Recombinant Erwinia carotovora subsp. atroseptica Disulfide bond formation protein B (dsbB)

What is the structural composition of Erwinia carotovora subsp. atroseptica dsbB protein?

Recombinant Erwinia carotovora subsp. atroseptica dsbB protein (UniProt ID: Q6D4M8) is a full-length protein consisting of 176 amino acids with the sequence: MLRFLNRCSRGRGAWLLLAFTALALELTALYFQHVMLLKPCVLCIYQRSALWGVFAAGIV GAIAPSSLLRYPAIALWIYSSYEGIRLAWKHTDILLNPSPFTTCDFFVSFPSWLPLDKWL PAIFNATGDCSERQWSFLSMEMPQWLLGIFAAYLLIAVLVLIAQPFRSKRRDLFSR . As a membrane protein, dsbB contains transmembrane domains that anchor it to the bacterial membrane. Structurally, dsbB proteins typically contain four transmembrane segments and two periplasmic loops with conserved cysteine residues that are essential for its oxidoreductase function. For detailed structural analysis, researchers should employ membrane protein crystallography techniques or cryo-electron microscopy to resolve its three-dimensional structure, taking into account the challenges associated with membrane protein structural determination. Analysis of the sequence reveals cysteine residues that likely participate in the catalytic activity and transmembrane regions that can be predicted using algorithms such as TMHMM or Phobius.

How is dsbB protein typically expressed and purified for research applications?

Expression and purification of recombinant dsbB protein from Erwinia carotovora subsp. atroseptica typically employs an E. coli expression system, as indicated in product information . For optimal expression, researchers should use E. coli BL21(DE3) strain with a specialized vector containing an N-terminal His-tag for subsequent affinity purification . The His-tag approach allows for efficient single-step purification using nickel or cobalt affinity chromatography. Due to its membrane-associated nature, expression protocols should incorporate specialized detergents during cell lysis and purification to maintain protein solubility and structural integrity. Typically, induction with IPTG at lower temperatures (16-20°C) helps prevent inclusion body formation and maintain proper folding of membrane proteins. Following affinity chromatography, size exclusion chromatography can be employed to enhance purity. Researchers should verify purification success through SDS-PAGE analysis, with the goal of achieving greater than 90% purity as noted for commercial preparations . Activity assays should be performed post-purification to ensure the protein retains its functional characteristics.

What are the optimal storage conditions for maintaining dsbB protein activity?

Optimal storage conditions for maintaining the activity of recombinant Erwinia carotovora subsp. atroseptica dsbB protein involve careful consideration of buffer composition, temperature, and handling protocols. According to product information, the purified protein should be stored in a Tris/PBS-based buffer with 6% trehalose at pH 8.0 . For long-term storage, aliquoting the protein and maintaining it at -20°C or preferably -80°C is recommended . The addition of 5-50% glycerol (with 50% being typical) as a cryoprotectant helps prevent protein denaturation during freeze-thaw cycles . It is crucial to avoid repeated freeze-thaw cycles, as these can significantly reduce protein activity. For working stocks, storage at 4°C for up to one week is acceptable . Prior to use, centrifuge the vial briefly to ensure all contents are at the bottom. For reconstitution of lyophilized preparations, use deionized sterile water to reach a concentration of 0.1-1.0 mg/mL . Researchers should implement regular activity assays after extended storage periods to verify that protein function has been maintained and adjust storage protocols based on empirical stability data.

How can researchers assess the disulfide bond formation activity of recombinant dsbB in vitro?

To assess the disulfide bond formation activity of recombinant Erwinia carotovora subsp. atroseptica dsbB protein in vitro, researchers should implement a multi-faceted approach focusing on its oxidoreductase function. A standard assay involves monitoring the oxidation of artificial substrates containing free thiol groups using spectrophotometric methods. For example, the reduction of ubiquinone can be measured by following the decrease in absorbance at 275 nm, which correlates with dsbB activity. Alternatively, researchers can employ fluorescence-based assays using substrates that exhibit different fluorescent properties in reduced versus oxidized states. For more direct physiological relevance, the ability of purified dsbB to reoxidize reduced DsbA (its natural partner in the disulfide bond formation pathway) can be evaluated using gel shift assays that distinguish between oxidized and reduced forms of DsbA. To confirm specificity, control experiments should include heat-inactivated dsbB protein and known inhibitors of disulfide bond formation pathways. When setting up these assays, it's essential to maintain anaerobic conditions to prevent non-enzymatic oxidation of substrates by atmospheric oxygen, which could confound results. This comprehensive approach ensures accurate assessment of dsbB's catalytic activity.

What experimental approaches can be used to study dsbB's role in bacterial virulence?

To investigate dsbB's role in Erwinia carotovora virulence, researchers should employ a comprehensive strategy combining genetic, biochemical, and infection model approaches. The foundation of such studies would be the creation of precise dsbB knockout mutants using techniques such as lambda Red recombineering or CRISPR-Cas9 genome editing in E. carotovora. These mutants should be complemented with wild-type dsbB to confirm phenotypic changes are specifically due to dsbB deletion. Given that Erwinia carotovora is known to infect both plant hosts and use Drosophila as a vector , researchers should assess virulence using both plant infection models (e.g., potato tuber maceration assays) and Drosophila oral infection models. For plant virulence, measure parameters such as tissue maceration, production of plant cell wall-degrading enzymes (PCWDEs), and bacterial proliferation in plant tissue. In Drosophila models, assess bacterial loads in the gut, gut morphology changes, and host survival rates . Since virulence in Erwinia is known to be regulated by quorum sensing , examine whether dsbB affects the production or sensing of acyl-homoserine lactone (AHL) signals using LC-MS detection methods and reporter strain assays. Additionally, investigate whether dsbB affects the proper folding and activity of known virulence factors by performing comparative proteomic analysis of secreted proteins from wild-type and dsbB mutant strains.

How does dsbB function within the bacterial membrane, and what techniques can be used to study its topology?

Studying the membrane topology and functional orientation of Erwinia carotovora subsp. atroseptica dsbB requires specialized approaches for membrane protein analysis. To determine membrane topology, researchers should consider implementing a combination of computational prediction and experimental verification. Begin with in silico prediction using algorithms like TMHMM, Phobius, or TOPCONS to identify potential transmembrane domains based on the amino acid sequence. For experimental verification, several techniques are recommended: (1) PhoA/LacZ fusion analysis, where fragments of dsbB are fused to reporters that function only in specific cellular compartments; (2) Substituted cysteine accessibility method (SCAM), which involves introducing cysteine residues at various positions and assessing their accessibility to membrane-impermeable thiol-reactive reagents; (3) Protease protection assays, where the protein's susceptibility to proteolytic digestion from either side of the membrane is evaluated; and (4) Immunofluorescence microscopy with domain-specific antibodies under permeabilizing and non-permeabilizing conditions. For studying functional aspects within the membrane, reconstitution into proteoliposomes followed by activity assays can provide insights into how the lipid environment affects dsbB function. Additionally, cross-linking studies coupled with mass spectrometry can identify proximal interaction partners within the membrane environment.

What expression systems yield the highest functional activity for recombinant dsbB protein?

For optimal expression of functionally active recombinant Erwinia carotovora subsp. atroseptica dsbB protein, researchers should systematically evaluate multiple expression systems with consideration for the protein's membrane-associated nature. While E. coli BL21(DE3) is commonly used and has been reported for dsbB expression , several modifications can enhance functional yield. Researchers should consider using specialized E. coli strains like C41(DE3) or C43(DE3), which are engineered specifically for membrane protein expression and minimize toxicity issues. For vector design, incorporating a mild promoter (such as pBAD or trc rather than strong T7) allows for more controlled expression rates, often resulting in better membrane integration and folding. The choice of fusion tag is critical; while His-tags are convenient for purification , other options like Mistic or SUMO fusions can improve membrane protein solubility and folding. For optimal induction conditions, researchers should test various temperatures (16-30°C), inducer concentrations, and induction durations through systematic optimization experiments. In cases where E. coli yields insufficient functional protein, alternative expression hosts such as Lactococcus lactis or insect cell systems using baculovirus vectors may prove advantageous for membrane proteins. For each system, functional activity should be quantitatively assessed using disulfide oxidoreductase activity assays rather than relying solely on expression level measurements.

How can researchers troubleshoot poor solubility issues when working with recombinant dsbB?

Addressing poor solubility of recombinant Erwinia carotovora subsp. atroseptica dsbB protein requires a systematic troubleshooting approach focused on both expression and extraction conditions. Since dsbB is a membrane protein, conventional solubility enhancement techniques must be adapted accordingly. First, optimize cellular expression conditions by reducing induction temperature (16-20°C), lowering inducer concentration, and extending induction time to allow proper membrane integration. For extraction and purification, evaluate a panel of detergents with varying properties: mild non-ionic detergents (DDM, LMNG), zwitterionic detergents (LDAO, FC-12), or mixed micelle systems. Perform small-scale extractions with different detergent concentrations (typically 1-2% for extraction, 0.05-0.1% for purification) and assess solubilization efficiency by Western blotting. If conventional detergents prove insufficient, consider newer solubilization approaches like styrene-maleic acid copolymer (SMA) lipid particles (SMALPs) or nanodiscs, which maintain the native lipid environment around the protein. Addition of stabilizing agents such as glycerol (10-20%), specific lipids (E. coli lipid extract), or cholesterol hemisuccinate can significantly improve stability after extraction. For proteins that remain recalcitrant to solubilization, fusion partner approaches (such as SUMO or MBP tags with specific solubility-enhancing properties) may prove beneficial. Throughout the optimization process, monitor not just protein presence by SDS-PAGE but also functional activity using appropriate enzymatic assays to ensure the solubilized protein maintains its native conformation.

What controls should be included when studying dsbB interactions with substrate proteins?

When investigating interactions between Erwinia carotovora subsp. atroseptica dsbB and its potential substrate proteins, researchers must implement a comprehensive set of controls to ensure specificity and biological relevance. For in vitro interaction studies such as pull-down assays or surface plasmon resonance (SPR), essential negative controls include: (1) A non-related membrane protein expressed and purified under identical conditions to rule out detergent or tag-mediated binding artifacts; (2) Denatured dsbB protein to distinguish between specific conformational interactions versus non-specific binding; and (3) Competition assays with known dsbB substrates or inhibitors to demonstrate binding site specificity. Positive controls should include known interacting partners from closely related bacterial systems, such as DsbA, which receives electrons from DsbB in the disulfide bond formation pathway. For in vivo interaction studies using techniques like bacterial two-hybrid systems or co-immunoprecipitation, controls should include: (1) Expression level verification of both bait and prey proteins to ensure comparable levels across experiments; (2) Subcellular localization confirmation to verify proper membrane integration of dsbB; and (3) Cysteine-to-serine mutants of the conserved redox-active sites in dsbB to differentiate between redox-dependent and structural interactions. When examining functional consequences of these interactions, researchers should assess the redox states of candidate substrate proteins in wild-type versus dsbB knockout strains, specifically analyzing the formation of disulfide bonds using non-reducing versus reducing SDS-PAGE conditions or mass spectrometry-based approaches.

How can researchers investigate the relationship between dsbB and bacterial quorum sensing systems?

To investigate potential connections between Erwinia carotovora subsp. atroseptica dsbB and quorum sensing systems, researchers should implement a multi-level experimental approach that examines both regulatory relationships and functional interdependencies. Since Erwinia carotovora utilizes acyl-homoserine lactone (AHL)-based quorum sensing to regulate virulence factors , begin by examining whether dsbB expression is regulated by quorum sensing. This can be accomplished by constructing transcriptional fusions of the dsbB promoter region to reporter genes (e.g., lacZ, gfp) and measuring expression in wild-type bacteria versus mutants lacking key quorum sensing components (expI, expR1, expR2) . Complement these studies by performing qRT-PCR analysis of dsbB transcript levels in response to exogenous AHLs or in quorum sensing mutant backgrounds. Conversely, investigate whether dsbB affects quorum sensing by comparing AHL production (using LC-MS/MS quantification) and quorum sensing-dependent gene expression in wild-type versus dsbB knockout strains. Since proper folding of proteins involved in AHL synthesis or detection might depend on functional disulfide bond formation, analyze the redox states of key quorum sensing proteins in the presence and absence of functional dsbB. Additionally, examine whether dsbB is required for the production of quorum sensing-regulated virulence factors such as plant cell wall-degrading enzymes (PCWDEs) and the Erwinia virulence factor (Evf) by conducting enzymatic activity assays and infection studies with dsbB mutants. This comprehensive approach will reveal whether dsbB and quorum sensing pathways intersect at regulatory levels, functional levels, or both.

What methods are recommended for studying dsbB's role in bacterial responses to environmental stresses?

To comprehensively evaluate the role of Erwinia carotovora subsp. atroseptica dsbB in environmental stress responses, researchers should implement a multi-faceted experimental strategy combining genetics, physiology, and molecular approaches. Begin by constructing a clean dsbB deletion mutant and complemented strain, then subject these strains along with the wild-type to a systematic panel of environmental stresses relevant to the bacterium's lifecycle: oxidative stress (H₂O₂, cumene hydroperoxide), temperature stress (heat shock, cold shock), pH extremes, osmotic stress, and antimicrobial compounds. For each stress condition, perform quantitative survival assays and growth curve analyses to identify specific sensitivities in the dsbB mutant. To understand the molecular basis of any observed phenotypes, conduct comparative transcriptomics (RNA-seq) and proteomics analyses of wild-type and dsbB mutant strains under both standard and stress conditions, focusing on changes in stress-responsive gene networks. For redox-related stresses, employ redox-sensitive fluorescent probes to measure intracellular redox potential changes in real-time, and perform non-reducing SDS-PAGE analysis to detect changes in disulfide bond formation patterns of periplasmic proteins. Since dsbB is involved in disulfide bond formation, assess the activity and folding status of specific periplasmic enzymes known to contain disulfide bonds and participate in stress responses. Finally, determine whether stress conditions alter the expression or activity of dsbB itself using promoter-reporter fusions and direct enzyme activity assays, which would indicate a regulatory feedback mechanism in stress response pathways.

What techniques can be used to identify protein partners that interact with dsbB in vivo?

To identify the interactome of Erwinia carotovora subsp. atroseptica dsbB protein in vivo, researchers should employ complementary approaches that overcome the challenges associated with studying membrane protein interactions. Begin with in vivo crosslinking using membrane-permeable crosslinkers like formaldehyde or DSP (dithiobis(succinimidyl propionate)), followed by affinity purification of His-tagged dsbB and mass spectrometry analysis of co-purified proteins. For higher specificity, implement proximity-based labeling techniques such as BioID or APEX2, where dsbB is fused to a biotin ligase or peroxidase that biotinylates nearby proteins, allowing for subsequent streptavidin-based purification and identification. Bacterial two-hybrid systems specifically optimized for membrane proteins, such as BACTH (Bacterial Adenylate Cyclase Two-Hybrid) or split-ubiquitin systems, can be used to verify specific interactions with candidate partners. For a focused analysis of the disulfide exchange pathway, trap mixed disulfide intermediates between dsbB and its substrates by using active site cysteine mutants that prevent completion of the disulfide exchange reaction, followed by non-reducing SDS-PAGE and mass spectrometry. Complement these approaches with comparative proteomic analysis of wild-type versus dsbB mutant strains, focusing on changes in the redox states of periplasmic proteins using differential thiol labeling techniques. For each identified interaction, validation should include co-immunoprecipitation with specific antibodies and functional assays demonstrating the physiological relevance of the interaction. This comprehensive strategy will reveal both stable binding partners and transient enzymatic substrates of dsbB in its native cellular context.

How can researchers overcome expression challenges for membrane proteins like dsbB?

Overcoming the challenges associated with expressing membrane proteins like Erwinia carotovora subsp. atroseptica dsbB requires a multi-faceted approach addressing the complex requirements for proper membrane insertion, folding, and function. Researchers should first optimize expression vector design by incorporating features that mitigate toxicity and improve membrane integration. These include using low-copy number plasmids, tightly regulated inducible promoters (such as rhamnose or arabinose-inducible systems rather than stronger IPTG-inducible systems), and optimized translation initiation regions. For E. coli expression, specialized strains like C41(DE3), C43(DE3), or Lemo21(DE3) are engineered specifically for membrane protein expression and should be tested alongside conventional BL21(DE3) strains . Optimize induction conditions by testing various temperatures (typically 16-25°C is better than 37°C for membrane proteins), inducer concentrations (often lower is better), and induction times (extended overnight induction at lower temperatures). Co-expression with molecular chaperones (GroEL/GroES, DnaK/DnaJ) or proteins that facilitate membrane insertion (YidC) can significantly improve functional yields. For proteins that remain difficult to express in E. coli, alternative hosts such as Lactococcus lactis, Bacillus subtilis, or eukaryotic systems like yeast (P. pastoris) or insect cells may provide better results due to differences in membrane composition and protein processing machinery. Throughout optimization, monitor not just total protein levels but also the proportion of correctly folded protein using activity assays specific to dsbB function, as high expression levels do not necessarily correlate with functional protein.

What strategies can be employed to improve the yield of functional dsbB protein?

To maximize the yield of functional Erwinia carotovora subsp. atroseptica dsbB protein, researchers should implement a comprehensive optimization strategy addressing each stage of the production pipeline. Beyond optimizing expression conditions as described previously, significant improvements can be achieved during cell lysis and protein extraction phases. Use gentle lysis methods such as enzymatic lysis with lysozyme combined with mild detergents rather than harsh sonication, which can denature membrane proteins. During membrane solubilization, systematically screen a panel of detergents (DDM, LMNG, LDAO, etc.) at different concentrations to identify optimal conditions that extract dsbB while maintaining its native conformation. The addition of specific lipids (E. coli lipid extract or defined phospholipid mixtures) during solubilization can provide a more native-like environment and enhance stability. For purification, implement a two-step approach using immobilized metal affinity chromatography via the His-tag followed by size exclusion chromatography to remove aggregates and misfolded species. Throughout purification, maintain an excess of the optimal detergent above its critical micelle concentration and consider adding stabilizing agents such as glycerol (10-20%), trehalose , specific lipids, or cholesterol. If conventional approaches yield insufficient functional protein, explore newer technologies such as SMALPs (styrene-maleic acid lipid particles) or nanodiscs, which extract membrane proteins with their surrounding lipid environment intact. For long-term stability, optimize buffer conditions (pH, ionic strength, specific ions) using thermal stability assays to identify formulations that maximize protein half-life. At each step, monitor not just protein purity by SDS-PAGE but also functional activity using appropriate enzymatic assays to ensure that purification conditions preserve the protein's native structure and activity.

How can researchers effectively generate and validate dsbB knockout mutants for functional studies?

Generating and validating dsbB knockout mutants in Erwinia carotovora subsp. atroseptica requires a systematic approach to ensure clean deletion and proper phenotypic characterization. For mutant construction, researchers should implement modern genome editing techniques such as lambda Red recombineering or CRISPR-Cas9 systems, which allow precise deletion without leaving selection markers or scars that might affect neighboring gene expression. Design deletion constructs that remove the coding sequence while preserving regulatory elements of adjacent genes. To address potential polar effects, complement the mutation by expressing dsbB from its native promoter on a low-copy plasmid or by reinserting it at a neutral site in the chromosome. For rigorous validation, perform multiple confirmatory analyses: (1) PCR verification with primers flanking the deletion site; (2) RT-PCR to confirm absence of dsbB transcript; (3) Western blotting with anti-dsbB antibodies to verify protein absence; and (4) Whole genome sequencing to rule out off-target mutations that might confound phenotypic analyses. For functional validation, assess known dsbB-dependent phenotypes such as sensitivity to oxidizing agents (e.g., copper ions, hydrogen peroxide) and reducing agents (e.g., DTT). Examine the redox states of periplasmic proteins known to contain structural disulfide bonds using non-reducing versus reducing SDS-PAGE, expecting to see mobility shifts indicative of improper disulfide bond formation in the mutant. Additionally, assess virulence factor production and activity, such as plant cell wall degrading enzymes and the Erwinia virulence factor (Evf) , as these may require proper disulfide bond formation for functionality. Complementation tests should restore wild-type phenotypes, confirming that observed defects are specifically due to dsbB deletion rather than polar or secondary effects.

What experimental models are appropriate for studying dsbB's role in plant pathogenesis?

For investigating the role of Erwinia carotovora subsp. atroseptica dsbB in plant pathogenesis, researchers should implement a hierarchical approach using multiple complementary model systems of increasing complexity and physiological relevance. Begin with in vitro assays measuring the activity of secreted plant cell wall-degrading enzymes (PCWDEs) such as pectate lyases, cellulases, and proteases in wild-type versus dsbB mutant bacterial cultures, as these enzymes are primary virulence factors in Erwinia and may require proper disulfide bond formation for activity. Next, employ detached plant tissue assays using potato tuber slices, which provide a simple, quantifiable system to measure tissue maceration capabilities - inoculate with wild-type, dsbB mutant, and complemented strains, then measure the area and weight of macerated tissue after 24-48 hours. For more comprehensive pathogenesis studies, whole plant infection models using potato plants (the natural host) should be implemented with both soil inoculation (to assess root infection) and stem/leaf inoculation (to assess systemic spread). Quantify bacterial colonization by tissue homogenization and serial dilution plating, and document symptom development through standardized disease scoring systems. For mechanistic insights, employ transgenic potato plants expressing fluorescent markers for defense responses, allowing visualization of plant-pathogen interactions using confocal microscopy. Additionally, conduct comparative transcriptomics of plant tissue infected with wild-type versus dsbB mutant bacteria to identify host defense pathways differentially activated in response to each strain. These multi-level approaches will collectively reveal whether dsbB plays a role in the production/activity of virulence factors, bacterial survival in the plant environment, or evasion/suppression of host immune responses.

How might dsbB function relate to Erwinia carotovora's ability to infect both plant and insect hosts?

To investigate the potential role of dsbB in Erwinia carotovora's dual host lifestyle spanning both plants and insect vectors, researchers should implement a comparative pathogenesis approach examining both host systems in parallel. Since E. carotovora uses distinct virulence mechanisms for plant infection (PCWDEs) versus Drosophila infection (Erwinia virulence factor, Evf) , determine whether dsbB differentially affects these host-specific virulence factors. For plant pathogenesis studies, compare the production and activity of PCWDEs in wild-type versus dsbB mutant strains using enzymatic assays, and assess their ability to macerate plant tissue as described previously. For insect host studies, use the established Drosophila melanogaster oral infection model to compare gut colonization efficiency between wild-type and dsbB mutant bacteria by quantifying bacterial loads at different timepoints post-infection. Examine whether dsbB affects the expression or activity of the Evf virulence factor using transcriptional reporter fusions and functional assays. Since insect infection by E. carotovora causes gut damage and developmental delays in Drosophila larvae , compare these phenotypes between larvae infected with wild-type versus dsbB mutant strains. At the molecular level, perform comparative redox proteomics to identify proteins whose disulfide bond formation is dsbB-dependent in each host environment, which may reveal host-specific substrates. Additionally, examine whether environmental signals from each host type (plant extracts versus insect gut extracts) differentially affect dsbB expression or activity, suggesting specialized roles in each host context. This comprehensive approach will determine whether dsbB serves as a common virulence determinant across different hosts or has host-specific functions, providing insights into how this pathogen manages its complex lifecycle.

What techniques can be used to investigate dsbB's potential role in bacterial adaptation to different host environments?

Investigating dsbB's role in Erwinia carotovora's adaptation to diverse host environments requires techniques that capture dynamic protein function across changing conditions. Researchers should first establish reporter systems to monitor dsbB expression in real-time, using transcriptional fusions (dsbB promoter driving luciferase or fluorescent protein expression) that can be tracked during transitions between host environments. To examine environment-specific activity, employ redox-sensitive fluorescent proteins fused to known dsbB substrates, allowing visualization of disulfide bond formation dynamics in living bacteria during host colonization. For in vitro simulation of host transitions, develop microfluidic systems that can rapidly shift bacteria between media mimicking plant tissue, insect gut, and environmental conditions while monitoring responses. To identify environment-specific dsbB substrates, implement SILAC (Stable Isotope Labeling by Amino acids in Cell culture) combined with diagonal gel electrophoresis to quantitatively compare the disulfide proteome under different host-mimicking conditions. For in vivo studies, use dual-fluorescence labeling to simultaneously track bacterial population dynamics and dsbB activity during host colonization, employing confocal microscopy for plants and whole-animal imaging for Drosophila. Comparative transcriptomics and proteomics should be performed on bacteria recovered from different host environments, comparing wild-type and dsbB mutant responses to identify dsbB-dependent adaptation pathways. Additionally, implement transposon sequencing (Tn-seq) in wild-type versus dsbB mutant backgrounds across different host conditions to identify genetic interactions that become essential in a host-specific manner. These approaches collectively will reveal whether dsbB functions as an environmental sensor, a general virulence factor, or a host-specific adaptation protein in this versatile plant pathogen.