Complete Genome Sequence of Pseudomonas amygdali pv. tabaci Strain 6605, a Causal Agent of Tobacco Wildfire Disease.
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ABSTRACT:
SUBMITTER: Matsui H
PROVIDER: S-EPMC8280867 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:To investigate the role of iron uptake mediated by the siderophore pyoverdine in the virulence of the plant pathogen Pseudomonas syringae pv. tabaci 6605, three predicted pyoverdine synthesis-related genes, pvdJ, pvdL, and fpvA, were mutated. The pvdJ, pvdL, and fpvA genes encode the pyoverdine side chain peptide synthetase III L-Thr-L-Ser component, the pyoverdine chromophore synthetase, and the TonB-dependent ferripyoverdine receptor, respectively. The Delta pvdJ and Delta pvdL mutants were unable to produce pyoverdine in mineral salts-glucose medium, which was used for the iron-depleted condition. Furthermore, the Delta pvdJ and Delta pvdL mutants showed lower abilities to produce tabtoxin, extracellular polysaccharide, and acyl homoserine lactones (AHLs), which are quorum-sensing molecules, and consequently had reduced virulence on host tobacco plants. In contrast, all of the mutants had accelerated swarming ability and increased biosurfactant production, suggesting that swarming motility and biosurfactant production might be negatively controlled by pyoverdine. Scanning electron micrographs of the surfaces of tobacco leaves inoculated with the mutant strains revealed only small amounts of extracellular polymeric matrix around these mutants, indicating disruption of the mature biofilm. Tolerance to antibiotics was drastically increased for the Delta pvdL mutant, as for the Delta psyI mutant, which is defective in AHL production. These results demonstrated that pyoverdine synthesis and the quorum-sensing system of Pseudomonas syringae pv. tabaci 6605 are indispensable for virulence in host tobacco infection and that AHL may negatively regulate tolerance to antibiotics.
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Project description:Pseudomonas syringae pv. tabaci 6605 (Pta6605) is a foliar plant pathogen that causes wildfire disease on tobacco plants. It requires chemotaxis to enter plants and establish infection. While chemotactic signals appear to be the main mechanism by which Pta6605 performs directional movement, the involvement of aerotaxis or energy taxis by this foliar pathogen is currently unknown. Based on domain structures and similarity with more than 50 previously identified putative methyl-accepting chemotaxis proteins (MCPs), the genome of Pta6605 encodes three potential aerotaxis transducers. We identified AerA as the main aerotaxis transducer and found that it possesses a taxis-to-serine-and-repellent (Tsr)-like domain structure that supports a periplasmic 4HB-type ligand-binding domain (LBD). The secondary aerotaxis transducer, AerB, possesses a cytosolic PAS-type LBD, similar to the Aer of Escherichia coli and Pseudomonas aeruginosa. Aerotaxis ability by single and double mutant strains of aerA and aerB was weaker than that by wild-type Pta6605. On the other hand, another cytosolic PAS-type LBD containing MCP did not make a major contribution to Pta6605 aerotaxis in our assay system. Furthermore, mutations in aerotaxis transducer genes did not affect surface motility or chemotactic attraction to yeast extract. Single and double mutant strains of aerA and aerB showed less colonization in the early stage of host plant infection and lower biofilm production than wild-type Pta6605. These results demonstrate the presence of aerotaxis transducers and their contribution to host plant infection by Pta6605.
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