Identification of the Genes of the Plant Pathogen Pseudomonas syringae MB03 Required for the Nematicidal Activity Against Caenorhabditis elegans Through an Integrated Approach

Abstract

Nematicidal potential of the common plant pathogen Pseudomonas syringae has been recently identified against Caenorhabditis elegans. The current study was designed to investigate the detailed genetic mechanism of the bacterial pathogenicity by applying comparative genomics, transcriptomics, mutant library screening, and protein expression. Results showed that P. syringae strain MB03 could kill C. elegans in the liquid assay by gut colonization. The genome of P. syringae MB03 was sequenced and comparative analysis including multi locus sequence typing, and genome-to-genome distance placed MB03 in phylogroup II of P. syringae. Furthermore, comparative genomics of MB03 with nematicidal strains of Pseudomonas aeruginosa (PAO1 and PA14) predicted 115 potential virulence factors in MB03. However, genes for previously reported nematicidal metabolites, such as phenazine, pyochelin, and pyrrolnitrin, were found absent in the MB03 genome. Transcriptomics analysis showed that the growth phase of the pathogen considerably affected the expression of virulence factors, as genes for the flagellum, glutamate ABC transporter, phoP/phoQ, fleS/fleR, type VI secretion system, and serralysin were highly up-regulated when stationary phase MB03 cells interacted with C. elegans. Additionally, screening of a transposon insertion mutant library led to the identification of other nematicidal genes such as acnA, gltP, oprD, and zapE. Finally, the nematicidal activity of selected proteins was confirmed by heterologous expression in Escherichia coli.

Nematicidal Activity and Action Receptor of a Methyl‐Accepting Chemotaxis Protein from the Phytopathogen Pseudomonas syringae against Caenorhabditis elegans

“…In P. syringae MB03 genome, total of 46 MCP-encoding genes (chemoreceptor genes) were annotated. Interestingly, the genome-wide prediction of nematicidal genes of P. syringae MB03 showed the nematicidal potential of MCP03 among these MCPs [23]. In consistent with this prediction, the bioassays of heterologously expressed MCP03 exhibited a significantly lethal activity again C. elegans, with an LC50 of 124.47 (99.22~147.47) μg mL -1 , and multiple detrimental effects on the growth, reproduction, and morphology of C. elegans.…”

“…The conventional phytopathogen P. syringae has been identified significant nematicidal activity against the model nematode Caenorhabditis elegans [21,22], and a recent genome-wide prediction analysis of nematicidal factors in a P. syringae wild-type strain MB03 revealed significant nematicidal virulence potential of an MCP (namely MCP03) against C. elegans [23]. However, the nematicidal activity and action mechanism of MCP03 remain understudied.…”

Repertoire and abundance of secreted virulence factors shape the pathogenic capacity of Pseudomonas syringae pv. aptata

“…The Hcp1 and VgrG proteins of cluster 1 were found to be secreted in high abundance by all strains, whereas another Hcp1, VgrG and a Rhs protein were distributed distinctly differently. By comparing the co-regulation of protein secretion in the tested strains, we identified several proteins as putative novel T6SS effectors, expanding the repertoire of putative effectors within the P. syringae species complex: Serralysin-like alkaline metalloproteases have also been detected to be co-regulated with T6SS proteins in P. syringae ( Ali et al, 2022 ). The family of YD repeat proteins includes many bacterial toxins and proteins involved in cell–cell contact and communication, some of which are T6SS effectors ( Koskiniemi et al, 2013 ).…”

Characterization of Nematicidal Activity and Nematode-Toxic Metabolites of a Soilborne Brevundimonas bullata Isolate

“…In recent years, many bacteria have been confirmed to have promising nematicidal activity. These bacteria include Bacillus subtilis [11], Bacillus thuringiensis [12,13], Bacillus amyloliquefaciens [14], Bacillus cereus [15], Bacillus firmus [16][17][18], Bacillus nematocida [19], Pseudomonas aeruginosa [20][21][22], Pseudomonas putida [23], Pseudomonas simiae [24], Pseudomonas syringae [25][26][27], Burkholderia cepacia [28], Streptomyces avermitilis [29,30], and Pasteuria penetrans [31]. These nematicidal bacteria affect the target nematodes through different mechanisms, such as restraining the growth and reproduction of nematodes and direct pathogenesis, which are carried out by the production of toxic proteins [32,33], enzymes [12,26,34], small-molecule metabolites [23,24,35], or invasive parasitization [36,37].…”