1
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Lin PH, Tsai ST, Chang YC, Chou YJ, Yeh YC. Harnessing split fluorescent proteins in modular protein logic for advanced whole-cell detection. Anal Chim Acta 2023; 1275:341593. [PMID: 37524469 DOI: 10.1016/j.aca.2023.341593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2023] [Accepted: 07/05/2023] [Indexed: 08/02/2023]
Abstract
Whole-cell biosensors have demonstrated promising capabilities in detecting target molecules. However, their limited selectivity and precision can be attributed to the broad substrate tolerance of natural proteins. In this study, we aim to enhance the performance of whole-cell biosensors by incorporating of logic AND gates. Specifically, we utilize the HrpR/S system, a widely employed hetero-regulation module from Pseudomonas syringae in synthetic biology, to construct an orthogonal AND gate in Escherichia coli. To accomplish this, we compare the HrpR/S system with self-associating split fluorescent proteins using the Spy Tag/Spy Catcher system. Our objective is to selectively activate a reporter gene in the presence of both IPTG and Hg(II) ions. Through systematic genetic engineering and evaluation of various biological parts under diverse working conditions, our research demonstrates the utility of self-associating split fluorescent proteins in developing high-performance whole-cell biosensors. This approach offers advantages such as engineering simplicity, reduced basal activity, and improved selectivity. Furthermore, the comparison with the HrpR/S system serves as a valuable control model, providing insights into the relative advantages and limitations of each approach. These findings present a systematic and adaptable strategy to overcome the substrate tolerance challenge faced by whole-cell biosensors.
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Affiliation(s)
- Ping-Heng Lin
- Department of Chemistry, National Taiwan Normal University, Taipei, 116, Taiwan
| | - Ssu-Tzu Tsai
- Department of Chemistry, National Taiwan Normal University, Taipei, 116, Taiwan
| | - Yu-Chia Chang
- Department of Chemistry, National Taiwan Normal University, Taipei, 116, Taiwan
| | - Yi-Ju Chou
- Institute of Applied Mechanics, National Taiwan University, Taipei, 106, Taiwan.
| | - Yi-Chun Yeh
- Department of Chemistry, National Taiwan Normal University, Taipei, 116, Taiwan.
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2
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Kotta-Loizou I, Giuliano MG, Jovanovic M, Schaefer J, Ye F, Zhang N, Irakleidi DA, Liu X, Zhang X, Buck M, Engl C. The RNA repair proteins RtcAB regulate transcription activator RtcR via its CRISPR-associated Rossmann fold domain. iScience 2022; 25:105425. [PMID: 36388977 PMCID: PMC9650030 DOI: 10.1016/j.isci.2022.105425] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 05/21/2022] [Accepted: 10/18/2022] [Indexed: 11/07/2022] Open
Abstract
CRISPR-associated Rossmann fold (CARF) domain signaling underpins modulation of CRISPR-Cas nucleases; however, the RtcR CARF domain controls expression of two conserved RNA repair enzymes, cyclase RtcA and ligase RtcB. Here, we demonstrate that RtcAB are required for RtcR-dependent transcription activation and directly bind to RtcR CARF. RtcAB catalytic activity is not required for complex formation with CARF, but is essential yet not sufficient for RtcRAB-dependent transcription activation, implying the need for an additional RNA repair-dependent activating signal. This signal differs from oligoadenylates, a known ligand of CARF domains, and instead appears to originate from the translation apparatus: RtcB repairs a tmRNA that rescues stalled ribosomes and increases translation elongation speed. Taken together, our data provide evidence for an expanded range for CARF domain signaling, including the first evidence of its control via in trans protein-protein interactions, and a feed-forward mechanism to regulate RNA repair required for a functioning translation apparatus.
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Affiliation(s)
- Ioly Kotta-Loizou
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, UK
| | - Maria Grazia Giuliano
- School of Biological and Behavioural Sciences, Queen Mary University of London, London E1 4NS, UK
| | - Milija Jovanovic
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, UK
| | - Jorrit Schaefer
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, UK
| | - Fuzhou Ye
- Section of Structural Biology, Faculty of Medicine, Imperial College London, London SW7 2AZ, UK
| | - Nan Zhang
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, UK
- Houston Methodist Research Institute, Houston, TX 77030, USA
| | - Danai Athina Irakleidi
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, UK
| | - Xiaojiao Liu
- Section of Structural Biology, Faculty of Medicine, Imperial College London, London SW7 2AZ, UK
- College of Food Science and Engineering, Northwest A&F University, Yangling 712100, China
| | - Xiaodong Zhang
- Section of Structural Biology, Faculty of Medicine, Imperial College London, London SW7 2AZ, UK
| | - Martin Buck
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, UK
| | - Christoph Engl
- Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London SW7 2AZ, UK
- School of Biological and Behavioural Sciences, Queen Mary University of London, London E1 4NS, UK
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3
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The OmpR-like Transcription Factor as a Negative Regulator of hrpR/S in Pseudomonas syringae pv. actinidiae. Int J Mol Sci 2022; 23:ijms232012306. [PMID: 36293158 PMCID: PMC9602974 DOI: 10.3390/ijms232012306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2022] [Revised: 09/28/2022] [Accepted: 10/10/2022] [Indexed: 11/05/2022] Open
Abstract
Bacterial canker of kiwifruit is a devastating disease caused by Pseudomonas syringae pv. actinidiae (Psa). The type III secretion system (T3SS), which translocates effectors into plant cells to subvert plant immunity and promote extracellular bacterial growth, is required for Psa virulence. Despite that the “HrpR/S-HrpL” cascade that sophisticatedly regulates the expression of T3SS and effectors has been well documented, the transcriptional regulators of hrpR/S remain to be determined. In this study, the OmpR-like transcription factor, previously identified by DNA pull-down assay, was found to be involved in the regulation of hrpR/S genes, and its regulatory mechanisms and other functions in Psa were explored through techniques including gene knockout and overexpression, ChIP-seq, and RNA-seq. The OmpR-like transcription factor had binding sites in the promoter region of the hrpR/S, and the transcriptional level of the hrpR/S increased after the deletion of OmpR-like and decreased upon its overexpression in an OmpR-like deletion background. Additionally, OmpR-like overexpression reduced the strain’s capacity to form biofilms and lipopolysaccharides, led to its slow growth in King’s B medium, and reduced its swimming ability, although there was no significant effect on its pathogenicity against kiwifruit hosts. Our results indicated that OmpR-like directly and negatively regulates the transcription of hrpR/S and may be involved in the regulation of multiple biological processes in Psa. Our results provide a basis for further understanding the transcriptional regulation mechanism of hrpR/S in Psa.
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Xie Y, Li J, Ding Y, Shao X, Sun Y, Xie F, Liu S, Tang S, Deng X. An atlas of bacterial two-component systems reveals function and plasticity in signal transduction. Cell Rep 2022; 41:111502. [DOI: 10.1016/j.celrep.2022.111502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2022] [Revised: 08/11/2022] [Accepted: 09/22/2022] [Indexed: 11/03/2022] Open
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5
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Li R, Chen S, Li Y, Chen X, Ye BC. Development of a "Turn off-on" whole-cell biosensor for sulforaphane detection based on the ultrasensitive activator HrpRS. Biotechnol Appl Biochem 2022; 70:798-810. [PMID: 36070874 DOI: 10.1002/bab.2400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Accepted: 08/13/2022] [Indexed: 11/09/2022]
Abstract
Sulforaphane (SFN), a defense secondary metabolite, can be used to predict the health status of plants and also has pharmacological effects, including anticancer, antioxidant, and anti-inflammatory properties. The detection of SFN is therefore of great significance for the prevention and treatment of diseases. In this study, a "Turn off" whole-cell biosensor that can rapidly and robustly respond to the presence of SFN was constructed based on the orthogonal genetic components (hrpR, hrpS, and PhrpL ) of Pseudomonas syringae (PS). The final optimized biosensor, p114(30R-30S), was able to inhibit 91.7% of the fluorescence intensity in the presence of 100-μM SFN. Subsequently, a HrpRS-regulated OFF-ON genetic switch was designed by reconstituting a reverse σ70 promoter on the σ54 -PhrpL promoter sequence; this was coupled with dual-color reporter genes to construct a "Turn off-on" whole-cell SFN biosensor. The PhrpLB variant increased the expression of green fluorescence a factor of 11.9 and reduced the expression of red fluorescence by 85.8% compared with the system in the absence of SFN. Thus, a robust switching of signal output from "turn off" to "turn on" was realized. In addition, the biosensor showed good linearity in the SFN concentration ranges of 0.1-10 μM (R2 = 0.99429) and 10-100 μM (R2 = 0.99465) and a detection limit of ⁓0.1 μM. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Renjie Li
- School of Chemistry and Chemical Engineering, Shihezi University, Shihezi, 832003, China
| | - Shengyan Chen
- School of Chemistry and Chemical Engineering, Shihezi University, Shihezi, 832003, China
| | - Yangguang Li
- School of Chemistry and Chemical Engineering, Shihezi University, Shihezi, 832003, China
| | - Xuan Chen
- School of Chemistry and Chemical Engineering, Shihezi University, Shihezi, 832003, China
| | - Bang-Ce Ye
- School of Chemistry and Chemical Engineering, Shihezi University, Shihezi, 832003, China.,Institute of Engineering Biology and Health, Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals, College of Pharmaceutical Sciences, Zhejiang University of Technology, Hangzhou, Zhejiang, 310014, China.,Lab of Biosystem and Microanalysis, State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China
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6
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O’Malley MR, Anderson JC. Regulation of the Pseudomonas syringae Type III Secretion System by Host Environment Signals. Microorganisms 2021; 9:microorganisms9061227. [PMID: 34198761 PMCID: PMC8228185 DOI: 10.3390/microorganisms9061227] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 05/30/2021] [Accepted: 06/01/2021] [Indexed: 12/12/2022] Open
Abstract
Pseudomonas syringae are Gram-negative, plant pathogenic bacteria that use a type III secretion system (T3SS) to disarm host immune responses and promote bacterial growth within plant tissues. Despite the critical role for type III secretion in promoting virulence, T3SS-encoding genes are not constitutively expressed by P. syringae and must instead be induced during infection. While it has been known for many years that culturing P. syringae in synthetic minimal media can induce the T3SS, relatively little is known about host signals that regulate the deployment of the T3SS during infection. The recent identification of specific plant-derived amino acids and organic acids that induce T3SS-inducing genes in P. syringae has provided new insights into host sensing mechanisms. This review summarizes current knowledge of the regulatory machinery governing T3SS deployment in P. syringae, including master regulators HrpRS and HrpL encoded within the T3SS pathogenicity island, and the environmental factors that modulate the abundance and/or activity of these key regulators. We highlight putative receptors and regulatory networks involved in linking the perception of host signals to the regulation of the core HrpRS–HrpL pathway. Positive and negative regulation of T3SS deployment is also discussed within the context of P. syringae infection, where contributions from distinct host signals and regulatory networks likely enable the fine-tuning of T3SS deployment within host tissues. Last, we propose future research directions necessary to construct a comprehensive model that (a) links the perception of host metabolite signals to T3SS deployment and (b) places these host–pathogen signaling events in the overall context of P. syringae infection.
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Hua C, Wang T, Shao X, Xie Y, Huang H, Liu J, Zhang W, Zhang Y, Ding Y, Jiang L, Wang X, Deng X. Pseudomonas syringaedual‐function protein Lon switches between virulence and metabolism by acting as bothDNA‐binding transcriptional regulator and protease in different environments. Environ Microbiol 2020; 22:2968-2988. [DOI: 10.1111/1462-2920.15067] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 05/09/2020] [Accepted: 05/11/2020] [Indexed: 12/19/2022]
Affiliation(s)
- Canfeng Hua
- Department of Biomedical SciencesCity University of Hong Kong, 83 Tat Chee Road, 16 Kowloon Tong, Hong Kong China
| | - Tingting Wang
- Department of Biomedical SciencesCity University of Hong Kong, 83 Tat Chee Road, 16 Kowloon Tong, Hong Kong China
| | - Xiaolong Shao
- Department of Biomedical SciencesCity University of Hong Kong, 83 Tat Chee Road, 16 Kowloon Tong, Hong Kong China
| | - Yingpeng Xie
- Department of Biomedical SciencesCity University of Hong Kong, 83 Tat Chee Road, 16 Kowloon Tong, Hong Kong China
| | - Hao Huang
- Department of Biomedical SciencesCity University of Hong Kong, 83 Tat Chee Road, 16 Kowloon Tong, Hong Kong China
| | - Jingui Liu
- Department of Biomedical SciencesCity University of Hong Kong, 83 Tat Chee Road, 16 Kowloon Tong, Hong Kong China
| | - Weitong Zhang
- Department of Biomedical SciencesCity University of Hong Kong, 83 Tat Chee Road, 16 Kowloon Tong, Hong Kong China
| | - Yingchao Zhang
- Department of Biomedical SciencesCity University of Hong Kong, 83 Tat Chee Road, 16 Kowloon Tong, Hong Kong China
| | - Yiqing Ding
- Department of Biomedical SciencesCity University of Hong Kong, 83 Tat Chee Road, 16 Kowloon Tong, Hong Kong China
| | - Lin Jiang
- Department of Biomedical SciencesCity University of Hong Kong, 83 Tat Chee Road, 16 Kowloon Tong, Hong Kong China
| | - Xin Wang
- Department of Biomedical SciencesCity University of Hong Kong, 83 Tat Chee Road, 16 Kowloon Tong, Hong Kong China
| | - Xin Deng
- Department of Biomedical SciencesCity University of Hong Kong, 83 Tat Chee Road, 16 Kowloon Tong, Hong Kong China
- Shenzhen Research InstituteCity University of Hong Kong Shenzhen Guangdong China
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8
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Pseudomonas syringae AlgU Downregulates Flagellin Gene Expression, Helping Evade Plant Immunity. J Bacteriol 2020; 202:JB.00418-19. [PMID: 31740494 DOI: 10.1128/jb.00418-19] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 11/08/2019] [Indexed: 12/15/2022] Open
Abstract
Flagella power bacterial movement through liquids and over surfaces to access or avoid certain environmental conditions, ultimately increasing a cell's probability of survival and reproduction. In some cases, flagella and chemotaxis are key virulence factors enabling pathogens to gain entry and attach to suitable host tissues. However, flagella are not always beneficial; both plant and animal immune systems have evolved receptors to sense the proteins that make up flagellar filaments as signatures of bacterial infection. Microbes poorly adapted to avoid or counteract these immune functions are unlikely to be successful in host environments, and this selective pressure has driven the evolution of diverse and often redundant pathogen compensatory mechanisms. We tested the role of AlgU, the Pseudomonas extracytoplasmic function sigma factor σE/σ22 ortholog, in regulating flagellar expression in the context of Pseudomonas syringae-plant interactions. We found that AlgU is necessary for downregulating bacterial flagellin expression in planta and that this results in a corresponding reduction in plant immune elicitation. This AlgU-dependent regulation of flagellin gene expression is beneficial to bacterial growth in the course of plant infection, and eliminating the plant's ability to detect flagellin makes this AlgU-dependent function irrelevant for bacteria growing in the apoplast. Together, these results add support to an emerging model in which P. syringae AlgU functions at a key control point that serves to optimize the expression of bacterial functions during host interactions, including minimizing the expression of immune elicitors and concomitantly upregulating beneficial virulence functions.IMPORTANCE Foliar plant pathogens, like Pseudomonas syringae, adjust their physiology and behavior to facilitate host colonization and disease, but the full extent of these adaptations is not known. Plant immune systems are triggered by bacterial molecules, such as the proteins that make up flagellar filaments. In this study, we found that during plant infection, AlgU, a gene expression regulator that is responsive to external stimuli, downregulates expression of fliC, which encodes the flagellin protein, a strong elicitor of plant immune systems. This change in gene expression and resultant change in behavior correlate with reduced plant immune activation and improved P. syringae plant colonization. The results of this study demonstrate the proximate and ultimate causes of flagellar regulation in a plant-pathogen interaction.
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Danson AE, Jovanovic M, Buck M, Zhang X. Mechanisms of σ 54-Dependent Transcription Initiation and Regulation. J Mol Biol 2019; 431:3960-3974. [PMID: 31029702 PMCID: PMC7057263 DOI: 10.1016/j.jmb.2019.04.022] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 04/16/2019] [Accepted: 04/16/2019] [Indexed: 02/02/2023]
Abstract
Cellular RNA polymerase is a multi-subunit macromolecular assembly responsible for gene transcription, a highly regulated process conserved from bacteria to humans. In bacteria, sigma factors are employed to mediate gene-specific expression in response to a variety of environmental conditions. The major variant σ factor, σ54, has a specific role in stress responses. Unlike σ70-dependent transcription, which often can spontaneously proceed to initiation, σ54-dependent transcription requires an additional ATPase protein for activation. As a result, structures of a number of distinct functional states during the dynamic process of transcription initiation have been captured using the σ54 system with both x-ray crystallography and cryo electron microscopy, furthering our understanding of σ54-dependent transcription initiation and DNA opening. Comparisons with σ70 and eukaryotic polymerases reveal unique and common features during transcription initiation.
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Affiliation(s)
- Amy E Danson
- Section of Structural Biology, Department of Medicine, Imperial College London, London SW7 2AZ, UK
| | - Milija Jovanovic
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Martin Buck
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Xiaodong Zhang
- Section of Structural Biology, Department of Medicine, Imperial College London, London SW7 2AZ, UK.
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Xie Y, Shao X, Deng X. Regulation of type III secretion system inPseudomonas syringae. Environ Microbiol 2019; 21:4465-4477. [DOI: 10.1111/1462-2920.14779] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 08/10/2019] [Accepted: 08/11/2019] [Indexed: 12/11/2022]
Affiliation(s)
- Yingpeng Xie
- Department of Biomedical SciencesCity University of Hong Kong Kowloon Tong Hong Kong SAR 999077 China
| | - Xiaolong Shao
- Department of Biomedical SciencesCity University of Hong Kong Kowloon Tong Hong Kong SAR 999077 China
| | - Xin Deng
- Department of Biomedical SciencesCity University of Hong Kong Kowloon Tong Hong Kong SAR 999077 China
- Shenzhen Research InstituteCity University of Hong Kong Shenzhen 518057 China
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11
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Migration of Type III Secretion System Transcriptional Regulators Links Gene Expression to Secretion. mBio 2018; 9:mBio.01096-18. [PMID: 30065089 PMCID: PMC6069116 DOI: 10.1128/mbio.01096-18] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Many plant-pathogenic bacteria of considerable economic importance rely on type III secretion systems (T3SSs) of the Hrc-Hrp 1 family to subvert their plant hosts. T3SS gene expression is regulated through the HrpG and HrpV proteins, while secretion is controlled by the gatekeeper HrpJ. A link between the two mechanisms was so far unknown. Here, we show that a mechanistic coupling exists between the expression and secretion cascades through the direct binding of the HrpG/HrpV heterodimer, acting as a T3SS chaperone, to HrpJ. The ternary complex is docked to the cytoplasmic side of the inner bacterial membrane and orchestrates intermediate substrate secretion, without affecting early substrate secretion. The anchoring of the ternary complex to the membranes potentially keeps HrpG/HrpV away from DNA. In their multiple roles as transcriptional regulators and gatekeeper chaperones, HrpV/HrpG provide along with HrpJ potentially attractive targets for antibacterial strategies. On the basis of scientific/economic importance, Pseudomonas syringae and Erwinia amylovora are considered among the top 10 plant-pathogenic bacteria in molecular plant pathology. Both employ type III secretion systems (T3SSs) of the Hrc-Hrp 1 family to subvert their plant hosts. For Hrc-Hrp 1, no functional link was known between the key processes of T3SS gene expression and secretion. Here, we show that a mechanistic coupling exists between expression and secretion cascades, through formation of a ternary complex involving the T3SS proteins HrpG, HrpV, and HrpJ. Our results highlight the functional and structural properties of a hitherto-unknown complex which orchestrates intermediate T3SS substrate secretion and may lead to better pathogen control through novel targets for antibacterial strategies.
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12
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Panopoulos NJ. A Career on Both Sides of the Atlantic: Memoirs of a Molecular Plant Pathologist. ANNUAL REVIEW OF PHYTOPATHOLOGY 2017; 55:1-21. [PMID: 28777925 DOI: 10.1146/annurev-phyto-080516-035506] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
This article recounts the experiences that shaped my career as a molecular plant pathologist. It focuses primarily on technical and conceptual developments in molecular phytobacteriology, shares some personal highlights and untold stories that impacted my professional development, and describes the early years of agricultural biotechnology. Writing this article required reflection on events occurring over several decades that were punctuated by a mid-career relocation across the Atlantic. I hope it will still be useful, informative, and enjoyable to read. An extended version of the abstract is provided in the Supplemental Materials , available online.
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Affiliation(s)
- Nickolas J Panopoulos
- Professor Emeritus, Department of Environmental Science, Policy and Management, University of California, Berkeley, California 94619
- Department of Biology, University of Crete, Heraklion, GR-71003, Greece;
- Hellenic Agricultural Academy, Agricultural University of Athens, 118 55 Athens, Greece
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Jovanovic M, Waite C, James E, Synn N, Simpson T, Kotta-Loizou I, Buck M. Functional Characterization of Key Residues in Regulatory Proteins HrpG and HrpV of Pseudomonas syringae pv. tomato DC3000. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2017; 30:656-665. [PMID: 28488468 DOI: 10.1094/mpmi-03-17-0073-r] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The plant pathogen Pseudomonas syringae pv. tomato DC3000 uses a type III secretion system (T3SS) to transfer effector proteins into the host. The expression of T3SS proteins is controlled by the HrpL σ factor. Transcription of hrpL is σ54-dependent and bacterial enhancer-binding proteins HrpR and HrpS coactivate the hrpL promoter. The HrpV protein imposes negative control upon HrpR and HrpS through direct interaction with HrpS. HrpG interacts with HrpV and relieves such negative control. The sequence alignments across Hrp group I-type plant pathogens revealed conserved HrpV and HrpG amino acids. To establish structure-function relationships in HrpV and HrpG, either truncated or alanine substitution mutants were constructed. Key functional residues in HrpV and HrpG are found within their C-terminal regions. In HrpG, L101 and L105 are indispensable for the ability of HrpG to directly interact with HrpV and suppress HrpV-dependent negative regulation of HrpR and HrpS. In HrpV, L108 and G110 are major determinants for interactions with HrpS and HrpG. We propose that mutually exclusive binding of HrpS and HrpG to the same binding site of HrpV governs a transition from negative control to activation of the HrpRS complex leading to HrpL expression and pathogenicity of P. syringae.
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Affiliation(s)
- Milija Jovanovic
- 1 Imperial College London, Imperial College Road, London, SW7 2AZ, U.K
| | - Christopher Waite
- 1 Imperial College London, Imperial College Road, London, SW7 2AZ, U.K
| | - Ellen James
- 2 Trio Medicines Ltd., Hammersmith Medicines Research, Cumberland Avenue, London, NW10 7EW, U.K.; and
| | - Nicholas Synn
- 1 Imperial College London, Imperial College Road, London, SW7 2AZ, U.K
| | - Timothy Simpson
- 3 Medical School, Queen's Medical Centre, Nottingham, NG7 2UH, U.K
| | - Ioly Kotta-Loizou
- 1 Imperial College London, Imperial College Road, London, SW7 2AZ, U.K
| | - Martin Buck
- 1 Imperial College London, Imperial College Road, London, SW7 2AZ, U.K
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Negative Autogenous Control of the Master Type III Secretion System Regulator HrpL in Pseudomonas syringae. mBio 2017; 8:mBio.02273-16. [PMID: 28119474 PMCID: PMC5263251 DOI: 10.1128/mbio.02273-16] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The type III secretion system (T3SS) is a principal virulence determinant of the model bacterial plant pathogen Pseudomonas syringae T3SS effector proteins inhibit plant defense signaling pathways in susceptible hosts and elicit evolved immunity in resistant plants. The extracytoplasmic function sigma factor HrpL coordinates the expression of most T3SS genes. Transcription of hrpL is dependent on sigma-54 and the codependent enhancer binding proteins HrpR and HrpS for hrpL promoter activation. hrpL is oriented adjacently to and divergently from the HrpL-dependent gene hrpJ, sharing an intergenic upstream regulatory region. We show that association of the RNA polymerase (RNAP)-HrpL complex with the hrpJ promoter element imposes negative autogenous control on hrpL transcription in P. syringae pv. tomato DC3000. The hrpL promoter was upregulated in a ΔhrpL mutant and was repressed by plasmid-borne hrpL In a minimal Escherichia coli background, the activity of HrpL was sufficient to achieve repression of reconstituted hrpL transcription. This repression was relieved if both the HrpL DNA-binding function and the hrp-box sequence of the hrpJ promoter were compromised, implying dependence upon the hrpJ promoter. DNA-bound RNAP-HrpL entirely occluded the HrpRS and partially occluded the integration host factor (IHF) recognition elements of the hrpL promoter in vitro, implicating inhibition of DNA binding by these factors as a cause of negative autogenous control. A modest increase in the HrpL concentration caused hypersecretion of the HrpA1 pilus protein but intracellular accumulation of later T3SS substrates. We argue that negative feedback on HrpL activity fine-tunes expression of the T3SS regulon to minimize the elicitation of plant defenses. IMPORTANCE The United Nations Food and Agriculture Organization has warned that agriculture will need to satisfy a 50% to 70% increase in global food demand if the human population reaches 9 billion by 2050 as predicted. However, diseases caused by microbial pathogens represent a major threat to food security, accounting for over 10% of estimated yield losses in staple wheat, rice, and maize crops. Understanding the decision-making strategies employed by pathogens to coordinate virulence and to evade plant defenses is vital for informing crop resistance traits and management strategies. Many plant-pathogenic bacteria utilize the needle-like T3SS to inject virulence factors into host plant cells to suppress defense signaling. Pseudomonas syringae is an economically and environmentally devastating plant pathogen. We propose that the master regulator of its entire T3SS gene set, HrpL, downregulates its own expression to minimize elicitation of plant defenses. Revealing such conserved regulatory strategies will inform future antivirulence strategies targeting plant pathogens.
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McCraw SL, Park DH, Jones R, Bentley MA, Rico A, Ratcliffe RG, Kruger NJ, Collmer A, Preston GM. GABA (γ-Aminobutyric Acid) Uptake Via the GABA Permease GabP Represses Virulence Gene Expression in Pseudomonas syringae pv. tomato DC3000. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2016; 29:938-949. [PMID: 28001093 DOI: 10.1094/mpmi-08-16-0172-r] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The nonprotein amino acid γ-aminobutyric acid (GABA) is the most abundant amino acid in the tomato (Solanum lycopersicum) leaf apoplast and is synthesized by Arabidopsis thaliana in response to infection by the bacterial pathogen Pseudomonas syringae pv. tomato DC3000 (hereafter called DC3000). High levels of exogenous GABA have previously been shown to repress the expression of the type III secretion system (T3SS) in DC3000, resulting in reduced elicitation of the hypersensitive response (HR) in the nonhost plant tobacco (Nicotiana tabacum). This study demonstrates that the GABA permease GabP provides the primary mechanism for GABA uptake by DC3000 and that the gabP deletion mutant ΔgabP is insensitive to GABA-mediated repression of T3SS expression. ΔgabP displayed an enhanced ability to elicit the HR in young tobacco leaves and in tobacco plants engineered to produce increased levels of GABA, which supports the hypothesis that GABA uptake via GabP acts to regulate T3SS expression in planta. The observation that P. syringae can be rendered insensitive to GABA through loss of gabP but that gabP is retained by this bacterium suggests that GabP is important for DC3000 in a natural setting, either for nutrition or as a mechanism for regulating gene expression. [Formula: see text] Copyright © 2016 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)
- S L McCraw
- 1 Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, U.K
| | - D H Park
- 2 Department of Applied Biology, College of Agriculture and Life Sciences, Kangwon National University, Chuncheon 200-701, Republic of Korea
| | - R Jones
- 1 Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, U.K
| | - M A Bentley
- 1 Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, U.K
| | - A Rico
- 3 Departamento de Didáctica de la 9 Matemática y de las Ciencias Experimentales, Faculty of Education and Sport, University of the Basque Country UPV/EHU, Juan Ibañez de Sto. Domingo 1, 01006 Vitoria-Gasteiz, Spain; and
| | - R G Ratcliffe
- 1 Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, U.K
| | - N J Kruger
- 1 Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, U.K
| | - A Collmer
- 4 School of Integrative Plant Science, Section of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, NY 14853, U.S.A
| | - G M Preston
- 1 Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, U.K
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Global Analysis of Type Three Secretion System and Quorum Sensing Inhibition of Pseudomonas savastanoi by Polyphenols Extracts from Vegetable Residues. PLoS One 2016; 11:e0163357. [PMID: 27668874 PMCID: PMC5036890 DOI: 10.1371/journal.pone.0163357] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Accepted: 09/06/2016] [Indexed: 11/30/2022] Open
Abstract
Protection of plants against bacterial diseases still mainly relies on the use of chemical pesticides, which in Europe correspond essentially to copper-based compounds. However, recently plant diseases control is oriented towards a rational use of molecules and extracts, generally with natural origin, with lower intrinsic toxicity and a reduced negative environmental impact. In this work, polyphenolic extracts from vegetable no food/feed residues of typical Mediterranean crops, as Olea europaea, Cynara scolymus, and Vitis vinifera were obtained and their inhibitory activity on the Type Three Secretion System (TTSS) and the Quorum Sensing (QS) of the Gram-negative phytopathogenic bacterium Pseudomonas savastanoi pv. nerii strain Psn23 was assessed. Extract from green tea (Camellia sinensis) was used as a positive control. Collectively, the data obtained through gfp-promoter fusion system and real-time PCR show that all the polyphenolic extracts here studied have a high inhibitory activity on both the TTSS and QS of Psn23, without any depressing effect on bacterial viability. Extracts from green tea and grape seeds were shown to be the most active. Such activity was confirmed in planta by a strong reduction in the ability of Psn23 to develop hyperplastic galls on explants from adult oleander plants, as well as to elicit hypersensitive response on tobacco. By using a newly developed Congo red assay and an ELISA test, we demonstrated that the TTSS-targeted activity of these polyphenolic extracts also affects the TTSS pilus assembly. In consideration of the potential application of polyphenolic extracts in plant protection, the absence of any toxicity of these polyphenolic compounds was also assessed. A widely and evolutionary conserved molecular target such as Ca2+-ATPase, essential for the survival of any living organism, was used for the toxicity assessment.
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17
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Huang YC, Lin YC, Wei CF, Deng WL, Huang HC. The pathogenicity factor HrpF interacts with HrpA and HrpG to modulate type III secretion system (T3SS) function and t3ss expression in Pseudomonas syringae pv. averrhoi. MOLECULAR PLANT PATHOLOGY 2016; 17:1080-94. [PMID: 26638129 PMCID: PMC6638529 DOI: 10.1111/mpp.12349] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 11/05/2015] [Accepted: 11/29/2015] [Indexed: 05/08/2023]
Abstract
To ensure the optimal infectivity on contact with host cells, pathogenic Pseudomonas syringae has evolved a complex mechanism to control the expression and construction of the functional type III secretion system (T3SS) that serves as a dominant pathogenicity factor. In this study, we showed that the hrpF gene of P. syringae pv. averrhoi, which is located upstream of hrpG, encodes a T3SS-dependent secreted/translocated protein. Mutation of hrpF leads to the loss of bacterial ability on elicitation of disease symptoms in the host and a hypersensitive response in non-host plants, and the secretion or translocation of the tested T3SS substrates into the bacterial milieu or plant cells. Moreover, overexpression of hrpF in the wild-type results in delayed HR and reduced t3ss expression. The results of protein-protein interactions demonstrate that HrpF interacts directly with HrpG and HrpA in vitro and in vivo, and protein stability assays reveal that HrpF assists HrpA stability in the bacterial cytoplasm, which is reduced by a single amino acid substitution at the 67th lysine residue of HrpF with alanine. Taken together, the data presented here suggest that HrpF has two roles in the assembly of a functional T3SS: one by acting as a negative regulator, possibly involved in the HrpSVG regulation circuit via binding to HrpG, and the other by stabilizing HrpA in the bacterial cytoplasm via HrpF-HrpA interaction prior to the secretion and formation of Hrp pilus on the bacterial surface.
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Affiliation(s)
- Yi-Chiao Huang
- Department of Plant Pathology, National Chung Hsing University, Taichung, 40227, Taiwan
- Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Yuan-Chuen Lin
- Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Chia-Fong Wei
- Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Wen-Ling Deng
- Department of Plant Pathology, National Chung Hsing University, Taichung, 40227, Taiwan
- Agricultural Biotechnology Center, National Chung Hsing University, Taichung, 40227, Taiwan
| | - Hsiou-Chen Huang
- Graduate Institute of Biotechnology, National Chung Hsing University, Taichung, 40227, Taiwan
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18
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Marcos-Torres FJ, Pérez J, Gómez-Santos N, Moraleda-Muñoz A, Muñoz-Dorado J. In depth analysis of the mechanism of action of metal-dependent sigma factors: characterization of CorE2 from Myxococcus xanthus. Nucleic Acids Res 2016; 44:5571-84. [PMID: 26951374 PMCID: PMC4937300 DOI: 10.1093/nar/gkw150] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 02/29/2016] [Indexed: 11/13/2022] Open
Abstract
Extracytoplasmic function sigma factors represent the third pillar of signal-transduction mechanisms in bacteria. The variety of stimuli they recognize and mechanisms of action they use have allowed their classification into more than 50 groups. We have characterized CorE2 from Myxococcus xanthus, which belongs to group ECF44 and upregulates the expression of two genes when it is activated by cadmium and zinc. Sigma factors of this group contain a Cys-rich domain (CRD) at the C terminus which is essential for detecting metals. Point mutations at the six Cys residues of the CRD have revealed the contribution of each residue to CorE2 activity. Some of them are essential, while others are either dispensable or their mutations only slightly affect the activity of the protein. However, importantly, mutation of Cys174 completely shifts the specificity of CorE2 from cadmium to copper, indicating that the Cys arrangement of the CRD determines the metal specificity. Moreover, the conserved CxC motif located between the σ2 domain and the σ4.2 region has also been found to be essential for activity. The results presented here contribute to our understanding of the mechanism of action of metal-dependent sigma factors and help to define new common features of the members of this group of regulators.
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Affiliation(s)
- Francisco Javier Marcos-Torres
- Departamento de Microbiología, Facultad de Ciencias, Universidad de Granada, Avda. Fuentenueva s/n, E-18071 Granada, Spain
| | - Juana Pérez
- Departamento de Microbiología, Facultad de Ciencias, Universidad de Granada, Avda. Fuentenueva s/n, E-18071 Granada, Spain
| | - Nuria Gómez-Santos
- Departamento de Microbiología, Facultad de Ciencias, Universidad de Granada, Avda. Fuentenueva s/n, E-18071 Granada, Spain
| | - Aurelio Moraleda-Muñoz
- Departamento de Microbiología, Facultad de Ciencias, Universidad de Granada, Avda. Fuentenueva s/n, E-18071 Granada, Spain
| | - José Muñoz-Dorado
- Departamento de Microbiología, Facultad de Ciencias, Universidad de Granada, Avda. Fuentenueva s/n, E-18071 Granada, Spain
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Gazi AD, Charova S, Aivaliotis M, Panopoulos NJ, Kokkinidis M. HrpG and HrpV proteins from the Type III secretion system of Erwinia amylovora form a stable heterodimer. FEMS Microbiol Lett 2014; 362:1-8. [PMID: 25790492 DOI: 10.1093/femsle/fnu011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Bacterial type III secretion systems (T3SSs) are specialized multicomponent nanomachines that mediate the transport of proteins either to extracellular locations or directly into eukaryotic host cell cytoplasm. Erwinia amylovora, the main agent of rosaceous plants fireblight disease, employs an Hrp/Hrc1 T3SS to accomplish its pathogenesis. The regulatory network that controls the activation of this T3SS is largely unknown in E. amylovora. However, in Pseudomonas syringae pathovars, the HrpG/HrpV complex has been shown to directly regulate the activity of transcription factor HrpS and consequently the upregulation of the Hrp/Hrc1 T3SS related genes. In this work, we report the successful recombinant production and purification of a stable E. amylovora HrpG/HrpV complex, using pPROpET, a bicistronic expression vector. Furthermore, we present the first solution structure of this complex based on small-angle X-ray scattering data.
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Affiliation(s)
- Anastasia D Gazi
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas (IMBB-FORTH), Nikolaou Plastira 100, GR-70013, Heraklion, Crete, Greece Biology Department, University of Crete, Vasilika Vouton, 71409 Heraklio, Crete, Greece
| | - Spyridoula Charova
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas (IMBB-FORTH), Nikolaou Plastira 100, GR-70013, Heraklion, Crete, Greece
| | - Michalis Aivaliotis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas (IMBB-FORTH), Nikolaou Plastira 100, GR-70013, Heraklion, Crete, Greece
| | - Nicholas J Panopoulos
- Professor Emeritus, Biology Department, University of Crete, Vasilika Vouton, 71409 Heraklio, Crete, Greece Professor Emeritus, Department of Environmental Sciences, Policy, and Management, University of California, Berkeley, 130 Mulford Hall, Berkeley, CA 94720-3114, USA
| | - Michael Kokkinidis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas (IMBB-FORTH), Nikolaou Plastira 100, GR-70013, Heraklion, Crete, Greece Biology Department, University of Crete, Vasilika Vouton, 71409 Heraklio, Crete, Greece
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