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  • Scientific Societies  (3)
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  • Scientific Societies  (3)
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  • 1
    Online Resource
    Online Resource
    Interactions of Pseudomonas syringae pv. glycinea with Host and Nonhost Plants in Relation to Temperature and Phytotoxin Synthesis
    Scientific Societies ; 2000
    In:  Molecular Plant-Microbe Interactions® Vol. 13, No. 9 ( 2000-09), p. 951-961
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    In: Molecular Plant-Microbe Interactions®, Scientific Societies, Vol. 13, No. 9 ( 2000-09), p. 951-961
    Abstract: Pseudomonas syringae pv. glycinea PG4180 causes bacterial blight of soybean and produces the phytotoxin coro-natine (COR) in a temperature-dependent manner. COR consists of a polyketide, coronafacic acid (CFA), and an amino acid derivative, coronamic acid, and is produced optimally at 18°C whereas no detectable synthesis occurs at 28°C. We investigated the impact of temperature on PG4180 during compatible and incompatible interactions with soybean and tobacco plants, respectively. After spray inoculation, PG4180 caused typical bacterial blight symptoms on soybean plants when the bacteria were grown at 18°C prior to inoculation but not when derived from cultures grown at 28°C. The disease outcome was quantified by determination of bacterial populations in planta. The temperature effect was not observed when PG4180 was artificially infiltrated into soybean leaves, indicating that the pre-inoculation temperature and phytotoxin synthesis were important for bacterial invasion via natural plant openings. In the incompatible interaction, PG4180 elicited the hypersensitive response (HR) on tobacco plants regardless of the bacterial pre-inoculation temperature. However, the HR was significantly delayed when tobacco plants were treated with cells of the CFA-overproducing derivative, PG4180.N9, which were derived from cultures grown at 18°C, compared with parallels incubated at 28°C. CFA biosynthesis by PG4180.N9 was optimal at 18°C and negligible at 28°C. The impact of CFA synthesis on the HR was studied with different growth media, mutants, and transconjugants of PG4180, indicating that the amount of synthesized CFA but not that of COR influenced the outcome of the HR. Feeding experiments with purified coronafacoyl compounds suggested that the observed delay of the HR was mediated by CFA, shedding further light on CFA's putative role as a molecular mimic of the plant signaling molecule, jasmonic acid.
    Type of Medium: Online Resource
    ISSN: 0894-0282 , 1943-7706
    URL: Article
    DOI: 10.1094/MPMI.2000.13.9.951
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2000
    detail.hit.zdb_id: 2037108-1
    SSG: 12
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    Online Resource
  • 2
    Online Resource
    Online Resource
    Impact of Temperature on In Planta Expression of Genes Involved in Synthesis of the Pseudomonas syringae Phytotoxin Coronatine
    Scientific Societies ; 2004
    In:  Molecular Plant-Microbe Interactions® Vol. 17, No. 10 ( 2004-10), p. 1095-1102
    Details
    In: Molecular Plant-Microbe Interactions®, Scientific Societies, Vol. 17, No. 10 ( 2004-10), p. 1095-1102
    Abstract: Coronatine (COR) is a chlorosis-inducing phytotoxin produced by the plant-pathogenic bacterium Pseudomonas syringae. Confocal laser scanning microscopy was used to investigate in vitro and in planta expression of COR genes by two model organisms, P. syringae pv. glycinea PG4180, a pathogen of soybean, and P. syringae pv. tomato DC3000, a pathogen of tomato and crucifers. Previously, it was shown in vitro that the cma operon involved in COR synthesis in PG4180 is expressed in a temperature-dependent manner, with maximal rates at 18°C and low activity at 28°C. However, nothing was known about the influence of temperature on the expression of COR biosynthetic genes in planta. Therefore, transcriptional fusions of the PG4180 and DC3000 cma promoter regions to a promoterless egfp gene were constructed and expressed in both P. syringae strains. The fluorescence patterns in response to temperature during growth of a strain in vitro were consistent with its COR production and the cma transcript abundance as revealed by RNA dot blot hybridization. Quantification of fluorescence indicated that cma promoter activity was dependent on the genetic background of the host strain. Expression of cma∷egfp in PG4180 was temperature-dependent in minimal medium as well as inside the plant tissue. In contrast, transcription of the cma operon was not significantly affected by temperature in DC3000. However, cells of DC3000 harboring the cma∷egfp fusions showed higher levels of fluorescence when recovered from infected host plants compared with cells grown in minimal medium. These results indicate that the signals for induction of COR biosynthesis differ significantly in PG4180 and DC3000.
    Type of Medium: Online Resource
    ISSN: 0894-0282 , 1943-7706
    URL: Article
    DOI: 10.1094/MPMI.2004.17.10.1095
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2004
    detail.hit.zdb_id: 2037108-1
    SSG: 12
    Location Call Number Limitation Availability
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    Online Resource
  • 3
    Online Resource
    Online Resource
    The Phytoalexin-Inducible Multidrug Efflux Pump AcrAB Contributes to Virulence in the Fire Blight Pathogen, Erwinia amylovora
    Scientific Societies ; 2004
    In:  Molecular Plant-Microbe Interactions® Vol. 17, No. 1 ( 2004-01), p. 43-54
    Details
    In: Molecular Plant-Microbe Interactions®, Scientific Societies, Vol. 17, No. 1 ( 2004-01), p. 43-54
    Abstract: The enterobacterium Erwinia amylovora causes fire blight on members of the family Rosaceae, with economic importance on apple and pear. During pathogenesis, the bacterium is exposed to a variety of plant-borne antimicrobial compounds. In plants of Rosaceae, many constitutively synthesized isoflavonoids affecting microorganisms were identified. Bacterial multidrug efflux transporters which mediate resistance toward structurally unrelated compounds might confer tolerance to these phytoalexins. To prove this hypothesis, we cloned the acrAB locus from E. amylovora encoding a resistance nodulation division-type transport system. In Escherichia coli, AcrAB of E. amylovora conferred resistance to hydrophobic and amphiphilic toxins. An acrB-deficient E. amylovora mutant was impaired in virulence on apple rootstock MM 106. Furthermore, it was susceptible toward extracts of leaves of MM 106 as well as to the apple phytoalexins phloretin, naringenin, quercetin, and (+)-catechin. The expression of acrAB was determined using the promoterless reporter gene egfp. The acrAB operon was up-regulated in vitro by the addition of phloretin and naringenin. The promoter activity of acrR, encoding a regulatory protein involved in acrAB expression, was increased by naringenin. In planta, an induction of acrAB was proved by confocal laser scanning microscopy. Our results strongly suggest that the AcrAB transport system plays an important role as a protein complex required for virulence of E. amylovora in resistance toward apple phytoalexins and that it is required for successful colonization of a host plant.
    Type of Medium: Online Resource
    ISSN: 0894-0282 , 1943-7706
    URL: Article
    DOI: 10.1094/MPMI.2004.17.1.43
    Language: English
    Publisher: Scientific Societies
    Publication Date: 2004
    detail.hit.zdb_id: 2037108-1
    SSG: 12
    Location Call Number Limitation Availability
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    Online Resource
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