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Yuan X, Eldred LI, Sundin GW. Exopolysaccharides amylovoran and levan contribute to sliding motility in the fire blight pathogen Erwinia amylovora. Environ Microbiol 2022; 24:4738-4754. [PMID: 36054324 PMCID: PMC9826367 DOI: 10.1111/1462-2920.16193] [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: 05/27/2022] [Accepted: 08/31/2022] [Indexed: 01/11/2023]
Abstract
Erwinia amylovora, the causative agent of fire blight, uses flagella-based motilities to translocate to host plant natural openings; however, little is known about how this bacterium migrates systemically in the apoplast. Here, we reveal a novel surface motility mechanism, defined as sliding, in E. amylovora. Deletion of flagella assembly genes did not affect this movement, whereas deletion of biosynthesis genes for the exopolysaccharides (EPSs) amylovoran and levan resulted in non-sliding phenotypes. Since EPS production generates osmotic pressure that potentially powers sliding, we validated this mechanism by demonstrating that water potential positively contributes to sliding. In addition, no sliding was observed when the water potential of the surface was lower than -0.5 MPa. Sliding is a passive motility mechanism. We further show that the force of gravity plays a critical role in directing E. amylovora sliding on unconfined surfaces but has a negligible effect when cells are sliding in confined microcapillaries, in which EPS-dependent osmotic pressure acts as the main force. Although amylovoran and levan are both required for sliding, we demonstrate that they exhibit different roles in bacterial communities. In summary, our study provides fundamental knowledge for a better understanding of mechanisms that drive bacterial sliding motility.
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Affiliation(s)
- Xiaochen Yuan
- Department of Plant, Soil, and Microbial SciencesMichigan State UniversityEast LansingMichiganUSA
| | - Lauren I. Eldred
- Department of Plant, Soil, and Microbial SciencesMichigan State UniversityEast LansingMichiganUSA
| | - George W. Sundin
- Department of Plant, Soil, and Microbial SciencesMichigan State UniversityEast LansingMichiganUSA
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2
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Schachterle JK, Gdanetz K, Pandya I, Sundin GW. Identification of novel virulence factors in Erwinia amylovora through temporal transcriptomic analysis of infected apple flowers under field conditions. MOLECULAR PLANT PATHOLOGY 2022; 23:855-869. [PMID: 35246928 PMCID: PMC9104256 DOI: 10.1111/mpp.13199] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 02/07/2022] [Indexed: 06/14/2023]
Abstract
The enterobacterial pathogen Erwinia amylovora uses multiple virulence-associated traits to cause fire blight, a devastating disease of apple and pear trees. Many virulence-associated phenotypes have been studied that are critical for virulence and pathogenicity. Despite the in vitro testing that has revealed how these systems are transcriptionally regulated, information on when and where in infected tissues these genes are being expressed is lacking. Here, we used a high-throughput sequencing approach to characterize the transcriptome of E. amylovora during disease progression on apple flowers under field infection conditions. We report that type III secretion system genes and flagellar genes are strongly co-expressed. Likewise, genes involved in biosynthesis of the exopolysaccharide amylovoran and sorbitol utilization had similar expression patterns. We further identified a group of 16 genes whose expression is increased and maintained at high levels throughout disease progression across time and tissues. We chose five of these genes for mutational analysis and observed that deletion mutants lacking these genes all display reduced symptom development on apple shoots. Furthermore, these induced genes were over-represented for genes involved in sulphur metabolism and cycling, suggesting the possibility of an important role for maintenance of oxidative homeostasis during apple flower infection.
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Affiliation(s)
- Jeffrey K. Schachterle
- Genetics and Genome Sciences ProgramMichigan State UniversityEast LansingMIUSA
- Department of Plant, Soil, and Microbial SciencesMichigan State UniversityEast LansingMIUSA
- Present address:
USDAARS, Cereal Crops Research UnitFargoNDUSA
| | - Kristi Gdanetz
- Department of Plant, Soil, and Microbial SciencesMichigan State UniversityEast LansingMIUSA
| | - Ishani Pandya
- Department of Plant, Soil, and Microbial SciencesMichigan State UniversityEast LansingMIUSA
| | - George W. Sundin
- Genetics and Genome Sciences ProgramMichigan State UniversityEast LansingMIUSA
- Department of Plant, Soil, and Microbial SciencesMichigan State UniversityEast LansingMIUSA
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3
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Yuan X, McGhee GC, Slack SM, Sundin GW. A Novel Signaling Pathway Connects Thiamine Biosynthesis, Bacterial Respiration, and Production of the Exopolysaccharide Amylovoran in Erwinia amylovora. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2021; 34:1193-1208. [PMID: 34081536 DOI: 10.1094/mpmi-04-21-0095-r] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Erwinia amylovora is a plant pathogen causing necrotrophic fire blight disease of apple, pear, and other rosaceous plants. This bacterium colonizes host vascular tissues via the production of exopolysaccharides (EPSs) including amylovoran. It is well-established that the nearly ubiquitous plasmid pEA29 of E. amylovora is an essential virulence factor, but the underlying mechanism remains uncharacterized. Here, we demonstrated that pEA29 was required for E. amylovora to produce amylovoran and to form a biofilm, and this regulation was dependent on the thiamine biosynthesis operon thiOSGF. We then conducted carbohydrate and genetic analyses demonstrating that the thiamine-mediated effect on amylovoran production was indirect, as cells lacking thiOSGF produced an EPS that did not contain glucuronic acid, one of the key components of amylovoran, whereas the transcriptional activity and RNA levels of the amylovoran biosynthesis genes were not altered. Alternatively, addition of exogenous thiamine restored amylovoran production in the pEA29-cured strain of E. amylovora and positively impacted amylovoran production in a dose-dependent manner. Individual deletion of several chromosomal thiamine biosynthesis genes also affected amylovoran production, implying that a complete thiamine biosynthesis pathway is required for the thiamine-mediated effect on amylovoran production in E. amylovora. Finally, we determined that an imbalanced tricarboxylic acid cycle negatively affected amylovoran production, which was restored by addition of exogenous thiamine or overexpression of the thiOSGF operon. In summary, our report revealed a novel signaling pathway that impacts E. amylovora virulence in which thiamine biosynthesis enhances bacterial respiration that provides energetic requirements for the biosynthesis of EPS amylovoran.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
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Affiliation(s)
- Xiaochen Yuan
- Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, MI 48824, U.S.A
| | - Gayle C McGhee
- United States Department of Agriculture, Agriculture Research Service, Horticultural Crops Research Laboratory, Corvallis, OR 97330, U.S.A
| | - Suzanne M Slack
- Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, MI 48824, U.S.A
| | - George W Sundin
- Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, MI 48824, U.S.A
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Sahebi M, Tarighi S, Taheri P. The Arac-like transcriptional regulator YqhC is involved in pathogenicity of Erwinia amylovora. J Appl Microbiol 2021; 132:1319-1329. [PMID: 34480830 DOI: 10.1111/jam.15286] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 08/28/2021] [Accepted: 08/30/2021] [Indexed: 11/29/2022]
Abstract
AIMS This study aimed to identify virulence-associated genes and functions that affect disease development on pear caused by Erwinia amylovora EaUMG3 isolated from Iran. METHODS AND RESULTS A mini-Tn5 transposon library was generated in EaUMG3. An E. amylovora mutant that had lost its ability to cause lesions on immature pear fruits, was selected for further analysis. This mutant was shown to have a transposon insertion in yqhC, a gene belongs to the AraC family of transcriptional regulators. A mutant of the wild-type EaUMG3 carrying an unmarked deletion of the yqhC gene was created using pDMS197. The Ea∆yqhC mutant showed reduced disease progression on immature pear fruits and pear plants, reduced motility and significantly lower levels of the virulence factors siderophore and amylovoran. Complementation with yqhC cloned in pBBR1MCS restored disease progression and the level of virulence factors to near wild type. CONCLUSION YqhC transcriptional regulator is necessary for full virulence of E. amylovora. In addition, this regulator affects virulence factors such as siderophore production, amylovoran production, and motility. SIGNIFICANCE AND IMPACT OF STUDY The identification of a novel transcriptional regulator with strong impact in the pathogenesis of E. amylovora, an organism causing significant economic losses in fruit production.
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Affiliation(s)
- Masood Sahebi
- Department of Plant Protection, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran
| | - Saeed Tarighi
- Department of Plant Protection, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran
| | - Parissa Taheri
- Department of Plant Protection, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran
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Kharadi RR, Schachterle JK, Yuan X, Castiblanco LF, Peng J, Slack SM, Zeng Q, Sundin GW. Genetic Dissection of the Erwinia amylovora Disease Cycle. ANNUAL REVIEW OF PHYTOPATHOLOGY 2021; 59:191-212. [PMID: 33945696 DOI: 10.1146/annurev-phyto-020620-095540] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Fire blight, caused by the bacterial phytopathogen Erwinia amylovora, is an economically important and mechanistically complex disease that affects apple and pear production in most geographic production hubs worldwide. We compile, assess, and present a genetic outlook on the progression of an E. amylovora infection in the host. We discuss the key aspects of type III secretion-mediated infection and systemic movement, biofilm formation in xylem, and pathogen dispersal via ooze droplets, a concentrated suspension of bacteria and exopolysaccharide components. We present an overall outlook on the genetic elements contributing to E. amylovora pathogenesis, including an exploration of the impact of floral microbiomes on E. amylovora colonization, and summarize the current knowledge of host responses to an incursion and how this response stimulates further infection and systemic spread. We hope to facilitate the identification of new, unexplored areas of research in this pathosystem that can help identify evolutionarily susceptible genetic targets to ultimately aid in the design of sustainable strategies for fire blight disease mitigation.
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Affiliation(s)
- Roshni R Kharadi
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, Michigan 48824, USA;
| | - Jeffrey K Schachterle
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, Michigan 48824, USA;
- Floral and Nursery Plants Research Unit, US National Arboretum, USDA-ARS, Beltsville, Maryland 20705, USA
| | - Xiaochen Yuan
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, Michigan 48824, USA;
| | - Luisa F Castiblanco
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, Michigan 48824, USA;
| | - Jingyu Peng
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, Michigan 48824, USA;
| | - Suzanne M Slack
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, Michigan 48824, USA;
| | - Quan Zeng
- Department of Plant Pathology and Ecology, The Connecticut Agricultural Experiment Station, New Haven, Connecticut 06511, USA
| | - George W Sundin
- Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, Michigan 48824, USA;
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Yuan X, Hulin MT, Sundin GW. Effectors, chaperones, and harpins of the Type III secretion system in the fire blight pathogen Erwinia amylovora: a review. JOURNAL OF PLANT PATHOLOGY 2021; 103:25-39. [PMID: 0 DOI: 10.1007/s42161-020-00623-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 07/23/2020] [Indexed: 05/20/2023]
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Puławska J, Kałużna M, Warabieda W, Pothier JF, Gétaz M, van der Wolf JM. Transcriptome analysis of Xanthomonas fragariae in strawberry leaves. Sci Rep 2020; 10:20582. [PMID: 33239704 PMCID: PMC7688646 DOI: 10.1038/s41598-020-77612-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Accepted: 11/09/2020] [Indexed: 11/21/2022] Open
Abstract
Xanthomonas fragariae is a quarantine bacterial pathogen that causes angular leaf spot on strawberry. The aim of our study was to analyse the mechanism of interaction of this bacterium with its host plant at the transcriptome level. For this purpose, mRNAs of X. fragariae growing in Wilbrink’s medium and from infected strawberry cv. Elsanta plants were isolated and sequenced using the Illumina MiSeq platform. The expression profiles of the bacteria in Wilbrink’s medium and in planta were very diverse. Of the 3939 CDSs recorded, 1995 had significantly different expression in planta (966 and 1029 genes were down- and upregulated, respectively). Among the genes showing increased expression in planta, those with eggNOG/COG (evolutionary genealogy of genes: Non-supervised Orthologous Groups/Cluster of Orthologous Groups) categories associated with bacterial cell motility, signal transduction, transport and metabolism of inorganic ions and carbohydrates and transcription were overrepresented. Among the genes with the most increased expression in planta, genes primarily associated with flagella synthesis and chemotaxis were found. It is also interesting to note that out of the 31 genes localized on a plasmid, 16 were expressed differently in planta, which may indicate their potential role in plant–pathogen interactions. Many genes with differentiated expression that were localized on chromosome and plasmid encode proteins of unknown function.
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Affiliation(s)
- Joanna Puławska
- Department of Phytopathology, Research Institute of Horticulture, 96-100, Skierniewice, Poland.
| | - Monika Kałużna
- Department of Phytopathology, Research Institute of Horticulture, 96-100, Skierniewice, Poland
| | - Wojciech Warabieda
- Department of Phytopathology, Research Institute of Horticulture, 96-100, Skierniewice, Poland
| | - Joël F Pothier
- Environmental Genomics and Systems Biology Research Group, Institute for Natural Resource Sciences, Zurich University of Applied Sciences (ZHAW), Wädenswil, Switzerland
| | - Michael Gétaz
- Environmental Genomics and Systems Biology Research Group, Institute for Natural Resource Sciences, Zurich University of Applied Sciences (ZHAW), Wädenswil, Switzerland
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Gatchell IT, Huntley RB, Schultes NP, Mourad GS. The guanine-hypoxanthine permease GhxP of Erwinia amylovora facilitates the influx of the toxic guanine derivative 6-thioguanine. J Appl Microbiol 2020; 130:2018-2028. [PMID: 33152175 DOI: 10.1111/jam.14925] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 11/02/2020] [Accepted: 11/02/2020] [Indexed: 01/08/2023]
Abstract
AIM Erwinia amylovora is the causal agent of fire blight, a devastating disease of apples and pears. This study determines whether the E. amylovora guanine-hypoxanthine transporter (EaGhxP) is required for virulence and if it can import the E. amylovora produced toxic analogue 6-thioguanine (6TG) into cells. METHODS AND RESULTS Characterization of EaGhxP in guanine transport deficient Escherichia coli reveals that it can transport guanine, hypoxanthine and the toxic analogues 8-azaguanine (8AG) and 6TG. Similarly, EaGhxP transports 8AG and 6TG into E. amylovora cells. EaGhxP has a high affinity for 6TG with a Ki of 3·7 µmol l-1 . An E. amylovora ⊿ghxP::Camr strain shows resistance to growth on 8AG and 6TG. Although EaGhxP is expressed during active disease propagation, it is not necessary for virulence as determined on immature apple and pear assays. CONCLUSIONS EaGhxP is not required for virulence, but it does import 6TG into E. amylovora cells. SIGNIFICANCE AND IMPACT OF THE STUDY As part of the disease establishment process, E. amylovora synthesizes and exports a toxic guanine derivative 6TG. Our results are counter intuitive and show that EaGhxP, an influx transporter, can move 6TG into cells raising questions regarding the role of 6TG in disease establishment.
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Affiliation(s)
- I T Gatchell
- Department of Biology, Purdue University Fort Wayne, Fort Wayne, IN, USA
| | - R B Huntley
- Department of Plant Pathology & Ecology, The Connecticut Agricultural Experiment Station, New Haven, CT, USA
| | - N P Schultes
- Department of Plant Pathology & Ecology, The Connecticut Agricultural Experiment Station, New Haven, CT, USA
| | - G S Mourad
- Department of Biology, Purdue University Fort Wayne, Fort Wayne, IN, USA
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Akremi I, Holtappels D, Brabra W, Jlidi M, Hadj Ibrahim A, Ben Ali M, Fortuna K, Ahmed M, Meerbeek BV, Rhouma A, Lavigne R, Ben Ali M, Wagemans J. First Report of Filamentous Phages Isolated from Tunisian Orchards to Control Erwinia amylovora. Microorganisms 2020; 8:microorganisms8111762. [PMID: 33182526 PMCID: PMC7697814 DOI: 10.3390/microorganisms8111762] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Revised: 10/20/2020] [Accepted: 10/22/2020] [Indexed: 01/28/2023] Open
Abstract
Newly discovered Erwinia amylovora phages PEar1, PEar2, PEar4 and PEar6 were isolated from three different orchards in North Tunisia to study their potential as biocontrol agents. Illumina sequencing revealed that the PEar viruses carry a single-strand DNA genome between 6608 and 6801 nucleotides and belong to the Inoviridae, making them the first described filamentous phages of E. amylovora. Interestingly, phage-infected cells show a decreased swimming and swarming motility and a cocktail of the four phages can significantly reduce infection of E. amylovora in a pear bioassay, potentially making them suitable candidates for phage biocontrol.
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Affiliation(s)
- Ismahen Akremi
- Laboratory of Microbial Biotechnology, Enzymatics and Biomolecules (LBMEB), Center of Biotechnology of Sfax (CBS), University of Sfax, Road of Sidi Mansour km 6, P.O. Box 1177, Sfax 3018, Tunisia; (I.A.); (W.B.); (M.J.); (A.H.I.); (M.B.A.); (M.B.A.)
- Laboratory of Gene Technology, Department of Biosystems, KU Leuven, Kasteelpark Arenberg 21-Box 2462, 3001 Leuven, Belgium; (D.H.); (K.F.); (R.L.)
| | - Dominique Holtappels
- Laboratory of Gene Technology, Department of Biosystems, KU Leuven, Kasteelpark Arenberg 21-Box 2462, 3001 Leuven, Belgium; (D.H.); (K.F.); (R.L.)
| | - Wided Brabra
- Laboratory of Microbial Biotechnology, Enzymatics and Biomolecules (LBMEB), Center of Biotechnology of Sfax (CBS), University of Sfax, Road of Sidi Mansour km 6, P.O. Box 1177, Sfax 3018, Tunisia; (I.A.); (W.B.); (M.J.); (A.H.I.); (M.B.A.); (M.B.A.)
- Astrum Biotech, Business Incubator, Center of Biotechnology of Sfax (CBS), University of Sfax, Road of Sidi Mansour km 6, P.O. Box 1177, Sfax 3018, Tunisia
| | - Mouna Jlidi
- Laboratory of Microbial Biotechnology, Enzymatics and Biomolecules (LBMEB), Center of Biotechnology of Sfax (CBS), University of Sfax, Road of Sidi Mansour km 6, P.O. Box 1177, Sfax 3018, Tunisia; (I.A.); (W.B.); (M.J.); (A.H.I.); (M.B.A.); (M.B.A.)
| | - Adel Hadj Ibrahim
- Laboratory of Microbial Biotechnology, Enzymatics and Biomolecules (LBMEB), Center of Biotechnology of Sfax (CBS), University of Sfax, Road of Sidi Mansour km 6, P.O. Box 1177, Sfax 3018, Tunisia; (I.A.); (W.B.); (M.J.); (A.H.I.); (M.B.A.); (M.B.A.)
| | - Manel Ben Ali
- Laboratory of Microbial Biotechnology, Enzymatics and Biomolecules (LBMEB), Center of Biotechnology of Sfax (CBS), University of Sfax, Road of Sidi Mansour km 6, P.O. Box 1177, Sfax 3018, Tunisia; (I.A.); (W.B.); (M.J.); (A.H.I.); (M.B.A.); (M.B.A.)
- Astrum Biotech, Business Incubator, Center of Biotechnology of Sfax (CBS), University of Sfax, Road of Sidi Mansour km 6, P.O. Box 1177, Sfax 3018, Tunisia
| | - Kiandro Fortuna
- Laboratory of Gene Technology, Department of Biosystems, KU Leuven, Kasteelpark Arenberg 21-Box 2462, 3001 Leuven, Belgium; (D.H.); (K.F.); (R.L.)
| | - Mohammed Ahmed
- Biomaterials Research Group (BIOMAT), Department of Oral Sciences, KU Leuven, Kapucijnenvoer 7-Block A Box 7001, 3000 Leuven, Belgium; (M.A.); (B.V.M.)
- Department of Dental Biomaterials, Tanta University, Biomedical Campus, 32511 Tanta, Gharbia Governorate, Egypt
| | - Bart Van Meerbeek
- Biomaterials Research Group (BIOMAT), Department of Oral Sciences, KU Leuven, Kapucijnenvoer 7-Block A Box 7001, 3000 Leuven, Belgium; (M.A.); (B.V.M.)
| | - Ali Rhouma
- Laboratory of Integrated Olive Production, Olive Tree Institute, BP208 Marhajene City, Tunis 1082, Tunisia;
| | - Rob Lavigne
- Laboratory of Gene Technology, Department of Biosystems, KU Leuven, Kasteelpark Arenberg 21-Box 2462, 3001 Leuven, Belgium; (D.H.); (K.F.); (R.L.)
| | - Mamdouh Ben Ali
- Laboratory of Microbial Biotechnology, Enzymatics and Biomolecules (LBMEB), Center of Biotechnology of Sfax (CBS), University of Sfax, Road of Sidi Mansour km 6, P.O. Box 1177, Sfax 3018, Tunisia; (I.A.); (W.B.); (M.J.); (A.H.I.); (M.B.A.); (M.B.A.)
- Astrum Biotech, Business Incubator, Center of Biotechnology of Sfax (CBS), University of Sfax, Road of Sidi Mansour km 6, P.O. Box 1177, Sfax 3018, Tunisia
| | - Jeroen Wagemans
- Laboratory of Gene Technology, Department of Biosystems, KU Leuven, Kasteelpark Arenberg 21-Box 2462, 3001 Leuven, Belgium; (D.H.); (K.F.); (R.L.)
- Correspondence: ; Tel.: +32-1637-4622
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Gétaz M, Puławska J, Smits TH, Pothier JF. Host-Pathogen Interactions between Xanthomonas fragariae and Its Host Fragaria × ananassa Investigated with a Dual RNA-Seq Analysis. Microorganisms 2020; 8:E1253. [PMID: 32824783 PMCID: PMC7465820 DOI: 10.3390/microorganisms8081253] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 08/11/2020] [Accepted: 08/14/2020] [Indexed: 12/31/2022] Open
Abstract
Strawberry is economically important and widely grown, but susceptible to a large variety of phytopathogenic organisms. Among them, Xanthomonas fragariae is a quarantine bacterial pathogen threatening strawberry productions by causing angular leaf spots. Using whole transcriptome sequencing, the gene expression of both plant and bacteria in planta was analyzed at two time points, 12 and 29 days post inoculation, in order to compare the pathogen and host response between the stages of early visible and of well-developed symptoms. Among 28,588 known genes in strawberry and 4046 known genes in X. fragariae expressed at both time points, a total of 361 plant and 144 bacterial genes were significantly differentially expressed, respectively. The identified higher expressed genes in the plants were pathogen-associated molecular pattern receptors and pathogenesis-related thaumatin encoding genes, whereas the more expressed early genes were related to chloroplast metabolism as well as photosynthesis related coding genes. Most X. fragariae genes involved in host interaction, recognition, and pathogenesis were lower expressed at late-phase infection. This study gives a first insight into the interaction of X. fragariae with its host. The strawberry plant changed gene expression in order to consistently adapt its metabolism with the progression of infection.
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Affiliation(s)
- Michael Gétaz
- Environmental Genomics and Systems Biology Research Group, Institute of Natural Resource Sciences, Zurich University of Applied Sciences (ZHAW), CH-8820 Wädenswil, Switzerland; (M.G.); (T.H.S.)
| | - Joanna Puławska
- Department of Phytopathology, Research Institute of Horticulture, 96-100 Skierniewice, Poland;
| | - Theo H.M. Smits
- Environmental Genomics and Systems Biology Research Group, Institute of Natural Resource Sciences, Zurich University of Applied Sciences (ZHAW), CH-8820 Wädenswil, Switzerland; (M.G.); (T.H.S.)
| | - Joël F. Pothier
- Environmental Genomics and Systems Biology Research Group, Institute of Natural Resource Sciences, Zurich University of Applied Sciences (ZHAW), CH-8820 Wädenswil, Switzerland; (M.G.); (T.H.S.)
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An Erwinia amylovora uracil transporter mutant retains virulence on immature apple and pear fruit. Microb Pathog 2020; 147:104363. [PMID: 32615243 DOI: 10.1016/j.micpath.2020.104363] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 06/23/2020] [Accepted: 06/24/2020] [Indexed: 12/13/2022]
Abstract
Erwinia amylovora is the causal agent of fire blight, a devastating disease of apples and pears. A previous study revealed that an E. amylovora uracil auxotroph was still virulent and can cause disease, suggesting that uracil can be obtained from the host environment. The E. amylovora genome contains a locus encoding for a uracil transporter belonging to the nucleobase cation symporter 2 family, displaying a high level of amino acid sequence similarity to the Escherichia coli UraA. Expression of E. amylovora UraA in nucleobase transporter-deficient E. coli strains, coupled with radiolabeled uptake studies reveal that E. amylovora UraA is a high affinity uracil transporter with a Km of 0.57 μM. Both E. coli and E. amylovora carrying extra copies of E. amylovora UraA are sensitive to growth on the toxic analog 5-fluorouracil. An E. amylovora ΔuraA::Camr mutant is still able to grow and cause disease symptoms on immature pears and apples.
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Sakai K, Yamaguchi A, Tsutsumi S, Kawai Y, Tsuzuki S, Suzuki H, Jindou S, Suzuki Y, Kajimura H, Kato M, Shimizu M. Characterization of FsXEG12A from the cellulose-degrading ectosymbiotic fungus Fusarium spp. strain EI cultured by the ambrosia beetle. AMB Express 2020; 10:96. [PMID: 32449090 PMCID: PMC7246284 DOI: 10.1186/s13568-020-01030-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Accepted: 05/16/2020] [Indexed: 12/02/2022] Open
Abstract
Despite the threat of Fusarium dieback posed due to ambrosia fungi cultured by ambrosia beetles such as Euwallacea spp., the wood-degradation mechanisms utilized by ambrosia fungi are not fully understood. In this study, we analyzed the 16S rRNA and 18S rRNA genes of the microbial community from the Ficus tree tunnel excavated by Euwallacea interjectus and isolated the cellulose-degrading fungus, Fusarium spp. strain EI, by enrichment culture with carboxymethyl cellulose as the sole carbon source. The cellulolytic enzyme secreted by the fungus was identified and expressed in Pichia pastoris, and its enzymatic properties were characterized. The cellulolytic enzyme, termed FsXEG12A, could hydrolyze carboxymethyl cellulose, microcrystalline cellulose, xyloglucan, lichenan, and glucomannan, indicating that the broad substrate specificity of FsXEG12A could be beneficial for degrading complex wood components such as cellulose, xyloglucan, and galactoglucomannan in angiosperms. Inhibition of FsXEG12A function is, thus, an effective target for Fusarium dieback caused by Euwallacea spp.
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Affiliation(s)
- Kiyota Sakai
- Faculty of Agriculture, Meijo University, Nagoya, Aichi, 468-8502, Japan
| | - Aya Yamaguchi
- Faculty of Agriculture, Meijo University, Nagoya, Aichi, 468-8502, Japan
| | - Seitaro Tsutsumi
- Faculty of Agriculture, Meijo University, Nagoya, Aichi, 468-8502, Japan
| | - Yuto Kawai
- Faculty of Agriculture, Meijo University, Nagoya, Aichi, 468-8502, Japan
| | - Sho Tsuzuki
- Faculty of Agriculture, Meijo University, Nagoya, Aichi, 468-8502, Japan
| | - Hiromitsu Suzuki
- Faculty of Agriculture, Meijo University, Nagoya, Aichi, 468-8502, Japan
| | - Sadanari Jindou
- Faculty of Science and Technology, Meijo University, Nagoya, Aichi, 468-8502, Japan
| | - Yoshihito Suzuki
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 464-8601, Japan
| | - Hisashi Kajimura
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 464-8601, Japan
| | - Masashi Kato
- Faculty of Agriculture, Meijo University, Nagoya, Aichi, 468-8502, Japan
| | - Motoyuki Shimizu
- Faculty of Agriculture, Meijo University, Nagoya, Aichi, 468-8502, Japan.
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Selection of reference genes for measuring the expression of aiiO in Ochrobactrum quorumnocens A44 using RT-qPCR. Sci Rep 2019; 9:13129. [PMID: 31511547 PMCID: PMC6739375 DOI: 10.1038/s41598-019-49474-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2019] [Accepted: 08/22/2019] [Indexed: 11/09/2022] Open
Abstract
Reverse transcription quantitative PCR (RT-qPCR), a method of choice for quantification of gene expression changes, requires stably expressed reference genes for normalization of data. So far, no reference genes were established for the Alphaproteobacteria of the genus Ochrobactrum. Here, we determined reference genes for gene expression studies in O. quorumnocens A44. Strain A44 was cultured under 10 different conditions and the stability of expression of 11 candidate genes was evaluated using geNorm, NormFinder and BestKeeper. Most stably expressed genes were found to be rho, gyrB and rpoD. Our results can facilitate the choice of reference genes in the related Ochrobactrum strains. O. quorumnocens A44 is able to inactivate a broad spectrum of N-acyl homoserine lactones (AHLs) - the quorum sensing molecules of many Gram-negative bacteria. This activity is attributed to AiiO hydrolase, yet it remains unclear whether AHLs are the primary substrate of this enzyme. Using the established RT-qPCR setup, we found that the expression of the aiiO gene upon exposure to two AHLs, C6-HLS and 3OC12-HSL, does not change above the 1-fold significance threshold. The implications of this finding are discussed in the light of the role of quorum sensing-interfering enzymes in the host strains.
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14
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mRNA extraction of Xanthomonas fragariae in strawberry and validation of reference genes for the RT-qPCR for study of bacterial gene expression. Mol Biol Rep 2019; 46:5723-5733. [PMID: 31368022 DOI: 10.1007/s11033-019-05006-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Accepted: 07/26/2019] [Indexed: 01/11/2023]
Abstract
This is the first study which describes a unique procedure of isolating of high-quality, intact RNA from strawberry leaves of Xanthomonas fragariae, three most suitable reference genes, crucial for the normalization of RT-qPCR data for this pathogen and accurate expression analysis of target genes. In our study, various mathematic algorithms: NormFinder geNorm, BestKeeper, the delta CT method, RefFinder were adopted for validation of most stable reference genes from nine candidate genes (ffh, glyA, gyrA, gyrB, proC, pykA, recA, rpoB, rpoD). The analyses allowing to select three most suitable pioneer reference genes, gyrB, ffh, and pykA, that we recommend for the normalization of RT-qPCR data and for the study of the expression of target genes in Xf. Moreover, their combination as references allowed for an accurate expression analysis and computation of the fold change of the flhF and iroN2 genes in Xf. These two genes are important for the success of the colonization of plant tissue and pathogenicity and sequences of primers designed to study these genes, are presented.
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15
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The Leucine-Responsive Regulatory Protein Lrp Participates in Virulence Regulation Downstream of Small RNA ArcZ in Erwinia amylovora. mBio 2019; 10:mBio.00757-19. [PMID: 31138749 PMCID: PMC6538786 DOI: 10.1128/mbio.00757-19] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Fire blight disease continues to plague the commercial production of apples and pears despite more than a century of research into disease epidemiology and disease control. The causative agent of fire blight, Erwinia amylovora coordinates turning on or off specific virulence-associated traits at the appropriate time during disease development. The development of novel control strategies requires an in-depth understanding of E. amylovora regulatory mechanisms, including regulatory control of virulence-associated traits. This study investigates how the small RNA ArcZ regulates motility at the transcriptional level and identifies the transcription factor Lrp as a novel participant in the regulation of several virulence-associated traits. We report that ArcZ and Lrp together affect key virulence-associated traits through integration of transcriptional and posttranscriptional mechanisms. Further understanding of the topology of virulence regulatory networks can uncover weak points that can subsequently be exploited to control E. amylovora. Erwinia amylovora causes the devastating fire blight disease of apple and pear trees. During systemic infection of host trees, pathogen cells must rapidly respond to changes in their environment as they move through different host tissues that present distinct challenges and sources of nutrition. Growing evidence indicates that small RNAs (sRNAs) play an important role in disease progression as posttranscriptional regulators. The sRNA ArcZ positively regulates the motility phenotype and transcription of flagellar genes in E. amylovora Ea1189 yet is a direct repressor of translation of the flagellar master regulator, FlhD. We utilized transposon mutagenesis to conduct a forward genetic screen and identified suppressor mutations that increase motility in the Ea1189ΔarcZ mutant background. This enabled us to determine that the mechanism of transcriptional activation of the flhDC mRNA by ArcZ is mediated by the leucine-responsive regulatory protein, Lrp. We show that Lrp contributes to expression of virulence and several virulence-associated traits, including production of the exopolysaccharide amylovoran, levansucrase activity, and biofilm formation. We further show that Lrp is regulated posttranscriptionally by ArcZ through destabilization of lrp mRNA. Thus, ArcZ regulation of FlhDC directly and indirectly through Lrp forms an incoherent feed-forward loop that regulates levansucrase activity and motility as outputs. This work identifies Lrp as a novel participant in virulence regulation in E. amylovora and places it in the context of a virulence-associated regulatory network.
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16
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Silva KJP, Singh J, Bednarek R, Fei Z, Khan A. Differential gene regulatory pathways and co-expression networks associated with fire blight infection in apple ( Malus × domestica). HORTICULTURE RESEARCH 2019; 6:35. [PMID: 30962933 PMCID: PMC6441656 DOI: 10.1038/s41438-019-0120-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Revised: 11/06/2018] [Accepted: 12/30/2018] [Indexed: 05/25/2023]
Abstract
Apple cultivars with durable resistance are needed for sustainable management of fire blight, the most destructive bacterial disease of apples. Although studies have identified genetic resistance to fire blight in both wild species and cultivated apples, more research is needed to understand the molecular mechanisms underlying host-pathogen interaction and differential genotypic responses to fire blight infection. We have analyzed phenotypic and transcriptional responses of 'Empire' and 'Gala' apple cultivars to fire blight by infecting them with a highly aggressive E. amylovora strain. Disease progress, based on the percentage of visual shoot necrosis, started showing significant (p < 0.001) differences between 'Empire' and 'Gala' 4 days after infection (dai). 'Empire' seems to slow down bacterial progress more rapidly after this point. We further compared transcriptome profiles of 'Empire' and 'Gala' at three different time points after fire blight infection. More genes showed differential expression in 'Gala' at earlier stages, but the number of differentially expressed genes increased in 'Empire' at 3 dai. Functional classes related to defense, cell cycle, response to stress, and biotic stress were identified and a few co-expression gene networks showed particular enrichment for plant defense and abiotic stress response genes. Several of these genes also co-localized in previously identified quantitative trait locus regions for fire blight resistance on linkage groups 7 and 12, and can serve as functional candidates for future research. These results highlight different molecular mechanisms for pathogen perception and control in two apple cultivars and will contribute toward better understanding of E. amylovora-Malus pathosystem.
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Affiliation(s)
| | - Jugpreet Singh
- 1Plant Pathology and Plant-Microbe Biology Section, Cornell University, Geneva, NY 14456 USA
| | - Ryland Bednarek
- 1Plant Pathology and Plant-Microbe Biology Section, Cornell University, Geneva, NY 14456 USA
- 2Boyce Thompson Institute, Cornell University, Ithaca, NY 14853 USA
| | - Zhangjun Fei
- 2Boyce Thompson Institute, Cornell University, Ithaca, NY 14853 USA
| | - Awais Khan
- 1Plant Pathology and Plant-Microbe Biology Section, Cornell University, Geneva, NY 14456 USA
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17
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Schachterle JK, Zeng Q, Sundin GW. Three Hfq-dependent small RNAs regulate flagellar motility in the fire blight pathogen Erwinia amylovora. Mol Microbiol 2019; 111:1476-1492. [PMID: 30821016 DOI: 10.1111/mmi.14232] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/26/2019] [Indexed: 12/13/2022]
Abstract
Erwinia amylovora, the causative agent of fire blight disease of apple and pear trees, causes disease on flowers by invading natural openings at the base of the floral cup. To reach these openings, the bacteria use flagellar motility to swim from stigma tips to the hypanthium and through nectar. We have previously shown that the Hfq-dependent sRNAs ArcZ, OmrAB and RmaA regulate swimming motility in E. amylovora. Here, we tested these three sRNAs to determine at what regulatory level they exert their effects and to what extent they can complement each other. We found that ArcZ and OmrAB repress the flagellar master regulator flhD post-transcriptionally. We also found that ArcZ and RmaA positively regulate flhD at the transcriptional level. The role of ArcZ as an activator of flagellar motility appears to be unique to E. amylovora and may have recently evolved. Our results suggest that the Hfq-dependent sRNAs ArcZ, OmrAB and RmaA play an integral role in regulation of flagellar motility by acting primarily on the master regulator, FlhD, but also through additional factors.
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Affiliation(s)
- Jeffrey K Schachterle
- Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, MI, USA
| | - Quan Zeng
- Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, MI, USA.,Department of Plant Pathology and Ecology, The Connecticut Agricultural Experiment Station, New Haven, CT, USA
| | - George W Sundin
- Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, MI, USA
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18
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Adaptations and evolution of a heritable leaf nodule symbiosis between Dioscorea sansibarensis and Orrella dioscoreae. ISME JOURNAL 2019; 13:1831-1844. [PMID: 30877285 DOI: 10.1038/s41396-019-0398-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 03/05/2019] [Accepted: 03/05/2019] [Indexed: 12/31/2022]
Abstract
Various plant species establish intimate symbioses with bacteria within their aerial organs. The bacteria are contained within nodules or glands often present in distinctive patterns on the leaves in what is commonly referred to as leaf nodule symbiosis. We describe here a highly specific symbiosis between a wild yam species from Madagascar, Dioscorea sansibarensis and bacteria of the species Orrella dioscoreae. Using whole-genome sequencing of plastids and bacteria from wild-collected samples, we show phylogenetic patterns consistent with a dominant vertical mode of transmission of the symbionts. Unique so far among leaf nodule symbioses, the bacteria can be cultured and are amenable to comparative transcriptomics, revealing a potential role in complementing the host's arsenal of secondary metabolites. We propose a recent establishment of a vertical mode of transmission in this symbiosis which, together with a large effective population size explains the cultivability and apparent lack of genome reductive evolution in O. dioscoreae. We leverage these unique features to reveal pathways and functions under positive selection in these specialized endophytes, highlighting the candidate mechanisms enabling a permanent association in the phyllosphere.
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