Chemoperception of Specific Amino Acids Controls Phytopathogenicity in Pseudomonas syringae pv. tomato

ABSTRACT Chemotaxis has been associated with the pathogenicity of bacteria in plants and was found to facilitate bacterial entry through stomata and wounds. However, knowledge regarding the plant signals involved in this process is scarce. We have addressed this issue using Pseudomonas syringae pv. tomato, which is a foliar pathogen that causes bacterial speck in tomato. We show that the chemoreceptor P. syringae pv. tomato PscA (PsPto-PscA) recognizes specifically and with high affinity l-Asp, l-Glu, and d-Asp. The mutation of the chemoreceptor gene largely reduced chemotaxis to these ligands but also altered cyclic di-GMP (c-di-GMP) levels, biofilm formation, and motility, pointing to cross talk between different chemosensory pathways. Furthermore, the PsPto-PscA mutant strain showed reduced virulence in tomato. Asp and Glu are the most abundant amino acids in plants and in particular in tomato apoplasts, and we hypothesize that this receptor may have evolved to specifically recognize these compounds to facilitate bacterial entry into the plant. Infection assays with the wild-type strain showed that the presence of saturating concentrations of d-Asp also reduced bacterial virulence. IMPORTANCE There is substantive evidence that chemotaxis is a key requisite for efficient pathogenesis in plant pathogens. However, information regarding particular bacterial chemoreceptors and the specific plant signal that they sense is scarce. Our work shows that the phytopathogenic bacterium Pseudomonas syringae pv. tomato mediates not only chemotaxis but also the control of pathogenicity through the perception of the plant abundant amino acids Asp and Glu. We describe the specificity of the perception of l- and d-Asp and l-Glu by the PsPto-PscA chemoreceptor and the involvement of this perception in the regulation of pathogenicity-related traits. Moreover, a saturating concentration of d-Asp reduces bacterial virulence, and we therefore propose that ligand-mediated interference of key chemoreceptors may be an alternative strategy to control virulence.

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Pseudomonas syringae AlgU Downregulates Flagellin Gene Expression, Helping Evade Plant Immunity

Journal of Bacteriology ◽

10.1128/jb.00418-19 ◽

2019 ◽

Vol 202 (4) ◽

Cited By ~ 1

Author(s):

Zhongmeng Bao ◽

Hai-Lei Wei ◽

Xing Ma ◽

Bryan Swingle

Keyword(s):

Gene Expression ◽

Pseudomonas Syringae ◽

Plant Pathogens ◽

Control Point ◽

Plant Colonization ◽

Compensatory Mechanisms ◽

Flagellin Gene ◽

Content Type ◽

Immune Systems ◽

Plant Infection

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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In planta bacterial multi-omics analysis illuminates regulatory principles underlying plant-pathogen interactions

10.1101/822932 ◽

2019 ◽

Cited By ~ 1

Author(s):

Tatsuya Nobori ◽

Yiming Wang ◽

Jingni Wu ◽

Sara Christina Stolze ◽

Yayoi Tsuda ◽

...

Keyword(s):

Gene Regulation ◽

Pseudomonas Syringae ◽

Protein Level ◽

Plant Pathogens ◽

Plant Immunity ◽

Bacterial Pathogen ◽

Bacterial Virulence ◽

In Planta ◽

Bacterial Gene ◽

Global Food Security

AbstractUnderstanding how gene expression is regulated in plant pathogens is crucial for pest control and thus global food security. An integrated understanding of bacterial gene regulation in the host is dependent on multi-omic datasets, but these are largely lacking. Here, we simultaneously characterized the transcriptome and proteome of a foliar bacterial pathogen, Pseudomonas syringae, in Arabidopsis thaliana and identified a number of bacterial processes influenced by plant immunity at the mRNA and the protein level. We found instances of both concordant and discordant regulation of bacterial mRNAs and proteins. Notably, the tip component of bacterial type III secretion system was selectively suppressed by the plant salicylic acid pathway at the protein level, suggesting protein-level targeting of the bacterial virulence system by plant immunity. Furthermore, gene co-expression analysis illuminated previously unknown gene regulatory modules underlying bacterial virulence and their regulatory hierarchy. Collectively, the integrated in planta bacterial omics approach provides molecular insights into multiple layers of bacterial gene regulation that contribute to bacterial growth in planta and elucidate the role of plant immunity in controlling pathogens.

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Identification of chemoreceptor proteins for amino acids involved in host plant infection in Pseudomonas syringae pv. tabaci 6605

Microbiological Research ◽

10.1016/j.micres.2021.126869 ◽

2021 ◽

pp. 126869

Author(s):

Stephany Angelia Tumewu ◽

Hidenori Matsui ◽

Mikihiro Yamamoto ◽

Yoshiteru Noutoshi ◽

Kazuhiro Toyoda ◽

...

Keyword(s):

Amino Acids ◽

Host Plant ◽

Pseudomonas Syringae ◽

Plant Infection

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Identification of themcpAandmcpMGenes, Encoding Methyl-Accepting Proteins Involved in Amino Acid and l-Malate Chemotaxis, and Involvement of McpM-Mediated Chemotaxis in Plant Infection by Ralstonia pseudosolanacearum (Formerly Ralstonia solanacearum Phylotypes I and III)

Applied and Environmental Microbiology ◽

10.1128/aem.01870-15 ◽

2015 ◽

Vol 81 (21) ◽

pp. 7420-7430 ◽

Cited By ~ 22

Author(s):

Akiko Hida ◽

Shota Oku ◽

Takeru Kawasaki ◽

Yutaka Nakashimada ◽

Takahisa Tajima ◽

...

Keyword(s):

Amino Acids ◽

Gene Deletion ◽

Pcr Analysis ◽

Deletion Mutants ◽

Wild Type ◽

Complete Collection ◽

Content Type ◽

Plant Infection ◽

Tomato Roots ◽

Ralstonia Pseudosolanacearum

ABSTRACTSequence analysis has revealed the presence of 22 putative methyl-accepting chemotaxis protein (mcp) genes in theRalstonia pseudosolanacearumGMI1000 genome. PCR analysis and DNA sequencing showed that the highly motileR. pseudosolanacearumstrain Ps29 possesses homologs of all 22R. pseudosolanacearumGMI1000mcpgenes. We constructed a complete collection of singlemcpgene deletion mutants ofR. pseudosolanacearumPs29 by unmarked gene deletion. Screening of the mutant collection revealed thatR. pseudosolanacearumPs29 mutants of RSp0507 and RSc0606 homologs were defective in chemotaxis tol-malate and amino acids, respectively. RSp0507 and RSc0606 homologs were designatedmcpMandmcpA. While wild-typeR. pseudosolanacearumstrain Ps29 displayed attraction to 16 amino acids, themcpAmutant showed no response to 12 of these amino acids and decreased responses to 4 amino acids. We constructedmcpAandmcpMdeletion mutants of highly virulentR. pseudosolanacearumstrain MAFF106611 to investigate the contribution of chemotaxis tol-malate and amino acids to tomato plant infection. Neither single mutant exhibited altered virulence for tomato plants when tested by root dip inoculation assays. In contrast, themcpMmutant (but not themcpAmutant) was significantly less infectious than the wild type when tested by a sand soak inoculation assay, which requires bacteria to locate and invade host roots from sand. Thus, McpM-mediated chemotaxis, possibly reflecting chemotaxis tol-malate, facilitatesR. pseudosolanacearummotility to tomato roots in sand.

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Comparative genomic insights into the epidemiology and virulence of plant pathogenic pseudomonads from Turkey

Microbial Genomics ◽

10.1099/mgen.0.000585 ◽

2021 ◽

Vol 7 (7) ◽

Author(s):

Marcus M. Dillon ◽

Tatiana Ruiz-Bedoya ◽

Cedoljub Bundalovic-Torma ◽

Kevin M. Guttman ◽

Haejin Kwak ◽

...

Keyword(s):

Pseudomonas Syringae ◽

Type Species ◽

Plant Pathogens ◽

Molecular Mechanisms ◽

Comparative Genomic ◽

Complex Nature ◽

Growth Promoter ◽

Content Type ◽

Link Type ◽

Species Complexes

Pseudomonas is a highly diverse genus that includes species that cause disease in both plants and animals. Recently, pathogenic pseudomonads from the Pseudomonas syringae and Pseudomonas fluorescens species complexes have caused significant outbreaks in several agronomically important crops in Turkey, including tomato, citrus, artichoke and melon. We characterized 169 pathogenic Pseudomonas strains associated with recent outbreaks in Turkey via multilocus sequence analysis and whole-genome sequencing, then used comparative and evolutionary genomics to characterize putative virulence mechanisms. Most of the isolates are closely related to other plant pathogens distributed among the primary phylogroups of P. syringae , although there are significant numbers of P. fluorescens isolates, which is a species better known as a rhizosphere-inhabiting plant-growth promoter. We found that all 39 citrus blast pathogens cluster in P. syringae phylogroup 2, although strains isolated from the same host do not cluster monophyletically, with lemon, mandarin orange and sweet orange isolates all being intermixed throughout the phylogroup. In contrast, 20 tomato pith pathogens are found in two independent lineages: one in the P. syringae secondary phylogroups, and the other from the P. fluorescens species complex. These divergent pith necrosis strains lack characteristic virulence factors like the canonical tripartite type III secretion system, large effector repertoires and the ability to synthesize multiple bacterial phytotoxins, suggesting they have alternative molecular mechanisms to cause disease. These findings highlight the complex nature of host specificity among plant pathogenic pseudomonads.

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UV Light Inactivation of Human and Plant Pathogens in Unfiltered Surface Irrigation Water

Applied and Environmental Microbiology ◽

10.1128/aem.02964-13 ◽

2013 ◽

Vol 80 (3) ◽

pp. 849-854 ◽

Cited By ~ 19

Author(s):

Lisa A. Jones ◽

Randy W. Worobo ◽

Christine D. Smart

Keyword(s):

Surface Water ◽

Pseudomonas Syringae ◽

Plant Pathogens ◽

Fruits And Vegetables ◽

Uv Light ◽

Phytophthora Capsici ◽

Treatment Options ◽

Plant Diseases ◽

Processing Unit ◽

Content Type

ABSTRACTFruit and vegetable growers continually battle plant diseases and food safety concerns. Surface water is commonly used in the production of fruits and vegetables and can harbor both human- and plant-pathogenic microorganisms that can contaminate crops when used for irrigation or other agricultural purposes. Treatment methods for surface water are currently limited, and there is a need for suitable treatment options. A liquid-processing unit that uses UV light for the decontamination of turbid juices was analyzed for its efficacy in the treatment of surface waters contaminated with bacterial or oomycete pathogens, i.e.,Escherichia coli,Salmonella enterica,Listeria monocytogenes,Clavibacter michiganensissubsp.michiganensis,Pseudomonas syringaepv. tomato, andPhytophthora capsici. Five-strain cocktails of each pathogen, containing approximately 108or 109CFU/liter for bacteria or 104or 105zoospores/liter forPh. capsici, were inoculated into aliquots of two turbid surface water irrigation sources and processed with the UV unit. Pathogens were enumerated before and after treatment. In general, as the turbidity of the water source increased, the effectiveness of the UV treatment decreased, but in all cases, 99.9% or higher inactivation was achieved. Log reductions ranged from 10.0 to 6.1 and from 5.0 to 4.2 for bacterial pathogens andPh. capsici, respectively.

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Dual Role of Auxin in Regulating Plant Defense and Bacterial Virulence Gene Expression During Pseudomonas syringae PtoDC3000 Pathogenesis

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-02-20-0047-r ◽

2020 ◽

Vol 33 (8) ◽

pp. 1059-1071 ◽

Cited By ~ 3

Author(s):

Arnaud T. Djami-Tchatchou ◽

Gregory A. Harrison ◽

Chris P. Harper ◽

Renhou Wang ◽

Michael J. Prigge ◽

...

Keyword(s):

Gene Expression ◽

Pseudomonas Syringae ◽

Bacterial Growth ◽

Plant Pathogens ◽

Virulence Gene ◽

Bacterial Virulence ◽

Auxin Signaling ◽

Host Defenses ◽

In Planta ◽

Virulence Gene Expression

Modification of host hormone biology is a common strategy used by plant pathogens to promote disease. For example, the bacterial pathogen strain Pseudomonas syringae DC3000 (PtoDC3000) produces the plant hormone auxin (indole-3-acetic acid [IAA]) to promote PtoDC3000 growth in plant tissue. Previous studies suggest that auxin may promote PtoDC3000 pathogenesis through multiple mechanisms, including both suppression of salicylic acid (SA)-mediated host defenses and via an unknown mechanism that appears to be independent of SA. To test if host auxin signaling is important during pathogenesis, we took advantage of Arabidopsis thaliana lines impaired in either auxin signaling or perception. We found that disruption of auxin signaling in plants expressing an inducible dominant axr2-1 mutation resulted in decreased bacterial growth and that this phenotype was suppressed by introducing the sid2-2 mutation, which impairs SA synthesis. Thus, host auxin signaling is required for normal susceptibility to PtoDC3000 and is involved in suppressing SA-mediated defenses. Unexpectedly, tir1 afb1 afb4 afb5 quadruple-mutant plants lacking four of the six known auxin coreceptors that exhibit decreased auxin perception, supported increased levels of bacterial growth. This mutant exhibited elevated IAA levels and reduced SA-mediated defenses, providing additional evidence that auxin promotes disease by suppressing host defense. We also investigated the hypothesis that IAA promotes PtoDC3000 virulence through a direct effect on the pathogen and found that IAA modulates expression of virulence genes, both in culture and in planta. Thus, in addition to suppressing host defenses, IAA acts as a microbial signaling molecule that regulates bacterial virulence gene expression.

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Sensory Repertoire of Bacterial Chemoreceptors

Microbiology and Molecular Biology Reviews ◽

10.1128/mmbr.00033-17 ◽

2017 ◽

Vol 81 (4) ◽

Cited By ~ 64

Author(s):

Álvaro Ortega ◽

Igor B. Zhulin ◽

Tino Krell

Keyword(s):

Model Organisms ◽

Signal Recognition ◽

Signaling Mechanism ◽

Content Type ◽

Future Studies ◽

Major Mode ◽

Bacterial Chemoreceptors ◽

Different Types ◽

Chemosensory Pathways ◽

Genome Analyses

SUMMARY Chemoreceptors in bacteria detect a variety of signals and feed this information into chemosensory pathways that represent a major mode of signal transduction. The five chemoreceptors from Escherichia coli have served as traditional models in the study of this protein family. Genome analyses revealed that many bacteria contain much larger numbers of chemoreceptors with broader sensory capabilities. Chemoreceptors differ in topology, sensing mode, cellular location, and, above all, the type of ligand binding domain (LBD). Here, we highlight LBD diversity using well-established and emerging model organisms as well as genomic surveys. Nearly a hundred different types of protein domains that are found in chemoreceptor sequences are known or predicted LBDs, but only a few of them are ubiquitous. LBDs of the same class recognize different ligands, and conversely, the same ligand can be recognized by structurally different LBDs; however, recent studies began to reveal common characteristics in signal-LBD relationships. Although signals can stimulate chemoreceptors in a variety of different ways, diverse LBDs appear to employ a universal transmembrane signaling mechanism. Current and future studies aim to establish relationships between LBD types, the nature of signals that they recognize, and the mechanisms of signal recognition and transduction.

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Chp8, a Diguanylate Cyclase from Pseudomonas syringae pv. Tomato DC3000, Suppresses the Pathogen-Associated Molecular Pattern Flagellin, Increases Extracellular Polysaccharides, and Promotes Plant Immune Evasion

mBio ◽

10.1128/mbio.01168-14 ◽

2014 ◽

Vol 5 (3) ◽

Cited By ~ 27

Author(s):

Christoph Engl ◽

Christopher J. Waite ◽

Joseph F. McKenna ◽

Mark H. Bennett ◽

Thorsten Hamann ◽

...

Keyword(s):

Pseudomonas Syringae ◽

Plant Pathogen ◽

Crop Yields ◽

Economic Losses ◽

Extracellular Polysaccharides ◽

Content Type ◽

Global Food Security ◽

Plant Infection ◽

Molecular Pattern ◽

Global Food

ABSTRACTThe bacterial plant pathogenPseudomonas syringaecauses disease in a wide range of plants. The associated decrease in crop yields results in economic losses and threatens global food security. Competition exists between the plant immune system and the pathogen, the basic principles of which can be applied to animal infection pathways.P. syringaeuses a type III secretion system (T3SS) to deliver virulence factors into the plant that promote survival of the bacterium. TheP. syringaeT3SS is a product of the hypersensitive response and pathogenicity (hrp) and hypersensitive response and conserved (hrc) gene cluster, which is strictly controlled by the codependent enhancer-binding proteins HrpR and HrpS. Through a combination of bacterial gene regulation and phenotypic studies, plant infection assays, and plant hormone quantifications, we now report that Chp8 (i) is embedded in the Hrp regulon and expressed in response to plant signals and HrpRS, (ii) is a functional diguanylate cyclase, (iii) decreases the expression of the major pathogen-associated molecular pattern (PAMP) flagellin and increases extracellular polysaccharides (EPS), and (iv) impacts the salicylic acid/jasmonic acid hormonal immune response and disease progression. We propose that Chp8 expression dampens PAMP-triggered immunity during early plant infection.IMPORTANCEThe global demand for food is projected to rise by 50% by 2030 and, as such, represents one of the major challenges of the 21st century, requiring improved crop management. Diseases caused by plant pathogens decrease crop yields, result in significant economic losses, and threaten global food security. Gaining mechanistic insights into the events at the plant-pathogen interface and employing this knowledge to make crops more resilient is one important strategy for improving crop management. Plant-pathogen interactions are characterized by the sophisticated interplay between plant immunity elicited upon pathogen recognition and immune evasion by the pathogen. Here, we identify Chp8 as a contributor to the major effort of the plant pathogenPseudomonas syringaepv. tomato DC3000 to evade immune responses of the plant.

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Dual role of auxin in regulating plant defense and bacterial virulence gene expression during Pseudomonas syringae PtoDC3000 pathogenesis

10.1101/2019.12.29.881581 ◽

2019 ◽

Author(s):

Arnaud T. Djami-Tchatchou ◽

Gregory A. Harrison ◽

Chris P. Harper ◽

Renhou Wang ◽

Michael J. Prigge ◽

...

Keyword(s):

Gene Expression ◽

Pseudomonas Syringae ◽

Bacterial Growth ◽

Plant Pathogens ◽

Virulence Gene ◽

Bacterial Virulence ◽

Auxin Signaling ◽

Host Defenses ◽

In Planta ◽

Virulence Gene Expression

ABSTRACTModification of host hormone biology is a common strategy used by plant pathogens to promote disease. For example, the bacterial pathogen Pseudomonas syringae strain PtoDC3000 produces the plant hormone auxin (Indole-3-acetic acid, or IAA) to promote PtoDC3000 growth in plant tissue. Previous studies suggest that auxin may promote PtoDC3000 pathogenesis through multiple mechanisms, including both suppression of salicylic acid (SA)-mediated host defenses and via an unknown mechanism that appears to be independent of SA. To test if host auxin signaling is important during pathogenesis, we took advantage of Arabidopsis thaliana lines impaired in either auxin signaling or perception. We found that disruption of auxin signaling in plants expressing an inducible dominant axr2-1 mutation resulted in decreased bacterial growth, demonstrating that host auxin signaling is required for normal susceptibility to PtoDC3000, and this phenotype was dependent on SA-mediated defenses. However, despite exhibiting decreased auxin perception, tir1 afb1 afb4 afb5 quadruple mutant plants lacking four of the six known auxin co-receptors supported increased levels of bacterial growth. This mutant also exhibited elevated IAA levels, suggesting that the increased IAA in these plants may promote PtoDC3000 growth independent of host auxin signaling, perhaps through a direct effect on the pathogen. In support of this, we found that IAA directly impacted the pathogen, by modulating expression of bacterial virulence genes, both in liquid culture and in planta. Thus, in addition to suppressing host defenses, IAA acts as a microbial signaling molecule that regulates bacterial virulence gene expression.

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