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Smith LM, Hampton HG, Yevstigneyeva MS, Mahler M, Paquet ZM, Fineran PC. CRISPR-Cas immunity is repressed by the LysR-type transcriptional regulator PigU. Nucleic Acids Res 2024; 52:755-768. [PMID: 38059344 PMCID: PMC10810281 DOI: 10.1093/nar/gkad1165] [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: 10/06/2023] [Revised: 11/17/2023] [Accepted: 11/27/2023] [Indexed: 12/08/2023] Open
Abstract
Bacteria protect themselves from infection by bacteriophages (phages) using different defence systems, such as CRISPR-Cas. Although CRISPR-Cas provides phage resistance, fitness costs are incurred, such as through autoimmunity. CRISPR-Cas regulation can optimise defence and minimise these costs. We recently developed a genome-wide functional genomics approach (SorTn-seq) for high-throughput discovery of regulators of bacterial gene expression. Here, we applied SorTn-seq to identify loci influencing expression of the two type III-A Serratia CRISPR arrays. Multiple genes affected CRISPR expression, including those involved in outer membrane and lipopolysaccharide synthesis. By comparing loci affecting type III CRISPR arrays and cas operon expression, we identified PigU (LrhA) as a repressor that co-ordinately controls both arrays and cas genes. By repressing type III-A CRISPR-Cas expression, PigU shuts off CRISPR-Cas interference against plasmids and phages. PigU also represses interference and CRISPR adaptation by the type I-F system, which is also present in Serratia. RNA sequencing demonstrated that PigU is a global regulator that controls secondary metabolite production and motility, in addition to CRISPR-Cas immunity. Increased PigU also resulted in elevated expression of three Serratia prophages, indicating their likely induction upon sensing PigU-induced cellular changes. In summary, PigU is a major regulator of CRISPR-Cas immunity in Serratia.
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Affiliation(s)
- Leah M Smith
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
- Genetics Otago, University of Otago, PO Box 56, Dunedin 9054, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Hannah G Hampton
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Mariya S Yevstigneyeva
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Marina Mahler
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
- Genetics Otago, University of Otago, PO Box 56, Dunedin 9054, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Otago, PO Box 56, Dunedin 9054, New Zealand
| | - Zacharie S M Paquet
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
- Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, Dreijenplein 10, 6703 HB Wageningen, The Netherlands
| | - Peter C Fineran
- Department of Microbiology and Immunology, University of Otago, PO Box 56, Dunedin 9054, New Zealand
- Genetics Otago, University of Otago, PO Box 56, Dunedin 9054, New Zealand
- Bioprotection Aotearoa, University of Otago, PO Box 56, Dunedin 9054, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, University of Otago, PO Box 56, Dunedin 9054, New Zealand
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Bartholomew HP, Reynoso G, Thomas BJ, Mullins CM, Smith C, Gentzel IN, Giese LA, Mackey D, Stevens AM. The Transcription Factor Lrp of Pantoea stewartii subsp. stewartii Controls Capsule Production, Motility, and Virulence Important for in planta Growth. Front Microbiol 2022; 12:806504. [PMID: 35237242 PMCID: PMC8882988 DOI: 10.3389/fmicb.2021.806504] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Accepted: 12/17/2021] [Indexed: 11/13/2022] Open
Abstract
The bacterial phytopathogen Pantoea stewartii subsp. stewartii causes leaf blight and Stewart's wilt disease in susceptible corn varieties. A previous RNA-Seq study examined P. stewartii gene expression patterns during late-stage infection in the xylem, and a Tn-Seq study using a P. stewartii mutant library revealed genes essential for colonization of the xylem. Based on these findings, strains with in-frame chromosomal deletions in the genes encoding seven transcription factors (NsrR, IscR, Nac, Lrp, DSJ_00125, DSJ_03645, and DSJ_18135) and one hypothetical protein (DSJ_21690) were constructed to further evaluate the role of the encoded gene products during in vitro and in planta growth. Assays for capsule production and motility indicate that Lrp plays a role in regulating these two key physiological outputs in vitro. Single infections of each deletion strain into the xylem of corn seedlings determined that Lrp plays a significant role in P. stewartii virulence. In planta xylem competition assays between co-inoculated deletion and the corresponding complementation or wild-type strains as well as in vitro growth curves determined that Lrp controls functions important for P. stewartii colonization and growth in corn plants, whereas IscR may have a more generalized impact on growth. Defining the role of essential transcription factors, such as Lrp, during in planta growth will enable modeling of key components of the P. stewartii regulatory network utilized during growth in corn plants.
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Affiliation(s)
| | - Guadalupe Reynoso
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, United States
| | - Brandi J. Thomas
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, United States
| | - Chase M. Mullins
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, United States
| | - Chastyn Smith
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, United States
| | - Irene N. Gentzel
- Department of Horticulture & Crop Science, The Ohio State University, Columbus, OH, United States
| | - Laura A. Giese
- Department of Horticulture & Crop Science, The Ohio State University, Columbus, OH, United States
| | - David Mackey
- Department of Horticulture & Crop Science, The Ohio State University, Columbus, OH, United States
- Department of Molecular Genetics and Center for Applied Plant Sciences, The Ohio State University, Columbus, OH, United States
| | - Ann M. Stevens
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, United States
- Center for Emerging, Zoonotic and Arthropod-Borne Pathogens, Virginia Tech, Blacksburg, VA, United States
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3
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Li J, Zhao X. Effects of quorum sensing on the biofilm formation and viable but non-culturable state. Food Res Int 2020; 137:109742. [DOI: 10.1016/j.foodres.2020.109742] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 09/08/2020] [Accepted: 09/18/2020] [Indexed: 02/07/2023]
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Kumar K, Chakraborty A, Chakrabarti S. PresRAT: a server for identification of bacterial small-RNA sequences and their targets with probable binding region. RNA Biol 2020; 18:1152-1159. [PMID: 33103602 DOI: 10.1080/15476286.2020.1836455] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
Abstract
Bacterial small-RNA (sRNA) sequences are functional RNAs, which play an important role in regulating the expression of a diverse class of genes. It is thus critical to identify such sRNA sequences and their probable mRNA targets. Here, we discuss new procedures to identify and characterize sRNA and their targets via the introduction of an integrated online platform 'PresRAT'. PresRAT uses the primary and secondary structural attributes of sRNA sequences to predict sRNA from a given sequence or bacterial genome. PresRAT also finds probable target mRNAs of sRNA sequences from a given bacterial chromosome and further concentrates on the identification of the probable sRNA-mRNA binding regions. Using PresRAT, we have identified a total of 66,209 potential sRNA sequences from 292 bacterial genomes and 2247 potential targets from 13 bacterial genomes. We have also implemented a protocol to build and refine 3D models of sRNA and sRNA-mRNA duplex regions and generated 3D models of 50 known sRNAs and 81 sRNA-mRNA duplexes using this platform. Along with the server part, PresRAT also contains a database section, which enlists the predicted sRNA sequences, sRNA targets, and their corresponding 3D models with structural dynamics information.
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Affiliation(s)
- Krishna Kumar
- Structural Biology and Bioinformatics Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India
| | - Abhijit Chakraborty
- Division of Vaccine-Discovery, La Jolla Institute for Immunology, San Diego, California, USA
| | - Saikat Chakrabarti
- Structural Biology and Bioinformatics Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India
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Duong DA, Jensen RV, Stevens AM. Discovery of Pantoea stewartii ssp. stewartii genes important for survival in corn xylem through a Tn-Seq analysis. MOLECULAR PLANT PATHOLOGY 2018; 19:1929-1941. [PMID: 29480976 PMCID: PMC6638119 DOI: 10.1111/mpp.12669] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 02/21/2018] [Accepted: 02/22/2018] [Indexed: 05/29/2023]
Abstract
The bacterium Pantoea stewartii ssp. stewartii causes Stewart's wilt disease in corn. Pantoea stewartii is transmitted to plants via corn flea beetles, where it first colonizes the apoplast causing water-soaked lesions, and then migrates to the xylem and forms a biofilm that blocks water transport. Bacterial quorum sensing ensures that the exopolysaccharide production necessary for biofilm formation occurs only at high cell density. A genomic-level transposon sequencing (Tn-Seq) analysis was performed to identify additional bacterial genes essential for survival in planta and to provide insights into the plant-microbe interactions occurring during wilt disease. A mariner transposon library of approximately 40 000 mutants was constructed and used to inoculate corn seedlings through a xylem infection model. Cultures of the library grown in Luria-Bertani (LB) broth served as the in vitro pre-inoculation control. Tn-Seq analysis showed that the number of transposon mutations was reduced by more than 10-fold for 486 genes in planta compared with the library that grew in LB, suggesting that they are important for xylem survival. Interestingly, a small set of genes had a higher abundance of mutants in planta versus in vitro conditions, indicating enhanced strain fitness with loss of these genes inside the host. In planta competition assays retested the trends of the Tn-Seq data for several genes, including two outer membrane proteins, Lon protease and two quorum sensing-associated transcription factors, RcsA and LrhA. Virulence assays were performed to check for correlation between growth/colonization and pathogenicity. This study demonstrates the capacity of a Tn-Seq approach to advance our understanding of P. stewartii-corn interactions.
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Affiliation(s)
- Duy An Duong
- Department of Biological SciencesVirginia TechBlacksburgVA 24061USA
| | | | - Ann M. Stevens
- Department of Biological SciencesVirginia TechBlacksburgVA 24061USA
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Duong DA, Stevens AM. Integrated downstream regulation by the quorum-sensing controlled transcription factors LrhA and RcsA impacts phenotypic outputs associated with virulence in the phytopathogen Pantoea stewartii subsp. stewartii. PeerJ 2017; 5:e4145. [PMID: 29230372 PMCID: PMC5723134 DOI: 10.7717/peerj.4145] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Accepted: 11/16/2017] [Indexed: 11/20/2022] Open
Abstract
Pantoea stewartii subsp. stewartii is a Gram-negative proteobacterium that causes leaf blight and Stewart’s wilt disease in corn. Quorum sensing (QS) controls bacterial exopolysaccharide production that blocks water transport in the plant xylem at high bacterial densities during the later stage of the infection, resulting in wilt. At low cell density the key master QS regulator in P. stewartii, EsaR, directly represses rcsA, encoding an activator of capsule biosynthesis genes, but activates lrhA, encoding a transcription factor that regulates surface motility. Both RcsA and LrhA have been shown to play a role in plant virulence. In this study, additional information about the downstream targets of LrhA and its interaction with RcsA was determined. A transcriptional fusion assay revealed autorepression of LrhA in P. stewartii and electrophoretic mobility shift assays (EMSA) using purified LrhA confirmed that LrhA binds to its own promoter. In addition, LrhA binds to the promoter for the RcsA gene, as well as those for putative fimbrial subunits and biosurfactant production enzymes in P. stewartii, but not to the flhDC promoter, which is the main direct target of LrhA in Escherichia coli. This work led to a reexamination of the physiological function of RcsA in P. stewartii and the discovery that it also plays a role in surface motility. These findings are broadening our understanding of the coordinated regulatory cascades utilized in the phytopathogen P. stewartii.
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Affiliation(s)
- Duy An Duong
- Department of Biological Sciences, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA, United States of America
| | - Ann M Stevens
- Department of Biological Sciences, Virginia Polytechnic Institute and State University (Virginia Tech), Blacksburg, VA, United States of America
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Tecon R, Leveau JHJ. Symplasmata are a clonal, conditional, and reversible type of bacterial multicellularity. Sci Rep 2016; 6:31914. [PMID: 27534795 PMCID: PMC4989142 DOI: 10.1038/srep31914] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Accepted: 07/29/2016] [Indexed: 01/29/2023] Open
Abstract
Microorganisms are capable of remarkable social behaviours, such as forming transient multicellular assemblages with properties and adaptive abilities exceeding those of individual cells. Here, we report on the formation and structure of genets known as symplasmata produced by Pantoea eucalypti bacteria. Each symplasmatum develops clonally and stochastically from a single bacterium into a membrane-delimited, capsule-embedded cluster of progeny cells and with a frequency that depends on temperature, pH, and nutrient availability. Transposon mutagenesis identified several gene products required for symplasmata formation, including master regulator LrhA, replication inhibitor CspD, polysaccharide transporter RfbX3, and autoinducer synthase PhzI. We also show that bacteria inside symplasmata are shaped irregularly with punctuated cell-to-cell contacts, metabolically responsive to environmental stimuli, dispersal-ready, and transcriptionally reprogrammed to anticipate multiple alternative futures in terms of carbon source availability. The structured and conditionable nature of symplasmata offers exciting prospects towards a mechanistic understanding of multicellular behaviours and their ecological significance.
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Affiliation(s)
- Robin Tecon
- Department of Plant Pathology, University of California, One Shields Ave, Davis, CA 95616, USA.,Department of Microbial Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Droevendaalsesteeg 10, 6708 PB Wageningen, the Netherlands
| | - Johan H J Leveau
- Department of Plant Pathology, University of California, One Shields Ave, Davis, CA 95616, USA
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Kernell Burke A, Duong DA, Jensen RV, Stevens AM. Analyzing the Transcriptomes of Two Quorum-Sensing Controlled Transcription Factors, RcsA and LrhA, Important for Pantoea stewartii Virulence. PLoS One 2015; 10:e0145358. [PMID: 26699719 PMCID: PMC4689408 DOI: 10.1371/journal.pone.0145358] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Accepted: 12/02/2015] [Indexed: 11/18/2022] Open
Abstract
The Gram-negative proteobacterium Pantoea stewartii subsp. stewartii causes wilt disease in corn plants. Wilting is primarily due to bacterial exopolysaccharide (EPS) production that blocks water transport in the xylem during the late stages of infection. EsaR, the master quorum-sensing (QS) regulator in P. stewartii, modulates EPS levels. At low cell densities EsaR represses or activates expression of a number of genes in the absence of its acyl homoserine lactone (AHL) ligand. At high cell densities, binding of AHL inactivates EsaR leading to derepression or deactivation of its direct targets. Two of these direct targets are the key transcription regulators RcsA and LrhA, which in turn control EPS production and surface motility/adhesion, respectively. In this study, RNA-Seq was used to further examine the physiological impact of deleting the genes encoding these two second-tier regulators. Quantitative reverse transcription PCR (qRT-PCR) was used to validate the regulation observed in the RNA-Seq data. A GFP transcriptional fusion reporter confirmed the existence of a regulatory feedback loop in the system between LrhA and RcsA. Plant virulence assays carried out with rcsA and lrhA deletion and complementation strains demonstrated that both transcription factors play roles during establishment of wilt disease in corn. These efforts further define the hierarchy of the QS-regulated network controlling plant virulence in P. stewartii.
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Affiliation(s)
- Alison Kernell Burke
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, United States of America
| | - Duy An Duong
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, United States of America
| | - Roderick V. Jensen
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, United States of America
| | - Ann M. Stevens
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24061, United States of America
- * E-mail:
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Acyl-homoserine lactone recognition and response hindering the quorum-sensing regulator EsaR. PLoS One 2014; 9:e107687. [PMID: 25238602 PMCID: PMC4169570 DOI: 10.1371/journal.pone.0107687] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Accepted: 08/14/2014] [Indexed: 11/19/2022] Open
Abstract
During quorum sensing in the plant pathogen Pantoea stewartii subsp. stewartii, EsaI, an acyl-homoserine lactone (AHL) synthase, and the transcription factor EsaR coordinately control capsular polysaccharide production. The capsule is expressed only at high cell density when AHL levels are high, leading to inactivation of EsaR. In lieu of detailed structural information, the precise mechanism whereby EsaR recognizes AHL and is hindered by it, in a response opposite to that of most other LuxR homologues, remains unresolved. Hence, a random mutagenesis genetic approach was designed to isolate EsaR* variants that are immune to the effects of AHL. Error-prone PCR was used to generate the desired mutants, which were subsequently screened for their ability to repress transcription in the presence of AHL. Following sequencing, site-directed mutagenesis was used to generate all possible mutations of interest as single, rather than multiple amino acid substitutions. Eight individual amino acids playing a critical role in the AHL-insensitive phenotype have been identified. The ability of EsaR* variants to bind AHL and the effect of individual substitutions on the overall conformation of the protein were examined through in vitro assays. Six EsaR* variants had a decreased ability to bind AHL. Fluorescence anisotropy was used to examine the relative DNA binding affinity of the final two EsaR* variants, which retained some AHL binding capability but remained unresponsive to it, perhaps due to an inability of the N-terminal domain to transduce information to the C-terminal domain.
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Transcriptome-based analysis of the Pantoea stewartii quorum-sensing regulon and identification of EsaR direct targets. Appl Environ Microbiol 2014; 80:5790-800. [PMID: 25015891 DOI: 10.1128/aem.01489-14] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pantoea stewartii subsp. stewartii is a proteobacterium that causes Stewart's wilt disease in corn plants. The bacteria form a biofilm in the xylem of infected plants and produce capsule that blocks water transport, eventually causing wilt. At low cell densities, the quorum-sensing (QS) regulatory protein EsaR is known to directly repress expression of esaR itself as well as the genes for the capsular synthesis operon transcription regulator, rcsA, and a 2,5-diketogluconate reductase, dkgA. It simultaneously directly activates expression of genes for a putative small RNA, esaS, the glycerol utilization operon, glpFKX, and another transcriptional regulator, lrhA. At high bacterial cell densities, all of this regulation is relieved when EsaR binds an acylated homoserine lactone signal, which is synthesized constitutively over growth. QS-dependent gene expression is critical for the establishment of disease in the plant. However, the identity of the full set of genes controlled by EsaR/QS is unknown. A proteomic approach previously identified around 30 proteins in the QS regulon. In this study, a whole-transcriptome, next-generation sequencing analysis of rRNA-depleted RNA from QS-proficient and -deficient P. stewartii strains was performed to identify additional targets of EsaR. EsaR-dependent transcriptional regulation of a subset of differentially expressed genes was confirmed by quantitative reverse transcription-PCR (qRT-PCR). Electrophoretic mobility shift assays demonstrated that EsaR directly bound 10 newly identified target promoters. Overall, the QS regulon of P. stewartii orchestrates three major physiological responses: capsule and cell envelope biosynthesis, surface motility and adhesion, and stress response.
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