1
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Vadillo‐Dieguez A, Zeng Z, Mansfield JW, Grinberg NF, Lynn SC, Gregg A, Connell J, Harrison RJ, Jackson RW, Hulin MT. Genetic dissection of the tissue-specific roles of type III effectors and phytotoxins in the pathogenicity of Pseudomonas syringae pv. syringae to cherry. MOLECULAR PLANT PATHOLOGY 2024; 25:e13451. [PMID: 38590135 PMCID: PMC11002349 DOI: 10.1111/mpp.13451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2024] [Revised: 03/13/2024] [Accepted: 03/19/2024] [Indexed: 04/10/2024]
Abstract
When compared with other phylogroups (PGs) of the Pseudomonas syringae species complex, P. syringae pv. syringae (Pss) strains within PG2 have a reduced repertoire of type III effectors (T3Es) but produce several phytotoxins. Effectors within the cherry pathogen Pss 9644 were grouped based on their frequency in strains from Prunus as the conserved effector locus (CEL) common to most P. syringae pathogens; a core of effectors common to PG2; a set of PRUNUS effectors common to cherry pathogens; and a FLEXIBLE set of T3Es. Pss 9644 also contains gene clusters for biosynthesis of toxins syringomycin, syringopeptin and syringolin A. After confirmation of virulence gene expression, mutants with a sequential series of T3E and toxin deletions were pathogenicity tested on wood, leaves and fruits of sweet cherry (Prunus avium) and leaves of ornamental cherry (Prunus incisa). The toxins had a key role in disease development in fruits but were less important in leaves and wood. An effectorless mutant retained some pathogenicity to fruit but not wood or leaves. Striking redundancy was observed amongst effector groups. The CEL effectors have important roles during the early stages of leaf infection and possibly acted synergistically with toxins in all tissues. Deletion of separate groups of T3Es had more effect in P. incisa than in P. avium. Mixed inocula were used to complement the toxin mutations in trans and indicated that strain mixtures may be important in the field. Our results highlight the niche-specific role of toxins in P. avium tissues and the complexity of effector redundancy in the pathogen Pss 9644.
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Affiliation(s)
- Andrea Vadillo‐Dieguez
- NIABCambridgeUK
- School of Biosciences and the Birmingham Institute of Forest ResearchUniversity of BirminghamBirminghamUK
| | | | | | | | | | | | | | - Richard J. Harrison
- NIABCambridgeUK
- School of Biosciences and the Birmingham Institute of Forest ResearchUniversity of BirminghamBirminghamUK
- Faculty of Natural Sciences, Plant Science GroupWageningen University and ResearchWageningenNetherlands
- Present address:
Faculty of Natural Sciences, Plant Science GroupWageningen University and ResearchWageningenNetherlands
| | - Robert W. Jackson
- School of Biosciences and the Birmingham Institute of Forest ResearchUniversity of BirminghamBirminghamUK
| | - Michelle T. Hulin
- NIABCambridgeUK
- Department of Plant Soil & Microbial SciencesMichigan State UniversityEast LansingUSA
- Present address:
Department of Plant Soil & Microbial SciencesMichigan State UniversityEast LansingUSA
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2
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Budil J, Lišková P. Current methods for monitoring Pseudomonas syringae biofilm development. Lett Appl Microbiol 2024; 77:ovae013. [PMID: 38337184 DOI: 10.1093/lambio/ovae013] [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: 11/14/2023] [Revised: 01/12/2024] [Accepted: 02/07/2004] [Indexed: 02/12/2024]
Abstract
This work reviews biofilm investigation techniques and highlights the benefits and drawbacks of each approach focusing especially on Pseudomonas syringae and may serve as a comprehensive guide for any early-career researchers starting with the topic of biofilm. Each approach with applications of individual microscopy and spectroscopy techniques is summarized together with characterization of Pseudomonas syringae and its role in pathogenesis.
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Affiliation(s)
- Jakub Budil
- Institute of Physics of the Czech Academy of Sciences, Cukrovarnická 10, 162 00, Prague 6, Czech Republic
- Department of Genetics and Microbiology, Faculty of Science, Charles University, Viničná 5, 128 43, Prague 2, Czech Republic
| | - Petra Lišková
- Department of Genetics and Microbiology, Faculty of Science, Charles University, Viničná 5, 128 43, Prague 2, Czech Republic
- Research and breeding institute of pomology Holovousy Ltd., Holovousy 129, 508 01, Horice, Czech Republic
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3
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Pintado A, Domínguez-Cerván H, Pastor V, Vincent M, Lee SG, Flors V, Ramos C. Allelic variation in the indoleacetic acid-lysine synthase gene of the bacterial pathogen Pseudomonas savastanoi and its role in auxin production. FRONTIERS IN PLANT SCIENCE 2023; 14:1176705. [PMID: 37346122 PMCID: PMC10280071 DOI: 10.3389/fpls.2023.1176705] [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: 02/28/2023] [Accepted: 05/23/2023] [Indexed: 06/23/2023]
Abstract
Indole-3-acetic acid (IAA) production is a pathogenicity/virulence factor in the Pseudomonas syringae complex, including Pseudomonas savastanoi. P. savastanoi pathovars (pvs.) genomes contain the iaaL gene, encoding an enzyme that catalyzes the biosynthesis of the less biologically active compound 3-indole-acetyl-ϵ-L-lysine (IAA-Lys). Previous studies have reported the identification of IAA-Lys in culture filtrates of P. savastanoi strains isolated from oleander (pv. nerii), but the conversion of IAA into a conjugate was not detectable in olive strains (pv. savastanoi). In this paper, we show the distribution of iaaL alleles in all available P. savastanoi genomes of strains isolated from woody hosts. Most strains encode two different paralogs, except for those isolated from broom (pv. retacarpa), which contain a single allele. In addition to the three previously reported iaaL alleles (iaaL Psv, iaaL Psn and iaaL Pto), we identified iaaL Psf, an exclusive allele of strains isolated from ash (pv. fraxini). We also found that the production of IAA-Lys in P. savastanoi pv. savastanoi and pv. nerii depends on a functional iaaL Psn allele, whereas in pv. fraxini depends on iaaL Psf. The production of IAA-Lys was detected in cultures of an olive strain heterologously expressing IaaLPsn-1, IaaLPsf-1 and IaaLPsf-3, but not when expressing IaaLPsv-1. In addition, Arabidopsis seedlings treated with the strains overproducing the conjugate, and thus reducing the free IAA content, alleviated the root elongation inhibitory effect of IAA. IAA-Lys synthase activity assays with purified allozymes confirmed the functionality and specificity of lysine as a substrate of IaaLPsn-1 and IaaLPsf-3, with IaaLPsf-3 showing the highest catalytic efficiency for both substrates. The IAA-Lys synthase activity of IaaLPsn-1 was abolished by the insertion of two additional tyrosine residues encoded in the inactive allozyme IaaLPsv-1. These results highlight the relevance of allelic variation in a phytohormone-related gene for the modulation of auxin production in a bacterial phytopathogen.
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Affiliation(s)
- Adrián Pintado
- Área de Genética, Facultad de Ciencias, Universidad de Málaga (UMA), Málaga, Spain
- Instituto de Hortofruticultura Subtropical y Mediterránea “La Mayora”, Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Málaga, Spain
| | - Hilario Domínguez-Cerván
- Área de Genética, Facultad de Ciencias, Universidad de Málaga (UMA), Málaga, Spain
- Instituto de Hortofruticultura Subtropical y Mediterránea “La Mayora”, Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Málaga, Spain
| | - Victoria Pastor
- Department of Biology, Biochemistry and Natural Sciences, Universitat Jaume I (UJI), Castelló de la Plana, Spain
| | - Marissa Vincent
- Department of Chemistry and Biochemistry, University of North Carolina Wilmington, Wilmington, NC, United States
| | - Soon Goo Lee
- Department of Molecular and Cellular Biology, Kennesaw State University, Kennesaw, GA, United States
| | - Víctor Flors
- Department of Biology, Biochemistry and Natural Sciences, Universitat Jaume I (UJI), Castelló de la Plana, Spain
| | - Cayo Ramos
- Área de Genética, Facultad de Ciencias, Universidad de Málaga (UMA), Málaga, Spain
- Instituto de Hortofruticultura Subtropical y Mediterránea “La Mayora”, Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Málaga, Spain
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4
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Artificial Cultivation Changes Foliar Endophytic Fungal Community of the Ornamental Plant Lirianthe delavayi. Microorganisms 2023; 11:microorganisms11030775. [PMID: 36985348 PMCID: PMC10059682 DOI: 10.3390/microorganisms11030775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 03/10/2023] [Accepted: 03/15/2023] [Indexed: 03/19/2023] Open
Abstract
Many wild ornamental plant species have been introduced to improve the landscape of cities; however, until now, no study has been performed to explore the composition and function of foliar endophytes associated with cultivated rare plants in cities after their introduction. In this study, we collected the leaves of the healthy ornamental plant Lirianthe delavayi from wild and artificially cultivated habitats in Yunnan and compared their diversity, species composition, and functional predictions of their foliar endophytic fungal community based on high-throughput sequencing technology. In total, 3125 ASVs of fungi were obtained. The alpha diversity indices of wild L. delavayi populations are similar to those of cultivated samples; however, the species compositions of endophytic fungal ASVs were significantly varied in the two habitats. The dominant phylum is Ascomycota, accounting for more than 90% of foliar endophytes in both populations; relatively, artificial cultivation trends to increase the frequency of common phytopathogens of L. delavayi, such as Alternaria, Erysiphe. The relative abundance of 55 functional predictions is different between wild and cultivated L. delavayi leaves (p < 0.05); in particular, chromosome, purine metabolism, and peptidases are significantly increased in wild samples, while flagellar assembly, bacterial chemotaxis, and fatty acid metabolism are significantly enhanced in cultivated samples. Our results indicated that artificial cultivation can greatly change the foliar endophytic fungal community of L. delavayi, which is valuable for understanding the influence of the domestication process on the foliar fungal community associated with rare ornamental plants in urban environments.
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Xie T, Wu X, Luo L, Qu Y, Fan R, Wu S, Long Y, Zhao Z. Natural variation in the hrpL promoter renders the phytopathogen Pseudomonas syringae pv. actinidiae nonpathogenic. MOLECULAR PLANT PATHOLOGY 2023; 24:262-271. [PMID: 36600466 PMCID: PMC9923390 DOI: 10.1111/mpp.13289] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 11/22/2022] [Accepted: 12/09/2022] [Indexed: 05/14/2023]
Abstract
The genetic basis underlying loss-of-virulence mutations that arise among natural phytopathogen populations is not well documented. In this study, we examined the virulence of 377 isolates of Pseudomonas syringae pv. actinidiae biovar 3 (Psa3) that were isolated from 76 kiwifruit orchards suffering from bacterial canker disease. Eighty-four nonpathogenic isolates were identified in 40 orchards. A nonpathogenic isolate G166 was found to be defective in hrpL transcription and the downstream type III secretion system (T3SS)-dependent phenotypes. Comparative genomics and complementary expression assay revealed that a single-base "G" insertion in the hrpL promoter blocks gene transcription by reducing promoter activity. The electrophoretic mobility shift assay showed that the genetic variation impairs σ54 /promoter binding during gene transcription under hrp-inducing conditions, resulting in lower expression of hrpL. A PCR-restriction fragment length polymorphism assay was performed to trace the evolutionary history of this mutation, which revealed the independent onset of genetic variations in natural Psa3 populations. We also found that nonpathogenic variants outperformed virulent Psa3 bacteria for both epiphytic and apoplast colonization of kiwifruit leaves in mixed inoculations. Our study highlights a novel mechanism for loss of virulence in Psa3 and provides insight into bacterial adaptive evolution under natural settings.
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Affiliation(s)
- Ting Xie
- Department of Plant Pathology, College of AgricultureGuizhou UniversityGuiyangChina
| | - Xiujiao Wu
- Department of Plant Pathology, College of AgricultureGuizhou UniversityGuiyangChina
| | - Le Luo
- Department of Plant Pathology, College of AgricultureGuizhou UniversityGuiyangChina
| | - Yuan Qu
- Department of Plant Pathology, College of AgricultureGuizhou UniversityGuiyangChina
| | - Rong Fan
- Kiwifruit Engineering & Technology Research CenterGuizhou UniversityGuiyangChina
| | - Shiping Wu
- Institute of Plant ProtectionGuizhou Academy of Agricultural SciencesGuiyangChina
| | - Youhua Long
- Kiwifruit Engineering & Technology Research CenterGuizhou UniversityGuiyangChina
| | - Zhibo Zhao
- Department of Plant Pathology, College of AgricultureGuizhou UniversityGuiyangChina
- Kiwifruit Engineering & Technology Research CenterGuizhou UniversityGuiyangChina
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6
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Light prevents pathogen-induced aqueous microenvironments via potentiation of salicylic acid signaling. Nat Commun 2023; 14:713. [PMID: 36759607 PMCID: PMC9911384 DOI: 10.1038/s41467-023-36382-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2022] [Accepted: 01/30/2023] [Indexed: 02/11/2023] Open
Abstract
Many plant pathogens induce water-soaked lesions in infected tissues. In the case of Pseudomonas syringae (Pst), water-soaking effectors stimulate abscisic acid (ABA) production and signaling, resulting in stomatal closure. This reduces transpiration, increases water accumulation, and induces an apoplastic microenvironment favorable for bacterial growth. Stomata are sensitive to environmental conditions, including light. Here, we show that a period of darkness is required for water-soaking, and that a constant light regime abrogates stomatal closure by Pst. We find that constant light induces resistance to Pst, and that this effect requires salicylic acid (SA). Constant light did not alter effector-induced accumulation of ABA, but induced greater SA production, promoting stomatal opening despite the presence of ABA. Furthermore, application of a SA analog was sufficient to prevent pathogen-induced stomatal closure and water-soaking. Our results suggest potential approaches for interfering with a common virulence strategy, as well as providing a physiological mechanism by which SA functions in defense against pathogens.
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7
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Escobar MR, Lepek VC, Basile LA. Influence of cyclic di-GMP metabolism to T3SS expression, biofilm formation and symbiosis efficiency in Mesorhizobium japonicum MAFF303099. FEMS Microbiol Lett 2023; 370:fnad087. [PMID: 37632199 DOI: 10.1093/femsle/fnad087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 07/26/2023] [Accepted: 08/22/2023] [Indexed: 08/27/2023] Open
Abstract
A link between the T3SS and inhibition of swimming motility by the transcriptional regulator TtsI in Mesorhizobium japonicum MAFF303099 has been previously reported. Here, we show that mutants in T3SS components display impaired biofilm formation capacity, indicating that a functional T3SS, or at least pili formation, is required for this process. As a first approach to the cdiG regulation network in this bacterium, we started a study of the second messenger cdiG by overexpressing or by deleting some genes encoding cdiG metabolizing enzymes. Overexpression of two putative PDEs as well as deletion of various DGCs led to reduced biofilm formation on glass tubes. Mutation of dgc9509 also affected negatively the nodulation and symbiosis efficiency on Lotus plants, which can be related to the observed reduction in adhesion to plant roots. Results from transcriptional nopX- and ttsI-promoter-lacZ fusions suggested that cdiG negatively regulates T3SS expression in M. japonicum MAFF303099.
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Affiliation(s)
- Mariel R Escobar
- Instituto de Investigaciones Biotecnológicas "Dr. Rodolfo Ugalde", Escuela de Bio y Nanotecnologías, Universidad Nacional de San Martín (IIBio-EByN-UNSAM), CONICET. Av. 25 de Mayo y Francia, San Martín, Buenos Aires, Argentina
| | - Viviana C Lepek
- Instituto de Investigaciones Biotecnológicas "Dr. Rodolfo Ugalde", Escuela de Bio y Nanotecnologías, Universidad Nacional de San Martín (IIBio-EByN-UNSAM), CONICET. Av. 25 de Mayo y Francia, San Martín, Buenos Aires, Argentina
| | - Laura A Basile
- Instituto de Investigaciones Biotecnológicas "Dr. Rodolfo Ugalde", Escuela de Bio y Nanotecnologías, Universidad Nacional de San Martín (IIBio-EByN-UNSAM), CONICET. Av. 25 de Mayo y Francia, San Martín, Buenos Aires, Argentina
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8
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Ishiga T, Sakata N, Usuki G, Nguyen VT, Gomi K, Ishiga Y. Large-Scale Transposon Mutagenesis Reveals Type III Secretion Effector HopR1 Is a Major Virulence Factor in Pseudomonas syringae pv. actinidiae. PLANTS (BASEL, SWITZERLAND) 2022; 12:plants12010141. [PMID: 36616271 PMCID: PMC9823363 DOI: 10.3390/plants12010141] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 12/11/2022] [Accepted: 12/16/2022] [Indexed: 05/27/2023]
Abstract
Bacterial canker of kiwifruit caused by Pseudomonas syringae pv. actinidiae (Psa) is a serious threat to kiwifruit production worldwide. Four biovars (Psa biovar 1; Psa1, Psa biovar 3; Psa3, Psa biovar 5; Psa5, and Psa biovar 6; Psa6) were reported in Japan, and virulent Psa3 strains spread rapidly to kiwifruit production areas worldwide. Therefore, there is an urgent need to develop critical management strategies for bacterial canker based on dissecting the dynamic interactions between Psa and kiwifruit. To investigate the molecular mechanism of Psa3 infection, we developed a rapid and reliable high-throughput flood-inoculation method using kiwifruit seedlings. Using this inoculation method, we screened 3000 Psa3 transposon insertion mutants and identified 91 reduced virulence mutants and characterized the transposon insertion sites in these mutants. We identified seven type III secretion system mutants, and four type III secretion effectors mutants including hopR1. Mature kiwifruit leaves spray-inoculated with the hopR1 mutant showed significantly reduced virulence compared to Psa3 wild-type, indicating that HopR1 has a critical role in Psa3 virulence. Deletion mutants of hopR1 in Psa1, Psa3, Psa5, and Psa6 revealed that the type III secretion effector HopR1 is a major virulence factor in these biovars. Moreover, hopR1 mutants of Psa3 failed to reopen stomata on kiwifruit leaves, suggesting that HopR1 facilitates Psa entry through stomata into plants. Furthermore, defense related genes were highly expressed in kiwifruit plants inoculated with hopR1 mutant compared to Psa wild-type, indicating that HopR1 suppresses defense-related genes of kiwifruit. These results suggest that HopR1 universally contributes to virulence in all Psa biovars by overcoming not only stomatal-based defense, but also apoplastic defense.
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Affiliation(s)
- Takako Ishiga
- Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8572, Ibaraki, Japan
| | - Nanami Sakata
- Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8572, Ibaraki, Japan
| | - Giyu Usuki
- Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8572, Ibaraki, Japan
| | - Viet Tru Nguyen
- Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8572, Ibaraki, Japan
- Western Highlands Agriculture and Forestry Science Institute, 53 Nguyen Luong Bang Street, Buon Ma Thuot City 630000, Vietnam
| | - Kenji Gomi
- Faculty of Agriculture, Kagawa University, Miki 761-0795, Kagawa, Japan
| | - Yasuhiro Ishiga
- Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8572, Ibaraki, Japan
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9
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The Cytoskeleton in Plant Immunity: Dynamics, Regulation, and Function. Int J Mol Sci 2022; 23:ijms232415553. [PMID: 36555194 PMCID: PMC9779068 DOI: 10.3390/ijms232415553] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 12/04/2022] [Accepted: 12/06/2022] [Indexed: 12/13/2022] Open
Abstract
The plant cytoskeleton, consisting of actin filaments and microtubules, is a highly dynamic filamentous framework involved in plant growth, development, and stress responses. Recently, research has demonstrated that the plant cytoskeleton undergoes rapid remodeling upon sensing pathogen attacks, coordinating the formation of microdomain immune complexes, the dynamic and turnover of pattern-recognizing receptors (PRRs), the movement and aggregation of organelles, and the transportation of defense compounds, thus serving as an important platform for responding to pathogen infections. Meanwhile, pathogens produce effectors targeting the cytoskeleton to achieve pathogenicity. Recent findings have uncovered several cytoskeleton-associated proteins mediating cytoskeletal remodeling and defense signaling. Furthermore, the reorganization of the actin cytoskeleton is revealed to further feedback-regulate reactive oxygen species (ROS) production and trigger salicylic acid (SA) signaling, suggesting an extremely complex role of the cytoskeleton in plant immunity. Here, we describe recent advances in understanding the host cytoskeleton dynamics upon sensing pathogens and summarize the effectors that target the cytoskeleton. We highlight advances in the regulation of cytoskeletal remodeling associated with the defense response and assess the important function of the rearrangement of the cytoskeleton in the immune response. Finally, we propose suggestions for future research in this area.
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10
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Kim M, Lee D, Cho HS, Chung YS, Park HJ, Jung HW. RNA-seq Gene Profiling Reveals Transcriptional Changes in the Late Phase during Compatible Interaction between a Korean Soybean Cultivar (Glycine max cv. Kwangan) and Pseudomonas syringae pv. syringae B728a. THE PLANT PATHOLOGY JOURNAL 2022; 38:603-615. [PMID: 36503189 PMCID: PMC9742799 DOI: 10.5423/ppj.oa.08.2022.0118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 09/23/2022] [Accepted: 09/26/2022] [Indexed: 06/17/2023]
Abstract
Soybean (Glycine max (L) Merr.) provides plant-derived proteins, soy vegetable oils, and various beneficial metabolites to humans and livestock. The importance of soybean is highly underlined, especially when carbon-negative sustainable agriculture is noticeable. However, many diseases by pests and pathogens threaten sustainable soybean production. Therefore, understanding molecular interaction between diverse cultivated varieties and pathogens is essential to developing disease-resistant soybean plants. Here, we established a pathosystem of the Korean domestic cultivar Kwangan against Pseudomonas syringae pv. syringae B728a. This bacterial strain caused apparent disease symptoms and grew well in trifoliate leaves of soybean plants. To examine the disease susceptibility of the cultivar, we analyzed transcriptional changes in soybean leaves on day 5 after P. syringae pv. syringae B728a infection. About 8,900 and 7,780 differentially expressed genes (DEGs) were identified in this study, and significant proportions of DEGs were engaged in various primary and secondary metabolisms. On the other hand, soybean orthologs to well-known plant immune-related genes, especially in plant hormone signal transduction, mitogen-activated protein kinase signaling, and plant-pathogen interaction, were mainly reduced in transcript levels at 5 days post inoculation. These findings present the feature of the compatible interaction between cultivar Kwangan and P. syringae pv. syringae B728a, as a hemibiotroph, at the late infection phase. Collectively, we propose that P. syringae pv. syringae B728a successfully inhibits plant immune response in susceptible plants and deregulates host metabolic processes for their colonization and proliferation, whereas host plants employ diverse metabolites to protect themselves against infection with the hemibiotrophic pathogen at the late infection phase.
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Affiliation(s)
- Myoungsub Kim
- Department of Applied Bioscience, Dong-A University, Busan 49315,
Korea
| | - Dohui Lee
- Department of Applied Bioscience, Dong-A University, Busan 49315,
Korea
| | - Hyun Suk Cho
- Department of Applied Bioscience, Dong-A University, Busan 49315,
Korea
| | - Young-Soo Chung
- Department of Applied Bioscience, Dong-A University, Busan 49315,
Korea
| | - Hee Jin Park
- Department of Molecular Genetics, Dong-A University, Busan 49315,
Korea
- Department of Biological Sciences, Chonnam National University, Gwangju 61186,
Korea
| | - Ho Won Jung
- Institute of Agricultural Life Science, Dong-A University, Busan 49315,
Korea
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11
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Correa F, Beltrán MF, Millas P, Moreno Z, Hinrichsen P, Meza P, Sagredo B. Genome Sequence Resources of Pseudomonas syringae Strains Isolated from Sweet Cherry Orchards in Chile. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2022; 35:933-937. [PMID: 36176216 DOI: 10.1094/mpmi-04-22-0092-a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Affiliation(s)
- Francisco Correa
- Instituto de Investigaciones Agropecuarias (INIA), INIA Rayentué. Avenida Salamanca s/n, Rengo, Chile
| | - M Francisca Beltrán
- Instituto de Investigaciones Agropecuarias (INIA), INIA Rayentué. Avenida Salamanca s/n, Rengo, Chile
- Programa de Doctorado en Ciencias Silvoagropecuarias y Veterinarias, Campus Sur Universidad de Chile, Santa Rosa 11315, La Pintana, Santiago, Chile
| | - Paz Millas
- Instituto de Investigaciones Agropecuarias (INIA), INIA Quilamapu. Avenida Vicente Méndez 515, Chillán, Chile
| | - Zoe Moreno
- Instituto de Investigaciones Agropecuarias (INIA), INIA Rayentué. Avenida Salamanca s/n, Rengo, Chile
| | - Patricio Hinrichsen
- Instituto de Investigaciones Agropecuarias (INIA), INIA La Platina. Avenida Santa Rosa 11610, La Pintana, Santiago, Chile
| | - Pablo Meza
- Instituto de Investigaciones Agropecuarias (INIA), INIA La Platina. Avenida Santa Rosa 11610, La Pintana, Santiago, Chile
| | - Boris Sagredo
- Instituto de Investigaciones Agropecuarias (INIA), INIA Rayentué. Avenida Salamanca s/n, Rengo, Chile
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12
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Draft Genome Sequence of Pseudomonas sp. Strain RGM 3321, a Phyllosphere Endophyte from Fragaria chiloensis subsp.
chiloensis
f.
patagonica. Microbiol Resour Announc 2022; 11:e0033522. [PMID: 35731123 PMCID: PMC9302079 DOI: 10.1128/mra.00335-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas sp. strain RGM 3321 is a phyllosphere endophyte from Fragaria chiloensis subsp. chiloensis f. patagonica that harbors genes associated with plant growth promotion pathways, as well as genes typically found in plant pathogens.
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13
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Molecular and Genomic Characterization of the Pseudomonas syringae Phylogroup 4: An Emerging Pathogen of Arabidopsis thaliana and Nicotiana benthamiana. Microorganisms 2022; 10:microorganisms10040707. [PMID: 35456758 PMCID: PMC9030749 DOI: 10.3390/microorganisms10040707] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2022] [Revised: 03/15/2022] [Accepted: 03/21/2022] [Indexed: 12/10/2022] Open
Abstract
Environmental fluctuations such as increased temperature, water availability, and air CO2 concentration triggered by climate change influence plant disease dynamics by affecting hosts, pathogens, and their interactions. Here, we describe a newly discovered Pseudomonas syringae strain found in a natural population of Arabidopsis thaliana collected from the southwest of France. This strain, called Psy RAYR-BL, is highly virulent on natural Arabidopsis accessions, Arabidopsis model accession Columbia 0, and tobacco plants. Despite the severe disease phenotype caused by the Psy RAYR-BL strain, we identified a reduced repertoire of putative Type III virulence effectors by genomic sequencing compared to P. syringae pv tomato (Pst) DC3000. Furthermore, hopBJ1Psy is found exclusively on the Psy RAYR-BL genome but not in the Pst DC3000 genome. The plant expression of HopBJ1Psy induces ROS accumulation and cell death. In addition, HopBJ1Psy participates as a virulence factor in this plant-pathogen interaction, likely explaining the severity of the disease symptoms. This research describes the characterization of a newly discovered plant pathogen strain and possible virulence mechanisms underlying the infection process shaped by natural and changing environmental conditions.
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Jeleńska J, Lee J, Manning AJ, Wolfgeher DJ, Ahn Y, Walters-Marrah G, Lopez IE, Garcia L, McClerklin SA, Michelmore RW, Kron SJ, Greenberg JT. Pseudomonas syringae effector HopZ3 suppresses the bacterial AvrPto1-tomato PTO immune complex via acetylation. PLoS Pathog 2021; 17:e1010017. [PMID: 34724007 PMCID: PMC8584673 DOI: 10.1371/journal.ppat.1010017] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Revised: 11/11/2021] [Accepted: 10/07/2021] [Indexed: 11/23/2022] Open
Abstract
The plant pathogen Pseudomonas syringae secretes multiple effectors that modulate plant defenses. Some effectors trigger defenses due to specific recognition by plant immune complexes, whereas others can suppress the resulting immune responses. The HopZ3 effector of P. syringae pv. syringae B728a (PsyB728a) is an acetyltransferase that modifies not only components of plant immune complexes, but also the Psy effectors that activate these complexes. In Arabidopsis, HopZ3 acetylates the host RPM1 complex and the Psy effectors AvrRpm1 and AvrB3. This study focuses on the role of HopZ3 during tomato infection. In Psy-resistant tomato, the main immune complex includes PRF and PTO, a RIPK-family kinase that recognizes the AvrPto effector. HopZ3 acts as a virulence factor on tomato by suppressing AvrPto1Psy-triggered immunity. HopZ3 acetylates AvrPto1Psy and the host proteins PTO, SlRIPK and SlRIN4s. Biochemical reconstruction and site-directed mutagenesis experiments suggest that acetylation acts in multiple ways to suppress immune signaling in tomato. First, acetylation disrupts the critical AvrPto1Psy-PTO interaction needed to initiate the immune response. Unmodified residues at the binding interface of both proteins and at other residues needed for binding are acetylated. Second, acetylation occurs at residues important for AvrPto1Psy function but not for binding to PTO. Finally, acetylation reduces specific phosphorylations needed for promoting the immune-inducing activity of HopZ3’s targets such as AvrPto1Psy and PTO. In some cases, acetylation competes with phosphorylation. HopZ3-mediated acetylation suppresses the kinase activity of SlRIPK and the phosphorylation of its SlRIN4 substrate previously implicated in PTO-signaling. Thus, HopZ3 disrupts the functions of multiple immune components and the effectors that trigger them, leading to increased susceptibility to infection. Finally, mass spectrometry used to map specific acetylated residues confirmed HopZ3’s unusual capacity to modify histidine in addition to serine, threonine and lysine residues. By secreting virulence proteins (effectors) into their hosts, pathogenic bacteria hijack host cellular processes to promote bacterial colonization and disease development. For the plant pathogen Pseudomonas syringae, the coordinated action of effectors often mediates modifications of host defense proteins to inhibit their function. However, plants have evolved the ability to induce innate immunity upon recognition of effector-induced modifications of host proteins. How do pathogens circumvent the immune-inducing activity of certain effectors? They deploy more effectors to suppress these defenses. HopZ3, an acetyltransferase from P. syringae, is unique among plant pathogen effectors characterized so far in its ability to modify not only multiple components of the effector-triggered immune pathway, but also the triggering effector itself. Through the direct acetylation of residues involved in the interaction and activation of the bacterial effector AvrPto1Psy and tomato kinase PTO, HopZ3 modifications disrupt their binding and block phosphorylations necessary for immune induction. Additionally, HopZ3 acetylates other possible components in the PTO signaling pathway, including activation sites in SlRIPK kinase, leading to suppression of its activity and reduced phosphorylation of SlRIN4s. Our study emphasizes the importance of HopZ3-dependent acetylation of immune complexes and bacterial effectors across plant species in the suppression of effector-induced immunity.
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Affiliation(s)
- Joanna Jeleńska
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, United States of America
| | - Jiyoung Lee
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, United States of America
| | - Andrew J. Manning
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, United States of America
| | - Donald J. Wolfgeher
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, United States of America
| | - Youngjoo Ahn
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, United States of America
| | - George Walters-Marrah
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, United States of America
| | - Ivan E. Lopez
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, United States of America
| | - Lissette Garcia
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, United States of America
| | - Sheri A. McClerklin
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, United States of America
| | - Richard W. Michelmore
- The Genome Center & Department of Plant Sciences, University of California, Davis, California, United States of America
| | - Stephen J. Kron
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, United States of America
| | - Jean T. Greenberg
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, Illinois, United States of America
- * E-mail:
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Li L, Verstraeten I, Roosjen M, Takahashi K, Rodriguez L, Merrin J, Chen J, Shabala L, Smet W, Ren H, Vanneste S, Shabala S, De Rybel B, Weijers D, Kinoshita T, Gray WM, Friml J. Cell surface and intracellular auxin signalling for H + fluxes in root growth. Nature 2021; 599:273-277. [PMID: 34707283 PMCID: PMC7612300 DOI: 10.1038/s41586-021-04037-6] [Citation(s) in RCA: 108] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2021] [Accepted: 09/17/2021] [Indexed: 11/09/2022]
Abstract
Growth regulation tailors development in plants to their environment. A prominent example of this is the response to gravity, in which shoots bend up and roots bend down1. This paradox is based on opposite effects of the phytohormone auxin, which promotes cell expansion in shoots while inhibiting it in roots via a yet unknown cellular mechanism2. Here, by combining microfluidics, live imaging, genetic engineering and phosphoproteomics in Arabidopsis thaliana, we advance understanding of how auxin inhibits root growth. We show that auxin activates two distinct, antagonistically acting signalling pathways that converge on rapid regulation of apoplastic pH, a causative determinant of growth. Cell surface-based TRANSMEMBRANE KINASE1 (TMK1) interacts with and mediates phosphorylation and activation of plasma membrane H+-ATPases for apoplast acidification, while intracellular canonical auxin signalling promotes net cellular H+ influx, causing apoplast alkalinization. Simultaneous activation of these two counteracting mechanisms poises roots for rapid, fine-tuned growth modulation in navigating complex soil environments.
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Affiliation(s)
- Lanxin Li
- Institute of Science and Technology (IST) Austria, Klosterneuburg, Austria
| | - Inge Verstraeten
- Institute of Science and Technology (IST) Austria, Klosterneuburg, Austria
| | - Mark Roosjen
- Laboratory of Biochemistry, Department of Agrotechnology and Food Sciences, Wageningen University, Wageningen, the Netherlands
| | - Koji Takahashi
- Institute of Transformative Bio-Molecules, Division of Biological Science, Nagoya University Chikusa, Nagoya, Japan
- Graduate School of Science, Nagoya University Chikusa, Nagoya, Japan
| | - Lesia Rodriguez
- Institute of Science and Technology (IST) Austria, Klosterneuburg, Austria
| | - Jack Merrin
- Institute of Science and Technology (IST) Austria, Klosterneuburg, Austria
| | - Jian Chen
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium
- VIB Center for Plant Systems Biology, Ghent, Belgium
| | - Lana Shabala
- Tasmanian Institute of Agriculture, College of Science and Engineering, University of Tasmania, Hobart, Tasmania, Australia
| | - Wouter Smet
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium
- VIB Center for Plant Systems Biology, Ghent, Belgium
| | - Hong Ren
- Department of Plant & Microbial Biology, University of Minnesota, St. Paul, MN, USA
| | - Steffen Vanneste
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium
- Laboratory of Plant Growth Analysis, Ghent University Global Campus, Incheon, Republic of Korea
- Department of Plants and Crops, HortiCell, Ghent University, Ghent, Belgium
| | - Sergey Shabala
- Tasmanian Institute of Agriculture, College of Science and Engineering, University of Tasmania, Hobart, Tasmania, Australia
- International Research Centre for Environmental Membrane Biology, Foshan University, Foshan, China
| | - Bert De Rybel
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Ghent, Belgium
- VIB Center for Plant Systems Biology, Ghent, Belgium
| | - Dolf Weijers
- Laboratory of Biochemistry, Department of Agrotechnology and Food Sciences, Wageningen University, Wageningen, the Netherlands
| | - Toshinori Kinoshita
- Institute of Transformative Bio-Molecules, Division of Biological Science, Nagoya University Chikusa, Nagoya, Japan
- Graduate School of Science, Nagoya University Chikusa, Nagoya, Japan
| | - William M Gray
- Department of Plant & Microbial Biology, University of Minnesota, St. Paul, MN, USA
| | - Jiří Friml
- Institute of Science and Technology (IST) Austria, Klosterneuburg, Austria.
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O’Malley MR, Anderson JC. Regulation of the Pseudomonas syringae Type III Secretion System by Host Environment Signals. Microorganisms 2021; 9:microorganisms9061227. [PMID: 34198761 PMCID: PMC8228185 DOI: 10.3390/microorganisms9061227] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 05/30/2021] [Accepted: 06/01/2021] [Indexed: 12/12/2022] Open
Abstract
Pseudomonas syringae are Gram-negative, plant pathogenic bacteria that use a type III secretion system (T3SS) to disarm host immune responses and promote bacterial growth within plant tissues. Despite the critical role for type III secretion in promoting virulence, T3SS-encoding genes are not constitutively expressed by P. syringae and must instead be induced during infection. While it has been known for many years that culturing P. syringae in synthetic minimal media can induce the T3SS, relatively little is known about host signals that regulate the deployment of the T3SS during infection. The recent identification of specific plant-derived amino acids and organic acids that induce T3SS-inducing genes in P. syringae has provided new insights into host sensing mechanisms. This review summarizes current knowledge of the regulatory machinery governing T3SS deployment in P. syringae, including master regulators HrpRS and HrpL encoded within the T3SS pathogenicity island, and the environmental factors that modulate the abundance and/or activity of these key regulators. We highlight putative receptors and regulatory networks involved in linking the perception of host signals to the regulation of the core HrpRS–HrpL pathway. Positive and negative regulation of T3SS deployment is also discussed within the context of P. syringae infection, where contributions from distinct host signals and regulatory networks likely enable the fine-tuning of T3SS deployment within host tissues. Last, we propose future research directions necessary to construct a comprehensive model that (a) links the perception of host metabolite signals to T3SS deployment and (b) places these host–pathogen signaling events in the overall context of P. syringae infection.
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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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18
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Jiang SC, Engle NL, Banday ZZ, Cecchini NM, Jung HW, Tschaplinski TJ, Greenberg JT. ALD1 accumulation in Arabidopsis epidermal plastids confers local and non-autonomous disease resistance. JOURNAL OF EXPERIMENTAL BOTANY 2021; 72:2710-2726. [PMID: 33463678 PMCID: PMC8006555 DOI: 10.1093/jxb/eraa609] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 12/24/2020] [Indexed: 05/10/2023]
Abstract
The Arabidopsis plastid-localized ALD1 protein acts in the lysine catabolic pathway that produces infection-induced pipecolic acid (Pip), Pip derivatives, and basal non-Pip metabolite(s). ALD1 is indispensable for disease resistance associated with Pseudomonas syringae infections of naïve plants as well as those previously immunized by a local infection, a phenomenon called systemic acquired resistance (SAR). Pseudomonas syringae is known to associate with mesophyll as well as epidermal cells. To probe the importance of epidermal cells in conferring bacterial disease resistance, we studied plants in which ALD1 was only detectable in the epidermal cells of specific leaves. Local disease resistance and many features of SAR were restored when ALD1 preferentially accumulated in the epidermal plastids at immunization sites. Interestingly, SAR restoration occurred without appreciable accumulation of Pip or known Pip derivatives in secondary distal leaves. Our findings establish that ALD1 has a non-autonomous effect on pathogen growth and defense activation. We propose that ALD1 is sufficient in the epidermis of the immunized leaves to activate SAR, but basal ALD1 and possibly a non-Pip metabolite(s) are also needed at all infection sites to fully suppress bacterial growth. Thus, epidermal plastids that contain ALD1 play a key role in local and whole-plant immune signaling.
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Affiliation(s)
- Shang-Chuan Jiang
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL, USA
| | | | - Zeeshan Zahoor Banday
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL, USA
| | - Nicolás M Cecchini
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL, USA
| | - Ho Won Jung
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL, USA
| | | | - Jean T Greenberg
- Department of Molecular Genetics and Cell Biology, The University of Chicago, Chicago, IL, USA
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19
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Karna SLR, Nguyen JQ, Evani SJ, Qian LW, Chen P, Abercrombie JJ, Sebastian EA, Fourcaudot AB, Leung KP. T3SS and alginate biosynthesis of Pseudomonas aeruginosa impair healing of infected rabbit wounds. Microb Pathog 2020; 147:104254. [PMID: 32416139 DOI: 10.1016/j.micpath.2020.104254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 05/05/2020] [Accepted: 05/08/2020] [Indexed: 10/24/2022]
Abstract
Pseudomonas aeruginosa (a Gram-negative bacterium) is an opportunistic pathogen found in many infected wounds and is known to impair healing. To test the hypothesis that knocking out P. aeruginosa genes that are overexpressed during wound infection can cripple a pathogen's ability to impair healing, we assessed two pathways: the Type III secretion system (T3SS) and alginate biosynthesis. We generated single- and double-mutant strains of ExsA (T3SS activator), AlgD (GDP- mannose 6-dehydrogenase of alginate biosynthesis) and their complemented strains and evaluated their pathogenicity in a rabbit ear full-thickness excision-wound infection model. Wounds were inoculated with different strains (wild type, mutants, and complementary strains) at 106 CFU/wound on post-wounding day 3. After 24 h, 5 days and 9 days post-infection, wounds were harvested for measuring bacterial counts (viable and total) and wound healing (epithelial gap). On day 9 post-infection, the viable counts of the double mutant, (exsA/algD)‾ were 100-fold lower than the counts of the wild type (PAO1), single mutants, or the complement double-mutant, (exsA/algD)‾/+. Also, when compared to wounds infected with wild type or control strains, wounds infected with the double-knockout mutant was less inhibitory to wound healing (p < 0.05). Additionally, the double mutant showed greater susceptibility to macrophage phagocytosis in vitro than all other strains (p < 0.001). In conclusion, compared to single gene knockouts, double knockout of virulence genes in T3SS pathway and alginate biosynthesis pathway is more effective in reducing P. aeruginosa pathogenicity and its ability to impair wound healing. This study highlights the necessity of a dual-targeted anti-virulence strategy to improve healing outcomes of P. aeruginosa-infected wounds.
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Affiliation(s)
- S L Rajasekhar Karna
- Division of Combat Wound Repair, US Army Institute of Surgical Research, JBSA Fort Sam Houston, TX, USA
| | - Jesse Q Nguyen
- Division of Combat Wound Repair, US Army Institute of Surgical Research, JBSA Fort Sam Houston, TX, USA
| | - Shankar Jaikishan Evani
- Division of Combat Wound Repair, US Army Institute of Surgical Research, JBSA Fort Sam Houston, TX, USA
| | - Li-Wu Qian
- Division of Combat Wound Repair, US Army Institute of Surgical Research, JBSA Fort Sam Houston, TX, USA
| | - Ping Chen
- Division of Combat Wound Repair, US Army Institute of Surgical Research, JBSA Fort Sam Houston, TX, USA
| | - Johnathan J Abercrombie
- Division of Combat Wound Repair, US Army Institute of Surgical Research, JBSA Fort Sam Houston, TX, USA
| | - Eliza A Sebastian
- Division of Combat Wound Repair, US Army Institute of Surgical Research, JBSA Fort Sam Houston, TX, USA
| | - Andrea B Fourcaudot
- Division of Combat Wound Repair, US Army Institute of Surgical Research, JBSA Fort Sam Houston, TX, USA
| | - Kai P Leung
- Division of Combat Wound Repair, US Army Institute of Surgical Research, JBSA Fort Sam Houston, TX, USA.
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20
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Pseudomonas syringae AlgU Downregulates Flagellin Gene Expression, Helping Evade Plant Immunity. J Bacteriol 2020; 202:JB.00418-19. [PMID: 31740494 DOI: 10.1128/jb.00418-19] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 11/08/2019] [Indexed: 12/15/2022] Open
Abstract
Flagella power bacterial movement through liquids and over surfaces to access or avoid certain environmental conditions, ultimately increasing a cell's probability of survival and reproduction. In some cases, flagella and chemotaxis are key virulence factors enabling pathogens to gain entry and attach to suitable host tissues. However, flagella are not always beneficial; both plant and animal immune systems have evolved receptors to sense the proteins that make up flagellar filaments as signatures of bacterial infection. Microbes poorly adapted to avoid or counteract these immune functions are unlikely to be successful in host environments, and this selective pressure has driven the evolution of diverse and often redundant pathogen compensatory mechanisms. We tested the role of AlgU, the Pseudomonas extracytoplasmic function sigma factor σE/σ22 ortholog, in regulating flagellar expression in the context of Pseudomonas syringae-plant interactions. We found that AlgU is necessary for downregulating bacterial flagellin expression in planta and that this results in a corresponding reduction in plant immune elicitation. This AlgU-dependent regulation of flagellin gene expression is beneficial to bacterial growth in the course of plant infection, and eliminating the plant's ability to detect flagellin makes this AlgU-dependent function irrelevant for bacteria growing in the apoplast. Together, these results add support to an emerging model in which P. syringae AlgU functions at a key control point that serves to optimize the expression of bacterial functions during host interactions, including minimizing the expression of immune elicitors and concomitantly upregulating beneficial virulence functions.IMPORTANCE Foliar plant pathogens, like Pseudomonas syringae, adjust their physiology and behavior to facilitate host colonization and disease, but the full extent of these adaptations is not known. Plant immune systems are triggered by bacterial molecules, such as the proteins that make up flagellar filaments. In this study, we found that during plant infection, AlgU, a gene expression regulator that is responsive to external stimuli, downregulates expression of fliC, which encodes the flagellin protein, a strong elicitor of plant immune systems. This change in gene expression and resultant change in behavior correlate with reduced plant immune activation and improved P. syringae plant colonization. The results of this study demonstrate the proximate and ultimate causes of flagellar regulation in a plant-pathogen interaction.
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Gutiérrez-Barranquero JA, Cazorla FM, de Vicente A. Pseudomonas syringae pv. syringae Associated With Mango Trees, a Particular Pathogen Within the "Hodgepodge" of the Pseudomonas syringae Complex. FRONTIERS IN PLANT SCIENCE 2019; 10:570. [PMID: 31139201 PMCID: PMC6518948 DOI: 10.3389/fpls.2019.00570] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Accepted: 04/15/2019] [Indexed: 05/29/2023]
Abstract
The Pseudomonas syringae complex comprises different genetic groups that include strains from both agricultural and environmental habitats. This complex group has been used for decades as a "hodgepodge," including many taxonomically related species. More than 60 pathovars of P. syringae have been described based on distinct host ranges and disease symptoms they cause. These pathovars cause disease relying on an array of virulence mechanisms. However, P. syringae pv. syringae (Pss) is the most polyphagous bacterium in the P. syringae complex, based on its wide host range, that primarily affects woody and herbaceous host plants. In early 1990s, bacterial apical necrosis (BAN) of mango trees, a critical disease elicited by Pss in Southern Spain was described for the first time. Pss exhibits important epiphytic traits and virulence factors, which may promote its survival and pathogenicity in mango trees and in other plant hosts. Over more than two decades, Pss strains isolated from mango trees have been comprehensively investigated to elucidate the mechanisms that governs their epiphytic and pathogenic lifestyles. In particular, the vast majority of Pss strains isolated from mango trees produce an antimetabolite toxin, called mangotoxin, whose leading role in virulence has been clearly demonstrated. Moreover, phenotypic, genetic and phylogenetic approaches support that Pss strains producers of BAN symptoms on mango trees all belong to a single phylotype within phylogroup 2, are adapted to the mango host, and produce mangotoxin. Remarkably, a genome sequencing project of the Pss model strain UMAF0158 revealed the presence of other factors that may play major roles in its different lifestyles, such as the presence of two different type III secretion systems, two type VI secretion systems and an operon for cellulose biosynthesis. The role of cellulose in increasing mango leaf colonization and biofilm formation, and impairing virulence of Pss, suggests that cellulose may play a pivotal role with regards to the balance of its different lifestyles. In addition, 62-kb plasmids belonging to the pPT23A-family of plasmids (PFPs) have been strongly associated with Pss strains that inhabit mango trees. Further, complete sequence and comparative genomic analyses revealed major roles of PFPs in detoxification of copper compounds and ultraviolet radiation resistance, both improving the epiphytic lifestyle of Pss on mango surfaces. Hence, in this review we summarize the research that has been conducted on Pss by our research group to elucidate the molecular mechanisms that underpin the epiphytic and pathogenic lifestyle on mango trees. Finally, future directions in this particular plant-pathogen story are discussed.
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Li JZ, Zhou LY, Peng YL, Fan J. Pseudomonas bacteriocin syringacin M released upon desiccation suppresses the growth of sensitive bacteria in plant necrotic lesions. Microb Biotechnol 2019; 13:134-147. [PMID: 30672132 PMCID: PMC6922522 DOI: 10.1111/1751-7915.13367] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2018] [Revised: 12/01/2018] [Accepted: 12/13/2018] [Indexed: 12/12/2022] Open
Abstract
Bacteriocins are regarded as important factors mediating microbial interactions, but their exact role in community ecology largely remains to be elucidated. Here, we report the characterization of a mutant strain, derived from Pseudomonas syringae pv. tomato DC3000 (Pst), that was incapable of growing in plant extracts and causing disease. Results showed that deficiency in a previously unannotated gene saxE led to the sensitivity of the mutant to Ca2+ in leaf extracts. Transposon insertions in the bacteriocin gene syrM, adjacent to saxE, fully rescued the bacterial virulence and growth of the ΔsaxE mutant in plant extracts, indicating that syrM‐saxE encode a pair of bacteriocin immunity proteins in Pst. To investigate whether the syrM‐saxE system conferred any advantage to Pst in competition with other SyrM‐sensitive pathovars, we compared the growth of a SyrM‐sensitive strain co‐inoculated with Pst strains with or without the syrM gene and observed a significant syrM‐dependent growth reduction of the sensitive bacteria on plate and in lesion tissues upon desiccation–rehydration treatment. These findings reveal an important biological role of SyrM‐like bacteriocins and help to understand the complex strategies used by P. syringae in adaptation to the phyllosphere niche in the context of plant disease.
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Affiliation(s)
- Jun-Zhou Li
- Ministry of Agriculture Key Laboratory for Crop Pest Monitoring and Green Control, China Agricultural University, Beijing, 100193, China
| | - Li-Ying Zhou
- Ministry of Agriculture Key Laboratory for Crop Pest Monitoring and Green Control, China Agricultural University, Beijing, 100193, China
| | - You-Liang Peng
- Ministry of Agriculture Key Laboratory for Crop Pest Monitoring and Green Control, China Agricultural University, Beijing, 100193, China.,State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing, 100193, China
| | - Jun Fan
- Ministry of Agriculture Key Laboratory for Crop Pest Monitoring and Green Control, China Agricultural University, Beijing, 100193, China.,Joint Laboratory for International Cooperation in Crop Molecular Breeding, Ministry of Education, China Agricultural University, Beijing, 100193, China
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Li J, Staiger CJ. Understanding Cytoskeletal Dynamics During the Plant Immune Response. ANNUAL REVIEW OF PHYTOPATHOLOGY 2018; 56:513-533. [PMID: 29975609 DOI: 10.1146/annurev-phyto-080516-035632] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
The plant cytoskeleton is a dynamic framework of cytoplasmic filaments that rearranges as the needs of the cell change during growth and development. Incessant turnover mechanisms allow these networks to be rapidly redeployed in defense of host cytoplasm against microbial invaders. Both chemical and mechanical stimuli are recognized as danger signals to the plant, and these are perceived and transduced into cytoskeletal dynamics and architecture changes through a collection of well-recognized, previously characterized players. Recent advances in quantitative cell biology approaches, along with the powerful molecular genetics techniques associated with Arabidopsis, have uncovered two actin-binding proteins as key intermediaries in the immune response to phytopathogens and defense signaling. Certain bacterial phytopathogens have adapted to the cytoskeletal-based defense mechanism during the basal immune response and have evolved effector proteins that target actin filaments and microtubules to subvert transcriptional reprogramming, secretion of defense-related proteins, and cell wall-based defenses. In this review, we describe current knowledge about host cytoskeletal dynamics operating at the crossroads of the molecular and cellular arms race between microbes and plants.
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Affiliation(s)
- Jiejie Li
- Department of Biological Sciences and Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907, USA;
- Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Science, Beijing Normal University, Beijing 100875, China
| | - Christopher J Staiger
- Department of Biological Sciences and Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907, USA;
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Santamaría-Hernando S, Rodríguez-Herva JJ, Martínez-García PM, Río-Álvarez I, González-Melendi P, Zamorano J, Tapia C, Rodríguez-Palenzuela P, López-Solanilla E. Pseudomonas syringae pv. tomato exploits light signals to optimize virulence and colonization of leaves. Environ Microbiol 2018; 20:4261-4280. [PMID: 30058114 DOI: 10.1111/1462-2920.14331] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 06/13/2018] [Accepted: 06/17/2018] [Indexed: 11/30/2022]
Abstract
Light is pervasive in the leaf environment, creating opportunities for both plants and pathogens to cue into light as a signal to regulate plant-microbe interactions. Light enhances plant defences and regulates opening of stomata, an entry point for foliar bacterial pathogens such as Pseudomonas syringae pv. tomato DC3000 (PsPto). The effect of light perception on gene expression and virulence was investigated in PsPto. Light induced genetic reprogramming in PsPto that entailed significant changes in stress tolerance and virulence. Blue light-mediated up-regulation of type three secretion system genes and red light-mediated down-regulation of coronatine biosynthesis genes. Cells exposed to white light, blue light or darkness before inoculation were more virulent when inoculated at dawn than dusk probably due to an enhanced entry through open stomata. Exposure to red light repressed coronatine biosynthesis genes which could lead to a reduced stomatal re-opening and PsPto entry. Photoreceptor were required for the greater virulence of light-treated and dark-treated PsPto inoculated at dawn as compared to dusk, indicating that these proteins sense the absence of light and contribute to priming of virulence in the dark. These results support a model in which PsPto exploits light changes to maximize survival, entry and virulence on plants.
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Affiliation(s)
- Saray Santamaría-Hernando
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM)-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA) Campus Montegancedo UPM, Pozuelo de Alarcón, 28223, Madrid, Spain
| | - José J Rodríguez-Herva
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM)-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA) Campus Montegancedo UPM, Pozuelo de Alarcón, 28223, Madrid, Spain.,Departamento de Biotecnología-Biología Vegetal, Escuela Técnica Superior de Ingeniería Agronómica, Alimentaria y de Biosistemas, UPM, Madrid, Spain
| | - Pedro M Martínez-García
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM)-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA) Campus Montegancedo UPM, Pozuelo de Alarcón, 28223, Madrid, Spain
| | - Isabel Río-Álvarez
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM)-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA) Campus Montegancedo UPM, Pozuelo de Alarcón, 28223, Madrid, Spain
| | - Pablo González-Melendi
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM)-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA) Campus Montegancedo UPM, Pozuelo de Alarcón, 28223, Madrid, Spain.,Departamento de Biotecnología-Biología Vegetal, Escuela Técnica Superior de Ingeniería Agronómica, Alimentaria y de Biosistemas, UPM, Madrid, Spain
| | - Jaime Zamorano
- Departamento de Astrofísica y CC. de la Atmósfera, Universidad Complutense, Madrid, Spain
| | - Carlos Tapia
- Departamento de Astrofísica y CC. de la Atmósfera, Universidad Complutense, Madrid, Spain
| | - Pablo Rodríguez-Palenzuela
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM)-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA) Campus Montegancedo UPM, Pozuelo de Alarcón, 28223, Madrid, Spain.,Departamento de Biotecnología-Biología Vegetal, Escuela Técnica Superior de Ingeniería Agronómica, Alimentaria y de Biosistemas, UPM, Madrid, Spain
| | - Emilia López-Solanilla
- Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM)-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA) Campus Montegancedo UPM, Pozuelo de Alarcón, 28223, Madrid, Spain.,Departamento de Biotecnología-Biología Vegetal, Escuela Técnica Superior de Ingeniería Agronómica, Alimentaria y de Biosistemas, UPM, Madrid, Spain
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25
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Preininger C, Sauer U, Bejarano A, Berninger T. Concepts and applications of foliar spray for microbial inoculants. Appl Microbiol Biotechnol 2018; 102:7265-7282. [PMID: 29961100 DOI: 10.1007/s00253-018-9173-4] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 06/12/2018] [Accepted: 06/13/2018] [Indexed: 11/27/2022]
Abstract
Damages of the (agro)ecosystem by extensive use of chemical fertilizers and pesticides, the global dying of bee populations possibly linked to pesticide spraying, and stricter regulations for pesticide use together with successful use of microbials in IPM programs are pushing on the development and commercialization of new microbial products and a large and growing biostimulants and biocontrol market. This review focuses on microbial inoculants including bacteria, fungi, and viruses used as biostimulant or biocontrol agent for foliar application and covers all important steps from inoculant development to successful field application. Topics presented comprise typical spraying equipment including the importance of the spraying process and relating effects, furthermore formulation development including classification and adjuvants, and thirdly regulatory aspects as currently applied or under discussion. Microbial inoculants for foliar spray reported in scientific literature are summarized and contrasted with selected commercial products. Special attention is given to factors most important in microbial spray: (a) type of active ingredient (bacteria, fungi, viruses), (b) mode of action (ingestion, contact, competition), (c) interaction with the plant leaf surface, (d) droplet size in terms of microbe concentration and leaf coverage, and (e) environmental conditions during spraying. Finally, we want to emphasize that timely administration is of utmost importance for successful spraying and maximum efficacy. This might be supported by weather stations and disease/pest models as an important step towards precision farming.
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Affiliation(s)
- Claudia Preininger
- Center for Health & Bioresources, AIT Austrian Institute of Technology GmbH, Konrad-Lorenz-Strasse 24, 3430, Tulln, Austria.
| | - Ursula Sauer
- Center for Health & Bioresources, AIT Austrian Institute of Technology GmbH, Konrad-Lorenz-Strasse 24, 3430, Tulln, Austria
| | - Ana Bejarano
- Center for Health & Bioresources, AIT Austrian Institute of Technology GmbH, Konrad-Lorenz-Strasse 24, 3430, Tulln, Austria
| | - Teresa Berninger
- Center for Health & Bioresources, AIT Austrian Institute of Technology GmbH, Konrad-Lorenz-Strasse 24, 3430, Tulln, Austria
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26
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Montano J, Melotto M. Stomatal Bioassay to Characterize Bacterial-Stimulated PTI at the Pre-Invasion Phase of Infection. Methods Mol Biol 2018; 1578:233-241. [PMID: 28220429 DOI: 10.1007/978-1-4939-6859-6_19] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/20/2023]
Abstract
Bacterium-triggered stomatal closure is a functional output of plant immunity, also known as stomatal defense. This is an early response mediated by the recognition of pathogen-associated molecular patterns (PAMPs) by the plant's pathogen recognition receptors (PRRs). Several approaches to analyzing stomatal movement in response to bacteria have been described, but difficulties in fine-tuning the experimental procedures still exist. Here we provide a detailed method for assessing stomatal defense via high-quality microscopic imaging and explain trouble-shooting steps to obtaining robust data. Although this procedure requires minimal manipulation of the leaf sample, it is crucial to control all environmental conditions and extrinsic variables that could interfere with stomatal movement. The method described here is also suitable for in vivo characterization of stomatal response in new pathosystems and can be used in conjunction with other profiling assays to gain a detailed understanding of early PAMP-triggered immunity (PTI).
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Affiliation(s)
- Jeanine Montano
- Department of Plant Sciences, University of California, Davis, CA, 95616, USA
| | - Maeli Melotto
- Department of Plant Sciences, University of California, Davis, CA, 95616, USA.
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27
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Rufián JS, Lucía A, Rueda-Blanco J, Zumaquero A, Guevara CM, Ortiz-Martín I, Ruiz-Aldea G, Macho AP, Beuzón CR, Ruiz-Albert J. Suppression of HopZ Effector-Triggered Plant Immunity in a Natural Pathosystem. FRONTIERS IN PLANT SCIENCE 2018; 9:977. [PMID: 30154802 PMCID: PMC6103241 DOI: 10.3389/fpls.2018.00977] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 06/15/2018] [Indexed: 05/13/2023]
Abstract
Many type III-secreted effectors suppress plant defenses, but can also activate effector-triggered immunity (ETI) in resistant backgrounds. ETI suppression has been shown for a number of type III effectors (T3Es) and ETI-suppressing effectors are considered part of the arms race model for the co-evolution of bacterial virulence and plant defense. However, ETI suppression activities have been shown mostly between effectors not being naturally expressed within the same strain. Furthermore, evolution of effector families is rarely explained taking into account that selective pressure against ETI-triggering effectors may be compensated by ETI-suppressing effector(s) translocated by the same strain. The HopZ effector family is one of the most diverse, displaying a high rate of loss and gain of alleles, which reflects opposing selective pressures. HopZ effectors trigger defense responses in a variety of crops and some have been shown to suppress different plant defenses. Mutational changes in the sequence of ETI-triggering effectors have been proposed to result in the avoidance of detection by their respective hosts, in a process called pathoadaptation. We analyze how deleting or overexpressing HopZ1a and HopZ3 affects virulence of HopZ-encoding and non-encoding strains. We find that both effectors trigger immunity in their plant hosts only when delivered from heterologous strains, while immunity is suppressed when delivered from their native strains. We carried out screens aimed at identifying the determinant(s) suppressing HopZ1a-triggered and HopZ3-triggered immunity within their native strains, and identified several effectors displaying suppression of HopZ3-triggered immunity. We propose effector-mediated cross-suppression of ETI as an additional force driving evolution of the HopZ family.
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Affiliation(s)
- José S. Rufián
- Departamento Biología Celular, Genética y Fisiología, Instituto de Hortofruticultura Subtropical y Mediterránea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas, Málaga, Spain
- Shanghai Center for Plant Stress Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Ainhoa Lucía
- Departamento Biología Celular, Genética y Fisiología, Instituto de Hortofruticultura Subtropical y Mediterránea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas, Málaga, Spain
| | - Javier Rueda-Blanco
- Departamento Biología Celular, Genética y Fisiología, Instituto de Hortofruticultura Subtropical y Mediterránea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas, Málaga, Spain
| | - Adela Zumaquero
- Departamento Biología Celular, Genética y Fisiología, Instituto de Hortofruticultura Subtropical y Mediterránea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas, Málaga, Spain
| | - Carlos M. Guevara
- Departamento Biología Celular, Genética y Fisiología, Instituto de Hortofruticultura Subtropical y Mediterránea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas, Málaga, Spain
| | - Inmaculada Ortiz-Martín
- Departamento Biología Celular, Genética y Fisiología, Instituto de Hortofruticultura Subtropical y Mediterránea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas, Málaga, Spain
| | - Gonzalo Ruiz-Aldea
- Departamento Biología Celular, Genética y Fisiología, Instituto de Hortofruticultura Subtropical y Mediterránea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas, Málaga, Spain
| | - Alberto P. Macho
- Shanghai Center for Plant Stress Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Carmen R. Beuzón
- Departamento Biología Celular, Genética y Fisiología, Instituto de Hortofruticultura Subtropical y Mediterránea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas, Málaga, Spain
| | - Javier Ruiz-Albert
- Departamento Biología Celular, Genética y Fisiología, Instituto de Hortofruticultura Subtropical y Mediterránea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas, Málaga, Spain
- *Correspondence: Javier Ruiz-Albert,
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28
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Henry E, Toruño TY, Jauneau A, Deslandes L, Coaker G. Direct and Indirect Visualization of Bacterial Effector Delivery into Diverse Plant Cell Types during Infection. THE PLANT CELL 2017; 29:1555-1570. [PMID: 28600390 PMCID: PMC5559743 DOI: 10.1105/tpc.17.00027] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 05/22/2017] [Accepted: 06/08/2017] [Indexed: 05/04/2023]
Abstract
To cause disease, diverse pathogens deliver effector proteins into host cells. Pathogen effectors can inhibit defense responses, alter host physiology, and represent important cellular probes to investigate plant biology. However, effector function and localization have primarily been investigated after overexpression in planta. Visualizing effector delivery during infection is challenging due to the plant cell wall, autofluorescence, and low effector abundance. Here, we used a GFP strand system to directly visualize bacterial effectors delivered into plant cells through the type III secretion system. GFP is a beta barrel that can be divided into 11 strands. We generated transgenic Arabidopsis thaliana plants expressing GFP1-10 (strands 1 to 10). Multiple bacterial effectors tagged with the complementary strand 11 epitope retained their biological function in Arabidopsis and tomato (Solanum lycopersicum). Infection of plants expressing GFP1-10 with bacteria delivering GFP11-tagged effectors enabled direct effector detection in planta. We investigated the temporal and spatial delivery of GFP11-tagged effectors during infection with the foliar pathogen Pseudomonas syringae and the vascular pathogen Ralstonia solanacearum Thus, the GFP strand system can be broadly used to investigate effector biology in planta.
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Affiliation(s)
- Elizabeth Henry
- Department of Plant Pathology, University of California, Davis, California 95616
| | - Tania Y Toruño
- Department of Plant Pathology, University of California, Davis, California 95616
| | - Alain Jauneau
- Institut Fédératif de Recherche 3450, Université de Toulouse, CNRS, UPS, Plateforme Imagerie TRI-Genotoul, Castanet-Tolosan 31326, France
| | - Laurent Deslandes
- LIPM, Université de Toulouse, INRA, CNRS, UPS, Castanet-Tolosan, France
| | - Gitta Coaker
- Department of Plant Pathology, University of California, Davis, California 95616
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29
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Corwin JA, Kliebenstein DJ. Quantitative Resistance: More Than Just Perception of a Pathogen. THE PLANT CELL 2017; 29:655-665. [PMID: 28302676 PMCID: PMC5435431 DOI: 10.1105/tpc.16.00915] [Citation(s) in RCA: 106] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 02/26/2017] [Accepted: 03/16/2017] [Indexed: 05/20/2023]
Abstract
Molecular plant pathology has focused on studying large-effect qualitative resistance loci that predominantly function in detecting pathogens and/or transmitting signals resulting from pathogen detection. By contrast, less is known about quantitative resistance loci, particularly the molecular mechanisms controlling variation in quantitative resistance. Recent studies have provided insight into these mechanisms, showing that genetic variation at hundreds of causal genes may underpin quantitative resistance. Loci controlling quantitative resistance contain some of the same causal genes that mediate qualitative resistance, but the predominant mechanisms of quantitative resistance extend beyond pathogen recognition. Indeed, most causal genes for quantitative resistance encode specific defense-related outputs such as strengthening of the cell wall or defense compound biosynthesis. Extending previous work on qualitative resistance to focus on the mechanisms of quantitative resistance, such as the link between perception of microbe-associated molecular patterns and growth, has shown that the mechanisms underlying these defense outputs are also highly polygenic. Studies that include genetic variation in the pathogen have begun to highlight a potential need to rethink how the field considers broad-spectrum resistance and how it is affected by genetic variation within pathogen species and between pathogen species. These studies are broadening our understanding of quantitative resistance and highlighting the potentially vast scale of the genetic basis of quantitative resistance.
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Affiliation(s)
- Jason A Corwin
- Department of Plant Sciences, University of California, Davis, California 95616
| | - Daniel J Kliebenstein
- Department of Plant Sciences, University of California, Davis, California 95616
- DynaMo Center of Excellence, University of Copenhagen, DK-1871 Frederiksberg C, Denmark
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30
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Pfeilmeier S, Caly DL, Malone JG. Bacterial pathogenesis of plants: future challenges from a microbial perspective: Challenges in Bacterial Molecular Plant Pathology. MOLECULAR PLANT PATHOLOGY 2016; 17:1298-313. [PMID: 27170435 PMCID: PMC6638335 DOI: 10.1111/mpp.12427] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2016] [Revised: 05/08/2016] [Accepted: 05/10/2016] [Indexed: 05/03/2023]
Abstract
Plant infection is a complicated process. On encountering a plant, pathogenic microorganisms must first adapt to life on the epiphytic surface, and survive long enough to initiate an infection. Responsiveness to the environment is critical throughout infection, with intracellular and community-level signal transduction pathways integrating environmental signals and triggering appropriate responses in the bacterial population. Ultimately, phytopathogens must migrate from the epiphytic surface into the plant tissue using motility and chemotaxis pathways. This migration is coupled with overcoming the physical and chemical barriers to entry into the plant apoplast. Once inside the plant, bacteria use an array of secretion systems to release phytotoxins and protein effectors that fulfil diverse pathogenic functions (Fig. ) (Melotto and Kunkel, ; Phan Tran et al., ). As our understanding of the pathways and mechanisms underpinning plant pathogenicity increases, a number of central research challenges are emerging that will profoundly shape the direction of research in the future. We need to understand the bacterial phenotypes that promote epiphytic survival and surface adaptation in pathogenic bacteria. How do these pathways function in the context of the plant-associated microbiome, and what impact does this complex microbial community have on the onset and severity of plant infections? The huge importance of bacterial signal transduction to every stage of plant infection is becoming increasingly clear. However, there is a great deal to learn about how these signalling pathways function in phytopathogenic bacteria, and the contribution they make to various aspects of plant pathogenicity. We are increasingly able to explore the structural and functional diversity of small-molecule natural products from plant pathogens. We need to acquire a much better understanding of the production, deployment, functional redundancy and physiological roles of these molecules. Type III secretion systems (T3SSs) are important and well-studied contributors to bacterial disease. Several key unanswered questions will shape future investigations of these systems. We need to define the mechanism of hierarchical and temporal control of effector secretion. For successful infection, effectors need to interact with host components to exert their function. Advanced biochemical, proteomic and cell biological techniques will enable us to study the function of effectors inside the host cell in more detail and on a broader scale. Population genomics analyses provide insight into evolutionary adaptation processes of phytopathogens. The determination of the diversity and distribution of type III effectors (T3Es) and other virulence genes within and across pathogenic species, pathovars and strains will allow us to understand how pathogens adapt to specific hosts, the evolutionary pathways available to them, and the possible future directions of the evolutionary arms race between effectors and molecular plant targets. Although pathogenic bacteria employ a host of different virulence and proliferation strategies, as a result of the space constraints, this review focuses mainly on the hemibiotrophic pathogens. We discuss the process of plant infection from the perspective of these important phytopathogens, and highlight new approaches to address the outstanding challenges in this important and fast-moving field.
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Affiliation(s)
- Sebastian Pfeilmeier
- The Sainsbury Laboratory, Norwich Research Park, Norwich, NR4 7UH, UK
- John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK
| | - Delphine L Caly
- Université de Lille, EA 7394, ICV - Institut Charles Viollette, Lille, F-59000, France
| | - Jacob G Malone
- John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK.
- University of East Anglia, Norwich, NR4 7TJ, UK.
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31
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Macho AP. Subversion of plant cellular functions by bacterial type-III effectors: beyond suppression of immunity. THE NEW PHYTOLOGIST 2016; 210:51-7. [PMID: 26306858 DOI: 10.1111/nph.13605] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Accepted: 07/10/2015] [Indexed: 05/20/2023]
Abstract
Most bacterial plant pathogens employ a type-III secretion system to inject type-III effector (T3E) proteins directly inside plant cells. These T3Es manipulate host cellular processes in order to create a permissive niche for bacterial proliferation, allowing development of the disease. An important role of T3Es in plant pathogenic bacteria is the suppression of plant immune responses. However, in recent years, research has uncovered T3E functions different from direct immune suppression, including the modulation of plant hormone signaling, metabolism or organelle function. This insight article discusses T3E functions other than suppression of immunity, which may contribute to the modulation of plant cells in order to promote bacterial survival, nutrient release, and bacterial replication and dissemination.
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Affiliation(s)
- Alberto P Macho
- Shanghai Center for Plant Stress Biology, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai, 201602, China
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32
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Castiblanco LF, Sundin GW. New insights on molecular regulation of biofilm formation in plant-associated bacteria. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2016; 58:362-72. [PMID: 26377849 DOI: 10.1111/jipb.12428] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 09/10/2015] [Indexed: 05/11/2023]
Abstract
Biofilms are complex bacterial assemblages with a defined three-dimensional architecture, attached to solid surfaces, and surrounded by a self-produced matrix generally composed of exopolysaccharides, proteins, lipids and extracellular DNA. Biofilm formation has evolved as an adaptive strategy of bacteria to cope with harsh environmental conditions as well as to establish antagonistic or beneficial interactions with their host. Plant-associated bacteria attach and form biofilms on different tissues including leaves, stems, vasculature, seeds and roots. In this review, we examine the formation of biofilms from the plant-associated bacterial perspective and detail the recently-described mechanisms of genetic regulation used by these organisms to orchestrate biofilm formation on plant surfaces. In addition, we describe plant host signals that bacterial pathogens recognize to activate the transition from a planktonic lifestyle to multicellular behavior.
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Affiliation(s)
- Luisa F Castiblanco
- Department of Plant, Soil and Microbial Sciences and Center for Microbial Pathogenesis, Michigan State University, East Lansing, Michigan, 48824, USA
| | - George W Sundin
- Department of Plant, Soil and Microbial Sciences and Center for Microbial Pathogenesis, Michigan State University, East Lansing, Michigan, 48824, USA
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Panchal S, Roy D, Chitrakar R, Price L, Breitbach ZS, Armstrong DW, Melotto M. Coronatine Facilitates Pseudomonas syringae Infection of Arabidopsis Leaves at Night. FRONTIERS IN PLANT SCIENCE 2016; 7:880. [PMID: 27446113 PMCID: PMC4914978 DOI: 10.3389/fpls.2016.00880] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 06/03/2016] [Indexed: 05/03/2023]
Abstract
In many land plants, the stomatal pore opens during the day and closes during the night. Thus, periods of darkness could be effective in decreasing pathogen penetration into leaves through stomata, the primary sites for infection by many pathogens. Pseudomonas syringae pv. tomato (Pst) DC3000 produces coronatine (COR) and opens stomata, raising an intriguing question as to whether this is a virulence strategy to facilitate bacterial infection at night. In fact, we found that (a) biological concentration of COR is effective in opening dark-closed stomata of Arabidopsis thaliana leaves, (b) the COR defective mutant Pst DC3118 is less effective in infecting Arabidopsis in the dark than under light and this difference in infection is reduced with the wild type bacterium Pst DC3000, and (c) cma, a COR biosynthesis gene, is induced only when the bacterium is in contact with the leaf surface independent of the light conditions. These findings suggest that Pst DC3000 activates virulence factors at the pre-invasive phase of its life cycle to infect plants even when environmental conditions (such as darkness) favor stomatal immunity. This functional attribute of COR may provide epidemiological advantages for COR-producing bacteria on the leaf surface.
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Affiliation(s)
- Shweta Panchal
- Department of Biology, University of Texas at ArlingtonArlington, TX, USA
| | - Debanjana Roy
- Department of Plant Sciences, University of California, DavisDavis, CA, USA
| | - Reejana Chitrakar
- Department of Biology, University of Texas at ArlingtonArlington, TX, USA
| | - Lenore Price
- Department of Biology, University of Texas at ArlingtonArlington, TX, USA
| | | | | | - Maeli Melotto
- Department of Plant Sciences, University of California, DavisDavis, CA, USA
- *Correspondence: Maeli Melotto,
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34
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Andam CP, Carver SM, Berthrong ST. Horizontal Gene Flow in Managed Ecosystems. ANNUAL REVIEW OF ECOLOGY EVOLUTION AND SYSTEMATICS 2015. [DOI: 10.1146/annurev-ecolsys-112414-054126] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Cheryl P. Andam
- Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, Massachusetts 02115;
| | - Sarah M. Carver
- Central Research, The Kraft Heinz Company, Glenview, Illinois 60025;
| | - Sean T. Berthrong
- Department of Biological Sciences, Butler University, Indianapolis, Indiana 46208;
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Lee J, Manning AJ, Wolfgeher D, Jelenska J, Cavanaugh KA, Xu H, Fernandez SM, Michelmore RW, Kron SJ, Greenberg JT. Acetylation of an NB-LRR Plant Immune-Effector Complex Suppresses Immunity. Cell Rep 2015; 13:1670-82. [PMID: 26586425 PMCID: PMC4967551 DOI: 10.1016/j.celrep.2015.10.029] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 09/10/2015] [Accepted: 10/09/2015] [Indexed: 12/21/2022] Open
Abstract
Modifications of plant immune complexes by secreted pathogen effectors can trigger strong immune responses mediated by the action of nucleotide binding-leucine-rich repeat immune receptors. Although some strains of the pathogen Pseudomonas syringae harbor effectors that individually can trigger immunity, the plant's response may be suppressed by other virulence factors. This work reveals a robust strategy for immune suppression mediated by HopZ3, an effector in the YopJ family of acetyltransferases. The suppressing HopZ3 effector binds to and can acetylate multiple members of the RPM1 immune complex, as well as two P. syringae effectors that together activate the RPM1 complex. These acetylations modify serine, threonine, lysine, and/or histidine residues in the targets. Through HopZ3-mediated acetylation, it is possible that the whole effector-immune complex is inactivated, leading to increased growth of the pathogen.
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Affiliation(s)
- Jiyoung Lee
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Andrew J Manning
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Donald Wolfgeher
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Joanna Jelenska
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Keri A Cavanaugh
- The Genome Center & Department of Plant Sciences, University of California, Davis, Davis, CA 95616, USA
| | - Huaqin Xu
- The Genome Center & Department of Plant Sciences, University of California, Davis, Davis, CA 95616, USA
| | - Sandra M Fernandez
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Richard W Michelmore
- The Genome Center & Department of Plant Sciences, University of California, Davis, Davis, CA 95616, USA
| | - Stephen J Kron
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA
| | - Jean T Greenberg
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA.
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Martínez-García PM, Rodríguez-Palenzuela P, Arrebola E, Carrión VJ, Gutiérrez-Barranquero JA, Pérez-García A, Ramos C, Cazorla FM, de Vicente A. Bioinformatics Analysis of the Complete Genome Sequence of the Mango Tree Pathogen Pseudomonas syringae pv. syringae UMAF0158 Reveals Traits Relevant to Virulence and Epiphytic Lifestyle. PLoS One 2015; 10:e0136101. [PMID: 26313942 PMCID: PMC4551802 DOI: 10.1371/journal.pone.0136101] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 07/29/2015] [Indexed: 01/11/2023] Open
Abstract
The genome sequence of more than 100 Pseudomonas syringae strains has been sequenced to date; however only few of them have been fully assembled, including P. syringae pv. syringae B728a. Different strains of pv. syringae cause different diseases and have different host specificities; so, UMAF0158 is a P. syringae pv. syringae strain related to B728a but instead of being a bean pathogen it causes apical necrosis of mango trees, and the two strains belong to different phylotypes of pv.syringae and clades of P. syringae. In this study we report the complete sequence and annotation of P. syringae pv. syringae UMAF0158 chromosome and plasmid pPSS158. A comparative analysis with the available sequenced genomes of other 25 P. syringae strains, both closed (the reference genomes DC3000, 1448A and B728a) and draft genomes was performed. The 5.8 Mb UMAF0158 chromosome has 59.3% GC content and comprises 5017 predicted protein-coding genes. Bioinformatics analysis revealed the presence of genes potentially implicated in the virulence and epiphytic fitness of this strain. We identified several genetic features, which are absent in B728a, that may explain the ability of UMAF0158 to colonize and infect mango trees: the mangotoxin biosynthetic operon mbo, a gene cluster for cellulose production, two different type III and two type VI secretion systems, and a particular T3SS effector repertoire. A mutant strain defective in the rhizobial-like T3SS Rhc showed no differences compared to wild-type during its interaction with host and non-host plants and worms. Here we report the first complete sequence of the chromosome of a pv. syringae strain pathogenic to a woody plant host. Our data also shed light on the genetic factors that possibly determine the pathogenic and epiphytic lifestyle of UMAF0158. This work provides the basis for further analysis on specific mechanisms that enable this strain to infect woody plants and for the functional analysis of host specificity in the P. syringae complex.
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Affiliation(s)
- Pedro Manuel Martínez-García
- Centro de Biotecnología y Genómica de Plantas UPM-INIA, Parque Científico y Tecnológico de la Universidad Politécnica de Madrid. Pozuelo de Alarcón, Madrid, Spain
- Instituto de Hortofruticultura Subtropical y Mediterránea “La Mayora”, Universidad de Málaga, Consejo Superior de Investigaciones Científicas, Área de Genética, Facultad de Ciencias, Málaga, Spain
| | - Pablo Rodríguez-Palenzuela
- Centro de Biotecnología y Genómica de Plantas UPM-INIA, Parque Científico y Tecnológico de la Universidad Politécnica de Madrid. Pozuelo de Alarcón, Madrid, Spain
| | - Eva Arrebola
- Instituto de Hortofruticultura Subtropical y Mediterránea “La Mayora”, Universidad de Málaga, Consejo Superior de Investigaciones Científicas, Estación Experimental La Mayora, Algarrobo-Costa, Málaga, Spain
| | - Víctor J. Carrión
- Instituto de Hortofruticultura Subtropical y Mediterránea “La Mayora”, Universidad de Málaga, Consejo Superior de Investigaciones Científicas, Departamento de Microbiología, Facultad de Ciencias, Málaga, Spain
| | - José Antonio Gutiérrez-Barranquero
- Instituto de Hortofruticultura Subtropical y Mediterránea “La Mayora”, Universidad de Málaga, Consejo Superior de Investigaciones Científicas, Departamento de Microbiología, Facultad de Ciencias, Málaga, Spain
| | - Alejandro Pérez-García
- Instituto de Hortofruticultura Subtropical y Mediterránea “La Mayora”, Universidad de Málaga, Consejo Superior de Investigaciones Científicas, Departamento de Microbiología, Facultad de Ciencias, Málaga, Spain
| | - Cayo Ramos
- Instituto de Hortofruticultura Subtropical y Mediterránea “La Mayora”, Universidad de Málaga, Consejo Superior de Investigaciones Científicas, Área de Genética, Facultad de Ciencias, Málaga, Spain
| | - Francisco M. Cazorla
- Instituto de Hortofruticultura Subtropical y Mediterránea “La Mayora”, Universidad de Málaga, Consejo Superior de Investigaciones Científicas, Departamento de Microbiología, Facultad de Ciencias, Málaga, Spain
| | - Antonio de Vicente
- Instituto de Hortofruticultura Subtropical y Mediterránea “La Mayora”, Universidad de Málaga, Consejo Superior de Investigaciones Científicas, Departamento de Microbiología, Facultad de Ciencias, Málaga, Spain
- * E-mail:
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Lee D, Bourdais G, Yu G, Robatzek S, Coaker G. Phosphorylation of the Plant Immune Regulator RPM1-INTERACTING PROTEIN4 Enhances Plant Plasma Membrane H⁺-ATPase Activity and Inhibits Flagellin-Triggered Immune Responses in Arabidopsis. THE PLANT CELL 2015; 27. [PMID: 26198070 PMCID: PMC4531345 DOI: 10.1105/tpc.114.132308] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The Pseudomonas syringae effector AvrB targets multiple host proteins during infection, including the plant immune regulator RPM1-INTERACTING PROTEIN4 (RIN4) and RPM1-INDUCED PROTEIN KINASE (RIPK). In the presence of AvrB, RIPK phosphorylates RIN4 at Thr-21, Ser-160, and Thr-166, leading to activation of the immune receptor RPM1. Here, we investigated the role of RIN4 phosphorylation in susceptible Arabidopsis thaliana genotypes. Using circular dichroism spectroscopy, we show that RIN4 is a disordered protein and phosphorylation affects protein flexibility. RIN4 T21D/S160D/T166D phosphomimetic mutants exhibited enhanced disease susceptibility upon surface inoculation with P. syringae, wider stomatal apertures, and enhanced plasma membrane H(+)-ATPase activity. The plasma membrane H(+)-ATPase AHA1 is highly expressed in guard cells, and its activation can induce stomatal opening. The ripk knockout also exhibited a strong defect in pathogen-induced stomatal opening. The basal level of RIN4 Thr-166 phosphorylation decreased in response to immune perception of bacterial flagellin. RIN4 Thr166D lines exhibited reduced flagellin-triggered immune responses. Flagellin perception did not lower RIN4 Thr-166 phosphorylation in the presence of strong ectopic expression of AvrB. Taken together, these results indicate that the AvrB effector targets RIN4 in order to enhance pathogen entry on the leaf surface as well as dampen responses to conserved microbial features.
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Affiliation(s)
- DongHyuk Lee
- Department of Plant Pathology, University of California, Davis, California 95616
| | | | - Gang Yu
- Department of Plant Pathology, University of California, Davis, California 95616
| | - Silke Robatzek
- The Sainsbury Laboratory, Norwich NR4 7UH, United Kingdom
| | - Gitta Coaker
- Department of Plant Pathology, University of California, Davis, California 95616
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Cecchini NM, Jung HW, Engle NL, Tschaplinski TJ, Greenberg JT. ALD1 Regulates Basal Immune Components and Early Inducible Defense Responses in Arabidopsis. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2015; 28:455-66. [PMID: 25372120 DOI: 10.1094/mpmi-06-14-0187-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: 05/07/2023]
Abstract
Robust immunity requires basal defense machinery to mediate timely responses and feedback cycles to amplify defenses against potentially spreading infections. AGD2-LIKE DEFENSE RESPONSE PROTEIN 1 (ALD1) is needed for the accumulation of the plant defense signal salicylic acid (SA) during the first hours after infection with the pathogen Pseudomonas syringae and is also upregulated by infection and SA. ALD1 is an aminotransferase with multiple substrates and products in vitro. Pipecolic acid (Pip) is an ALD1-dependent bioactive product induced by P. syringae. Here, we addressed roles of ALD1 in mediating defense amplification as well as the levels and responses of basal defense machinery. ALD1 needs immune components PAD4 and ICS1 (an SA synthesis enzyme) to confer disease resistance, possibly through a transcriptional amplification loop between them. Furthermore, ALD1 affects basal defense by controlling microbial-associated molecular pattern (MAMP) receptor levels and responsiveness. Vascular exudates from uninfected ALD1-overexpressing plants confer local immunity to the wild type and ald1 mutants yet are not enriched for Pip. We infer that, in addition to affecting Pip accumulation, ALD1 produces non-Pip metabolites that play roles in immunity. Thus, distinct metabolite signals controlled by the same enzyme affect basal and early defenses versus later defense responses, respectively.
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Affiliation(s)
- Nicolás M Cecchini
- 1 Department of Molecular Genetics and Cell Biology, The University of Chicago, 929 East 57th Street GCIS 524W, Chicago 60637, U.S.A
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39
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Chatnaparat T, Li Z, Korban SS, Zhao Y. The bacterial alarmone (p)ppGpp is required for virulence and controls cell size and survival of Pseudomonas syringae on plants. Environ Microbiol 2015; 17:4253-70. [PMID: 25626964 DOI: 10.1111/1462-2920.12744] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Revised: 11/29/2014] [Accepted: 12/06/2014] [Indexed: 11/29/2022]
Abstract
The stringent response, mediated by second messenger (p)ppGpp, results in swift and massive transcriptional reprogramming under nutrient limited conditions. In this study, the role of (p)ppGpp on virulence of Pseudomonas syringae pv. syringae B728a (PssB728a) was investigated. The virulence of the relA/spoT (ppGpp(0) ) double mutant was completely impaired on bean, and bacterial growth was significantly reduced, suggesting that (p)ppGpp is required for full virulence of P. syringae. Expression of T3SS and other virulence genes was reduced in ppGpp(0) mutants. In addition, ppGpp deficiency resulted in loss of swarming motility, reduction of pyoverdine production, increased sensitivity to oxidative stress and antibiotic tolerance, as well as reduced ability to utilize γ-amino butyric acid. Increased levels of ppGpp resulted in reduced cell size of PssB728a when grown in a minimal medium and on plant surfaces, while most ppGpp(0) mutant cells were not viable on plant surfaces 24 h after spray inoculation, suggesting that ppGpp-mediated stringent response temporarily limits cell growth, and might control cell survival on plants by limiting their growth. These results demonstrated that ppGpp-mediated stringent response plays a central role in P. syringae virulence and survival and indicated that ppGpp serves as a global signal for regulating various virulence traits in PssB728a.
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Affiliation(s)
- Tiyakhon Chatnaparat
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Zhong Li
- Metabolomics Center, Roy J. Carver Biotechnology Center, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - Schuyler S Korban
- Department of Natural Resources and Environmental Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.,Department of Biology, University of Massachusetts Boston, Boston, MA, 02125, USA
| | - Youfu Zhao
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
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40
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Lewis JD, Wilton M, Mott G.A, Lu W, Hassan JA, Guttman DS, Desveaux D. Immunomodulation by the Pseudomonas syringae HopZ type III effector family in Arabidopsis. PLoS One 2014; 9:e116152. [PMID: 25546415 PMCID: PMC4278861 DOI: 10.1371/journal.pone.0116152] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 12/04/2014] [Indexed: 11/19/2022] Open
Abstract
Pseudomonas syringae employs a type III secretion system to inject 20-30 different type III effector (T3SE) proteins into plant host cells. A major role of T3SEs is to suppress plant immune responses and promote bacterial infection. The YopJ/HopZ acetyltransferases are a superfamily of T3SEs found in both plant and animal pathogenic bacteria. In P. syringae, this superfamily includes the evolutionarily diverse HopZ1, HopZ2 and HopZ3 alleles. To investigate the roles of the HopZ family in immunomodulation, we generated dexamethasone-inducible T3SE transgenic lines of Arabidopsis for HopZ family members and characterized them for immune suppression phenotypes. We show that all of the HopZ family members can actively suppress various facets of Arabidopsis immunity in a catalytic residue-dependent manner. HopZ family members can differentially suppress the activation of mitogen-activated protein (MAP) kinase cascades or the production of reactive oxygen species, whereas all members can promote the growth of non-virulent P. syringae. Localization studies show that four of the HopZ family members containing predicted myristoylation sites are localized to the vicinity of the plasma membrane while HopZ3 which lacks the myristoylation site is at least partially nuclear localized, suggesting diversification of immunosuppressive mechanisms. Overall, we demonstrate that despite significant evolutionary diversification, all HopZ family members can suppress immunity in Arabidopsis.
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Affiliation(s)
- Jennifer D. Lewis
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
- Plant Gene Expression Center, United States Department of Agriculture, Albany, California, United States of America
- Department of Plant and Microbial Biology, University of California, Berkeley, California, United States of America
| | - Mike Wilton
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - G . Adam Mott
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Wenwan Lu
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Jana A. Hassan
- Department of Plant and Microbial Biology, University of California, Berkeley, California, United States of America
| | - David S. Guttman
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
- Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Ontario, Canada
| | - Darrell Desveaux
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
- Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, Ontario, Canada
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Hurley B, Lee D, Mott A, Wilton M, Liu J, Liu YC, Angers S, Coaker G, Guttman DS, Desveaux D. The Pseudomonas syringae type III effector HopF2 suppresses Arabidopsis stomatal immunity. PLoS One 2014; 9:e114921. [PMID: 25503437 PMCID: PMC4263708 DOI: 10.1371/journal.pone.0114921] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 11/14/2014] [Indexed: 12/22/2022] Open
Abstract
Pseudomonas syringae subverts plant immune signalling through injection of type III secreted effectors (T3SE) into host cells. The T3SE HopF2 can disable Arabidopsis immunity through Its ADP-ribosyltransferase activity. Proteomic analysis of HopF2 interacting proteins identified a protein complex containing ATPases required for regulating stomatal aperture, suggesting HopF2 may manipulate stomatal immunity. Here we report HopF2 can inhibit stomatal immunity independent of its ADP-ribosyltransferase activity. Transgenic expression of HopF2 in Arabidopsis inhibits stomatal closing in response to P. syringae and increases the virulence of surface inoculated P. syringae. Further, transgenic expression of HopF2 inhibits flg22 induced reactive oxygen species production. Intriguingly, ADP-ribosyltransferase activity is dispensable for inhibiting stomatal immunity and flg22 induced reactive oxygen species. Together, this implies HopF2 may be a bifunctional T3SE with ADP-ribosyltransferase activity required for inhibiting apoplastic immunity and an independent function required to inhibit stomatal immunity.
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Affiliation(s)
- Brenden Hurley
- Department of Cell & Systems Biology, University of Toronto, 25 Willcocks St., Toronto, Ontario, Canada
| | - Donghyuk Lee
- Department of Plant Pathology, University of California Davis, Davis, CA, United States of America
| | - Adam Mott
- Department of Cell & Systems Biology, University of Toronto, 25 Willcocks St., Toronto, Ontario, Canada
| | - Michael Wilton
- Department of Cell & Systems Biology, University of Toronto, 25 Willcocks St., Toronto, Ontario, Canada
| | - Jun Liu
- Department of Plant Pathology, University of California Davis, Davis, CA, United States of America
| | - Yulu C. Liu
- Leslie Dan Faculty of Pharmacy, Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Stephane Angers
- Leslie Dan Faculty of Pharmacy, Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Gitta Coaker
- Department of Plant Pathology, University of California Davis, Davis, CA, United States of America
| | - David S. Guttman
- Department of Cell & Systems Biology, University of Toronto, 25 Willcocks St., Toronto, Ontario, Canada
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Ontario, Canada
- * E-mail: (DSG); (DD)
| | - Darrell Desveaux
- Department of Cell & Systems Biology, University of Toronto, 25 Willcocks St., Toronto, Ontario, Canada
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Ontario, Canada
- * E-mail: (DSG); (DD)
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Dudnik A, Dudler R. Virulence determinants of Pseudomonas syringae strains isolated from grasses in the context of a small type III effector repertoire. BMC Microbiol 2014; 14:304. [PMID: 25472590 PMCID: PMC4262972 DOI: 10.1186/s12866-014-0304-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Accepted: 11/20/2014] [Indexed: 11/10/2022] Open
Abstract
Background Pseudomonas syringae is pathogenic to a large number of plant species. For host colonization and disease progression, strains of this bacterium utilize an array of type III-secreted effectors and other virulence factors, including small secreted molecules such as syringolin A, a peptide derivative that inhibits the eukaryotic proteasome. In strains colonizing dicotyledonous plants, the compound was demonstrated to suppress the salicylic-acid-dependent defense pathway. Here, we analyze virulence factors of three strains colonizing wheat (Triticum aestivum): P. syringae pathovar syringae (Psy) strains B64 and SM, as well as P. syringae BRIP34876. These strains have a relatively small repertoire of only seven to eleven type III secreted effectors (T3Es) and differ in their capacity to produce syringolin A. The aim of this study was to analyze the contribution of various known virulence factors in the context of a small T3E repertoire. Results We demonstrate that syringolin A production enhances disease symptom development upon direct infiltration of strains into wheat leaves. However, it is not universally required for colonization, as Psy SM, which lacks syringolin biosynthesis genes, reaches cell densities comparable to syringolin A producer P. syringae BRIP34876. Next, we show that despite the small set of T3E-encoding genes, the type III secretion system remains the key pathogenicity determinant in these strains, and that phenotypic effects of deleting T3E-coding genes become apparent only when multiple effectors are removed. Conclusions Whereas production of syringolin A is not required for successful colonization of wheat leaves by P. syringae strains, its production results in increased lesion formation. Despite the small number of known T3Es encoded by the analyzed strains, the type III secretion system is essential for endophytic growth of these strains. Electronic supplementary material The online version of this article (doi:10.1186/s12866-014-0304-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Alexey Dudnik
- Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, Zurich, 8008, Switzerland. .,Present address: Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kogle Allé 4, Hørsholm, 2970, Denmark.
| | - Robert Dudler
- Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, Zurich, 8008, Switzerland.
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Resistance inducers modulate Pseudomonas syringae pv. tomato strain DC3000 response in tomato plants. PLoS One 2014; 9:e106429. [PMID: 25244125 PMCID: PMC4171367 DOI: 10.1371/journal.pone.0106429] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Accepted: 07/30/2014] [Indexed: 01/01/2023] Open
Abstract
The efficacy of hexanoic acid (Hx) as an inducer of resistance in tomato plants against Pseudomonas syringae pv. tomato DC3000 was previously demonstrated, and the plant response was characterized. Because little is known about the reaction of the pathogen to this effect, the goal of the present work was to determine whether the changes in the plant defence system affect the pathogen behaviour. This work provides the first demonstration of the response of the pathogen to the changes observed in plants after Hx application in terms of not only the population size but also the transcriptional levels of genes involved in quorum sensing establishment and pathogenesis. Therefore, it is possible that Hx treatment attenuates the virulence and survival of bacteria by preventing or diminishing the appearance of symptoms and controlling the growth of the bacteria in the mesophyll. It is interesting to note that the gene transcriptional changes in the bacteria from the treated plants occur at the same time as the changes in the plants. Hx is able to alter bacteria pathogenesis and survival only when it is applied as a resistance inducer because the changes that it promotes in plants affect the bacteria.
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Transcriptional analysis of the global regulatory networks active in Pseudomonas syringae during leaf colonization. mBio 2014; 5:e01683-14. [PMID: 25182327 PMCID: PMC4173789 DOI: 10.1128/mbio.01683-14] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The plant pathogen Pseudomonas syringae pv. syringae B728a grows and survives on leaf surfaces and in the leaf apoplast of its host, bean (Phaseolus vulgaris). To understand the contribution of distinct regulators to B728a fitness and pathogenicity, we performed a transcriptome analysis of strain B728a and nine regulatory mutants recovered from the surfaces and interior of leaves and exposed to environmental stresses in culture. The quorum-sensing regulators AhlR and AefR influenced few genes in planta or in vitro. In contrast, GacS and a downstream regulator, SalA, formed a large regulatory network that included a branch that regulated diverse traits and was independent of plant-specific environmental signals and a plant signal-dependent branch that positively regulated secondary metabolite genes and negatively regulated the type III secretion system. SalA functioned as a central regulator of iron status based on its reciprocal regulation of pyoverdine and achromobactin genes and also sulfur uptake, suggesting a role in the iron-sulfur balance. RetS functioned almost exclusively to repress secondary metabolite genes when the cells were not on leaves. Among the sigma factors examined, AlgU influenced many more genes than RpoS, and most AlgU-regulated genes depended on RpoN. RpoN differentially impacted many AlgU- and GacS-activated genes in cells recovered from apoplastic versus epiphytic sites, suggesting differences in environmental signals or bacterial stress status in these two habitats. Collectively, our findings illustrate a central role for GacS, SalA, RpoN, and AlgU in global regulation in B728a in planta and a high level of plasticity in these regulators’ responses to distinct environmental signals. Leaves harbor abundant microorganisms, all of which must withstand challenges such as active plant defenses and a highly dynamic environment. Some of these microbes can influence plant health. Despite knowledge of individual regulators that affect the fitness or pathogenicity of foliar pathogens, our understanding of the relative importance of various global regulators to leaf colonization is limited. Pseudomonas syringae strain B728a is a plant pathogen and a good colonist of both the surfaces and interior of leaves. This study used global transcript profiles of strain B728a to investigate the complex regulatory network of putative quorum-sensing regulators, two-component regulators, and sigma factors in cells colonizing the leaf surface and leaf interior under stressful in vitro conditions. The results highlighted the value of evaluating these networks in planta due to the impact of leaf-specific environmental signals and suggested signal differences that may enable cells to differentiate surface versus interior leaf habitats.
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45
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Hung NB, Ramkumar G, Lee YH. An effector gene hopA1 influences on virulence, host specificity, and lifestyles of Pseudomonas cichorii JBC1. Res Microbiol 2014; 165:620-9. [PMID: 25127676 DOI: 10.1016/j.resmic.2014.08.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2014] [Revised: 08/05/2014] [Accepted: 08/05/2014] [Indexed: 11/30/2022]
Abstract
Pseudomonas cichorii is a devastating pathogen which infects a wide range of ornamental as well as agricultural crops worldwide. Characterization of virulence genes helps to understand pathogens' infection processes, which may lead to development of resistant crops. For functional validation of novel genes, we re-constructed pUCP18 vector with λ phage red operon and sacB gene (pUCP18_RedS), which simplified conventional marker exchange system. The effector gene hopA1 of P. cichorii JBC1 was marker exchanged with PCR product of kanamycin gene flanked by hopA1 flanking region using pUCP18_RedS. The virulence and internal growth of hopA1 defective mutant (ΔhopA1) in tomato seedlings was significantly reduced compared to wild type (WT) and hopA1 complemented strain (ΔhopA1::phopA1). The analysis on role of hopA1 in host range revealed that P. cichorii was hopA1-dependent to infect cabbage, tomato, soybean, hot pepper, and cucumber, but not melon and eggplant. Despite the similarity in growth pattern, the biofilm formation and swarming motility of ΔhopA1 were significantly reduced compared to WT and ΔhopA1::phopA1. The results of this study indicate that hopA1 plays a significant role not only in virulence and host specificity, but also motility and biofilm formation of P. cichorii which may influence the infection processes.
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Affiliation(s)
- Nguyen Bao Hung
- Division of Biotechnology, Chonbuk National University, 79 Gobong-ro, Iksan-si, Jeollabuk-do 570-752, Republic of Korea
| | - Gandhimani Ramkumar
- Division of Biotechnology, Chonbuk National University, 79 Gobong-ro, Iksan-si, Jeollabuk-do 570-752, Republic of Korea
| | - Yong Hoon Lee
- Division of Biotechnology, Chonbuk National University, 79 Gobong-ro, Iksan-si, Jeollabuk-do 570-752, Republic of Korea; Advanced Institute of Environment and Bioscience, and Plant Medical Research Center, Chonbuk National University, Republic of Korea.
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Melotto M, Panchal S, Roy D. Plant innate immunity against human bacterial pathogens. Front Microbiol 2014; 5:411. [PMID: 25157245 PMCID: PMC4127659 DOI: 10.3389/fmicb.2014.00411] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 07/21/2014] [Indexed: 11/13/2022] Open
Abstract
Certain human bacterial pathogens such as the enterohemorrhagic Escherichia coli and Salmonella enterica are not proven to be plant pathogens yet. Nonetheless, under certain conditions they can survive on, penetrate into, and colonize internal plant tissues causing serious food borne disease outbreaks. In this review, we highlight current understanding on the molecular mechanisms of plant responses against human bacterial pathogens and discuss salient common and contrasting themes of plant interactions with phytopathogens or human pathogens.
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Affiliation(s)
- Maeli Melotto
- Department of Plant Sciences, University of CaliforniaDavis, CA, USA
| | - Shweta Panchal
- Department of Biology, University of TexasArlington, TX, USA
| | - Debanjana Roy
- Department of Biology, University of TexasArlington, TX, USA
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Zimaro T, Thomas L, Marondedze C, Sgro GG, Garofalo CG, Ficarra FA, Gehring C, Ottado J, Gottig N. The type III protein secretion system contributes to Xanthomonas citri subsp. citri biofilm formation. BMC Microbiol 2014; 14:96. [PMID: 24742141 PMCID: PMC4021560 DOI: 10.1186/1471-2180-14-96] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Accepted: 04/09/2014] [Indexed: 11/19/2022] Open
Abstract
Background Several bacterial plant pathogens colonize their hosts through the secretion of effector proteins by a Type III protein secretion system (T3SS). The role of T3SS in bacterial pathogenesis is well established but whether this system is involved in multicellular processes, such as bacterial biofilm formation has not been elucidated. Here, the phytopathogen Xanthomonas citri subsp. citri (X. citri) was used as a model to gain further insights about the role of the T3SS in biofilm formation. Results The capacity of biofilm formation of different X. citri T3SS mutants was compared to the wild type strain and it was observed that this secretion system was necessary for this process. Moreover, the T3SS mutants adhered proficiently to leaf surfaces but were impaired in leaf-associated growth. A proteomic study of biofilm cells showed that the lack of the T3SS causes changes in the expression of proteins involved in metabolic processes, energy generation, exopolysaccharide (EPS) production and bacterial motility as well as outer membrane proteins. Furthermore, EPS production and bacterial motility were also altered in the T3SS mutants. Conclusions Our results indicate a novel role for T3SS in X. citri in the modulation of biofilm formation. Since this process increases X. citri virulence, this study reveals new functions of T3SS in pathogenesis.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Natalia Gottig
- Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas (IBR-CONICET) and Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Ocampo y Esmeralda, Rosario 2000, Argentina.
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Cardinale M. Scanning a microhabitat: plant-microbe interactions revealed by confocal laser microscopy. Front Microbiol 2014; 5:94. [PMID: 24639675 PMCID: PMC3945399 DOI: 10.3389/fmicb.2014.00094] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Accepted: 02/20/2014] [Indexed: 12/03/2022] Open
Abstract
No plant or cryptogam exists in nature without microorganisms associated with its tissues. Plants as microbial hosts are puzzles of different microhabitats, each of them colonized by specifically adapted microbiomes. The interactions with such microorganisms have drastic effects on the host fitness. Since the last 20 years, the combination of microscopic tools and molecular approaches contributed to new insights into microbe-host interactions. Particularly, confocal laser scanning microscopy (CLSM) facilitated the exploration of microbial habitats and allowed the observation of host-associated microorganisms in situ with an unprecedented accuracy. Here I present an overview of the progresses made in the study of the interactions between microorganisms and plants or plant-like organisms, focusing on the role of CLSM for the understanding of their significance. I critically discuss risks of misinterpretation when procedures of CLSM are not properly optimized. I also review approaches for quantitative and statistical analyses of CLSM images, the combination with other molecular and microscopic methods, and suggest the re-evaluation of natural autofluorescence. In this review, technical aspects were coupled with scientific outcomes, to facilitate the readers in identifying possible CLSM applications in their research or to expand their existing potential. The scope of this review is to highlight the importance of confocal microscopy in the study of plant-microbe interactions and also to be an inspiration for integrating microscopy with molecular techniques in future researches of microbial ecology.
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Affiliation(s)
- Massimiliano Cardinale
- Institute of Plant Sciences, University of GrazGraz, Austria
- Institute of Environmental Biotechnology, Graz University of TechnologyGraz, Austria
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Ralstonia solanacearum requires PopS, an ancient AvrE-family effector, for virulence and To overcome salicylic acid-mediated defenses during tomato pathogenesis. mBio 2013; 4:e00875-13. [PMID: 24281716 PMCID: PMC3870264 DOI: 10.1128/mbio.00875-13] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
During bacterial wilt of tomato, the plant pathogen Ralstonia solanacearum upregulates expression of popS, which encodes a type III-secreted effector in the AvrE family. PopS is a core effector present in all sequenced strains in the R. solanacearum species complex. The phylogeny of popS mirrors that of the species complex as a whole, suggesting that this is an ancient, vertically inherited effector needed for association with plants. A popS mutant of R. solanacearum UW551 had reduced virulence on agriculturally important Solanum spp., including potato and tomato plants. However, the popS mutant had wild-type virulence on a weed host, Solanum dulcamara, suggesting that some species can avoid the effects of PopS. The popS mutant was also significantly delayed in colonization of tomato stems compared to the wild type. Some AvrE-type effectors from gammaproteobacteria suppress salicylic acid (SA)-mediated plant defenses, suggesting that PopS, a betaproteobacterial ortholog, has a similar function. Indeed, the popS mutant induced significantly higher expression of tomato SA-triggered pathogenesis-related (PR) genes than the wild type. Further, pretreatment of roots with SA exacerbated the popS mutant virulence defect. Finally, the popS mutant had no colonization defect on SA-deficient NahG transgenic tomato plants. Together, these results indicate that this conserved effector suppresses SA-mediated defenses in tomato roots and stems, which are R. solanacearum’s natural infection sites. Interestingly, PopS did not trigger necrosis when heterologously expressed in Nicotiana leaf tissue, unlike the AvrE homolog DspEPcc from the necrotroph Pectobacterium carotovorum subsp. carotovorum. This is consistent with the differing pathogenesis modes of necrosis-causing gammaproteobacteria and biotrophic R. solanacearum. The type III-secreted AvrE effector family is widely distributed in high-impact plant-pathogenic bacteria and is known to suppress plant defenses for virulence. We characterized the biology of PopS, the only AvrE homolog made by the bacterial wilt pathogen Ralstonia solanacearum. To our knowledge, this is the first study of R. solanacearum effector function in roots and stems, the natural infection sites of this pathogen. Unlike the functionally redundant R. solanacearum effectors studied to date, PopS is required for full virulence and wild-type colonization of two natural crop hosts. R. solanacearum is a biotrophic pathogen that causes a nonnecrotic wilt. Consistent with this, PopS suppressed plant defenses but did not elicit cell death, unlike AvrE homologs from necrosis-causing plant pathogens. We propose that AvrE family effectors have functionally diverged to adapt to the necrotic or nonnecrotic lifestyle of their respective pathogens.
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Pérez-Pantoja D, Nikel PI, Chavarría M, de Lorenzo V. Endogenous stress caused by faulty oxidation reactions fosters evolution of 2,4-dinitrotoluene-degrading bacteria. PLoS Genet 2013; 9:e1003764. [PMID: 24009532 PMCID: PMC3757077 DOI: 10.1371/journal.pgen.1003764] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Accepted: 07/16/2013] [Indexed: 01/13/2023] Open
Abstract
Environmental strain Burkholderia sp. DNT mineralizes the xenobiotic compound 2,4-dinitrotoluene (DNT) owing to the catabolic dnt genes borne by plasmid DNT, but the process fails to promote significant growth. To investigate this lack of physiological return of such an otherwise complete metabolic route, cells were exposed to DNT under various growth conditions and the endogenous formation of reactive oxygen species (ROS) monitored in single bacteria. These tests revealed the buildup of a strong oxidative stress in the population exposed to DNT. By either curing the DNT plasmid or by overproducing the second activity of the biodegradation route (DntB) we could trace a large share of ROS production to the first reaction of the route, which is executed by the multicomponent dioxygenase encoded by the dntA gene cluster. Naphthalene, the ancestral substrate of the dioxygenase from which DntA has evolved, also caused significant ROS formation. That both the old and the new substrate brought about a considerable cellular stress was indicative of a still-evolving DntA enzyme which is neither optimal any longer for naphthalene nor entirely advantageous yet for growth of the host strain on DNT. We could associate endogenous production of ROS with likely error-prone repair mechanisms of DNA damage, and the ensuing stress-induced mutagenesis in cells exposed to DNT. It is thus plausible that the evolutionary roadmap for biodegradation of xenobiotic compounds like DNT was largely elicited by mutagenic oxidative stress caused by faulty reactions of precursor enzymes with novel but structurally related substrates-to-be. Many bacteria have acquired the capacity of metabolizing chemical compounds that have never been in the Biosphere before the onset of contemporary synthetic chemistry. However, the factors that shape the new metabolic properties of such microorganisms remain obscure. We examined the performance of a still-evolving metabolic pathway for biodegradation of 2,4-dinitrotoluene (DNT, an archetypal xenobiotic compound) borne by a Burkholderia strain isolated from soil in an ammunition plant. The biodegradation pathway likely arose from a precursor set of genes for catabolism of naphthalene (although Burkholderia does not degrade this compound any longer), and is now advancing towards the new substrate, DNT. We found that the action of the first enzyme of the biodegradation pathway, a Rieske-type dioxygenase, on the still-suboptimal substrate (DNT) generates a high level of endogenous reactive oxygen species. This, in turn, damages DNA and increases mutagenesis, ultimately resulting in the creation of novelty that may foster evolution of xenobiotic-degrading variants of the strain hosting the biodegradation pathway. The very metabolic problem thus somehow seems to stimulate the exploration of the solution space. Our data is fully consistent with the notion that stress caused by faulty dioxygenation of DNT accelerates the rate of bacterial evolution.
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Affiliation(s)
- Danilo Pérez-Pantoja
- Systems and Synthetic Biology Program, Centro Nacional de Biotecnología, CSIC, Campus de Cantoblanco, Madrid, Spain
| | - Pablo I. Nikel
- Systems and Synthetic Biology Program, Centro Nacional de Biotecnología, CSIC, Campus de Cantoblanco, Madrid, Spain
| | - Max Chavarría
- Systems and Synthetic Biology Program, Centro Nacional de Biotecnología, CSIC, Campus de Cantoblanco, Madrid, Spain
| | - Víctor de Lorenzo
- Systems and Synthetic Biology Program, Centro Nacional de Biotecnología, CSIC, Campus de Cantoblanco, Madrid, Spain
- * E-mail:
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