromatin landscape of the euryarchaeon Haloferax volcanii. Genome Biol 2023; 24:253. [PMID: 37932847 PMCID: PMC10626798 DOI: 10.1186/s13059-023-03095-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 10/24/2023] [Indexed: 11/08/2023] Open
Abstract
BACKGROUND Archaea, together with Bacteria, represent the two main divisions of life on Earth, with many of the defining characteristics of the more complex eukaryotes tracing their origin to evolutionary innovations first made in their archaeal ancestors. One of the most notable such features is nucleosomal chromatin, although archaeal histones and chromatin differ significantly from those of eukaryotes, not all archaea possess histones and it is not clear if histones are a main packaging component for all that do. Despite increased interest in archaeal chromatin in recent years, its properties have been little studied using genomic tools. RESULTS Here, we adapt the ATAC-seq assay to archaea and use it to map the accessible landscape of the genome of the euryarchaeote Haloferax volcanii. We integrate the resulting datasets with genome-wide maps of active transcription and single-stranded DNA (ssDNA) and find that while H. volcanii promoters exist in a preferentially accessible state, unlike most eukaryotes, modulation of transcriptional activity is not associated with changes in promoter accessibility. Applying orthogonal single-molecule footprinting methods, we quantify the absolute levels of physical protection of H. volcanii and find that Haloferax chromatin is similarly or only slightly more accessible, in aggregate, than that of eukaryotes. We also evaluate the degree of coordination of transcription within archaeal operons and make the unexpected observation that some CRISPR arrays are associated with highly prevalent ssDNA structures. CONCLUSIONS Our results provide the first comprehensive maps of chromatin accessibility and active transcription in Haloferax across conditions and thus a foundation for future functional studies of archaeal chromatin.
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Affiliation(s)
- Georgi K Marinov
- Department of Genetics, Stanford University, Stanford, CA, 94305, USA.
| | - S Tansu Bagdatli
- Department of Genetics, Stanford University, Stanford, CA, 94305, USA
| | - Tong Wu
- Department of Chemistry and Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL, 60637, USA
| | - Chuan He
- Department of Chemistry and Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL, 60637, USA
- Department of Biochemistry and Molecular Biology and Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL, 60637, USA
- Howard Hughes Medical Institute, The University of Chicago, Chicago, IL, 60637, USA
| | - Anshul Kundaje
- Department of Genetics, Stanford University, Stanford, CA, 94305, USA
- Department of Computer Science, Stanford University, Stanford, CA, 94305, USA
| | - William J Greenleaf
- Department of Genetics, Stanford University, Stanford, CA, 94305, USA
- Center for Personal Dynamic Regulomes, Stanford University, Stanford, CA, 94305, USA
- Department of Applied Physics, Stanford University, Stanford, CA, 94305, USA
- Chan Zuckerberg Biohub, San Francisco, CA, USA
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Marinov GK, Doughty B, Kundaje A, Greenleaf WJ. The landscape of the histone-organized chromatin of Bdellovibrionota bacteria. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.30.564843. [PMID: 37961278 PMCID: PMC10634947 DOI: 10.1101/2023.10.30.564843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Histone proteins have traditionally been thought to be restricted to eukaryotes and most archaea, with eukaryotic nucleosomal histones deriving from their archaeal ancestors. In contrast, bacteria lack histones as a rule. However, histone proteins have recently been identified in a few bacterial clades, most notably the phylum Bdellovibrionota, and these histones have been proposed to exhibit a range of divergent features compared to histones in archaea and eukaryotes. However, no functional genomic studies of the properties of Bdellovibrionota chromatin have been carried out. In this work, we map the landscape of chromatin accessibility, active transcription and three-dimensional genome organization in a member of Bdellovibrionota (a Bacteriovorax strain). We find that, similar to what is observed in some archaea and in eukaryotes with compact genomes such as yeast, Bacteriovorax chromatin is characterized by preferential accessibility around promoter regions. Similar to eukaryotes, chromatin accessibility in Bacteriovorax positively correlates with gene expression. Mapping active transcription through single-strand DNA (ssDNA) profiling revealed that unlike in yeast, but similar to the state of mammalian and fly promoters, Bacteriovorax promoters exhibit very strong polymerase pausing. Finally, similar to that of other bacteria without histones, the Bacteriovorax genome exists in a three-dimensional (3D) configuration organized by the parABS system along the axis defined by replication origin and termination regions. These results provide a foundation for understanding the chromatin biology of the unique Bdellovibrionota bacteria and the functional diversity in chromatin organization across the tree of life.
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Affiliation(s)
- Georgi K Marinov
- Department of Genetics, Stanford University, Stanford, California 94305, USA
| | - Benjamin Doughty
- Department of Genetics, Stanford University, Stanford, California 94305, USA
| | - Anshul Kundaje
- Department of Genetics, Stanford University, Stanford, California 94305, USA
- Department of Computer Science, Stanford University, Stanford, California 94305, USA
| | - William J Greenleaf
- Department of Genetics, Stanford University, Stanford, California 94305, USA
- Center for Personal Dynamic Regulomes, Stanford University, Stanford, California 94305, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
- Arc Institute, Palo Alto, California, USA
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Ofer S, Blombach F, Erkelens AM, Barker D, Soloviev Z, Schwab S, Smollett K, Matelska D, Fouqueau T, van der Vis N, Kent NA, Thalassinos K, Dame RT, Werner F. DNA-bridging by an archaeal histone variant via a unique tetramerisation interface. Commun Biol 2023; 6:968. [PMID: 37740023 PMCID: PMC10516927 DOI: 10.1038/s42003-023-05348-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Accepted: 09/12/2023] [Indexed: 09/24/2023] Open
Abstract
In eukaryotes, histone paralogues form obligate heterodimers such as H3/H4 and H2A/H2B that assemble into octameric nucleosome particles. Archaeal histones are dimeric and assemble on DNA into 'hypernucleosome' particles of varying sizes with each dimer wrapping 30 bp of DNA. These are composed of canonical and variant histone paralogues, but the function of these variants is poorly understood. Here, we characterise the structure and function of the histone paralogue MJ1647 from Methanocaldococcus jannaschii that has a unique C-terminal extension enabling homotetramerisation. The 1.9 Å X-ray structure of a dimeric MJ1647 species, structural modelling of the tetramer, and site-directed mutagenesis reveal that the C-terminal tetramerization module consists of two alpha helices in a handshake arrangement. Unlike canonical histones, MJ1647 tetramers can bridge two DNA molecules in vitro. Using single-molecule tethered particle motion and DNA binding assays, we show that MJ1647 tetramers bind ~60 bp DNA and compact DNA in a highly cooperative manner. We furthermore show that MJ1647 effectively competes with the transcription machinery to block access to the promoter in vitro. To the best of our knowledge, MJ1647 is the first histone shown to have DNA bridging properties, which has important implications for genome structure and gene expression in archaea.
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Affiliation(s)
- Sapir Ofer
- Institute for Structural and Molecular Biology, Division of Biosciences, University College London, Darwin Building, Gower Street, London, WC1E 6BT, UK
| | - Fabian Blombach
- Institute for Structural and Molecular Biology, Division of Biosciences, University College London, Darwin Building, Gower Street, London, WC1E 6BT, UK
| | - Amanda M Erkelens
- Leiden Institute of Chemistry, Leiden University, Leiden, the Netherlands
| | - Declan Barker
- Institute for Structural and Molecular Biology, Division of Biosciences, University College London, Darwin Building, Gower Street, London, WC1E 6BT, UK
| | - Zoja Soloviev
- Institute for Structural and Molecular Biology, Division of Biosciences, University College London, Darwin Building, Gower Street, London, WC1E 6BT, UK
| | - Samuel Schwab
- Leiden Institute of Chemistry, Leiden University, Leiden, the Netherlands
| | - Katherine Smollett
- Institute for Structural and Molecular Biology, Division of Biosciences, University College London, Darwin Building, Gower Street, London, WC1E 6BT, UK
| | - Dorota Matelska
- Institute for Structural and Molecular Biology, Division of Biosciences, University College London, Darwin Building, Gower Street, London, WC1E 6BT, UK
- Centre for Genomics Research, Discovery Sciences, BioPharmaceuticals R&D, AstraZeneca, Cambridge, UK
| | - Thomas Fouqueau
- Institute for Structural and Molecular Biology, Division of Biosciences, University College London, Darwin Building, Gower Street, London, WC1E 6BT, UK
| | - Nico van der Vis
- Leiden Institute of Chemistry, Leiden University, Leiden, the Netherlands
| | - Nicholas A Kent
- School of Biosciences, Cardiff University, Museum Avenue, Cardiff, CF10 3AX, UK
| | - Konstantinos Thalassinos
- Institute for Structural and Molecular Biology, Division of Biosciences, University College London, Darwin Building, Gower Street, London, WC1E 6BT, UK
| | - Remus T Dame
- Leiden Institute of Chemistry, Leiden University, Leiden, the Netherlands.
| | - Finn Werner
- Institute for Structural and Molecular Biology, Division of Biosciences, University College London, Darwin Building, Gower Street, London, WC1E 6BT, UK.
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Integrative Multiomics Analysis of the Heat Stress Response of Enterococcus faecium. Biomolecules 2023; 13:biom13030437. [PMID: 36979372 PMCID: PMC10046512 DOI: 10.3390/biom13030437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2022] [Revised: 02/20/2023] [Accepted: 02/22/2023] [Indexed: 03/02/2023] Open
Abstract
A continuous heat-adaptation test was conducted for one Enterococcus faecium (E. faecium) strain wild-type (WT) RS047 to obtain a high-temperature-resistant strain. After domestication, the strain was screened with a significantly higher ability of heat resistance. which is named RS047-wl. Then a multi-omics analysis of transcriptomics and metabolomics was used to analyze the mechanism of the heat resistance of the mutant. A total of 98 differentially expressed genes (DEGs) and 115 differential metabolites covering multiple metabolic processes were detected in the mutant, which indicated that the tolerance of heat resistance was regulated by multiple mechanisms. The changes in AgrB, AgrC, and AgrA gene expressions were involved in quorum-sensing (QS) system pathways, which regulate biofilm formation. Second, highly soluble osmotic substances such as putrescine, spermidine, glycine betaine (GB), and trehalose-6P were accumulated for the membrane transport system. Third, organic acids metabolism and purine metabolism were down-regulated. The findings can provide target genes for subsequent genetic modification of E. faecium, and provide indications for screening heat-resistant bacteria, so as to improve the heat-resistant ability of E. faecium for production.
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Stevens KM, Warnecke T. Histone variants in archaea - An undiscovered country. Semin Cell Dev Biol 2023; 135:50-58. [PMID: 35221208 DOI: 10.1016/j.semcdb.2022.02.016] [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: 11/12/2021] [Revised: 02/20/2022] [Accepted: 02/20/2022] [Indexed: 12/23/2022]
Abstract
Exchanging core histones in the nucleosome for paralogous variants can have important functional ramifications. Many of these variants, and their physiological roles, have been characterized in exquisite detail in model eukaryotes, including humans. In comparison, our knowledge of histone biology in archaea remains rudimentary. This is true in particular for our knowledge of histone variants. Many archaea encode several histone genes that differ in sequence, but do these paralogs make distinct, adaptive contributions to genome organization and regulation in a manner comparable to eukaryotes? Below, we review what we know about histone variants in archaea at the level of structure, regulation, and evolution. In all areas, our knowledge pales when compared to the wealth of insight that has been gathered for eukaryotes. Recent findings, however, provide tantalizing glimpses into a rich and largely undiscovered country that is at times familiar and eukaryote-like and at times strange and uniquely archaeal. We sketch a preliminary roadmap for further exploration of this country; an undertaking that may ultimately shed light not only on chromatin biology in archaea but also on the origin of histone-based chromatin in eukaryotes.
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Affiliation(s)
- Kathryn M Stevens
- Medical Research Council London Institute of Medical Sciences, London, United Kingdom; Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - Tobias Warnecke
- Medical Research Council London Institute of Medical Sciences, London, United Kingdom; Institute of Clinical Sciences, Faculty of Medicine, Imperial College London, London, United Kingdom.
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The Hypersaline Archaeal Histones HpyA and HstA Are DNA Binding Proteins That Defy Categorization According to Commonly Used Functional Criteria. mBio 2023; 14:e0344922. [PMID: 36779711 PMCID: PMC10128011 DOI: 10.1128/mbio.03449-22] [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] [Indexed: 02/14/2023] Open
Abstract
Histone proteins are found across diverse lineages of Archaea, many of which package DNA and form chromatin. However, previous research has led to the hypothesis that the histone-like proteins of high-salt-adapted archaea, or halophiles, function differently. The sole histone protein encoded by the model halophilic species Halobacterium salinarum, HpyA, is nonessential and expressed at levels too low to enable genome-wide DNA packaging. Instead, HpyA mediates the transcriptional response to salt stress. Here we compare the features of genome-wide binding of HpyA to those of HstA, the sole histone of another model halophile, Haloferax volcanii. hstA, like hpyA, is a nonessential gene. To better understand HpyA and HstA functions, protein-DNA binding data (chromatin immunoprecipitation sequencing [ChIP-seq]) of these halophilic histones are compared to publicly available ChIP-seq data from DNA binding proteins across all domains of life, including transcription factors (TFs), nucleoid-associated proteins (NAPs), and histones. These analyses demonstrate that HpyA and HstA bind the genome infrequently in discrete regions, which is similar to TFs but unlike NAPs, which bind a much larger genomic fraction. However, unlike TFs that typically bind in intergenic regions, HpyA and HstA binding sites are located in both coding and intergenic regions. The genome-wide dinucleotide periodicity known to facilitate histone binding was undetectable in the genomes of both species. Instead, TF-like and histone-like binding sequence preferences were detected for HstA and HpyA, respectively. Taken together, these data suggest that halophilic archaeal histones are unlikely to facilitate genome-wide chromatin formation and that their function defies categorization as a TF, NAP, or histone. IMPORTANCE Most cells in eukaryotic species-from yeast to humans-possess histone proteins that pack and unpack DNA in response to environmental cues. These essential proteins regulate genes necessary for important cellular processes, including development and stress protection. Although the histone fold domain originated in the domain of life Archaea, the function of archaeal histone-like proteins is not well understood relative to those of eukaryotes. We recently discovered that, unlike histones of eukaryotes, histones in hypersaline-adapted archaeal species do not package DNA and can act as transcription factors (TFs) to regulate stress response gene expression. However, the function of histones across species of hypersaline-adapted archaea still remains unclear. Here, we compare hypersaline histone function to a variety of DNA binding proteins across the tree of life, revealing histone-like behavior in some respects and specific transcriptional regulatory function in others.
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Low Salt Influences Archaellum-Based Motility, Glycerol Metabolism, and Gas Vesicles Biogenesis in Halobacterium salinarum. Microorganisms 2022; 10:microorganisms10122442. [PMID: 36557695 PMCID: PMC9786353 DOI: 10.3390/microorganisms10122442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2022] [Revised: 12/05/2022] [Accepted: 12/05/2022] [Indexed: 12/14/2022] Open
Abstract
Halobacterium salinarum NRC-1 is an extremophile that grows optimally at 4.3 M NaCl concentration. In spite of being an established model microorganism for the archaea domain, direct comparisons between its proteome and transcriptome during osmotic stress are still not available. Through RNA-seq-based transcriptomics, we compared a low salt (2.6 M NaCl) stress condition with 4.3 M of NaCl and found 283 differentially expressed loci. The more commonly found classes of genes were: ABC-type transporters and transcription factors. Similarities, and most importantly, differences between our findings and previously published datasets in similar experimental conditions are discussed. We validated three important biological processes differentially expressed: gas vesicles production (due to down-regulation of gvpA1b, gvpC1b, gvpN1b, and gvpO1b); archaellum formation (due to down-regulation of arlI, arlB1, arlB2, and arlB3); and glycerol metabolism (due to up-regulation of glpA1, glpB, and glpC). Direct comparison between transcriptomics and proteomics showed 58% agreement between mRNA and protein level changes, pointing to post-transcriptional regulation candidates. From those genes, we highlight rpl15e, encoding for the 50S ribosomal protein L15e, for which we hypothesize an ionic strength-dependent conformational change that guides post-transcriptional processing of its mRNA and, thus, possible salt-dependent regulation of the translation machinery.
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11
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Abstract
Oxidative stress causes cellular damage, including DNA mutations, protein dysfunction, and loss of membrane integrity. Here, we discovered that a TrmB (transcription regulator of mal operon) family protein (Pfam PF01978) composed of a single winged-helix DNA binding domain (InterPro IPR002831) can function as thiol-based transcriptional regulator of oxidative stress response. Using the archaeon Haloferax volcanii as a model system, we demonstrate that the TrmB-like OxsR is important for recovery of cells from hypochlorite stress. OxsR is shown to bind specific regions of genomic DNA, particularly during hypochlorite stress. OxsR-bound intergenic regions were found proximal to oxidative stress operons, including genes associated with thiol relay and low molecular weight thiol biosynthesis. Further analysis of a subset of these sites revealed OxsR to function during hypochlorite stress as a transcriptional activator and repressor. OxsR was shown to require a conserved cysteine (C24) for function and to use a CG-rich motif upstream of conserved BRE/TATA box promoter elements for transcriptional activation. Protein modeling suggested the C24 is located at a homodimer interface formed by antiparallel α helices, and that oxidation of this cysteine would result in the formation of an intersubunit disulfide bond. This covalent linkage may promote stabilization of an OxsR homodimer with the enhanced DNA binding properties observed in the presence of hypochlorite stress. The phylogenetic distribution TrmB family proteins, like OxsR, that have a single winged-helix DNA binding domain and conserved cysteine residue suggests this type of redox signaling mechanism is widespread in Archaea.
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12
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Genetic Mapping to Detect Stringent QTLs Using 1k-RiCA SNP Genotyping Platform from the New Landrace Associated with Salt Tolerance at the Seedling Stage in Rice. PLANTS 2022; 11:plants11111409. [PMID: 35684182 PMCID: PMC9183132 DOI: 10.3390/plants11111409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Revised: 05/20/2022] [Accepted: 05/23/2022] [Indexed: 12/02/2022]
Abstract
Rice is the world’s most important food crop, providing the daily calorie intake for more than half of the world’s population. Rice breeding has always been preoccupied with maximizing yield potential. However, numerous abiotic factors, such as salt, cold, drought, and heat, significantly reduce rice productivity. Salinity, one of the major abiotic stresses, reduces rice yield worldwide. This study was conducted to determine new quantitative trait loci (QTLs) that regulate salt tolerance in rice seedlings. One F2:3 mapping population was derived from a cross between BRRI dhan49 (a popular but sensitive rainfed rice variety) and Akundi (a salt-tolerant rice landrace in Bangladesh used as a donor parent). The 1k-Rice Custom Amplicon (1k-RiCA) single-nucleotide polymorphism (SNP) markers were used to genotype this mapping population. After removing segregation distortion and monomorphic markers, 884 SNPs generated a 1526.8 cM-long genetic linkage map with a mean marker density of 1.7 cM for the 12 linkage groups. By exploiting QGene and ICIM-ADD, a sum of 15 QTLs for nine traits was identified in salt stress on seven chromosomes. Four important genomic loci were identified (qSES1, qSL1, qSUR1 and qRL1) on chromosome 1. Out of these 15 QTLs, 14 QTLs are unique, as no other study has mapped in the same chromosomal location. We also detected 15 putative candidate genes and their functions. The ICIM-EPI approach identified 43 significant pairwise epistasis interactions between regions associated with and unassociated with QTLs. Apart from more well-known donors, Akundi serves as an important new donor source for global salt tolerance breeding initiatives, including Bangladesh. The introgression of the novel QTLs identified in this study will accelerate the development of new salt-tolerant varieties that are highly resistant to salt stress using marker-enabled breeding.
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Pastor MM, Sakrikar S, Rodriguez DN, Schmid AK. Comparative Analysis of rRNA Removal Methods for RNA-Seq Differential Expression in Halophilic Archaea. Biomolecules 2022; 12:biom12050682. [PMID: 35625610 PMCID: PMC9138242 DOI: 10.3390/biom12050682] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 05/04/2022] [Accepted: 05/06/2022] [Indexed: 11/16/2022] Open
Abstract
Despite intense recent research interest in archaea, the scientific community has experienced a bottleneck in the study of genome-scale gene expression experiments by RNA-seq due to the lack of commercial and specifically designed rRNA depletion kits. The high rRNA:mRNA ratio (80–90%: ~10%) in prokaryotes hampers global transcriptomic analysis. Insufficient ribodepletion results in low sequence coverage of mRNA, and therefore, requires a substantially higher number of replicate samples and/or sequencing reads to achieve statistically reliable conclusions regarding the significance of differential gene expression between case and control samples. Here, we show that after the discontinuation of the previous version of RiboZero (Illumina, San Diego, CA, USA) that was useful in partially or completely depleting rRNA from archaea, archaeal transcriptomics studies have experienced a slowdown. To overcome this limitation, here, we analyze the efficiency for four different hybridization-based kits from three different commercial suppliers, each with two sets of sequence-specific probes to remove rRNA from four different species of halophilic archaea. We conclude that the key for transcriptomic success with the currently available tools is the probe-specificity for the rRNA sequence hybridization. With this paper, we provide insights into the archaeal community for selecting certain reagents and strategies over others depending on the archaeal species of interest. These methods yield improved RNA-seq sensitivity and enhanced detection of low abundance transcripts.
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Affiliation(s)
- Mar Martinez Pastor
- Biology Department, Duke University, Durham, NC 27708, USA; (M.M.P.); (S.S.)
| | - Saaz Sakrikar
- Biology Department, Duke University, Durham, NC 27708, USA; (M.M.P.); (S.S.)
- University Program in Genetics and Genomics, Duke University, Durham, NC 27708, USA
| | | | - Amy K. Schmid
- Biology Department, Duke University, Durham, NC 27708, USA; (M.M.P.); (S.S.)
- University Program in Genetics and Genomics, Duke University, Durham, NC 27708, USA
- Correspondence: ; Tel.: +919-613-4464
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