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Huang J, Zhou H, Zhou M, Li N, Jiang B, He Y. Functional Analysis of Type III Effectors in Xanthomonas campestris pv. campestris Reveals Distinct Roles in Modulating Arabidopsis Innate Immunity. Pathogens 2024; 13:448. [PMID: 38921746 PMCID: PMC11206781 DOI: 10.3390/pathogens13060448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2024] [Revised: 05/19/2024] [Accepted: 05/23/2024] [Indexed: 06/27/2024] Open
Abstract
Xanthomonas campestris pv. campestris (Xcc) is a significant phytopathogen causing black rot disease in crucifers. Its virulence relies heavily on the type III secretion system (T3SS), facilitating effector translocation into plant cells. The type III effectors (T3Es) disrupt cellular processes, promoting pathogen proliferation. However, only a few T3Es from Xcc have been thoroughly characterized. In this study, we further investigated two effectors using the T3Es-deficient mutant and the Arabidopsis protoplast system. XopE2Xcc triggers Arabidopsis immune responses via an unidentified activator of the salicylic acid (SA) signaling pathway, whereas XopLXcc suppresses the expression of genes associated with patterns-triggered immunity (PTI) and the SA signaling pathway. These two effectors exert opposing effects on Arabidopsis immune responses. Additionally, we examined the relationship between the specific domains and functions of these two effector proteins. Our findings demonstrate that the N-myristoylation motif and N-terminal domain are essential for the subcellular localization and virulence of XopE2Xcc and XopLXcc, respectively. These novel insights enhance our understanding of the pathogenic mechanisms of T3Es and contribute to developing effective strategies for controlling bacterial disease.
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Affiliation(s)
- Jing Huang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, Nanning 530005, China; (J.H.); (B.J.)
| | - Hao Zhou
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, Nanning 530005, China; (J.H.); (B.J.)
- Guangxi Key Laboratory for Polysaccharide Materials and Modifications, Guangxi Minzu University, Nanning 530006, China
| | - Min Zhou
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, Nanning 530005, China; (J.H.); (B.J.)
| | - Nana Li
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, Nanning 530005, China; (J.H.); (B.J.)
| | - Bole Jiang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, Nanning 530005, China; (J.H.); (B.J.)
| | - Yongqiang He
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, Nanning 530005, China; (J.H.); (B.J.)
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Lauber E, González-Fuente M, Escouboué M, Vicédo C, Luneau JS, Pouzet C, Jauneau A, Gris C, Zhang ZM, Pichereaux C, Carrère S, Deslandes L, Noël LD. Bacterial host adaptation through sequence and structural variations of a single type III effector gene. iScience 2024; 27:109224. [PMID: 38439954 PMCID: PMC10909901 DOI: 10.1016/j.isci.2024.109224] [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: 02/15/2023] [Revised: 12/02/2023] [Accepted: 02/08/2024] [Indexed: 03/06/2024] Open
Abstract
Molecular mechanisms underlying quantitative variations of pathogenicity remain elusive. Here, we identified the Xanthomonas campestris XopJ6 effector that triggers disease resistance in cauliflower and Arabidopsis thaliana. XopJ6 is a close homolog of the Ralstoniapseudosolanacearum PopP2 YopJ family acetyltransferase. XopJ6 is recognized by the RRS1-R/RPS4 NLR pair that integrates a WRKY decoy domain mimicking effector targets. We identified a XopJ6 natural variant carrying a single residue substitution in XopJ6 WRKY-binding site that disrupts interaction with WRKY proteins. This mutation allows XopJ6 to evade immune perception while retaining some XopJ6 virulence functions. Interestingly, xopJ6 resides in a Tn3-family transposon likely contributing to xopJ6 copy number variation (CNV). Using synthetic biology, we demonstrate that xopJ6 CNV tunes pathogen virulence on Arabidopsis through gene dosage-mediated modulation of xopJ6 expression. Together, our findings highlight how sequence and structural genetic variations restricted at a particular effector gene contribute to bacterial host adaptation.
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Affiliation(s)
- Emmanuelle Lauber
- Laboratoire des Interactions Plantes-Microbes-Environnement (LIPME), Université de Toulouse, INRAE, CNRS, F-31326 Castanet-Tolosan, France
| | - Manuel González-Fuente
- Laboratoire des Interactions Plantes-Microbes-Environnement (LIPME), Université de Toulouse, INRAE, CNRS, F-31326 Castanet-Tolosan, France
| | - Maxime Escouboué
- Laboratoire des Interactions Plantes-Microbes-Environnement (LIPME), Université de Toulouse, INRAE, CNRS, F-31326 Castanet-Tolosan, France
| | - Céline Vicédo
- Laboratoire des Interactions Plantes-Microbes-Environnement (LIPME), Université de Toulouse, INRAE, CNRS, F-31326 Castanet-Tolosan, France
| | - Julien S. Luneau
- Laboratoire des Interactions Plantes-Microbes-Environnement (LIPME), Université de Toulouse, INRAE, CNRS, F-31326 Castanet-Tolosan, France
| | - Cécile Pouzet
- TRI-FRAIB Imaging Platform Facilities, FRAIB, Université de Toulouse, CNRS, UPS, 31320 Castanet-Tolosan, France
| | - Alain Jauneau
- TRI-FRAIB Imaging Platform Facilities, FRAIB, Université de Toulouse, CNRS, UPS, 31320 Castanet-Tolosan, France
| | - Carine Gris
- Laboratoire des Interactions Plantes-Microbes-Environnement (LIPME), Université de Toulouse, INRAE, CNRS, F-31326 Castanet-Tolosan, France
| | - Zhi-Min Zhang
- International Cooperative Laboratory of Traditional Chinese Medicine Modernization and Innovative Drug Development of Chinese Ministry of Education (MOE), College of Pharmacy, Jinan University, Guangzhou 510632, China
| | - Carole Pichereaux
- Fédération de Recherche Agrobiosciences, Interactions et Biodiversité (FRAIB), Université de Toulouse, CNRS, Université de Toulouse III - Paul Sabatier (UT3), Auzeville-Tolosane, France
- Institut de Pharmacologie et de Biologie Structurale (IPBS), Université de Toulouse, CNRS, Université de Toulouse III - Paul Sabatier (UT3), Toulouse, France
- Infrastructure nationale de protéomique, ProFI, FR 2048, Toulouse, France
| | - Sébastien Carrère
- Laboratoire des Interactions Plantes-Microbes-Environnement (LIPME), Université de Toulouse, INRAE, CNRS, F-31326 Castanet-Tolosan, France
| | - Laurent Deslandes
- Laboratoire des Interactions Plantes-Microbes-Environnement (LIPME), Université de Toulouse, INRAE, CNRS, F-31326 Castanet-Tolosan, France
| | - Laurent D. Noël
- Laboratoire des Interactions Plantes-Microbes-Environnement (LIPME), Université de Toulouse, INRAE, CNRS, F-31326 Castanet-Tolosan, France
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Xie Q, Wei B, Zhan Z, He Q, Wu K, Chen Y, Liu S, He C, Niu X, Li C, Tang C, Tao J. Arabidopsis membrane protein AMAR1 interaction with type III effector XopAM triggers a hypersensitive response. PLANT PHYSIOLOGY 2023; 193:2768-2787. [PMID: 37648267 DOI: 10.1093/plphys/kiad478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 06/07/2023] [Accepted: 07/27/2023] [Indexed: 09/01/2023]
Abstract
The efficient infection of plants by the bacteria Xanthomonas campestris pv. campestris (Xcc) depends on its type III effectors (T3Es). Although the functions of AvrE family T3Es have been reported in some bacteria, the member XopAM in Xcc has not been studied. As XopAM has low sequence similarity to reported AvrE-T3Es and different reports have shown that these T3Es have different targets in hosts, we investigated the functions of XopAM in the Xcc-plant interaction. Deletion of xopAM from Xcc reduced its virulence in cruciferous crops but increased virulence in Arabidopsis (Arabidopsis thaliana) Col-0, indicating that XopAM may perform opposite functions depending on the host species. We further found that XopAM is a lipase that may target the cytomembrane and that this activity might be enhanced by its membrane-targeted protein XOPAM-ACTIVATED RESISTANCE 1 (AMAR1) in Arabidopsis Col-0. The binding of XopAM to AMAR1 induced an intense hypersensitive response that restricted Xcc proliferation. Our results showed that the roles of XopAM in Xcc infection are not the same as those of other AvrE-T3Es, indicating that the functions of this type of T3E have differentiated during long-term bacterium‒host interactions.
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Affiliation(s)
- Qingbiao Xie
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
| | - Bingzheng Wei
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
| | - Zhaohong Zhan
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
| | - Qiguang He
- Rubber Research Institute, Chinese Academy of Tropical Agricultural Science, Haikou 571101, China
| | - Kejian Wu
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
| | - Yu Chen
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
| | - Shiyao Liu
- Sanya Nanfan Research Institute, Hainan University, Sanya 572024, China
| | - Chaozu He
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
- Sanya Nanfan Research Institute, Hainan University, Sanya 572024, China
- Hainan Yazhou Bay Seed Laboratory, Sanya 572025, China
| | - Xiaolei Niu
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
- Sanya Nanfan Research Institute, Hainan University, Sanya 572024, China
| | - Chunxia Li
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
- Hainan Yazhou Bay Seed Laboratory, Sanya 572025, China
| | - Chaorong Tang
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
| | - Jun Tao
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresources, School of Tropical Agriculture and Forestry, Hainan University, Haikou 570228, China
- Hainan Yazhou Bay Seed Laboratory, Sanya 572025, China
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Langin G, González-Fuente M, Üstün S. The Plant Ubiquitin-Proteasome System as a Target for Microbial Manipulation. ANNUAL REVIEW OF PHYTOPATHOLOGY 2023; 61:351-375. [PMID: 37253695 DOI: 10.1146/annurev-phyto-021622-110443] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The plant immune system perceives pathogens to trigger defense responses. In turn, pathogens secrete effector molecules to subvert these defense responses. The initiation and maintenance of defense responses involve not only de novo synthesis of regulatory proteins and enzymes but also their regulated degradation. The latter is achieved through protein degradation pathways such as the ubiquitin-proteasome system (UPS). The UPS regulates all stages of immunity, from the perception of the pathogen to the execution of the response, and, therefore, constitutes an ideal candidate for microbial manipulation of the host. Pathogen effector molecules interfere with the plant UPS through several mechanisms. This includes hijacking general UPS functions or perturbing its ability to degrade specific targets. In this review, we describe how the UPS regulates different immunity-related processes and how pathogens subvert this to promote disease.
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Affiliation(s)
- Gautier Langin
- Centre for Plant Molecular Biology (ZMBP), University of Tübingen, Tübingen, Germany;
- Faculty of Biology and Biotechnology, Ruhr-University Bochum, Bochum, Germany
| | | | - Suayib Üstün
- Faculty of Biology and Biotechnology, Ruhr-University Bochum, Bochum, Germany
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Ortmann S, Marx J, Lampe C, Handrick V, Ehnert TM, Zinecker S, Reimers M, Bonas U, Erickson JL. A conserved microtubule-binding region in Xanthomonas XopL is indispensable for induced plant cell death reactions. PLoS Pathog 2023; 19:e1011263. [PMID: 37578981 PMCID: PMC10449215 DOI: 10.1371/journal.ppat.1011263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 08/24/2023] [Accepted: 07/17/2023] [Indexed: 08/16/2023] Open
Abstract
Pathogenic Xanthomonas bacteria cause disease on more than 400 plant species. These Gram-negative bacteria utilize the type III secretion system to inject type III effector proteins (T3Es) directly into the plant cell cytosol where they can manipulate plant pathways to promote virulence. The host range of a given Xanthomonas species is limited, and T3E repertoires are specialized during interactions with specific plant species. Some effectors, however, are retained across most strains, such as Xanthomonas Outer Protein L (XopL). As an 'ancestral' effector, XopL contributes to the virulence of multiple xanthomonads, infecting diverse plant species. XopL homologs harbor a combination of a leucine-rich-repeat (LRR) domain and an XL-box which has E3 ligase activity. Despite similar domain structure there is evidence to suggest that XopL function has diverged, exemplified by the finding that XopLs expressed in plants often display bacterial species-dependent differences in their sub-cellular localization and plant cell death reactions. We found that XopL from X. euvesicatoria (XopLXe) directly associates with plant microtubules (MTs) and causes strong cell death in agroinfection assays in N. benthamiana. Localization of XopLXe homologs from three additional Xanthomonas species, of diverse infection strategy and plant host, revealed that the distantly related X. campestris pv. campestris harbors a XopL (XopLXcc) that fails to localize to MTs and to cause plant cell death. Comparative sequence analyses of MT-binding XopLs and XopLXcc identified a proline-rich-region (PRR)/α-helical region important for MT localization. Functional analyses of XopLXe truncations and amino acid exchanges within the PRR suggest that MT-localized XopL activity is required for plant cell death reactions. This study exemplifies how the study of a T3E within the context of a genus rather than a single species can shed light on how effector localization is linked to biochemical activity.
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Affiliation(s)
- Simon Ortmann
- Department of Genetics, Institute for Biology, Martin Luther University Halle-Wittenberg, Halle, Germany
- Department of Biochemistry of Plant Interactions, Leibniz Institute for Plant Biochemistry, Halle, Germany
| | - Jolina Marx
- Department of Genetics, Institute for Biology, Martin Luther University Halle-Wittenberg, Halle, Germany
| | - Christina Lampe
- Department of Genetics, Institute for Biology, Martin Luther University Halle-Wittenberg, Halle, Germany
| | - Vinzenz Handrick
- Department of Biochemistry of Plant Interactions, Leibniz Institute for Plant Biochemistry, Halle, Germany
| | - Tim-Martin Ehnert
- Department of Biochemistry of Plant Interactions, Leibniz Institute for Plant Biochemistry, Halle, Germany
| | - Sarah Zinecker
- Department of Plant Physiology, Institute for Biology, Martin Luther University Halle-Wittenberg, Halle, Germany
| | - Matthias Reimers
- Department of Plant Physiology, Institute for Biology, Martin Luther University Halle-Wittenberg, Halle, Germany
| | - Ulla Bonas
- Department of Genetics, Institute for Biology, Martin Luther University Halle-Wittenberg, Halle, Germany
| | - Jessica Lee Erickson
- Department of Genetics, Institute for Biology, Martin Luther University Halle-Wittenberg, Halle, Germany
- Department of Biochemistry of Plant Interactions, Leibniz Institute for Plant Biochemistry, Halle, Germany
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Sanguankiattichai N, Buscaill P, Preston GM. How bacteria overcome flagellin pattern recognition in plants. CURRENT OPINION IN PLANT BIOLOGY 2022; 67:102224. [PMID: 35533494 DOI: 10.1016/j.pbi.2022.102224] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 03/03/2022] [Accepted: 03/29/2022] [Indexed: 06/14/2023]
Abstract
Efficient plant immune responses depend on the ability to recognise an invading microbe. The 22-amino acids in the N-terminal domain and the 28-amino acids in the central region of the bacterial flagellin, called flg22 and flgII-28, respectively, are important elicitors of plant immunity. Plant immunity is activated after flg22 or flgII-28 recognition by the plant transmembrane receptors FLS2 or FLS3, respectively. There is strong selective pressure on many plant pathogenic and endophytic bacteria to overcome flagellin-triggered immunity. Here we provide an overview of recent developments in our understanding of the evasion and suppression of flagellin pattern recognition by plant-associated bacteria.
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Affiliation(s)
| | - Pierre Buscaill
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
| | - Gail M Preston
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK.
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Promnuan Y, Promsai S, Pathom-aree W, Meelai S. Apis andreniformis associated Actinomycetes show antimicrobial activity against black rot pathogen ( Xanthomonas campestris pv. campestris). PeerJ 2021; 9:e12097. [PMID: 34589300 PMCID: PMC8435200 DOI: 10.7717/peerj.12097] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 08/10/2021] [Indexed: 11/23/2022] Open
Abstract
This study aimed to investigate cultivable actinomycetes associated with rare honey bee species in Thailand and their antagonistic activity against plant pathogenic bacteria. Actinomycetes were selectively isolated from the black dwarf honey bee (Apis andreniformis). A total of 64 actinomycete isolates were obtained with Streptomyces as the predominant genus (84.4%) followed by Micromonospora (7.8%), Nonomuraea (4.7%) and Actinomadura (3.1%). All isolates were screened for antimicrobial activity against Xanthomonas campestris pv. campestris, Pectobacterium carotovorum and Pseudomonas syringae pv. sesame. Three isolates inhibited the growth of X. campestris pv. campestris during in vitro screening. The crude extracts of two isolates (ASC3-2 and ASC5-7P) had a minimum inhibitory concentration (MIC) of 128 mg L-1against X. campestris pv. campestris. For isolate ACZ2-27, its crude extract showed stronger inhibitory effect with a lower MIC value of 64 mg L-1 against X. campestris pv. campestris. These three active isolates were identified as members of the genus Streptomyces based on their 16S rRNA gene sequences. Phylogenetic analysis based on the maximum likelihood algorithm showed that isolate ACZ2-27, ASC3-2 and ASC5-7P were closely related to Streptomyces misionensis NBRC 13063T (99.71%), Streptomyces cacaoi subsp. cacaoi NBRC 12748T (100%) and Streptomyces puniceus NBRC 12811T (100%), respectively. In addition, representative isolates from non-Streptomyces groups were identified by 16S rRNA gene sequence analysis. High similarities were found with members of the genera Actinomadura, Micromonospora and Nonomuraea. Our study provides evidence of actinomycetes associated with the black dwarf honey bee including members of rare genera. Antimicrobial potential of these insect associated Streptomyces was also demonstrated especially the antibacterial activity against phytopathogenic bacteria.
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Affiliation(s)
- Yaowanoot Promnuan
- Department of Microbiology, Faculty of Liberal Arts and Science, Kasetsart University –Kamphaeng Saen campus, Kamphaeng Saen, Nakhon Pathom, Thailand
| | - Saran Promsai
- Department of Microbiology, Faculty of Liberal Arts and Science, Kasetsart University –Kamphaeng Saen campus, Kamphaeng Saen, Nakhon Pathom, Thailand
| | - Wasu Pathom-aree
- Department of Biology, Faculty of Science, Chiang Mai University, Chiang Mai, Thailand
- Research Center in Bioresources for Agriculture, Industry and Medicine, Faculty of Science, Chiang Mai University, Chiang Mai, Thailand
| | - Sujinan Meelai
- Department of Microbiology, Faculty of Science, Silpakorn University –Sanam Chandra Palace campus, Nakhon Pathom, Nakhon Pathom, Thailand
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Webster J, Bogema D, Chapman TA. Comparative Genomics of Xanthomonas citri pv. citri A* Pathotype Reveals Three Distinct Clades with Varying Plasmid Distribution. Microorganisms 2020; 8:microorganisms8121947. [PMID: 33302542 PMCID: PMC7764509 DOI: 10.3390/microorganisms8121947] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 12/04/2020] [Accepted: 12/07/2020] [Indexed: 11/23/2022] Open
Abstract
Citrus bacterial canker (CBC) is an important disease of citrus cultivars worldwide that causes blister-like lesions on host plants and leads to more severe symptoms such as plant defoliation and premature fruit drop. The causative agent, Xanthomonas citri pv. citri, exists as three pathotypes—A, A*, and Aw—which differ in their host range and elicited host response. To date, comparative analyses have been hampered by the lack of closed genomes for the A* pathotype. In this study, we sequenced and assembled six CBC isolates of pathotype A* using second- and third-generation sequencing technologies to produce complete, closed assemblies. Analysis of these genomes and reference A, A*, and Aw sequences revealed genetic groups within the A* pathotype. Investigation of accessory genomes revealed virulence factors, including type IV secretion systems and heavy metal resistance genes, differentiating the genetic groups. Genomic comparisons of closed genome assemblies also provided plasmid distribution information for the three genetic groups of A*. The genomes presented here complement existing closed genomes of A and Aw pathotypes that are publicly available and open opportunities to investigate the evolution of X. citri pv. citri and the virulence factors that contribute to this serious pathogen.
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Huang Y, Li T, Xu T, Tang Z, Guo J, Cai Y. Multiple Xanthomonas campestris pv. campestris 8004 type III effectors inhibit immunity induced by flg22. PLANTA 2020; 252:88. [PMID: 33057902 DOI: 10.1007/s00425-020-03484-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Accepted: 09/30/2020] [Indexed: 06/11/2023]
Abstract
Xanthomonas campestris pv. campestris 8004 secretes several effector proteins that interfere with plant phosphorylation. Xanthomonas campestris pv. campestris (Xcc) can infect cruciferous plants and cause black rot. The strain Xcc8004 secretes effector proteins that interfere with plant cellular processes into host cells using a type III secretion (T3S) system. Several of the 24 predicted T3S effectors in the Xcc8004 genome have been implicated in the suppression of the Arabidopsis thaliana pattern-triggered immunity (PTI) response. We used an A. thaliana mesophyll protoplast-based assay to identify Xcc8004 T3S effectors that effectively interfere with PTI signalling induced by the bacterial peptide flg22. 11 of the 24 tested effector proteins (XopK, XopQ, HrpW, XopN, XopAC, XopD, XopZ1, XopAG, AvrBs2, XopL and XopX-1) inhibited expression of the flg22-inducible gene FRK1, and five effectors (XopK, XopG, XopQ, XopL and XopX-1) inhibited the expression of the flg22-inducible gene WRKY33. Therefore, there are 12 effector proteins that can inhibit the expression of relevant flg22-inducible genes. It was further investigated whether the 12 effector proteins affect the phosphorylation activation of mitogen-activated protein (MAP) kinases MPK3/MPK6, and four effector proteins (XopK, XopQ, XopZ1 and XopX-1) were found to markedly inhibit MPK3/MPK6 activation. Moreover, a subcellular localisation analysis revealed that the tested effectors were localised within various subcellular compartments. These results indicate that multiple T3S effectors in the Xcc8004 genome interfere with flg22-induced PTI signalling via various molecular mechanisms.
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Affiliation(s)
- Yan Huang
- School of Life Sciences, Sichuan Agricultural University, Ya'an, 625014, China
| | - Tongqi Li
- School of Life Sciences, Sichuan Agricultural University, Ya'an, 625014, China
| | - Ting Xu
- School of Life Sciences, Sichuan Agricultural University, Ya'an, 625014, China
| | - Zizhong Tang
- School of Life Sciences, Sichuan Agricultural University, Ya'an, 625014, China
| | - Jingya Guo
- School of Life Sciences, Sichuan Agricultural University, Ya'an, 625014, China
| | - Yi Cai
- School of Life Sciences, Sichuan Agricultural University, Ya'an, 625014, China.
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