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Fromm K, Ortelli M, Boegli A, Dehio C. Translocation of YopJ family effector proteins through the VirB/VirD4 T4SS of Bartonella. Proc Natl Acad Sci U S A 2024; 121:e2310348121. [PMID: 38709922 PMCID: PMC11098119 DOI: 10.1073/pnas.2310348121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Accepted: 03/25/2024] [Indexed: 05/08/2024] Open
Abstract
The evolutionary conserved YopJ family comprises numerous type-III-secretion system (T3SS) effectors of diverse mammalian and plant pathogens that acetylate host proteins to dampen immune responses. Acetylation is mediated by a central acetyltransferase domain that is flanked by conserved regulatory sequences, while a nonconserved N-terminal extension encodes the T3SS-specific translocation signal. Bartonella spp. are facultative-intracellular pathogens causing intraerythrocytic bacteremia in their mammalian reservoirs and diverse disease manifestations in incidentally infected humans. Bartonellae do not encode a T3SS, but most species possess a type-IV-secretion system (T4SS) to translocate Bartonella effector proteins (Beps) into host cells. Here we report that the YopJ homologs present in Bartonellae species represent genuine T4SS effectors. Like YopJ family T3SS effectors of mammalian pathogens, the "Bartonella YopJ-like effector A" (ByeA) of Bartonella taylorii also targets MAP kinase signaling to dampen proinflammatory responses, however, translocation depends on a functional T4SS. A split NanoLuc luciferase-based translocation assay identified sequences required for T4SS-dependent translocation in conserved regulatory regions at the C-terminus and proximal to the N-terminus of ByeA. The T3SS effectors YopP from Yersinia enterocolitica and AvrA from Salmonella Typhimurium were also translocated via the Bartonella T4SS, while ByeA was not translocated via the Yersinia T3SS. Our data suggest that YopJ family T3SS effectors may have evolved from an ancestral T4SS effector, such as ByeA of Bartonella. In this evolutionary scenario, the signal for T4SS-dependent translocation encoded by N- and C-terminal sequences remained functional in the derived T3SS effectors due to the essential role these sequences coincidentally play in regulating acetyltransferase activity.
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Affiliation(s)
- Katja Fromm
- Biozentrum, University of Basel, Basel4056, Switzerland
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Heiden N, Roman-Reyna V, Curland RD, Dill-Macky R, Jacobs JM. Comparative Genomics of Barley-Infecting Xanthomonas translucens Shows Overall Genetic Similarity but Globally Distributed Virulence Factor Diversity. PHYTOPATHOLOGY 2023; 113:2056-2061. [PMID: 35727947 DOI: 10.1094/phyto-04-22-0113-sc] [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: 05/05/2023]
Abstract
Xanthomonas translucens pv. translucens (Xtt) is a global barley patho-gen and a concern for resistance breeding and regulation. Long-read whole genome sequences allow in-depth understanding of pathogen diversity. We have completed long-read PacBio sequencing of two Minnesotan Xtt strains and an in-depth analysis of available Xtt genomes. We found that average nucleotide identity (ANI)-based approaches organize Xtt strains different from the previous standard multilocus sequencing analysis approach. According to ANI, Xtt forms a separate clade from X. translucens pv. undulosa and consists of three main groups which are represented on multiple continents. Some virulence factors, such as 17 Type III-secreted effectors, are highly conserved and offer potential targets for the elicitation of broad resistance. However, there is a high degree of variation in virulence factors, meaning that germplasm should be screened for resistance with a diverse panel of Xtt.
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Affiliation(s)
- Nathaniel Heiden
- Department of Plant Pathology, The Ohio State University, Columbus, OH 43210
- Infectious Diseases Institute, The Ohio State University, Columbus, OH 43210
| | - Veronica Roman-Reyna
- Department of Plant Pathology, The Ohio State University, Columbus, OH 43210
- Infectious Diseases Institute, The Ohio State University, Columbus, OH 43210
| | - Rebecca D Curland
- Department of Plant Pathology, University of Minnesota, St. Paul, MN 55108
| | - Ruth Dill-Macky
- Department of Plant Pathology, University of Minnesota, St. Paul, MN 55108
| | - Jonathan M Jacobs
- Department of Plant Pathology, The Ohio State University, Columbus, OH 43210
- Infectious Diseases Institute, The Ohio State University, Columbus, OH 43210
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Heiden N, Broders KA, Hutin M, Castro MO, Roman-Reyna V, Toth H, Jacobs JM. Bacterial Leaf Streak Diseases of Plants: Symptom Convergence in Monocot Plants by Distant Pathogenic Xanthomonas Species. PHYTOPATHOLOGY 2023; 113:2048-2055. [PMID: 37996392 DOI: 10.1094/phyto-05-23-0155-ia] [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: 11/25/2023]
Abstract
Bacterial leaf streak (BLS) is a disease of monocot plants caused by Xanthomonas translucens on small grains, X. vasicola on maize and sorghum, and X. oryzae on rice. These three pathogens cause remarkably similar symptomology in their host plants. Despite causing similar symptoms, BLS pathogens are dispersed throughout the larger Xanthomonas phylogeny. Each aforementioned species includes strain groups that do not cause BLS and instead cause vascular disease. In this commentary, we hypothesize that strains of X. translucens, X. vasicola, and X. oryzae convergently evolved to cause BLS due to shared evolutionary pressures. We examined the diversity of secreted effectors, which may be important virulence factors for BLS pathogens and their evolution. We discuss evidence that differences in gene regulation and abilities to manipulate plant hormones may also separate BLS pathogens from other Xanthomonas species or pathovars. BLS is becoming an increasing issue across the three pathosystems. Overall, we hope that a better understanding of conserved mechanisms used by BLS pathogens will enable researchers to translate findings across production systems and guide approaches to control this (re)emerging threat.
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Affiliation(s)
- Nathaniel Heiden
- Department of Plant Pathology, The Ohio State University, Columbus, OH 43210, U.S.A
- Infectious Diseases Institute, The Ohio State University, Columbus, OH 43210, U.S.A
| | - Kirk A Broders
- U.S. Department of Agriculture-Agricultural Research Service, National Center for Agricultural Utilization Research, Mycotoxin Prevention and Applied Microbiology Research Unit, Peoria, IL 61604, U.S.A
| | - Mathilde Hutin
- Plant Health Institute of Montpellier, University of Montpellier, IRD, CIRAD, INRAE, Institut Agro, Montpellier, France
| | - Mary Ortiz Castro
- Horticulture and Extension Programs, Colorado State University, Castle Rock, CO 80106, U.S.A
| | - Verónica Roman-Reyna
- Department of Plant Pathology, The Ohio State University, Columbus, OH 43210, U.S.A
- Infectious Diseases Institute, The Ohio State University, Columbus, OH 43210, U.S.A
- Department of Plant Pathology and Environmental Microbiology, Pennsylvania State University, University Park, PA 16802, U.S.A
| | - Hannah Toth
- Department of Plant Pathology, The Ohio State University, Columbus, OH 43210, U.S.A
- Infectious Diseases Institute, The Ohio State University, Columbus, OH 43210, U.S.A
| | - Jonathan M Jacobs
- Department of Plant Pathology, The Ohio State University, Columbus, OH 43210, U.S.A
- Infectious Diseases Institute, The Ohio State University, Columbus, OH 43210, U.S.A
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Drehkopf S, Scheibner F, Büttner D. Functional characterization of VirB/VirD4 and Icm/Dot type IV secretion systems from the plant-pathogenic bacterium Xanthomonas euvesicatoria. Front Cell Infect Microbiol 2023; 13:1203159. [PMID: 37593760 PMCID: PMC10432156 DOI: 10.3389/fcimb.2023.1203159] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Accepted: 07/17/2023] [Indexed: 08/19/2023] Open
Abstract
Introduction Many Gram-negative plant- and animal-pathogenic bacteria employ type IV secretion (T4S) systems to transport proteins or DNA/protein complexes into eukaryotic or bacterial target cells. T4S systems have been divided into minimized and expanded T4S systems and resemble the VirB/VirD4 T4S system from the plant pathogen Agrobacterium tumefaciens and the Icm/Dot T4S system from the human pathogen Legionella pneumophila, respectively. The only known plant pathogen with both types of T4S systems is Xanthomonas euvesicatoria which is the causal agent of bacterial spot disease on pepper and tomato plants. Results and discussion In the present study, we show that virB/virD4 and icm/dot T4S genes are expressed and encode components of oligomeric complexes corresponding to known assemblies of VirB/VirD4 and Icm/Dot proteins. Both T4S systems are dispensable for the interaction of X. euvesicatoria with its host plants and do not seem to confer contact-dependent lysis of other bacteria, which was previously shown for the chromosomally encoded VirB/VirD4 T4S system from Xanthomonas axonopodis pv. citri. The corresponding chromosomal T4S gene cluster from X. euvesicatoria is incomplete, however, the second plasmid-localized vir gene cluster encodes a functional VirB/VirD4 T4S system which contributes to plasmid transfer. In agreement with this finding, we identified the predicted relaxase TraI as substrate of the T4S systems from X. euvesicatoria. TraI and additional candidate T4S substrates with homology to T4S effectors from X. axonopodis pv. citri interact with the T4S coupling protein VirD4. Interestingly, however, the predicted C-terminal VirD4-binding sites are not sufficient for T4S, suggesting the contribution of additional yet unknown mechanisms to the targeting of T4S substrates from X. euvesicatoria to both VirB/VirD4 and Icm/Dot T4S systems.
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Affiliation(s)
| | | | - Daniela Büttner
- Institute for Biology, Department of Genetics, Martin-Luther University Halle-Wittenberg, Halle (Saale), Germany
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Paauw M, van Hulten M, Chatterjee S, Berg JA, Taks NW, Giesbers M, Richard MMS, van den Burg HA. Hydathode immunity protects the Arabidopsis leaf vasculature against colonization by bacterial pathogens. Curr Biol 2023; 33:697-710.e6. [PMID: 36731466 DOI: 10.1016/j.cub.2023.01.013] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 10/27/2022] [Accepted: 01/09/2023] [Indexed: 02/04/2023]
Abstract
Plants prevent disease by passively and actively protecting potential entry routes against invading microbes. For example, the plant immune system actively guards roots, wounds, and stomata. How plants prevent vascular disease upon bacterial entry via guttation fluids excreted from specialized glands at the leaf margin remains largely unknown. These so-called hydathodes release xylem sap when root pressure is too high. By studying hydathode colonization by both hydathode-adapted (Xanthomonas campestris pv. campestris) and non-adapted pathogenic bacteria (Pseudomonas syringae pv. tomato) in immunocompromised Arabidopsis mutants, we show that the immune hubs BAK1 and EDS1-PAD4-ADR1 restrict bacterial multiplication in hydathodes. Both immune hubs effectively confine bacterial pathogens to hydathodes and lower the number of successful escape events of an hydathode-adapted pathogen toward the xylem. A second layer of defense, which is dependent on the plant hormones' pipecolic acid and to a lesser extent on salicylic acid, reduces the vascular spread of the pathogen. Thus, besides glands, hydathodes represent a potent first line of defense against leaf-invading microbes.
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Affiliation(s)
- Misha Paauw
- Molecular Plant Pathology, Swammerdam Institute for Life Sciences (SILS), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Marieke van Hulten
- Molecular Plant Pathology, Swammerdam Institute for Life Sciences (SILS), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Sayantani Chatterjee
- Molecular Plant Pathology, Swammerdam Institute for Life Sciences (SILS), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Jeroen A Berg
- Molecular Plant Pathology, Swammerdam Institute for Life Sciences (SILS), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Nanne W Taks
- Molecular Plant Pathology, Swammerdam Institute for Life Sciences (SILS), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Marcel Giesbers
- Wageningen Electron Microscopy Centre, Department of Plant Sciences, Wageningen University & Research, Droevendaalsesteeg 4, 6708 PB Wageningen, The Netherlands
| | - Manon M S Richard
- Molecular Plant Pathology, Swammerdam Institute for Life Sciences (SILS), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Harrold A van den Burg
- Molecular Plant Pathology, Swammerdam Institute for Life Sciences (SILS), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.
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Zhao JY, Chen J, Shi Y, Fu HY, Huang MT, Rott PC, Gao SJ. Sugarcane responses to two strains of Xanthomonas albilineans differing in pathogenicity through a differential modulation of salicylic acid and reactive oxygen species. FRONTIERS IN PLANT SCIENCE 2022; 13:1087525. [PMID: 36589125 PMCID: PMC9798216 DOI: 10.3389/fpls.2022.1087525] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Accepted: 12/02/2022] [Indexed: 06/17/2023]
Abstract
Leaf scald caused by Xanthomonas albilineans is one of the major bacterial diseases of sugarcane that threaten the sugar industry worldwide. Pathogenic divergence among strains of X. albilineans and interactions with the sugarcane host remain largely unexplored. In this study, 40 strains of X. albilineans from China were distributed into three distinct evolutionary groups based on multilocus sequence analysis and simple sequence repeats loci markers. In pathogenicity assays, the 40 strains of X. albilineans from China were divided into three pathogenicity groups (low, medium, and high). Twenty-four hours post inoculation (hpi) of leaf scald susceptible variety GT58, leaf populations of X. albilineans strain XaCN51 (high pathogenicity group) determined by qPCR were 3-fold higher than those of strain XaCN24 (low pathogenicity group). Inoculated sugarcane plants modulated the reactive oxygen species (ROS) homoeostasis by enhancing respiratory burst oxidase homolog (ScRBOH) expression and superoxide dismutase (SOD) activity and by decreasing catalase (CAT) activity, especially after infection by X. albilineans XaCN51. Furthermore, at 24 hpi, plants infected with XaCN51 maintained a lower content of endogenous salicylic acid (SA) and a lower expression level of SA-mediated genes (ScNPR3, ScTGA4, ScPR1, and ScPR5) as compared to plants infected with XaCN24. Altogether, these data revealed that the ROS production-scavenging system and activation of the SA pathway were involved in the sugarcane defense response to an attack by X. albilineans.
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Affiliation(s)
- Jian-Ying Zhao
- National Engineering Research Center for Sugarcane, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
| | - Juan Chen
- National Engineering Research Center for Sugarcane, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
| | - Yang Shi
- National Engineering Research Center for Sugarcane, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
| | - Hua-Ying Fu
- National Engineering Research Center for Sugarcane, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
| | - Mei-Ting Huang
- National Engineering Research Center for Sugarcane, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
| | - Philippe C. Rott
- CIRAD, UMR PHIM, Montpellier, France, and PHIM Plant Health Institute, Univ Montpellier, CIRAD, INRAE, Institut Agro, IRD, Montpellier, France
| | - San-Ji Gao
- National Engineering Research Center for Sugarcane, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
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Li M, Bao Y, Li Y, Akbar S, Wu G, Du J, Wen R, Chen B, Zhang M. Comparative genome analysis unravels pathogenicity of Xanthomonas albilineans causing sugarcane leaf scald disease. BMC Genomics 2022; 23:671. [PMID: 36162999 PMCID: PMC9513982 DOI: 10.1186/s12864-022-08900-2] [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: 06/27/2022] [Accepted: 09/19/2022] [Indexed: 11/28/2022] Open
Abstract
Background Xanthomonas is a genus of gram-negative bacterium containing more than 35 species. Among these pathogenic species, Xanthomonas albilineans (Xal) is of global interest, responsible for leaf scald disease in sugarcane. Another notable Xanthomonas species is Xanthomonas sachari (Xsa), a sugarcane-associated agent of chlorotic streak disease. Result The virulence of 24 Xanthomonas strains was evaluated by disease index (DI) and Area Under Disease Progress Curve (AUDPC) in the susceptible inoculated plants (GT 46) and clustered into three groups of five highly potent, seven mild virulent, and twelve weak virulent strains. The highly potent strain (X. albilineans, Xal JG43) and its weak virulent related strain (X. sacchari, Xsa DD13) were sequenced, assembled, and annotated in the circular genomes. The genomic size of JG43 was smaller than that of DD13. Both strains (JG43 and DD13) lacked a Type III secretory system (T3SS) and T6SS. However, JG43 possessed Salmonella pathogenicity island-1 (SPI-1). More pathogen-host interaction (PHI) genes and virulent factors in 17 genomic islands (GIs) were detected in JG43, among which six were related to pathogenicity. Albicidin and a two-component system associated with virulence were also detected in JG43. Furthermore, 23 Xanthomonas strains were sequenced and classified into three categories based on Single Nucleotide Polymorphism (SNP) mutation loci and pathogenicity, using JG43 as a reference genome. Transitions were dominant SNP mutations, while structural variation (SV) is frequent intrachromosomal rearrangement (ITX). Two essential genes (rpfC/rpfG) of the two-component system and another gene related to SNP were mutated to understand their virulence effect. The mutation of rpfG resulted in a decrease in pathogenicity. Conclusion These findings revealed virulence of 24 Xanthomonas strains and variations by 23 Xanthomonas strains. We sequenced, assembled, and annotated the circular genomes of Xal JG43 and Xsa DD13, identifying diversity detected by pathogenic factors and systems. Furthermore, complete genomic sequences and sequenced data will provide a theoretical basis for identifying pathogenic factors responsible for sugarcane leaf scald disease. Supplementary Information The online version contains supplementary material available at 10.1186/s12864-022-08900-2.
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Affiliation(s)
- MeiLin Li
- State Key Laboratory of Conservation and Utilization for Subtropical Agri-Biological Resources & Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530005, Guangxi, China
| | - YiXue Bao
- State Key Laboratory of Conservation and Utilization for Subtropical Agri-Biological Resources & Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530005, Guangxi, China
| | - YiSha Li
- State Key Laboratory of Conservation and Utilization for Subtropical Agri-Biological Resources & Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530005, Guangxi, China
| | - Sehrish Akbar
- State Key Laboratory of Conservation and Utilization for Subtropical Agri-Biological Resources & Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530005, Guangxi, China
| | - GuangYue Wu
- State Key Laboratory of Conservation and Utilization for Subtropical Agri-Biological Resources & Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530005, Guangxi, China
| | - JinXia Du
- State Key Laboratory of Conservation and Utilization for Subtropical Agri-Biological Resources & Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530005, Guangxi, China
| | - Ronghui Wen
- State Key Laboratory of Conservation and Utilization for Subtropical Agri-Biological Resources & Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530005, Guangxi, China
| | - Baoshan Chen
- State Key Laboratory of Conservation and Utilization for Subtropical Agri-Biological Resources & Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530005, Guangxi, China
| | - MuQing Zhang
- State Key Laboratory of Conservation and Utilization for Subtropical Agri-Biological Resources & Guangxi Key Laboratory for Sugarcane Biology, Guangxi University, Nanning, 530005, Guangxi, China.
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Drehkopf S, Otten C, Büttner D. Recognition of a translocation motif in the regulator HpaA from Xanthomonas euvesicatoria is controlled by the type III secretion chaperone HpaB. FRONTIERS IN PLANT SCIENCE 2022; 13:955776. [PMID: 35968103 PMCID: PMC9366055 DOI: 10.3389/fpls.2022.955776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Accepted: 07/08/2022] [Indexed: 06/15/2023]
Abstract
The Gram-negative plant-pathogenic bacterium Xanthomonas euvesicatoria is the causal agent of bacterial spot disease in pepper and tomato plants. Pathogenicity of X. euvesicatoria depends on a type III secretion (T3S) system which translocates effector proteins into plant cells and is associated with an extracellular pilus and a translocon in the plant plasma membrane. Effector protein translocation is activated by the cytoplasmic T3S chaperone HpaB which presumably targets effectors to the T3S system. We previously reported that HpaB is controlled by the translocated regulator HpaA which binds to and inactivates HpaB during the assembly of the T3S system. In the present study, we show that translocation of HpaA depends on the T3S substrate specificity switch protein HpaC and likely occurs after pilus and translocon assembly. Translocation of HpaA requires the presence of a translocation motif (TrM) in the N-terminal region. The TrM consists of an arginine-and proline-rich amino acid sequence and is also essential for the in vivo function of HpaA. Mutation of the TrM allowed the translocation of HpaA in hpaB mutant strains but not in the wild-type strain, suggesting that the recognition of the TrM depends on HpaB. Strikingly, the contribution of HpaB to the TrM-dependent translocation of HpaA was independent of the presence of the C-terminal HpaB-binding site in HpaA. We propose that HpaB generates a recognition site for the TrM at the T3S system and thus restricts the access to the secretion channel to effector proteins. Possible docking sites for HpaA at the T3S system were identified by in vivo and in vitro interaction studies and include the ATPase HrcN and components of the predicted cytoplasmic sorting platform of the T3S system. Notably, the TrM interfered with the efficient interaction of HpaA with several T3S system components, suggesting that it prevents premature binding of HpaA. Taken together, our data highlight a yet unknown contribution of the TrM and HpaB to substrate recognition and suggest that the TrM increases the binding specificity between HpaA and T3S system components.
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An Extracytoplasmic Function Sigma Factor Required for Full Virulence in Xanthomonas citri pv. citri. J Bacteriol 2022; 204:e0062421. [PMID: 35446118 DOI: 10.1128/jb.00624-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The genus Xanthomonas includes more than 30 phytopathogenic species that infect a wide range of plants and cause severe diseases that greatly impact crop productivity. These bacteria are highly adapted to the soil and plant environment, being found in decaying material, as epiphytes, and colonizing the plant mesophyll. Signal transduction mechanisms involved in the responses of Xanthomonas to environmental changes are still poorly characterized. Xanthomonad genomes typically encode several representatives of the extracytoplasmic function σ (σECF) factors, whose physiological roles remain elusive. In this work, we functionally characterized the Xanthomonas citri pv. citri EcfL, a σECF factor homologous to members of the iron-responsive FecI-like group. We show that EcfL is not required or induced during iron starvation, despite presenting the common features of other FecI-like σECF factors. EcfL positively regulates one operon composed of three genes that encode a TonB-dependent receptor involved in cell surface signaling, an acid phosphatase, and a lectin-domain containing protein. Furthermore, we demonstrate that EcfL is required for full virulence in citrus, and its regulon is induced inside the plant mesophyll and in response to acid stress. Together, our study suggests a role for EcfL in the adaptation of X. citri to the plant environment, in this way contributing to its ability to cause citrus canker disease. IMPORTANCE The Xanthomonas genus comprises a large number of phytopathogenic species that infect a wide variety of economically important plants worldwide. Bacterial adaptation to the plant and soil environment relies on their repertoire of signal transduction pathways, including alternative sigma factors of the extracytoplasmic function family (σECF). Here, we describe a new σECF factor found in several Xanthomonas species, demonstrating its role in Xanthomonas citri virulence to citrus plants. We show that EcfL regulates a single operon containing three genes, which are also conserved in other Xanthomonas species. This study further expands our knowledge on the functions of the widespread family of σECF factors in phytopathogenic bacteria.
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Agrobacterium expressing a type III secretion system delivers Pseudomonas effectors into plant cells to enhance transformation. Nat Commun 2022; 13:2581. [PMID: 35546550 PMCID: PMC9095702 DOI: 10.1038/s41467-022-30180-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Accepted: 04/20/2022] [Indexed: 01/07/2023] Open
Abstract
Agrobacterium-mediated plant transformation (AMT) is the basis of modern-day plant biotechnology. One major drawback of this technology is the recalcitrance of many plant species/varieties to Agrobacterium infection, most likely caused by elicitation of plant defense responses. Here, we develop a strategy to increase AMT by engineering Agrobacterium tumefaciens to express a type III secretion system (T3SS) from Pseudomonas syringae and individually deliver the P. syringae effectors AvrPto, AvrPtoB, or HopAO1 to suppress host defense responses. Using the engineered Agrobacterium, we demonstrate increase in AMT of wheat, alfalfa and switchgrass by ~250%–400%. We also show that engineered A. tumefaciens expressing a T3SS can deliver a plant protein, histone H2A-1, to enhance AMT. This strategy is of great significance to both basic research and agricultural biotechnology for transient and stable transformation of recalcitrant plant species/varieties and to deliver proteins into plant cells in a non-transgenic manner. Agrobacterium infection can cause defense responses in many plants, which leads to transformation recalcitrance. Here, the authors express type III secretion system in Agrobacterium to deliver effector proteins into plant cells to suppress host defense responses and thus enhance transformation in some plant species.
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Rosenthal E, Potnis N, Bull CT. Comparative Genomic Analysis of the Lettuce Bacterial Leaf Spot Pathogen, Xanthomonas hortorum pv. vitians, to Investigate Race Specificity. Front Microbiol 2022; 13:840311. [PMID: 35516433 PMCID: PMC9062649 DOI: 10.3389/fmicb.2022.840311] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 02/09/2022] [Indexed: 01/01/2023] Open
Abstract
Bacterial leaf spot (BLS) of lettuce caused by Xanthomonas hortorum pv. vitians (Xhv) was first described over 100 years ago and remains a significant threat to lettuce cultivation today. This study investigated the genetic relatedness of the Xhv strains and the possible genetic sources of this race-specific pathogenicity. Whole genome sequences of eighteen Xhv strains representing the three races, along with eight related Xanthomonas strains, were included in the analysis. A maximum likelihood phylogeny based on concatenated whole genome SNPs confirmed previous results describing two major lineages of Xhv strains. Gene clusters encoding secretion systems, secondary metabolites, and bacteriocins were assessed to identify putative virulence factors that distinguish the Xhv races. Genome sequences were mined for effector genes, which have been shown to be involved in race specificity in other systems. Two effectors identified in this study, xopAQ and the novel variant xopAF2, were revealed as possible mediators of a gene-for-gene interaction between Xhv race 1 and 3 strains and wild lettuce Lactuca serriola ARM-09-161-10-1. Transposase sequence identified downstream of xopAF2 and prophage sequence found nearby within Xhv race 1 and 3 insertion sequences suggest that this gene may have been acquired through phage-mediated gene transfer. No other factors were identified from these analyses that distinguish the Xhv races.
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Affiliation(s)
- Emma Rosenthal
- Department of Plant Pathology and Environmental Microbiology, Pennsylvania State University, University Park, PA, United States
| | - Neha Potnis
- Department of Entomology and Plant Pathology, Auburn University, Auburn, AL, United States
| | - Carolee T Bull
- Department of Plant Pathology and Environmental Microbiology, Pennsylvania State University, University Park, PA, United States
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12
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BDSF Is a Degradation-Prone Quorum-Sensing Signal Detected by the Histidine Kinase RpfC of Xanthomonas campestris pv. campestris. Appl Environ Microbiol 2022; 88:e0003122. [PMID: 35369702 DOI: 10.1128/aem.00031-22] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Diffusible signal factors (DSFs) are medium-chain fatty acids that induce bacterial quorum sensing. Among these compounds, BDSF is a structural analog of DSF that is commonly detected in bacterial species, and it is the predominant in planta quorum-sensing signal in Xanthomonas campestris. How BDSF is sensed in Xanthomonas spp. and the functional diversity between BDSF and DSF remain unclear. In this study, we generated genetic and biochemical evidence that BDSF is a low-active regulator of X. campestris pv. campestris quorum sensing, whereas trans-BDSF does not seem to be a signaling compound. BDSF is detected by the sensor histidine kinase RpfC. Although BDSF has relatively low physiological activities, it binds to the RpfC sensor with a high affinity and activates RpfC autophosphorylation to a level that is similar to that induced by DSF in vitro. The inconsistency in the physiological and biochemical activities of BDSF is not due to RpfC-RpfG phosphorylation or RpfG hydrolase. Neither BDSF nor DSF controls the phosphotransferase and phosphatase activities of RpfC or the ability of RpfG hydrolase activity to degrade the bacterial second messenger cyclic di-GMP. We demonstrated that BDSF is prone to degradation by RpfB, a critical fatty acyl coenzyme A ligase involved in the turnover of DSF-family signals. rpfB mutations lead to substantial increases in BDSF-induced quorum sensing. Although DSF and BDSF are similarly detected by RpfC, our data suggest that their differential degradation in cells is the major factor responsible for the diversity in their physiological effects. IMPORTANCE The diffusible signal factor (DSF) family consists of quorum-sensing signals employed by Gram-negative bacteria. These signals are a group of cis-2-unsaturated fatty acids, such as DSF, BDSF, IDSF, CDSF, and SDSF. However, the functional divergence of various DSF signals remains unclear. The present study demonstrates that though BDSF is a low active quorum-sensing signal, it binds histidine kinase RpfC with a higher affinity and activates RpfC autophosphorylation to the similar level as DSF. Rather than regulation of enzymatic activities of RpfC and its cognate response regulator RpfG encoding a c-di-GMP hydrolase, BDSF is prone to degradation in bacterial cells by RpfB, which effectively avoided the inhibition of bacterial growth by accumulating high concentrations of BDSF. Therefore, our study sheds new light on the functional differences of quorum-sensing signals and shows that bacteria balance quorum sensing and growth by fine-tuning concentrations of signaling chemicals.
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13
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Schreiber KJ, Chau-Ly IJ, Lewis JD. What the Wild Things Do: Mechanisms of Plant Host Manipulation by Bacterial Type III-Secreted Effector Proteins. Microorganisms 2021; 9:1029. [PMID: 34064647 PMCID: PMC8150971 DOI: 10.3390/microorganisms9051029] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 05/03/2021] [Accepted: 05/04/2021] [Indexed: 01/05/2023] Open
Abstract
Phytopathogenic bacteria possess an arsenal of effector proteins that enable them to subvert host recognition and manipulate the host to promote pathogen fitness. The type III secretion system (T3SS) delivers type III-secreted effector proteins (T3SEs) from bacterial pathogens such as Pseudomonas syringae, Ralstonia solanacearum, and various Xanthomonas species. These T3SEs interact with and modify a range of intracellular host targets to alter their activity and thereby attenuate host immune signaling. Pathogens have evolved T3SEs with diverse biochemical activities, which can be difficult to predict in the absence of structural data. Interestingly, several T3SEs are activated following injection into the host cell. Here, we review T3SEs with documented enzymatic activities, as well as T3SEs that facilitate virulence-promoting processes either indirectly or through non-enzymatic mechanisms. We discuss the mechanisms by which T3SEs are activated in the cell, as well as how T3SEs modify host targets to promote virulence or trigger immunity. These mechanisms may suggest common enzymatic activities and convergent targets that could be manipulated to protect crop plants from infection.
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Affiliation(s)
- Karl J. Schreiber
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94710, USA; (K.J.S.); (I.J.C.-L.)
| | - Ilea J. Chau-Ly
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94710, USA; (K.J.S.); (I.J.C.-L.)
| | - Jennifer D. Lewis
- Department of Plant and Microbial Biology, University of California, Berkeley, CA 94710, USA; (K.J.S.); (I.J.C.-L.)
- Plant Gene Expression Center, United States Department of Agriculture, University of California, Berkeley, CA 94710, USA
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14
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Otten C, Büttner D. HrpB4 from Xanthomonas campestris pv. vesicatoria acts similarly to SctK proteins and promotes the docking of the predicted sorting platform to the type III secretion system. Cell Microbiol 2021; 23:e13327. [PMID: 33733571 DOI: 10.1111/cmi.13327] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Revised: 02/28/2021] [Accepted: 03/15/2021] [Indexed: 11/28/2022]
Abstract
The Gram-negative bacterium Xanthomonas campestris pv. vesicatoria is the causal agent of bacterial spot disease on pepper and tomato plants. Pathogenicity of X. campestris pv. vesicatoria depends on a type III secretion (T3S) system which translocates bacterial effector proteins into plant cells. At least nine membrane-associated and cytoplasmic components of the secretion apparatus are homologous to corresponding Sct (secretion and cellular translocation) proteins from animal pathogens, suggesting a similar structural organisation of T3S systems in different bacterial species. T3S in X. campestris pv. vesicatoria also depends on non-conserved proteins with yet unknown function including the essential pathogenicity factor HrpB4. Here, we show that HrpB4 localises to the cytoplasm and the bacterial membranes and interacts with the cytoplasmic domain of the inner membrane (IM) ring component HrcD and the cytoplasmic HrcQ protein. The analysis of HrpB4 deletion derivatives revealed that deletion of the N- or C-terminal protein region affects the interaction of HrpB4 with HrcQ and HrcD as well as its contribution to pathogenicity. HrcQ is a component of the predicted sorting platform, which was identified in animal pathogens as a dynamic heterooligomeric protein complex and associates with the IM ring via SctK proteins. HrcQ complex formation was previously shown by fluorescent microscopy analysis and depends on the presence of the T3S system. In the present study, we provide experimental evidence that the absence of HrpB4 severely affects the docking of HrcQ complexes to the T3S system but does not significantly interfere with HrcQ complex formation in the bacterial cytoplasm. Taken together, our data suggest that HrpB4 links the predicted cytoplasmic sorting platform to the IM rings of the T3S system.
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Affiliation(s)
- Christian Otten
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Daniela Büttner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
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15
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Hotinger JA, Pendergrass HA, May AE. Molecular Targets and Strategies for Inhibition of the Bacterial Type III Secretion System (T3SS); Inhibitors Directly Binding to T3SS Components. Biomolecules 2021; 11:biom11020316. [PMID: 33669653 PMCID: PMC7922566 DOI: 10.3390/biom11020316] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 02/16/2021] [Accepted: 02/17/2021] [Indexed: 01/01/2023] Open
Abstract
The type III secretion system (T3SS) is a virulence apparatus used by many Gram-negative pathogenic bacteria to cause infections. Pathogens utilizing a T3SS are responsible for millions of infections yearly. Since many T3SS knockout strains are incapable of causing systemic infection, the T3SS has emerged as an attractive anti-virulence target for therapeutic design. The T3SS is a multiprotein molecular syringe that enables pathogens to inject effector proteins into host cells. These effectors modify host cell mechanisms in a variety of ways beneficial to the pathogen. Due to the T3SS’s complex nature, there are numerous ways in which it can be targeted. This review will be focused on the direct targeting of components of the T3SS, including the needle, translocon, basal body, sorting platform, and effector proteins. Inhibitors will be considered a direct inhibitor if they have a binding partner that is a T3SS component, regardless of the inhibitory effect being structural or functional.
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16
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Guzman AR, Kim JG, Taylor KW, Lanver D, Mudgett MB. Tomato Atypical Receptor Kinase1 Is Involved in the Regulation of Preinvasion Defense. PLANT PHYSIOLOGY 2020; 183:1306-1318. [PMID: 32385090 PMCID: PMC7333691 DOI: 10.1104/pp.19.01400] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Accepted: 04/29/2020] [Indexed: 05/19/2023]
Abstract
Tomato Atypical Receptor Kinase 1 (TARK1) is a pseudokinase required for postinvasion immunity. TARK1 was originally identified as a target of the Xanthomonas euvesicatoria effector protein Xanthomonas outer protein N (XopN), a suppressor of early defense signaling. How TARK1 participates in immune signal transduction is not well understood. To gain insight into TARK1's role in tomato (Solanum lycopersicum) immunity, we used a proteomics approach to isolate and identify TARK1-associated immune complexes formed during infection. We found that TARK1 interacts with proteins predicted to be associated with stomatal movement. TARK1 CRISPR mutants and overexpression (OE) lines did not display differences in light-induced stomatal opening or abscisic acid-induced stomatal closure; however, they did show altered stomatal movement responses to bacteria and biotic elicitors. Notably, we found that TARK1 CRISPR plants were resistant to Pseudomonas syringae pathovar tomato strain DC3000-induced stomatal reopening, and TARK1 OE plants were insensitive to P syringae pathovar tomato strain DC3118 (coronatine deficit)-induced stomatal closure. We also found that TARK1 OE in leaves resulted in increased susceptibility to bacterial invasion. Collectively, our results indicate that TARK1 functions in stomatal movement only in response to biotic elicitors and support a model in which TARK1 regulates stomatal opening postelicitation.
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Affiliation(s)
- Andrew R Guzman
- Department of Biology, Stanford University, Stanford, California 94305-5020
| | - Jung-Gun Kim
- Department of Biology, Stanford University, Stanford, California 94305-5020
| | - Kyle W Taylor
- Department of Biology, Stanford University, Stanford, California 94305-5020
| | - Daniel Lanver
- Department of Biology, Stanford University, Stanford, California 94305-5020
| | - Mary Beth Mudgett
- Department of Biology, Stanford University, Stanford, California 94305-5020
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17
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Timilsina S, Potnis N, Newberry EA, Liyanapathiranage P, Iruegas-Bocardo F, White FF, Goss EM, Jones JB. Xanthomonas diversity, virulence and plant-pathogen interactions. Nat Rev Microbiol 2020; 18:415-427. [PMID: 32346148 DOI: 10.1038/s41579-020-0361-8] [Citation(s) in RCA: 132] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/19/2020] [Indexed: 12/19/2022]
Abstract
Xanthomonas spp. encompass a wide range of plant pathogens that use numerous virulence factors for pathogenicity and fitness in plant hosts. In this Review, we examine recent insights into host-pathogen co-evolution, diversity in Xanthomonas populations and host specificity of Xanthomonas spp. that have substantially improved our fundamental understanding of pathogen biology. We emphasize the virulence factors in xanthomonads, such as type III secreted effectors including transcription activator-like effectors, type II secretion systems, diversity resulting in host specificity, evolution of emerging strains, activation of susceptibility genes and strategies of host evasion. We summarize the genomic diversity in several Xanthomonas spp. and implications for disease outbreaks, management strategies and breeding for disease resistance.
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Affiliation(s)
- Sujan Timilsina
- Plant Pathology Department, University of Florida, Gainesville, FL, USA
| | - Neha Potnis
- Entomology and Plant Pathology, Auburn University, Auburn, AL, USA
| | - Eric A Newberry
- Entomology and Plant Pathology, Auburn University, Auburn, AL, USA
| | | | | | - Frank F White
- Plant Pathology Department, University of Florida, Gainesville, FL, USA
| | - Erica M Goss
- Plant Pathology Department, University of Florida, Gainesville, FL, USA. .,Emerging Pathogens Institute, University of Florida, Gainesville, FL, USA.
| | - Jeffrey B Jones
- Plant Pathology Department, University of Florida, Gainesville, FL, USA.
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18
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Drehkopf S, Otten C, Hausner J, Seifert T, Büttner D. HrpB7 from
Xanthomonas campestris
pv.
vesicatoria
is an essential component of the type III secretion system and shares features of HrpO/FliJ/YscO family members. Cell Microbiol 2020; 22:e13160. [DOI: 10.1111/cmi.13160] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 12/16/2019] [Accepted: 12/24/2019] [Indexed: 12/22/2022]
Affiliation(s)
- Sabine Drehkopf
- Department of Genetics, Institute of BiologyMartin Luther University Halle‐Wittenberg Halle (Saale) Germany
| | - Christian Otten
- Department of Genetics, Institute of BiologyMartin Luther University Halle‐Wittenberg Halle (Saale) Germany
| | - Jens Hausner
- Department of Genetics, Institute of BiologyMartin Luther University Halle‐Wittenberg Halle (Saale) Germany
| | - Tanja Seifert
- Department of Genetics, Institute of BiologyMartin Luther University Halle‐Wittenberg Halle (Saale) Germany
| | - Daniela Büttner
- Department of Genetics, Institute of BiologyMartin Luther University Halle‐Wittenberg Halle (Saale) Germany
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19
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Perez-Quintero AL, Szurek B. A Decade Decoded: Spies and Hackers in the History of TAL Effectors Research. ANNUAL REVIEW OF PHYTOPATHOLOGY 2019; 57:459-481. [PMID: 31387457 DOI: 10.1146/annurev-phyto-082718-100026] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Transcription activator-like effectors (TALEs) from the genus Xanthomonas are proteins with the remarkable ability to directly bind the promoters of genes in the plant host to induce their expression, which often helps bacterial colonization. Metaphorically, TALEs act as spies that infiltrate the plant disguised as high-ranking civilians (transcription factors) to trick the plant into activating weak points that allow an invasion. Current knowledge of how TALEs operate allows researchers to predict their activity (counterespionage) and exploit their function, engineering them to do our bidding (a Manchurian agent). This has been possible thanks particularly to the discovery of their DNA binding mechanism, which obeys specific amino acid-DNA correspondences (the TALE code). Here, we review the history of how researchers discovered the way these proteins work and what has changed in the ten years since the discovery of the code. Recommended music for reading this review can be found in the Supplemental Material.
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Affiliation(s)
- Alvaro L Perez-Quintero
- Department of Bioagricultural Sciences and Pest Management, Colorado State University, Fort Collins, Colorado 80523-1177, USA;
- IRD, CIRAD, Université Montpellier, IPME, 34000 Montpellier, France;
| | - Boris Szurek
- IRD, CIRAD, Université Montpellier, IPME, 34000 Montpellier, France;
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20
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Hausner J, Jordan M, Otten C, Marillonnet S, Büttner D. Modular Cloning of the Type III Secretion Gene Cluster from the Plant-Pathogenic Bacterium Xanthomonas euvesicatoria. ACS Synth Biol 2019; 8:532-547. [PMID: 30694661 DOI: 10.1021/acssynbio.8b00434] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Type III secretion (T3S) systems are essential pathogenicity factors of most Gram-negative bacteria and translocate effector proteins into plant or animal cells. T3S systems can, therefore, be used as tools for protein delivery into eukaryotic cells, for instance after transfer of the T3S gene cluster into nonpathogenic recipient strains. Here, we report the modular cloning of the T3S gene cluster from the plant-pathogenic bacterium Xanthomonas euvesicatoria. The resulting multigene construct encoded a functional T3S system and delivered effector proteins into plant cells. The modular design of the T3S gene cluster allowed the efficient replacement and rearrangement of single genes or operons and the insertion of reporter genes for functional studies. In the present study, we used the modular T3S system to analyze the assembly of a fluorescent fusion of the predicted cytoplasmic ring protein HrcQ. Our studies demonstrate the use of the modular T3S gene cluster for functional analyses and mutant approaches in X. euvesicatoria. A potential application of the modular T3S system as protein delivery tool is discussed.
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Affiliation(s)
- Jens Hausner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Weinbergweg 10, 06120 Halle, Saale, Germany
| | - Michael Jordan
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Weinbergweg 10, 06120 Halle, Saale, Germany
| | - Christian Otten
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Weinbergweg 10, 06120 Halle, Saale, Germany
| | | | - Daniela Büttner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Weinbergweg 10, 06120 Halle, Saale, Germany
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21
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Zhang X, Zhao M, Yan J, Yang L, Yang Y, Guan W, Walcott R, Zhao T. Involvement of hrpX and hrpG in the Virulence of Acidovorax citrulli Strain Aac5, Causal Agent of Bacterial Fruit Blotch in Cucurbits. Front Microbiol 2018; 9:507. [PMID: 29636729 PMCID: PMC5880930 DOI: 10.3389/fmicb.2018.00507] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2017] [Accepted: 03/06/2018] [Indexed: 01/01/2023] Open
Abstract
Acidovorax citrulli causes bacterial fruit blotch, a disease that poses a global threat to watermelon and melon production. Despite its economic importance, relatively little is known about the molecular mechanisms of pathogenicity and virulence of A. citrulli. Like other plant-pathogenic bacteria, A. citrulli relies on a type III secretion system (T3SS) for pathogenicity. On the basis of sequence and operon arrangement analyses, A. citrulli was found to have a class II hrp gene cluster similar to those of Xanthomonas and Ralstonia spp. In the class II hrp cluster, hrpG and hrpX play key roles in the regulation of T3SS effectors. However, little is known about the regulation of the T3SS in A. citrulli. This study aimed to investigate the roles of hrpG and hrpX in A. citrulli pathogenicity. We found that hrpG or hrpX deletion mutants of the A. citrulli group II strain Aac5 had reduced pathogenicity on watermelon seedlings, failed to induce a hypersensitive response in tobacco, and elicited higher levels of reactive oxygen species in Nicotiana benthamiana than the wild-type strain. Additionally, we demonstrated that HrpG activates HrpX in A. citrulli. Moreover, transcription and translation of the type 3-secreted effector (T3E) gene Aac5_2166 were suppressed in hrpG and hrpX mutants. Notably, hrpG and hrpX appeared to modulate biofilm formation. These results suggest that hrpG and hrpX are essential for pathogenicity, regulation of T3Es, and biofilm formation in A. citrulli.
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Affiliation(s)
- Xiaoxiao Zhang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Mei Zhao
- Department of Plant Pathology, University of Georgia, Athens, GA, United States
| | - Jianpei Yan
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.,Faculty of Agronomy, Jilin Agricultural University, Changchun, China
| | - Linlin Yang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China.,Plant Protection College, Shenyang Agricultural University, Shenyang, China
| | - Yuwen Yang
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Wei Guan
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
| | - Ron Walcott
- Department of Plant Pathology, University of Georgia, Athens, GA, United States
| | - Tingchang Zhao
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
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22
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Chalupowicz L, Nissan G, Brandl MT, McClelland M, Sessa G, Popov G, Barash I, Manulis-Sasson S. Assessing the Ability of Salmonella enterica to Translocate Type III Effectors Into Plant Cells. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2018; 31:233-239. [PMID: 28952399 DOI: 10.1094/mpmi-07-17-0166-r] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Salmonella enterica serovar Typhimurium, a human enteric pathogen, has the ability to multiply and survive endophytically in plants. Genes encoding the type III secretion system (T3SS) or its effectors (T3Es) may contribute to its colonization. Two reporter plasmids for T3E translocation into plant cells that are based on hypersensitive response domains of avirulence proteins from the Pantoea agglomerans-beet and Xanthomonas euvesicatoria-pepper pathosystems were employed in this study to investigate the role of T3Es in the interaction of Salmonella ser. Typhimurium 14028 with plants. The T3Es of Salmonella ser. Typhimurium, SipB and SifA, which are translocated into animal cells, could not be delivered by Salmonella ser. Typhimurium into cells of beet roots or pepper leaves. In contrast, these effectors were translocated into plant cells by the phytopathogenic bacteria P. agglomerans pv. betae, Erwinia amylovora, and X. euvesicatoria. Similarly, HsvG, a T3E of P. agglomerans pv. gypsophilae, and XopAU of X. euvesicatoria could be translocated into beet roots and pepper leaves, respectively, by the plant pathogens but not by Salmonella ser. Typhimurium. Mutations in Salmonella ser. Typhimurium T3SS genes invA, ssaV, sipB, or sifA, did not affect its endophytic colonization of lettuce leaves, supporting the notion that S. enterica cannot translocate T3Es into plant cells.
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Affiliation(s)
- Laura Chalupowicz
- 1 Department of Plant Pathology and Weed Research, Agricultural Research Organization, The Volcani Center, Rishon LeZion 7528809, Israel
| | - Gal Nissan
- 1 Department of Plant Pathology and Weed Research, Agricultural Research Organization, The Volcani Center, Rishon LeZion 7528809, Israel
- 2 School of Plant Sciences and Food Security, Faculty of Life Sciences, Tel-Aviv 69978, Israel
| | - Maria T Brandl
- 3 Produce Safety and Microbiology Research Unit, USDA, ARS, WRRC, 800 Buchanan St., Albany, CA 94710, U.S.A.; and
| | - Michael McClelland
- 4 Department of Microbiology, School of Medicine, University of California, Irvine, CA 92697-4025, U.S.A
| | - Guido Sessa
- 2 School of Plant Sciences and Food Security, Faculty of Life Sciences, Tel-Aviv 69978, Israel
| | - Georgy Popov
- 2 School of Plant Sciences and Food Security, Faculty of Life Sciences, Tel-Aviv 69978, Israel
| | - Isaac Barash
- 2 School of Plant Sciences and Food Security, Faculty of Life Sciences, Tel-Aviv 69978, Israel
| | - Shulamit Manulis-Sasson
- 1 Department of Plant Pathology and Weed Research, Agricultural Research Organization, The Volcani Center, Rishon LeZion 7528809, Israel
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23
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Artier J, da Silva Zandonadi F, de Souza Carvalho FM, Pauletti BA, Leme AFP, Carnielli CM, Selistre‐de‐Araujo HS, Bertolini MC, Ferro JA, Belasque Júnior J, de Oliveira JCF, Novo‐Mansur MTM. Comparative proteomic analysis of Xanthomonas citri ssp. citri periplasmic proteins reveals changes in cellular envelope metabolism during in vitro pathogenicity induction. MOLECULAR PLANT PATHOLOGY 2018; 19:143-157. [PMID: 27798950 PMCID: PMC6638008 DOI: 10.1111/mpp.12507] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Citrus canker is a plant disease caused by Gram-negative bacteria from the genus Xanthomonas. The most virulent species is Xanthomonas citri ssp. citri (XAC), which attacks a wide range of citrus hosts. Differential proteomic analysis of the periplasm-enriched fraction was performed for XAC cells grown in pathogenicity-inducing (XAM-M) and pathogenicity-non-inducing (nutrient broth) media using two-dimensional electrophoresis combined with liquid chromatography-tandem mass spectrometry. Amongst the 40 proteins identified, transglycosylase was detected in a highly abundant spot in XAC cells grown under inducing condition. Additional up-regulated proteins related to cellular envelope metabolism included glucose-1-phosphate thymidylyltransferase, dTDP-4-dehydrorhamnose-3,5-epimerase and peptidyl-prolyl cis-trans-isomerase. Phosphoglucomutase and superoxide dismutase proteins, known to be involved in pathogenicity in other Xanthomonas species or organisms, were also detected. Western blot and quantitative real-time polymerase chain reaction analyses for transglycosylase and superoxide dismutase confirmed that these proteins were up-regulated under inducing condition, consistent with the proteomic results. Multiple spots for the 60-kDa chaperonin and glyceraldehyde-3-phosphate dehydrogenase were identified, suggesting the presence of post-translational modifications. We propose that substantial alterations in cellular envelope metabolism occur during the XAC infectious process, which are related to several aspects, from defence against reactive oxygen species to exopolysaccharide synthesis. Our results provide new candidates for virulence-related proteins, whose abundance correlates with the induction of pathogenicity and virulence genes, such as hrpD6, hrpG, hrpB7, hpa1 and hrpX. The results present new potential targets against XAC to be investigated in further functional studies.
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Affiliation(s)
- Juliana Artier
- Laboratório de Bioquímica e Biologia Molecular Aplicada, Departamento de Genética e EvoluçãoUniversidade Federal de São Carlos, UFSCarSão CarlosSP13565‐905Brazil
| | - Flávia da Silva Zandonadi
- Laboratório de Bioquímica e Biologia Molecular Aplicada, Departamento de Genética e EvoluçãoUniversidade Federal de São Carlos, UFSCarSão CarlosSP13565‐905Brazil
| | - Flávia Maria de Souza Carvalho
- Departamento de Tecnologia, Faculdade de Ciências Agrárias e Veterinárias de Jaboticabal, UNESPUniversidade Estadual PaulistaJaboticabalSP14884‐900Brazil
| | - Bianca Alves Pauletti
- LNBio, CNPEMLaboratório de Espectrometria de Massas, Laboratório Nacional de BiociênciasCampinasSP13083‐970Brazil
| | - Adriana Franco Paes Leme
- LNBio, CNPEMLaboratório de Espectrometria de Massas, Laboratório Nacional de BiociênciasCampinasSP13083‐970Brazil
| | - Carolina Moretto Carnielli
- Laboratório de Bioquímica e Biologia Molecular Aplicada, Departamento de Genética e EvoluçãoUniversidade Federal de São Carlos, UFSCarSão CarlosSP13565‐905Brazil
| | | | - Maria Célia Bertolini
- Departamento de Bioquímica e Tecnologia Química, Instituto de Química, UNESPUniversidade Estadual PaulistaAraraquaraSP14800‐060Brazil
| | - Jesus Aparecido Ferro
- Departamento de Tecnologia, Faculdade de Ciências Agrárias e Veterinárias de Jaboticabal, UNESPUniversidade Estadual PaulistaJaboticabalSP14884‐900Brazil
| | - José Belasque Júnior
- Departamento de Fitopatologia e Nematologia, Escola Superior de Agricultura ‘Luiz de Queiroz’Universidade de São PauloPiracicabaSP13418‐900Brazil
| | - Julio Cezar Franco de Oliveira
- Laboratório de Interações Microbianas, Departamento de Ciências BiológicasUniversidade Federal de São Paulo, UNIFESPDiademaSP09913‐030Brazil
| | - Maria Teresa Marques Novo‐Mansur
- Laboratório de Bioquímica e Biologia Molecular Aplicada, Departamento de Genética e EvoluçãoUniversidade Federal de São Carlos, UFSCarSão CarlosSP13565‐905Brazil
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24
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Scheibner F, Hartmann N, Hausner J, Lorenz C, Hoffmeister AK, Büttner D. The Type III Secretion Chaperone HpaB Controls the Translocation of Effector and Noneffector Proteins From Xanthomonas campestris pv. vesicatoria. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2018; 31:61-74. [PMID: 28771395 DOI: 10.1094/mpmi-06-17-0138-r] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Pathogenicity of the gram-negative bacterium Xanthomonas campestris pv. vesicatoria depends on a type III secretion (T3S) system, which translocates effector proteins into plant cells. Effector proteins contain N-terminal T3S and translocation signals and interact with the T3S chaperone HpaB, which presumably escorts effectors to the secretion apparatus. The molecular mechanisms underlying the recognition of effectors by the T3S system are not yet understood. In the present study, we analyzed T3S and translocation signals in the type III effectors XopE2 and XopJ from X. campestris pv. vesicatoria. Both effectors contain minimal translocation signals, which are only recognized in the absence of HpaB. Additional N-terminal signals promote translocation of XopE2 and XopJ in the wild-type strain. The results of translocation and interaction studies revealed that the interaction of XopE2 and XopJ with HpaB and a predicted cytoplasmic substrate docking site of the T3S system is not sufficient for translocation. In agreement with this finding, we show that the presence of an artificial HpaB-binding site does not promote translocation of the noneffector XopA in the wild-type strain. Our data, therefore, suggest that the T3S chaperone HpaB not only acts as an escort protein but also controls the recognition of translocation signals.
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Affiliation(s)
- Felix Scheibner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany
| | - Nadine Hartmann
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany
| | - Jens Hausner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany
| | - Christian Lorenz
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany
| | - Anne-Katrin Hoffmeister
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany
| | - Daniela Büttner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany
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25
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Schultink A, Qi T, Lee A, Steinbrenner AD, Staskawicz B. Roq1 mediates recognition of the Xanthomonas and Pseudomonas effector proteins XopQ and HopQ1. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 92:787-795. [PMID: 28891100 DOI: 10.1111/tpj.13715] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2017] [Revised: 08/30/2017] [Accepted: 09/04/2017] [Indexed: 05/12/2023]
Abstract
Xanthomonas spp. are phytopathogenic bacteria that can cause disease on a wide variety of plant species resulting in significant impacts on crop yields. Limited genetic resistance is available in most crop species and current control methods are often inadequate, particularly when environmental conditions favor disease. The plant Nicotiana benthamiana has been shown to be resistant to Xanthomonas and Pseudomonas due to an immune response triggered by the bacterial effector proteins XopQ and HopQ1, respectively. We used a reverse genetic screen to identify Recognition of XopQ 1 (Roq1), a nucleotide-binding leucine-rich repeat (NLR) protein with a Toll-like interleukin-1 receptor (TIR) domain, which mediates XopQ recognition in N. benthamiana. Roq1 orthologs appear to be present only in the Nicotiana genus. Expression of Roq1 was found to be sufficient for XopQ recognition in both the closely-related Nicotiana sylvestris and the distantly-related beet plant (Beta vulgaris). Roq1 was found to co-immunoprecipitate with XopQ, suggesting a physical association between the two proteins. Roq1 is able to recognize XopQ alleles from various Xanthomonas species, as well as HopQ1 from Pseudomonas, demonstrating widespread potential application in protecting crop plants from these pathogens.
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Affiliation(s)
- Alex Schultink
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
| | - Tiancong Qi
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
| | - Arielle Lee
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
| | - Adam D Steinbrenner
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
| | - Brian Staskawicz
- Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA
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26
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Scheibner F, Marillonnet S, Büttner D. The TAL Effector AvrBs3 from Xanthomonas campestris pv. vesicatoria Contains Multiple Export Signals and Can Enter Plant Cells in the Absence of the Type III Secretion Translocon. Front Microbiol 2017; 8:2180. [PMID: 29170655 PMCID: PMC5684485 DOI: 10.3389/fmicb.2017.02180] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 10/24/2017] [Indexed: 12/27/2022] Open
Abstract
Pathogenicity of the Gram-negative plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria depends on a type III secretion (T3S) system which translocates effector proteins into plant cells. Effector protein delivery is controlled by the T3S chaperone HpaB, which presumably escorts effector proteins to the secretion apparatus. One intensively studied effector is the transcription activator-like (TAL) effector AvrBs3, which binds to promoter sequences of plant target genes and activates plant gene expression. It was previously reported that type III-dependent delivery of AvrBs3 depends on the N-terminal protein region. The signals that control T3S and translocation of AvrBs3, however, have not yet been characterized. In the present study, we show that T3S and translocation of AvrBs3 depend on the N-terminal 10 and 50 amino acids, respectively. Furthermore, we provide experimental evidence that additional signals in the N-terminal 30 amino acids and the region between amino acids 64 and 152 promote translocation of AvrBs3 in the absence of HpaB. Unexpectedly, in vivo translocation assays revealed that AvrBs3 is delivered into plant cells even in the absence of HrpF, which is the predicted channel-forming component of the T3S translocon in the plant plasma membrane. The presence of HpaB- and HrpF-independent transport routes suggests that the delivery of AvrBs3 is initiated during early stages of the infection process, presumably before the activation of HpaB or the insertion of the translocon into the plant plasma membrane.
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Affiliation(s)
- Felix Scheibner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Halle, Germany
| | | | - Daniela Büttner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Halle, Germany
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27
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Swain DM, Yadav SK, Tyagi I, Kumar R, Kumar R, Ghosh S, Das J, Jha G. A prophage tail-like protein is deployed by Burkholderia bacteria to feed on fungi. Nat Commun 2017; 8:404. [PMID: 28864820 PMCID: PMC5581363 DOI: 10.1038/s41467-017-00529-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 07/05/2017] [Indexed: 11/09/2022] Open
Abstract
Some bacteria can feed on fungi, a phenomenon known as mycophagy. Here we show that a prophage tail-like protein (Bg_9562) is essential for mycophagy in Burkholderia gladioli strain NGJ1. The purified protein causes hyphal disintegration and inhibits growth of several fungal species. Disruption of the Bg_9562 gene abolishes mycophagy. Bg_9562 is a potential effector secreted by a type III secretion system (T3SS) and is translocated into fungal mycelia during confrontation. Heterologous expression of Bg_9562 in another bacterial species, Ralstonia solanacearum, confers mycophagous ability in a T3SS-dependent manner. We propose that the ability to feed on fungi conferred by Bg_9562 may help the bacteria to survive in certain ecological niches. Furthermore, considering its broad-spectrum antifungal activity, the protein may be potentially useful in biotechnological applications to control fungal diseases.Some bacteria can feed on live fungi through unclear mechanisms. Here, the authors show that a T3SS-secreted protein, which is homologous to phage tail proteins, allows a Burkholderia gladioli strain to kill and feed on various fungal species.
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Affiliation(s)
- Durga Madhab Swain
- Plant Microbe Interactions Laboratory, National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Sunil Kumar Yadav
- Plant Microbe Interactions Laboratory, National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Isha Tyagi
- Plant Microbe Interactions Laboratory, National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Rahul Kumar
- Plant Microbe Interactions Laboratory, National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Rajeev Kumar
- Plant Microbe Interactions Laboratory, National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Srayan Ghosh
- Plant Microbe Interactions Laboratory, National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Joyati Das
- Plant Microbe Interactions Laboratory, National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Gopaljee Jha
- Plant Microbe Interactions Laboratory, National Institute of Plant Genome Research, Aruna Asaf Ali Marg, New Delhi, 110067, India.
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28
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HpaB-Dependent Secretion of Type III Effectors in the Plant Pathogens Ralstonia solanacearum and Xanthomonas campestris pv. vesicatoria. Sci Rep 2017; 7:4879. [PMID: 28687734 PMCID: PMC5501821 DOI: 10.1038/s41598-017-04853-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Accepted: 05/10/2017] [Indexed: 01/16/2023] Open
Abstract
Plant pathogenic bacteria exerts their pathogenicity through the injection of large repertoires of type III effectors (T3Es) into plant cells, a mechanism controlled in part by type III chaperones (T3Cs). In Ralstonia solanacearum, the causal agent of bacterial wilt, little is known about the control of type III secretion at the post-translational level. Here, we provide evidence that the HpaB and HpaD proteins do act as bona fide R. solanacearum class IB chaperones that associate with several T3Es. Both proteins can dimerize but do not interact with each other. After screening 38 T3Es for direct interactions, we highlighted specific and common interacting partners, thus revealing the first picture of the R. solanacearum T3C-T3E network. We demonstrated that the function of HpaB is conserved in two phytopathogenic bacteria, R. solanacearum and Xanthomonas campestris pv. vesicatoria (Xcv). HpaB from Xcv is able to functionally complement a R. solanacearum hpaB mutant for hypersensitive response elicitation on tobacco plants. Likewise, Xcv is able to translocate a heterologous T3E from R. solanacearum in an HpaB-dependent manner. This study underlines the central role of the HpaB class IB chaperone family and its potential contribution to the bacterial plasticity to acquire and deliver new virulence factors.
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29
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Vander Broek CW, Stevens JM. Type III Secretion in the Melioidosis Pathogen Burkholderia pseudomallei. Front Cell Infect Microbiol 2017; 7:255. [PMID: 28664152 PMCID: PMC5471309 DOI: 10.3389/fcimb.2017.00255] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 05/31/2017] [Indexed: 02/03/2023] Open
Abstract
Burkholderia pseudomallei is a Gram-negative intracellular pathogen and the causative agent of melioidosis, a severe disease of both humans and animals. Melioidosis is an emerging disease which is predicted to be vastly under-reported. Type III Secretion Systems (T3SSs) are critical virulence factors in Gram negative pathogens of plants and animals. The genome of B. pseudomallei encodes three T3SSs. T3SS-1 and -2, of which little is known, are homologous to Hrp2 secretion systems of the plant pathogens Ralstonia and Xanthomonas. T3SS-3 is better characterized and is homologous to the Inv/Mxi-Spa secretion systems of Salmonella spp. and Shigella flexneri, respectively. Upon entry into the host cell, B. pseudomallei requires T3SS-3 for efficient escape from the endosome. T3SS-3 is also required for full virulence in both hamster and murine models of infection. The regulatory cascade which controls T3SS-3 expression and the secretome of T3SS-3 have been described, as well as the effect of mutations of some of the structural proteins. Yet only a few effector proteins have been functionally characterized to date and very little work has been carried out to understand the hierarchy of assembly, secretion and temporal regulation of T3SS-3. This review aims to frame current knowledge of B. pseudomallei T3SSs in the context of other well characterized model T3SSs, particularly those of Salmonella and Shigella.
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Affiliation(s)
- Charles W Vander Broek
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of EdinburghMidlothian, United Kingdom
| | - Joanne M Stevens
- The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of EdinburghMidlothian, United Kingdom
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30
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Cerutti A, Jauneau A, Auriac MC, Lauber E, Martinez Y, Chiarenza S, Leonhardt N, Berthomé R, Noël LD. Immunity at Cauliflower Hydathodes Controls Systemic Infection by Xanthomonas campestris pv campestris. PLANT PHYSIOLOGY 2017; 174:700-716. [PMID: 28184011 PMCID: PMC5462019 DOI: 10.1104/pp.16.01852] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 02/06/2017] [Indexed: 05/20/2023]
Abstract
Hydathodes are water pores found on leaves of a wide range of vascular plants and are the sites of guttation. We report here on the detailed anatomy of cauliflower (Brassicaoleracea) and Arabidopsis (Arabidopsis thaliana) hydathodes. Hydathode surface presents pores resembling stomata giving access to large cavities. Beneath, the epithem is composed of a lacunar and highly vascularized parenchyma offering a direct connection between leaf surface and xylem vessels. Arabidopsis hydathode pores were responsive to ABA and light similar to stomata. The flg22 flagellin peptide, a well-characterized elicitor of plant basal immunity, did not induce closure of hydathode pores in contrast to stomata. Because hydathodes are natural infection routes for several pathogens, we investigated hydathode infection by the adapted vascular phytopathogenic bacterium Xanthomonas campestris pv campestris (Xcc), the causal agent of black rot disease of Brassicaceae. Microscopic observations of hydathodes six days postinoculation indicated a digestion of the epithem cells and a high bacterial multiplication. Postinvasive immunity was shown to limit pathogen growth in the epithem and is actively suppressed by the type III secretion system and its effector proteins. Altogether, these results give a detailed anatomic description of Brassicaceae hydathodes and highlight the efficient use of this tissue as an initial niche for subsequent vascular systemic dissemination of Xcc in distant plant tissues.
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Affiliation(s)
- Aude Cerutti
- LIPM, Université de Toulouse, INRA, CNRS, UPS, F-31326 Castanet-Tolosan, France (A.C., E.L., R.B., L.D.N.)
- Institut Fédératif de Recherche 3450, Plateforme Imagerie, Pôle de Biotechnologie Végétale, F-31326 Castanet-Tolosan, France (A.J., M.-C.A., Y.M.); and
- UMR7265, Laboratoire de Biologie du Développement des Plantes, Service de Biologie Végétale et de Microbiologie Environnementales, Institut de Biologie Environnementale et Biotechnologie, Centre National de la Recherche Scientifique-Commissariat à l'Energie Atomique-Université Aix-Marseille, F-13108 Saint Paul-Les-Durance, France (S.C., N.L.)
| | - Alain Jauneau
- LIPM, Université de Toulouse, INRA, CNRS, UPS, F-31326 Castanet-Tolosan, France (A.C., E.L., R.B., L.D.N.)
- Institut Fédératif de Recherche 3450, Plateforme Imagerie, Pôle de Biotechnologie Végétale, F-31326 Castanet-Tolosan, France (A.J., M.-C.A., Y.M.); and
- UMR7265, Laboratoire de Biologie du Développement des Plantes, Service de Biologie Végétale et de Microbiologie Environnementales, Institut de Biologie Environnementale et Biotechnologie, Centre National de la Recherche Scientifique-Commissariat à l'Energie Atomique-Université Aix-Marseille, F-13108 Saint Paul-Les-Durance, France (S.C., N.L.)
| | - Marie-Christine Auriac
- LIPM, Université de Toulouse, INRA, CNRS, UPS, F-31326 Castanet-Tolosan, France (A.C., E.L., R.B., L.D.N.)
- Institut Fédératif de Recherche 3450, Plateforme Imagerie, Pôle de Biotechnologie Végétale, F-31326 Castanet-Tolosan, France (A.J., M.-C.A., Y.M.); and
- UMR7265, Laboratoire de Biologie du Développement des Plantes, Service de Biologie Végétale et de Microbiologie Environnementales, Institut de Biologie Environnementale et Biotechnologie, Centre National de la Recherche Scientifique-Commissariat à l'Energie Atomique-Université Aix-Marseille, F-13108 Saint Paul-Les-Durance, France (S.C., N.L.)
| | - Emmanuelle Lauber
- LIPM, Université de Toulouse, INRA, CNRS, UPS, F-31326 Castanet-Tolosan, France (A.C., E.L., R.B., L.D.N.)
- Institut Fédératif de Recherche 3450, Plateforme Imagerie, Pôle de Biotechnologie Végétale, F-31326 Castanet-Tolosan, France (A.J., M.-C.A., Y.M.); and
- UMR7265, Laboratoire de Biologie du Développement des Plantes, Service de Biologie Végétale et de Microbiologie Environnementales, Institut de Biologie Environnementale et Biotechnologie, Centre National de la Recherche Scientifique-Commissariat à l'Energie Atomique-Université Aix-Marseille, F-13108 Saint Paul-Les-Durance, France (S.C., N.L.)
| | - Yves Martinez
- LIPM, Université de Toulouse, INRA, CNRS, UPS, F-31326 Castanet-Tolosan, France (A.C., E.L., R.B., L.D.N.)
- Institut Fédératif de Recherche 3450, Plateforme Imagerie, Pôle de Biotechnologie Végétale, F-31326 Castanet-Tolosan, France (A.J., M.-C.A., Y.M.); and
- UMR7265, Laboratoire de Biologie du Développement des Plantes, Service de Biologie Végétale et de Microbiologie Environnementales, Institut de Biologie Environnementale et Biotechnologie, Centre National de la Recherche Scientifique-Commissariat à l'Energie Atomique-Université Aix-Marseille, F-13108 Saint Paul-Les-Durance, France (S.C., N.L.)
| | - Serge Chiarenza
- LIPM, Université de Toulouse, INRA, CNRS, UPS, F-31326 Castanet-Tolosan, France (A.C., E.L., R.B., L.D.N.)
- Institut Fédératif de Recherche 3450, Plateforme Imagerie, Pôle de Biotechnologie Végétale, F-31326 Castanet-Tolosan, France (A.J., M.-C.A., Y.M.); and
- UMR7265, Laboratoire de Biologie du Développement des Plantes, Service de Biologie Végétale et de Microbiologie Environnementales, Institut de Biologie Environnementale et Biotechnologie, Centre National de la Recherche Scientifique-Commissariat à l'Energie Atomique-Université Aix-Marseille, F-13108 Saint Paul-Les-Durance, France (S.C., N.L.)
| | - Nathalie Leonhardt
- LIPM, Université de Toulouse, INRA, CNRS, UPS, F-31326 Castanet-Tolosan, France (A.C., E.L., R.B., L.D.N.)
- Institut Fédératif de Recherche 3450, Plateforme Imagerie, Pôle de Biotechnologie Végétale, F-31326 Castanet-Tolosan, France (A.J., M.-C.A., Y.M.); and
- UMR7265, Laboratoire de Biologie du Développement des Plantes, Service de Biologie Végétale et de Microbiologie Environnementales, Institut de Biologie Environnementale et Biotechnologie, Centre National de la Recherche Scientifique-Commissariat à l'Energie Atomique-Université Aix-Marseille, F-13108 Saint Paul-Les-Durance, France (S.C., N.L.)
| | - Richard Berthomé
- LIPM, Université de Toulouse, INRA, CNRS, UPS, F-31326 Castanet-Tolosan, France (A.C., E.L., R.B., L.D.N.)
- Institut Fédératif de Recherche 3450, Plateforme Imagerie, Pôle de Biotechnologie Végétale, F-31326 Castanet-Tolosan, France (A.J., M.-C.A., Y.M.); and
- UMR7265, Laboratoire de Biologie du Développement des Plantes, Service de Biologie Végétale et de Microbiologie Environnementales, Institut de Biologie Environnementale et Biotechnologie, Centre National de la Recherche Scientifique-Commissariat à l'Energie Atomique-Université Aix-Marseille, F-13108 Saint Paul-Les-Durance, France (S.C., N.L.)
| | - Laurent D Noël
- LIPM, Université de Toulouse, INRA, CNRS, UPS, F-31326 Castanet-Tolosan, France (A.C., E.L., R.B., L.D.N.);
- Institut Fédératif de Recherche 3450, Plateforme Imagerie, Pôle de Biotechnologie Végétale, F-31326 Castanet-Tolosan, France (A.J., M.-C.A., Y.M.); and
- UMR7265, Laboratoire de Biologie du Développement des Plantes, Service de Biologie Végétale et de Microbiologie Environnementales, Institut de Biologie Environnementale et Biotechnologie, Centre National de la Recherche Scientifique-Commissariat à l'Energie Atomique-Université Aix-Marseille, F-13108 Saint Paul-Les-Durance, France (S.C., N.L.)
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31
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Li L, Li RF, Ming ZH, Lu GT, Tang JL. Identification of a novel type III secretion-associated outer membrane-bound protein from Xanthomonas campestris pv. campestris. Sci Rep 2017; 7:42724. [PMID: 28198457 PMCID: PMC5309889 DOI: 10.1038/srep42724] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Accepted: 01/13/2017] [Indexed: 12/31/2022] Open
Abstract
Many bacterial pathogens employ the type III secretion system (T3SS) to translocate effector proteins into eukaryotic cells to overcome host defenses. To date, most of our knowledge about the T3SS molecular architecture comes from the studies on animal pathogens. In plant pathogens, nine Hrc proteins are believed to be structural components of the T3SS, of which HrcC and HrcJ form the outer and inner rings of the T3SS, respectively. Here, we demonstrated that a novel outer membrane-bound protein (HpaM) of Xanthomonas campestris pv. campestris is critical for the type III secretion and is structurally and functionally conserved in phytopathogenic Xanthomonas spp. We showed that the C-terminus of HpaM extends into the periplasm to interact physically with HrcJ and the middle part of HpaM interacts physically with HrcC. It is clear that the outer and inner rings compose the main basal body of the T3SS apparatus in animal pathogens. Therefore, we presume that HpaM may act as a T3SS structural component, or play a role in assisting assembling or affecting the stability of the T3SS apparatus. HpaM is a highly prevalent and specific protein in Xanthomonas spp., suggesting that the T3SS of Xanthomonas is distinctive in some aspects from other pathogens.
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Affiliation(s)
- Lei Li
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China
| | - Rui-Fang Li
- Guangxi Key Laboratory of Biology for Crop Diseases and Insect Pests, Plant Protection Research Institute, Guangxi Academy of Agricultural Sciences, 174 Daxue Road, Nanning, Guangxi 530007, China
| | - Zhen-Hua Ming
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China
| | - Guang-Tao Lu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China
| | - Ji-Liang Tang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, China
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32
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Hausner J, Hartmann N, Jordan M, Büttner D. The Predicted Lytic Transglycosylase HpaH from Xanthomonas campestris pv. vesicatoria Associates with the Type III Secretion System and Promotes Effector Protein Translocation. Infect Immun 2017; 85:e00788-16. [PMID: 27895129 PMCID: PMC5278175 DOI: 10.1128/iai.00788-16] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 11/20/2016] [Indexed: 02/08/2023] Open
Abstract
The pathogenicity of the Gram-negative plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria depends on a type III secretion (T3S) system, which spans both bacterial membranes and translocates effector proteins into plant cells. The assembly of the T3S system presumably involves the predicted lytic transglycosylase (LT) HpaH, which is encoded adjacent to the T3S gene cluster. Bacterial LTs degrade peptidoglycan and often promote the formation of membrane-spanning macromolecular protein complexes. In the present study, we show that HpaH localizes to the bacterial periplasm and binds to peptidoglycan as well as to components of the T3S system, including the predicted periplasmic inner rod proteins HrpB1 and HrpB2 as well as the pilus protein HrpE. In vivo translocation assays revealed that HpaH promotes the translocation of various effector proteins and of early substrates of the T3S system, suggesting a general contribution of HpaH to type III-dependent protein export. Mutant studies and the analysis of reporter fusions showed that the N-terminal region of HpaH contributes to protein function and is proteolytically cleaved. The N-terminally truncated HpaH cleavage product is secreted into the extracellular milieu by a yet-unknown transport pathway, which is independent of the T3S system.
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Affiliation(s)
- Jens Hausner
- Institute of Biology, Genetics Department, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Nadine Hartmann
- Institute of Biology, Genetics Department, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Michael Jordan
- Institute of Biology, Genetics Department, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Daniela Büttner
- Institute of Biology, Genetics Department, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
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Drehkopf S, Hausner J, Jordan M, Scheibner F, Bonas U, Büttner D. A TAL-Based Reporter Assay for Monitoring Type III-Dependent Protein Translocation in Xanthomonas. Methods Mol Biol 2017; 1531:121-139. [PMID: 27837487 DOI: 10.1007/978-1-4939-6649-3_11] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Gram-negative plant- and animal-pathogenic bacteria use type III secretion (T3S) systems to translocate effector proteins into eukaryotic host cells. Type III-dependent delivery of effector proteins depends on a secretion and translocation signal, which is often located in the N-terminal protein region and is not conserved on the amino acid level. Translocation signals in effector proteins have been experimentally confirmed by employing reporter proteins, which are specifically activated inside eukaryotic cells. Here, we describe a method to monitor effector protein translocation using a deletion derivative of the transcription activator-like (TAL) effector protein AvrBs3 as reporter. AvrBs3 is a type III effector of the tomato and pepper pathogen X. campestris pv. vesicatoria and is imported into the plant cell nucleus where it binds to specific promoter elements of target genes and activates their transcription. The N-terminal deletion derivative AvrBs3∆2 lacks a functional T3S and translocation signal but contains the effector domain and induces plant gene expression when fused to a functional translocation signal. In resistant pepper plants, AvrBs3 and translocated AvrBs3∆2 fusion proteins induce the expression of the Bs3-resistance gene, which triggers a strong, macroscopically visible defense response. The protocol for translocation assays with AvrBs3∆2 fusion proteins includes (1) the generation of expression constructs by Golden Gate cloning, (2) the transfer of expression constructs into bacterial recipient strains, (3) in vitro secretion assays with reporter fusion proteins and (4) infection of AvrBs3-responsive pepper plants.
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Affiliation(s)
- Sabine Drehkopf
- Department of Genetics, Institute for Biology, Martin Luther University Halle-Wittenberg, Weinbergweg 10, 06120, Halle (Saale), Germany
| | - Jens Hausner
- Department of Genetics, Institute for Biology, Martin Luther University Halle-Wittenberg, Weinbergweg 10, 06120, Halle (Saale), Germany
| | - Michael Jordan
- Department of Genetics, Institute for Biology, Martin Luther University Halle-Wittenberg, Weinbergweg 10, 06120, Halle (Saale), Germany
| | - Felix Scheibner
- Department of Genetics, Institute for Biology, Martin Luther University Halle-Wittenberg, Weinbergweg 10, 06120, Halle (Saale), Germany
| | - Ulla Bonas
- Department of Genetics, Institute for Biology, Martin Luther University Halle-Wittenberg, Weinbergweg 10, 06120, Halle (Saale), Germany
| | - Daniela Büttner
- Department of Genetics, Institute for Biology, Martin Luther University Halle-Wittenberg, Weinbergweg 10, 06120, Halle (Saale), Germany.
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Read AC, Rinaldi FC, Hutin M, He YQ, Triplett LR, Bogdanove AJ. Suppression of Xo1-Mediated Disease Resistance in Rice by a Truncated, Non-DNA-Binding TAL Effector of Xanthomonas oryzae. FRONTIERS IN PLANT SCIENCE 2016; 7:1516. [PMID: 27790231 PMCID: PMC5062187 DOI: 10.3389/fpls.2016.01516] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2016] [Accepted: 09/26/2016] [Indexed: 05/19/2023]
Abstract
Delivered into plant cells by type III secretion from pathogenic Xanthomonas species, TAL (transcription activator-like) effectors are nuclear-localized, DNA-binding proteins that directly activate specific host genes. Targets include genes important for disease, genes that confer resistance, and genes inconsequential to the host-pathogen interaction. TAL effector specificity is encoded by polymorphic repeats of 33-35 amino acids that interact one-to-one with nucleotides in the recognition site. Activity depends also on N-terminal sequences important for DNA binding and C-terminal nuclear localization signals (NLS) and an acidic activation domain (AD). Coding sequences missing much of the N- and C-terminal regions due to conserved, in-frame deletions are present and annotated as pseudogenes in sequenced strains of Xanthomonas oryzae pv. oryzicola (Xoc) and pv. oryzae (Xoo), which cause bacterial leaf streak and bacterial blight of rice, respectively. Here we provide evidence that these sequences encode proteins we call "truncTALEs," for "truncated TAL effectors." We show that truncTALE Tal2h of Xoc strain BLS256, and by correlation truncTALEs in other strains, specifically suppress resistance mediated by the Xo1 locus recently described in the heirloom rice variety Carolina Gold. Xo1-mediated resistance is triggered by different TAL effectors from diverse X. oryzae strains, irrespective of their DNA binding specificity, and does not require the AD. This implies a direct protein-protein rather than protein-DNA interaction. Similarly, truncTALEs exhibit diverse predicted DNA recognition specificities. And, in vitro, Tal2h did not bind any of several potential recognition sites. Further, a single candidate NLS sequence in Tal2h was dispensable for resistance suppression. Many truncTALEs have one 28 aa repeat, a length not observed previously. Tested in an engineered TAL effector, this repeat required a single base pair deletion in the DNA, suggesting that it or a neighbor disengages. The presence of the 28 aa repeat, however, was not required for resistance suppression. TruncTALEs expand the paradigm for TAL effector-mediated effects on plants. We propose that Tal2h and other truncTALEs act as dominant negative ligands for an immune receptor encoded by the Xo1 locus, likely a nucleotide binding, leucine-rich repeat protein. Understanding truncTALE function and distribution will inform strategies for disease control.
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Affiliation(s)
- Andrew C. Read
- Plant Pathology and Plant-Microbe Biology Section, School of Integrative Plant Science, Cornell UniversityIthaca, NY, USA
| | - Fabio C. Rinaldi
- Plant Pathology and Plant-Microbe Biology Section, School of Integrative Plant Science, Cornell UniversityIthaca, NY, USA
| | - Mathilde Hutin
- Plant Pathology and Plant-Microbe Biology Section, School of Integrative Plant Science, Cornell UniversityIthaca, NY, USA
| | - Yong-Qiang He
- Plant Pathology and Plant-Microbe Biology Section, School of Integrative Plant Science, Cornell UniversityIthaca, NY, USA
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, and College of Life Science and Technology, Guangxi UniversityNanning, China
| | - Lindsay R. Triplett
- Department of Plant Pathology and Ecology, The Connecticut Agricultural Experiment StationNew Haven, CT, USA
| | - Adam J. Bogdanove
- Plant Pathology and Plant-Microbe Biology Section, School of Integrative Plant Science, Cornell UniversityIthaca, NY, USA
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Chatnaparat T, Prathuangwong S, Lindow SE. Global Pattern of Gene Expression of Xanthomonas axonopodis pv. glycines Within Soybean Leaves. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2016; 29:508-22. [PMID: 27003800 DOI: 10.1094/mpmi-01-16-0007-r] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
To better understand the behavior of Xanthomonas axonopodis pv. glycines, the causal agent of bacterial pustule of soybean within its host, its global transcriptome within soybean leaves was compared with that in a minimal medium in vitro, using deep sequencing of mRNA. Of 5,062 genes predicted from a draft genome of X. axonopodis pv. glycines, 534 were up-regulated in the plant, while 289 were down-regulated. Genes encoding YapH, a cell-surface adhesin, as well as several others encoding cell-surface proteins, were down-regulated in soybean. Many genes encoding the type III secretion system and effector proteins, cell wall-degrading enzymes and phosphate transporter proteins were strongly expressed at early stages of infection. Several genes encoding RND multidrug efflux pumps were induced in planta and by isoflavonoids in vitro and were required for full virulence of X. axonopodis pv. glycines, as well as resistance to soybean phytoalexins. Genes encoding consumption of malonate, a compound abundant in soybean, were induced in planta and by malonate in vitro. Disruption of the malonate decarboxylase operon blocked growth in minimal media with malonate as the sole carbon source but did not significantly alter growth in soybean, apparently because genes for sucrose and fructose uptake were also induced in planta. Many genes involved in phosphate metabolism and uptake were induced in planta. While disruption of genes encoding high-affinity phosphate transport did not alter growth in media varying in phosphate concentration, the mutants were severely attenuated for growth in soybean. This global transcriptional profiling has provided insight into both the intercellular environment of this soybean pathogen and traits used by X. axonopodis pv. glycines to promote disease.
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Affiliation(s)
- Tiyakhon Chatnaparat
- 1 Department of Plant Pathology, Kasetsart University, Thailand
- 2 Center for Advanced Studies in Tropical Natural Resources, Kasetsart University, Bangkok, Thailand; and
| | - Sutruedee Prathuangwong
- 1 Department of Plant Pathology, Kasetsart University, Thailand
- 2 Center for Advanced Studies in Tropical Natural Resources, Kasetsart University, Bangkok, Thailand; and
| | - Steven E Lindow
- 3 Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720, U.S.A
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Scheibner F, Schulz S, Hausner J, Marillonnet S, Büttner D. Type III-Dependent Translocation of HrpB2 by a Nonpathogenic hpaABC Mutant of the Plant-Pathogenic Bacterium Xanthomonas campestris pv. vesicatoria. Appl Environ Microbiol 2016; 82:3331-3347. [PMID: 27016569 PMCID: PMC4959247 DOI: 10.1128/aem.00537-16] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Accepted: 03/21/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED The plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria employs a type III secretion (T3S) system to translocate effector proteins into plant cells. The T3S apparatus spans both bacterial membranes and is associated with an extracellular pilus and a channel-like translocon in the host plasma membrane. T3S is controlled by the switch protein HpaC, which suppresses secretion and translocation of the predicted inner rod protein HrpB2 and promotes secretion of translocon and effector proteins. We previously reported that HrpB2 interacts with HpaC and the cytoplasmic domain of the inner membrane protein HrcU (C. Lorenz, S. Schulz, T. Wolsch, O. Rossier, U. Bonas, and D. Büttner, PLoS Pathog 4:e1000094, 2008, http://dx.doi.org/10.1371/journal.ppat.1000094). However, the molecular mechanisms underlying the control of HrpB2 secretion are not yet understood. Here, we located a T3S and translocation signal in the N-terminal 40 amino acids of HrpB2. The results of complementation experiments with HrpB2 deletion derivatives revealed that the T3S signal of HrpB2 is essential for protein function. Furthermore, interaction studies showed that the N-terminal region of HrpB2 interacts with the cytoplasmic domain of HrcU, suggesting that the T3S signal of HrpB2 contributes to substrate docking. Translocation of HrpB2 is suppressed not only by HpaC but also by the T3S chaperone HpaB and its secreted regulator, HpaA. Deletion of hpaA, hpaB, and hpaC leads to a loss of pathogenicity but allows the translocation of fusion proteins between the HrpB2 T3S signal and effector proteins into leaves of host and non-host plants. IMPORTANCE The T3S system of the plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria is essential for pathogenicity and delivers effector proteins into plant cells. T3S depends on HrpB2, which is a component of the predicted periplasmic inner rod structure of the secretion apparatus. HrpB2 is secreted during the early stages of the secretion process and interacts with the cytoplasmic domain of the inner membrane protein HrcU. Here, we localized the secretion and translocation signal of HrpB2 in the N-terminal 40 amino acids and show that this region is sufficient for the interaction with the cytoplasmic domain of HrcU. Our results suggest that the T3S signal of HrpB2 is required for the docking of HrpB2 to the secretion apparatus. Furthermore, we provide experimental evidence that the N-terminal region of HrpB2 is sufficient to target effector proteins for translocation in a nonpathogenic X. campestris pv. vesicatoria strain.
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Affiliation(s)
- Felix Scheibner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Steve Schulz
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | - Jens Hausner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
| | | | - Daniela Büttner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
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Abe A, Nishimura R, Tanaka N, Kurushima J, Kuwae A. The Bordetella Secreted Regulator BspR Is Translocated into the Nucleus of Host Cells via Its N-Terminal Moiety: Evaluation of Bacterial Effector Translocation by the Escherichia coli Type III Secretion System. PLoS One 2015; 10:e0135140. [PMID: 26247360 PMCID: PMC4527748 DOI: 10.1371/journal.pone.0135140] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Accepted: 07/17/2015] [Indexed: 11/27/2022] Open
Abstract
Bordetella bronchiseptica is genetically related to B. pertussis and B. parapertussis, which cause respiratory tract infections in humans. These pathogens possess a large number of virulence factors, including the type III secretion system (T3SS), which is required for the delivery of effectors into the host cells. In a previous study, we identified a transcriptional regulator, BspR, that is involved in the regulation of the T3SS-related genes in response to iron-starved conditions. A unique feature of BspR is that this regulator is secreted into the extracellular milieu via the T3SS. To further characterize the role of BspR in extracellular localization, we constructed various truncated derivatives of BspR and investigated their translocation into the host cells using conventional translocation assays. In this study, the effector translocation was evaluated by the T3SS of enteropathogenic E. coli (EPEC), since the exogenous expression of BspR triggers severe repression of the Bordetella T3SS expression. The results of the translocation assays using the EPEC T3SS showed that the N-terminal 150 amino acid (aa) residues of BspR are sufficient for translocation into the host cells in a T3SS-dependent manner. In addition, exogenous expression of BspR in HeLa cells demonstrated that the N-terminal 100 aa residues are involved in the nuclear localization. In contrast, the N-terminal 54 aa residues are sufficient for the extracellular secretion into the bacterial culture supernatant via the EPEC T3SS. Thus, BspR is not only a transcriptional regulator in bacteria cytosol, but also functions as an effector that translocates into the nuclei of infected host cells.
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Affiliation(s)
- Akio Abe
- Laboratory of Bacterial Infection, Graduate School of Infection Control Sciences, Kitasato University, Tokyo 108-8641, Japan
- * E-mail:
| | - Ryutaro Nishimura
- Laboratory of Bacterial Infection, Graduate School of Infection Control Sciences, Kitasato University, Tokyo 108-8641, Japan
| | - Naomichi Tanaka
- Laboratory of Bacterial Infection, Graduate School of Infection Control Sciences, Kitasato University, Tokyo 108-8641, Japan
| | - Jun Kurushima
- Laboratory of Bacterial Infection, Graduate School of Infection Control Sciences, Kitasato University, Tokyo 108-8641, Japan
| | - Asaomi Kuwae
- Laboratory of Bacterial Infection, Graduate School of Infection Control Sciences, Kitasato University, Tokyo 108-8641, Japan
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Xanthomonas campestris pv. vesicatoria Secretes Proteases and Xylanases via the Xps Type II Secretion System and Outer Membrane Vesicles. J Bacteriol 2015; 197:2879-93. [PMID: 26124239 DOI: 10.1128/jb.00322-15] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2015] [Accepted: 06/19/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Many plant-pathogenic bacteria utilize type II secretion (T2S) systems to secrete degradative enzymes into the extracellular milieu. T2S substrates presumably mediate the degradation of plant cell wall components during the host-pathogen interaction and thus promote bacterial virulence. Previously, the Xps-T2S system from Xanthomonas campestris pv. vesicatoria was shown to contribute to extracellular protease activity and the secretion of a virulence-associated xylanase. The identities and functions of additional T2S substrates from X. campestris pv. vesicatoria, however, are still unknown. In the present study, the analysis of 25 candidate proteins from X. campestris pv. vesicatoria led to the identification of two type II secreted predicted xylanases, a putative protease and a lipase which was previously identified as a virulence factor of X. campestris pv. vesicatoria. Studies with mutant strains revealed that the identified xylanases and the protease contribute to virulence and in planta growth of X. campestris pv. vesicatoria. When analyzed in the related pathogen X. campestris pv. campestris, several T2S substrates from X. campestris pv. vesicatoria were secreted independently of the T2S systems, presumably because of differences in the T2S substrate specificities of the two pathogens. Furthermore, in X. campestris pv. vesicatoria T2S mutants, secretion of T2S substrates was not completely absent, suggesting the contribution of additional transport systems to protein secretion. In line with this hypothesis, T2S substrates were detected in outer membrane vesicles, which were frequently observed for X. campestris pv. vesicatoria. We, therefore, propose that extracellular virulence-associated enzymes from X. campestris pv. vesicatoria are targeted to the Xps-T2S system and to outer membrane vesicles. IMPORTANCE The virulence of plant-pathogenic bacteria often depends on TS2 systems, which secrete degradative enzymes into the extracellular milieu. T2S substrates are being studied in several plant-pathogenic bacteria, including Xanthomonas campestris pv. vesicatoria, which causes bacterial spot disease in tomato and pepper. Here, we show that the T2S system from X. campestris pv. vesicatoria secretes virulence-associated xylanases, a predicted protease, and a lipase. Secretion assays with the related pathogen X. campestris pv. campestris revealed important differences in the T2S substrate specificities of the two pathogens. Furthermore, electron microscopy showed that T2S substrates from X. campestris pv. vesicatoria are targeted to outer membrane vesicles (OMVs). Our results, therefore, suggest that OMVs provide an alternative transport route for type II secreted extracellular enzymes.
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A TALE of transposition: Tn3-like transposons play a major role in the spread of pathogenicity determinants of Xanthomonas citri and other xanthomonads. mBio 2015; 6:e02505-14. [PMID: 25691597 PMCID: PMC4337579 DOI: 10.1128/mbio.02505-14] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Members of the genus Xanthomonas are among the most important phytopathogens. A key feature of Xanthomonas pathogenesis is the translocation of type III secretion system (T3SS) effector proteins (T3SEs) into the plant target cells via a T3SS. Several T3SEs and a murein lytic transglycosylase gene (mlt, required for citrus canker symptoms) are found associated with three transposition-related genes in Xanthomonas citri plasmid pXAC64. These are flanked by short inverted repeats (IRs). The region was identified as a transposon, TnXax1, with typical Tn3 family features, including a transposase and two recombination genes. Two 14-bp palindromic sequences within a 193-bp potential resolution site occur between the recombination genes. Additional derivatives carrying different T3SEs and other passenger genes occur in different Xanthomonas species. The T3SEs include transcription activator-like effectors (TALEs). Certain TALEs are flanked by the same IRs as found in TnXax1 to form mobile insertion cassettes (MICs), suggesting that they may be transmitted horizontally. A significant number of MICs carrying other passenger genes (including a number of TALE genes) were also identified, flanked by the same TnXax1 IRs and delimited by 5-bp target site duplications. We conclude that a large fraction of T3SEs, including individual TALEs and potential pathogenicity determinants, have spread by transposition and that TnXax1, which exhibits all of the essential characteristics of a functional transposon, may be involved in driving MIC transposition. We also propose that TALE genes may diversify by fork slippage during the replicative Tn3 family transposition. These mechanisms may play a crucial role in the emergence of Xanthomonas pathogenicity. Xanthomonas genomes carry many insertion sequences (IS) and transposons, which play an important role in their evolution and architecture. This study reveals a key relationship between transposons and pathogenicity determinants in Xanthomonas. We propose that several transposition events mediated by a Tn3-like element carrying different sets of passenger genes, such as different type III secretion system effectors (including transcription activation-like effectors [TALEs]), were determinant in the evolution and emergence of Xanthomonas pathogenicity. TALE genes are DNA-binding effectors that modulate plant transcription. We also present a model for generating TALE gene diversity based on fork slippage associated with the replicative transposition mechanism of Tn3-like transposons. This may provide a mechanism for niche adaptation, specialization, host-switching, and other lifestyle changes. These results will also certainly lead to novel insights into the evolution and emergence of the various diseases caused by different Xanthomonas species and pathovars.
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Stork W, Kim JG, Mudgett MB. Functional Analysis of Plant Defense Suppression and Activation by the Xanthomonas Core Type III Effector XopX. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2015; 28:180-94. [PMID: 25338145 PMCID: PMC4293322 DOI: 10.1094/mpmi-09-14-0263-r] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Many phytopathogenic type III secretion effector proteins (T3Es) have been shown to target and suppress plant immune signaling but perturbation of the plant immune system by T3Es can also elicit a plant response. XopX is a "core" Xanthomonas T3E that contributes to growth and symptom development during Xanthomonas euvesicatoria infection of tomato but its functional role is undefined. We tested the effect of XopX on several aspects of plant immune signaling. XopX promoted ethylene production and plant cell death (PCD) during X. euvesicatoria infection of susceptible tomato and in transient expression assays in Nicotiana benthamiana, which is consistent with its requirement for the development of X. euvesicatoria-induced disease symptoms. Additionally, although XopX suppressed flagellin-induced reactive oxygen species, it promoted the accumulation of pattern-triggered immunity (PTI) gene transcripts. Surprisingly, XopX coexpression with other PCD elicitors resulted in delayed PCD, suggesting antagonism between XopX-dependent PCD and other PCD pathways. However, we found no evidence that XopX contributed to the suppression of effector-triggered immunity during X. euvesicatoria-tomato interactions, suggesting that XopX's primary virulence role is to modulate PTI. These results highlight the dual role of a core Xanthomonas T3E in simultaneously suppressing and activating plant defense responses.
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Zhou X, Hu X, Li J, Wang N. A Novel Periplasmic Protein, VrpA, Contributes to Efficient Protein Secretion by the Type III Secretion System in Xanthomonas spp. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2015; 28:143-153. [PMID: 25338144 DOI: 10.1094/mpmi-10-14-0309-r] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Efficient secretion of type III effector proteins from the bacterial cytoplasm to host cell cytosol via a type III secretion system (T3SS) is crucial for virulence of plant-pathogenic bacterium. Our previous study revealed a conserved hypothetical protein, virulence-related periplasm protein A (VrpA), which was identified as a critical virulence factor for Xanthomonas citri subsp. citri. In this study, we demonstrate that mutation of vrpA compromises X. citri subsp. citri virulence and hypersensitive response induction. This deficiency is also observed in the X. campestris pv. campestris strain, suggesting a functional conservation of VrpA in Xanthomonas spp. Our study indicates that VrpA is required for efficient protein secretion via T3SS, which is supported by multiple lines of evidence. A CyaA reporter assay shows that VrpA is involved in type III effector secretion; quantitative reverse-transcription polymerase chain reaction analysis suggests that the vrpA mutant fails to activate citrus-canker-susceptible gene CsLOB1, which is transcriptionally activated by transcription activator-like effector PthA4; in vitro secretion study reveals that VrpA plays an important role in secretion of T3SS pilus, translocon, and effector proteins. Our data also indicate that VrpA in X. citri subsp. citri localizes to bacterial periplasmic space and the periplasmic localization is required for full function of VrpA and X. citri subsp. citri virulence. Protein-protein interaction studies show that VrpA physically interacts with periplasmic T3SS components HrcJ and HrcC. However, the mutation of VrpA does not affect T3SS gene expression. Additionally, VrpA is involved in X. citri subsp. citri tolerance of oxidative stress. Our data contribute to the mechanical understanding of an important periplasmic protein VrpA in Xanthomonas spp.
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Tan L, Rong W, Luo H, Chen Y, He C. The Xanthomonas campestris effector protein XopDXcc8004 triggers plant disease tolerance by targeting DELLA proteins. THE NEW PHYTOLOGIST 2014; 204:595-608. [PMID: 25040905 DOI: 10.1111/nph.12918] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2014] [Accepted: 05/29/2014] [Indexed: 05/09/2023]
Abstract
Plants protect themselves from the harmful effects of pathogens by resistance and tolerance. Disease resistance, which eliminates pathogens, can be modulated by bacterial type III effectors. Little is known about whether disease tolerance, which sustains host fitness with a given pathogen burden, is regulated by effectors. Here, we examined the effects of the Xanthomonas effector protein XopDXcc8004 on plant disease defenses by constructing knockout and complemented Xanthomonas strains, and performing inoculation studies in radish (Raphanus sativus L. var. radiculus XiaoJinZhong) and Arabidopsis plants. XopDXcc8004 suppresses disease symptoms without changing bacterial titers in infected leaves. In Arabidopsis, XopDXcc8004 delays the hormone gibberellin (GA)-mediated degradation of RGA (repressor of ga1-3), one of five DELLA proteins that repress GA signaling and promote plant tolerance under biotic and abiotic stresses. The ERF-associated amphiphilic repression (EAR) motif-containing region of XopDXcc8004 interacts with the DELLA domain of RGA and might interfere with the GA-induced binding of GID1, a GA receptor, to RGA. The EAR motif was found to be present in a number of plant transcriptional regulators. Thus, our data suggest that bacterial pathogens might have evolved effectors, which probably mimic host components, to initiate disease tolerance and enhance their survival.
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Affiliation(s)
- Leitao Tan
- State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
- Hainan Key Laboratory of Sustainable Utilization of Tropical Bioresources, Hainan University, Haikou, 570228, China
- University of Chinese Academy of Sciences, Beijing, 100039, China
| | - Wei Rong
- Hainan Key Laboratory of Sustainable Utilization of Tropical Bioresources, Hainan University, Haikou, 570228, China
| | - Hongli Luo
- Hainan Key Laboratory of Sustainable Utilization of Tropical Bioresources, Hainan University, Haikou, 570228, China
| | - Yinhua Chen
- State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
- Hainan Key Laboratory of Sustainable Utilization of Tropical Bioresources, Hainan University, Haikou, 570228, China
| | - Chaozu He
- State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
- Hainan Key Laboratory of Sustainable Utilization of Tropical Bioresources, Hainan University, Haikou, 570228, China
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Abstract
Xanthomonas phytopathogenic bacteria produce unique transcription activator-like effector (TALE) proteins that recognize and activate specific plant promoters through a set of tandem repeats. A unique TALE-DNA-binding code uses two polymorphic amino acids in each repeat to mediate recognition of specific nucleotides. The order of repeats determines effector’s specificity toward the cognate nucleotide sequence of the sense DNA strand. Artificially designed TALE-DNA-binding domains fused to nuclease or activation and repressor domains provide an outstanding toolbox for targeted gene editing and gene regulation in research, biotechnology and gene therapy. Gene editing with custom-designed TALE nucleases (TALENs) extends the repertoire of targeted genome modifications across a broad spectrum of organisms ranging from plants and insect to mammals.
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44
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Fichtner F, Urrea Castellanos R, Ülker B. Precision genetic modifications: a new era in molecular biology and crop improvement. PLANTA 2014; 239:921-39. [PMID: 24510124 DOI: 10.1007/s00425-014-2029-y] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Accepted: 01/06/2014] [Indexed: 05/26/2023]
Abstract
Recently, the use of programmable DNA-binding proteins such as ZFP/ZFNs, TALE/TALENs and CRISPR/Cas has produced unprecedented advances in gene targeting and genome editing in prokaryotes and eukaryotes. These advances allow researchers to specifically alter genes, reprogram epigenetic marks, generate site-specific deletions and potentially cure diseases. Unlike previous methods, these precision genetic modification techniques (PGMs) are specific, efficient, easy to use and economical. Here we discuss the capabilities and pitfalls of PGMs and highlight the recent, exciting applications of PGMs in molecular biology and crop genetic engineering. Further improvement of the efficiency and precision of PGM techniques will enable researchers to precisely alter gene expression and biological/chemical pathways, probe gene function, modify epigenetic marks and improve crops by increasing yield, quality and tolerance to limiting biotic and abiotic stress conditions.
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Affiliation(s)
- Franziska Fichtner
- Plant Molecular Engineering Group, Institute of Cellular and Molecular Botany, University of Bonn, Kirschallee 1, 53115, Bonn, Germany
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45
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Abendroth U, Schmidtke C, Bonas U. Small non-coding RNAs in plant-pathogenic Xanthomonas spp. RNA Biol 2014; 11:457-63. [PMID: 24667380 DOI: 10.4161/rna.28240] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The genus Xanthomonas comprises a large group of plant-pathogenic bacteria. The infection and bacterial multiplication in the plant tissue depends on the type III secretion system and other virulence determinants. Recent studies revealed that bacterial virulence is also controlled at the post-transcriptional level by small non-coding RNAs (sRNAs). In this review, we highlight our current knowledge about sRNAs and RNA-binding proteins in Xanthomonas species.
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Affiliation(s)
- Ulrike Abendroth
- Dept. of Genetics; Martin-Luther-Universität Halle-Wittenberg; Halle, Germany
| | - Cornelius Schmidtke
- Dept. of Genetics; Martin-Luther-Universität Halle-Wittenberg; Halle, Germany
| | - Ulla Bonas
- Dept. of Genetics; Martin-Luther-Universität Halle-Wittenberg; Halle, Germany
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46
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Hausner J, Büttner D. The YscU/FlhB homologue HrcU from Xanthomonas controls type III secretion and translocation of early and late substrates. MICROBIOLOGY-SGM 2014; 160:576-588. [PMID: 24425767 DOI: 10.1099/mic.0.075176-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The majority of Gram-negative plant- and animal-pathogenic bacteria employ a type III secretion (T3S) system to deliver effector proteins to eukaryotic cells. Members of the YscU protein family are essential components of the T3S system and consist of a transmembrane and a cytoplasmic region that is autocatalytically cleaved at a conserved NPTH motif. YscU homologues interact with T3S substrate specificity switch (T3S4) proteins that alter the substrate specificity of the T3S system after assembly of the secretion apparatus. We previously showed that the YscU homologue HrcU from the plant pathogen Xanthomonas campestris pv. vesicatoria interacts with the T3S4 protein HpaC and is required for the secretion of translocon and effector proteins. In the present study, analysis of HrcU deletion, insertion and point mutant derivatives led to the identification of amino acid residues in the cytoplasmic region of HrcU (HrcUC) that control T3S and translocation of the predicted inner rod protein HrpB2, the translocon protein HrpF and the effector protein AvrBs3. Mutations in the vicinity of the NPTH motif interfered with HrcU cleavage and/or the interaction of HrcUC with HrpB2 and the T3S4 protein HpaC. However, HrcU function was not completely abolished, suggesting that HrcU cleavage is not crucial for pathogenicity and T3S. Given that mutations in HrcU differentially affected T3S and translocation of HrpB2 and effector proteins, we propose that HrcU controls the secretion of different T3S substrate classes by independent mechanisms.
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Affiliation(s)
- Jens Hausner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Weinbergweg 10, 06120 Halle (Saale), Germany
| | - Daniela Büttner
- Institute of Biology, Department of Genetics, Martin Luther University Halle-Wittenberg, Weinbergweg 10, 06120 Halle (Saale), Germany
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47
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Abstract
Human pluripotent stem cells (hPSCs) have the potential to generate all adult cell types, including rare or inaccessible human cell populations, thus providing a unique platform for disease studies. To realize this promise, it is essential to develop methods for efficient genetic manipulations in hPSCs. Established using TALEN (transcription activator-like effector nuclease) and CRISPR (clustered regularly interspaced short palindromic repeats)/Cas (CRISPR-associated) systems, the iCRISPR platform supports a variety of genome-engineering approaches with high efficiencies. Here, we first describe the establishment of the iCRISPR platform through TALEN-mediated targeting of inducible Cas9 expression cassettes into the AAVS1 locus. Next, we provide a series of technical procedures for using iCRISPR to achieve one-step knockout of one or multiple gene(s), "scarless" introduction of precise nucleotide alterations, as well as inducible knockout during hPSC differentiation. We present an optimized workflow, as well as guidelines for the selection of CRISPR targeting sequences and the design of single-stranded DNA (ssDNA) homology-directed DNA repair templates for the introduction of specific nucleotide alterations. We have successfully used these protocols in four different hPSC lines, including human embryonic stem cells and induced pluripotent stem cells. Once the iCRISPR platform is established, clonal lines with desired genetic modifications can be established in as little as 1 month. The methods described here enable a wide range of genome-engineering applications in hPSCs, thus providing a valuable resource for the creation of diverse hPSC-based disease models with superior speed and ease.
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Affiliation(s)
- Zengrong Zhu
- Developmental Biology Program, Sloan-Kettering Institute, New York, USA
| | - Federico González
- Developmental Biology Program, Sloan-Kettering Institute, New York, USA
| | - Danwei Huangfu
- Developmental Biology Program, Sloan-Kettering Institute, New York, USA.
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48
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Hartmann N, Büttner D. The inner membrane protein HrcV from Xanthomonas spp. is involved in substrate docking during type III secretion. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2013; 26:1176-1189. [PMID: 23777429 DOI: 10.1094/mpmi-01-13-0019-r] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Pathogenicity of the gram-negative plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria depends on a membrane-spanning type III secretion (T3S) system, which translocates effector proteins into eukaryotic host cells. In this study, we characterized the T3S system component HrcV, which is a member of the YscV/FlhA family of inner membrane proteins. HrcV consists of eight transmembrane helices and a cytoplasmic region (HrcVC). Mutant and protein-protein interaction studies showed that HrcVC is essential for protein function and binds to T3S substrates, including the early substrate HrpB2, the pilus protein HrpE, and effector proteins. Furthermore, HrcVC interacts with itself and with components and control proteins of the T3S apparatus. The interaction of HrcVC with HrpB2, HrpE, and T3S system components depends on amino acid residues in a conserved motif, designated flagella/hypersensitive response/invasion proteins export pore (FHIPEP), which is located in a cytoplasmic loop between transmembrane helix four and five of HrcV. Mutations in the FHIPEP motif abolish HrcV function but do not affect the interaction of HrcVC with effector proteins.
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49
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Hausner J, Hartmann N, Lorenz C, Büttner D. The periplasmic HrpB1 protein from Xanthomonas spp. binds to peptidoglycan and to components of the type III secretion system. Appl Environ Microbiol 2013; 79:6312-24. [PMID: 23934485 PMCID: PMC3811196 DOI: 10.1128/aem.01226-13] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Accepted: 07/31/2013] [Indexed: 11/20/2022] Open
Abstract
The plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria employs a type III secretion (T3S) system to translocate bacterial effector proteins into eukaryotic host cells. The membrane-spanning secretion apparatus consists of 11 core components and several associated proteins with yet unknown functions. In this study, we analyzed the role of HrpB1, which was previously shown to be essential for T3S and the formation of the extracellular T3S pilus. We provide experimental evidence that HrpB1 localizes to the bacterial periplasm and binds to peptidoglycan, which is in agreement with its predicted structural similarity to the putative peptidoglycan-binding domain of the lytic transglycosylase Slt70 from Escherichia coli. Interaction studies revealed that HrpB1 forms protein complexes and binds to T3S system components, including the inner membrane protein HrcD, the secretin HrcC, the pilus protein HrpE, and the putative inner rod protein HrpB2. The analysis of deletion and point mutant derivatives of HrpB1 led to the identification of amino acid residues that contribute to the interaction of HrpB1 with itself and HrcD and/or to protein function. The finding that HrpB1 and HrpB2 colocalize to the periplasm and both interact with HrcD suggests that they are part of a periplasmic substructure of the T3S system.
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Affiliation(s)
- Jens Hausner
- Institute of Biology, Department of Genetics, Martin-Luther University Halle-Wittenberg, Halle (Saale), Germany
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50
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Guy E, Lautier M, Chabannes M, Roux B, Lauber E, Arlat M, Noël LD. xopAC-triggered immunity against Xanthomonas depends on Arabidopsis receptor-like cytoplasmic kinase genes PBL2 and RIPK. PLoS One 2013; 8:e73469. [PMID: 23951354 PMCID: PMC3739749 DOI: 10.1371/journal.pone.0073469] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 07/23/2013] [Indexed: 12/22/2022] Open
Abstract
Xanthomonas campestris pv. campestris (Xcc) colonizes the vascular system of Brassicaceae and ultimately causes black rot. In susceptible Arabidopsis plants, XopAC type III effector inhibits by uridylylation positive regulators of the PAMP-triggered immunity such as the receptor-like cytoplasmic kinases (RLCK) BIK1 and PBL1. In the resistant ecotype Col-0, xopAC is a major avirulence gene of Xcc. In this study, we show that both the RLCK interaction domain and the uridylyl transferase domain of XopAC are required for avirulence. Furthermore, xopAC can also confer avirulence to both the vascular pathogen Ralstonia solanacearum and the mesophyll-colonizing pathogen Pseudomonas syringae indicating that xopAC-specified effector-triggered immunity is not specific to the vascular system. In planta, XopAC-YFP fusions are localized at the plasma membrane suggesting that XopAC might interact with membrane-localized proteins. Eight RLCK of subfamily VII predicted to be localized at the plasma membrane and interacting with XopAC in yeast two-hybrid assays have been isolated. Within this subfamily, PBL2 and RIPK RLCK genes but not BIK1 are important for xopAC-specified effector-triggered immunity and Arabidopsis resistance to Xcc.
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Affiliation(s)
- Endrick Guy
- INRA, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR 441, Castanet-Tolosan, France
- CNRS, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR 2594, Castanet-Tolosan, France
| | - Martine Lautier
- INRA, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR 441, Castanet-Tolosan, France
- CNRS, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR 2594, Castanet-Tolosan, France
- Université de Toulouse, Université Paul Sabatier, Toulouse, France
| | - Matthieu Chabannes
- INRA, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR 441, Castanet-Tolosan, France
- CNRS, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR 2594, Castanet-Tolosan, France
| | - Brice Roux
- INRA, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR 441, Castanet-Tolosan, France
- CNRS, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR 2594, Castanet-Tolosan, France
| | - Emmanuelle Lauber
- INRA, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR 441, Castanet-Tolosan, France
- CNRS, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR 2594, Castanet-Tolosan, France
| | - Matthieu Arlat
- INRA, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR 441, Castanet-Tolosan, France
- CNRS, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR 2594, Castanet-Tolosan, France
- Université de Toulouse, Université Paul Sabatier, Toulouse, France
| | - Laurent D. Noël
- INRA, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR 441, Castanet-Tolosan, France
- CNRS, Laboratoire des Interactions Plantes Micro-organismes (LIPM), UMR 2594, Castanet-Tolosan, France
- * E-mail:
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