Recombinant Pectobacterium carotovorum subsp. carotovorum Probable intracellular septation protein A (PC1_1997)

What is Pectobacterium carotovorum and why is it significant in plant pathology research?

Pectobacterium carotovorum is an economically important phytopathogen identified as a major causative agent of bacterial soft rot in various plants, including carrots. This pathogen belongs to the group of Soft Rot Enterobacteriaceae (SRE) that secrete Plant Cell Wall Degrading Enzymes (PCWDEs) primarily through a type II secretion system (T2SS) . The significance of P. carotovorum in plant pathology stems from its ability to cause extensive maceration of plant tissue, leading to substantial economic losses worldwide. The pathogen accomplishes this through the secretion of PCWDEs along with additional virulence factors that promote plant cell death to provide nutrients for bacterial multiplication and colonization . Understanding the molecular mechanisms of this pathogen is crucial for developing effective control strategies to minimize harvest losses, particularly as fully efficient control measures remain unavailable .

How does the expression pattern of PC1_1997 correlate with infection stages?

Based on transcriptome analysis of P. carotovorum during infection, genes related to cell division and growth, including PC1_1997, show distinct expression patterns that correlate with infection stages. In the early infection stage (before 4 hours after inoculation), bacterial multiplication is relatively slow, with corresponding lower expression of cell division proteins . As infection progresses, particularly after reaching the population threshold of approximately 5 × 10^6 cfu at 12 hours after inoculation, expression of cell division genes including PC1_1997 increases significantly to support the rapid bacterial population growth . This expression pattern reflects the adaptation of P. carotovorum to the host environment and suggests that PC1_1997 is part of the gene network that responds to quorum sensing signals when the bacterial population reaches the critical threshold needed for effective virulence expression.

How might PC1_1997 interact with the Type II Secretion System during pathogenesis?

While direct evidence of PC1_1997 interaction with the Type II Secretion System (T2SS) is not explicitly documented, advanced research suggests potential functional coordination between septation proteins and secretion systems. The T2SS in P. carotovorum is essential for the secretion of PCWDEs that facilitate host tissue maceration . PC1_1997, as a septation protein, may influence the spatial organization of secretion systems during cell division, ensuring their proper distribution to daughter cells.

A proposed interaction model suggests that:

• PC1_1997 may help localize T2SS components during cell division

• The protein could influence membrane integrity at division sites where secretion systems are embedded

• Coordinated expression of PC1_1997 with T2SS components may ensure synchronized cell division and virulence factor secretion

This potential relationship is particularly significant during the rapid growth phase of infection (after 12 HAI) when both cell division and secretion of virulence factors are highly active .

What are the potential differences in PC1_1997 function between P. carotovorum and related phytopathogens?

Comparative genomic analyses of Pectobacterium species and related phytopathogens reveal subtle but potentially significant variations in septation proteins like PC1_1997. These differences may contribute to the host specificity and virulence capacity observed among different pathogens.

Advanced research questions exploring these differences include:

• How do amino acid sequence variations in PC1_1997 among Pectobacterium species correlate with host range?

• Are there structural modifications in PC1_1997 that influence cell division rates under different environmental conditions?

• Does PC1_1997 interact with species-specific regulatory networks that control the transition from early to late infection stages?

Investigating these questions requires sophisticated comparative transcriptomic and proteomic approaches to identify species-specific adaptations in septation processes that may contribute to the ecological success of different Pectobacterium pathovars .

How does bacterial phage interaction affect PC1_1997 expression and function?

The interaction between P. carotovorum and bacteriophages like vB_PcaM_P7_Pc (P7_Pc) presents an intriguing area for advanced research into PC1_1997 regulation. P7_Pc is a myovirus with an exclusively lytic lifecycle that can effectively target P. carotovorum . Phage infection could potentially modulate PC1_1997 expression in several ways:

• Phage-mediated disruption of cell division processes might alter PC1_1997 expression or function

• Bacterial defense responses against phage infection could indirectly regulate septation protein activity

• Phage-resistant bacterial populations may exhibit altered PC1_1997 expression profiles

Understanding these interactions is particularly relevant for phage-based biocontrol strategies targeting P. carotovorum, as modulation of septation processes could influence the effectiveness of such approaches . Research in this area requires sophisticated experimental designs combining transcriptomics, proteomics, and high-resolution microscopy to track septation dynamics during phage-bacteria interactions.

What are the optimal expression systems for recombinant production of PC1_1997?

Based on successful approaches with other bacterial proteins, the following expression system considerations are recommended for PC1_1997:

The recommended methodology involves:

• Gene synthesis with codon optimization for the selected expression system

• Cloning into a vector with an appropriate fusion tag (His10-tag similar to that used in Proprotein Convertase 1 expression )

• Expression in the selected system with careful optimization of temperature, IPTG concentration, and induction duration

• Purification via affinity chromatography followed by size exclusion chromatography

For optimal results, a C-terminal 10-His tag similar to that used in other recombinant protein productions may provide good yields while maintaining protein functionality . Expression should be carried out at reduced temperatures (16-18°C) to minimize inclusion body formation, with careful optimization of induction parameters.

How can RNA-Seq be optimized for studying PC1_1997 expression during infection?

RNA-Seq has proven valuable for analyzing transcriptome profiles of P. carotovorum during infection, revealing that approximately 50% of genes in the genome (including those involved in cell division like PC1_1997) show differential expression during host colonization . To optimize this approach specifically for PC1_1997 studies:

• Sampling strategy:

  • Collect bacterial RNA at multiple timepoints (0, 4, 8, 12, 24, and 48 hours after inoculation)

  • Include both in planta and control conditions (minimal and rich media)

  • Use technical triplicates and biological duplicates to ensure statistical robustness

• Library preparation:

  • Employ bacterial enrichment methods to reduce host RNA contamination

  • Use strand-specific library preparation to detect potential antisense regulation

  • Include spike-in controls for accurate quantification

• Bioinformatic analysis:

  • Apply a minimum log2-fold ratio ≥ 2.0 to identify significantly differentially expressed genes

  • Use time-series clustering to identify co-regulated genes

  • Compare expression patterns with known cell division gene networks

This optimized approach can reveal the dynamic regulation of PC1_1997 within the context of infection progression and identify potential regulatory networks controlling its expression .

What protein interaction studies are most suitable for characterizing PC1_1997's role in the divisome complex?

Understanding PC1_1997's role in the divisome complex requires sophisticated protein interaction studies:

For optimal characterization of PC1_1997's divisome interactions:

• Begin with B2H screening against known divisome components

• Verify positive interactions using Co-IP with PC1_1997-specific antibodies

• Perform FRET analysis with fluorescently tagged proteins to visualize interactions during cell division

• Apply XL-MS to identify the complete interactome of PC1_1997 during different growth conditions

These approaches can reveal how PC1_1997 participates in the coordination of chromosome segregation with cell division, potentially identifying targets for antimicrobial interventions .

How can gene knockout and complementation strategies be designed to study PC1_1997 function?

To study PC1_1997 function through gene knockout and complementation:

• Knockout strategy:

  • Use homologous recombination or CRISPR-Cas9 to create clean deletions of PC1_1997

  • Verify deletion by PCR and sequencing

  • Assess phenotypic changes including:

    • Growth rate and cell morphology

    • Cell division defects using fluorescent membrane stains

    • Virulence in plant infection assays

• Complementation strategy:

  • Create an expression construct with PC1_1997 under native or inducible promoter

  • Introduce the construct into the knockout strain

  • Verify expression by RT-qPCR and Western blot

  • Assess restoration of wild-type phenotypes

• Domain analysis:

  • Generate truncated or point-mutated versions of PC1_1997

  • Introduce these variants into the knockout strain

  • Determine which domains/residues are essential for function

This experimental approach can definitively establish the role of PC1_1997 in P. carotovorum growth and virulence, potentially revealing intervention points for controlling bacterial soft rot .

How can transcriptome data be integrated with phenotypic assays to understand PC1_1997 function?

Integrating transcriptome data with phenotypic assays provides a comprehensive understanding of PC1_1997 function:

• Correlation analysis:

  • Map PC1_1997 expression patterns against bacterial growth curves during infection

  • Identify expression clusters containing PC1_1997 to establish functional associations

  • Correlate expression with virulence factor production and host tissue maceration

• Comparative phenotypic analysis:

  • Compare wild-type, PC1_1997 knockout, and complemented strains for:

    • Growth rate in various media

    • Cell morphology and division patterns

    • Virulence factor secretion

    • Host colonization efficiency

• Data visualization and integration:

  • Use principal component analysis to identify relationships between gene expression and phenotypic outcomes

  • Create network models linking PC1_1997 expression to downstream cellular processes

  • Generate predictive models for PC1_1997 function based on integrated datasets

What bioinformatic pipelines are most effective for structural prediction and comparative analysis of PC1_1997?

For structural prediction and comparative analysis of PC1_1997:

The recommended pipeline includes:

• Initial sequence analysis:

  • Multiple sequence alignment with homologs from related species

  • Identification of conserved domains using InterPro and Pfam

  • Phylogenetic analysis to identify evolutionary relationships

• Structural prediction:

  • Generate multiple structural models using AlphaFold2

  • Refine models based on molecular dynamics simulations

  • Validate models using Ramachandran plots and QMEANDisCo scores

• Functional analysis:

  • Identify potential binding sites and interaction surfaces

  • Map conserved residues onto the structural model

  • Predict post-translational modifications and their impact

This comprehensive bioinformatic approach can provide insights into PC1_1997 structure and function, guiding experimental design for targeted functional studies .