Pathovar-specific requirement for the Pseudomonas syringae lemA gene in disease lesion formation

Rich, J J; Hirano, Susan S.; Willis, David K.

doi:10.1128/aem.58.5.1440-1446.1992

Cited by 39 publications

(12 citation statements)

References 26 publications

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“…In P. syringae pv. syringae, the lemA gene is required for the production of syringomycin, extracellular protease (25,40), and presumably other unidentified genes that are required for disease. In P. syringae pv.…”

Section: Discussionmentioning

confidence: 99%

“…syringae B728a lemA gene (which will be designated hereafter lemA4p,) is contained within the insert of the plasmid pEMH97 and is required for disease symptoms on bean, as well as for the in vitro production of syringomycin and protease by P. syringae pv. syringae B728a (22,23,40,61). In addition, Southern blot analysis showed that pLEM57, the restoring subclone from the P. syringae pv.…”

Section: -Kbmentioning

confidence: 99%

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Regulation of tabtoxin production by the lemA gene in Pseudomonas syringae

1992

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Pseudomonas syringae pv. coronafaciens, a pathogen of oats, was mutagenized with Tn5 to generate mutants defective in tabtoxin production. From a screen of 3,400 kanamycin-resistant transconjugants, seven independent mutants that do not produce tabtoxin (Tox-) were isolated. Although the Tn5 insertions within these seven mutants were linked, they were not located in the previously described tabtoxin biosynthetic region of P. syringae. Instead, all of the insertions were within the P. syringae pv. coronafaciens lemA gene. The lemA gene is required by strains of P. syringae pv. syringae for pathogenicity on bean plants (Phaseolus vulgaris). In contrast to the phenotype of a P. syringae pv. syringae lemA mutant, the Tox- mutants of P. syringae pv. coronafaciens were still able to produce necrotic lesions on oat plants (Avena sativa), although without the chlorosis associated with tabtoxin production. Northern (RNA) hybridization experiments indicated that a functional lemA gene was required for the detection of a transcript produced from the tblA locus located in the tabtoxin biosynthetic region. Marker exchange mutagenesis of the tblA locus resulted in loss of tabtoxin production. Therefore, both the tblA and lemA genes are required for tabtoxin biosynthesis, and the regulation of tabtoxin production by lemA probably occurs at the transcriptional level.

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Section: Discussionmentioning

confidence: 99%

Section: -Kbmentioning

confidence: 99%

Regulation of tabtoxin production by the lemA gene in Pseudomonas syringae

1992

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“…Previous work had demonstrated that gacS (as lemA) was as important for the development of brown spot symptoms by a set of recent field isolates as it was for B728a (22). Three of these isolates were checked both for the ability to swarm and for the involvement of gacS in the swarming process.…”

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Swarming by Pseudomonas syringae B728a Requires gacS ( lemA ) and gacA but Not the Acyl-Homoserine Lactone Biosynthetic Gene ahlI

1999

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Pseudomonas syringae pv. syringae B728a, a causal agent of bacterial brown spot on snap beans, swarms with a characteristic dendritic pattern on semisolid (0.4%) agar plates. Filamentation of swarming cells of B728a was not observed. Mutations in either thegacS (formerly lemA) or gacA gene of B728a eliminate the ability of this P. syringae isolate to swarm without obvious effects on bacterial motility. Three field isolates showed a similar dependence on gacS for swarming. Since gacS and gacA mutants are known to be deficient in N-acyl-l-homoserine lactone (acyl-HSL) production, a mutant was constructed by disruption of theahlI gene of B728a. This mutant did not make any acyl-HSL detectable by the Agrobacterium traG::lacZ reporter system, yet was unaffected in its ability to swarm. Other phenotypes ofgacS and gacA mutations were similarly unaffected in the ahlI mutant.

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“…The gacA (for global antibiotic and cyanide control) gene was first described for Pseudomonas fluorescens as a regulator of production of a number of secondary metabolites that contribute to its biocontrol activity against a fungal root rot disease of tobacco (18). Homologs of lemA and/or gacA have since been identified in a number of pseudomonads, including other pathovars of P. syringae (1,27) and other species of Pseudomonas (4,7,17,20).…”

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Contribution of the Regulatory Gene lemA to Field Fitness of Pseudomonas syringae pv. syringae

Hirano¹,

Ostertag²,

Savage³

et al. 1997

Appl Environ Microbiol

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In Pseudomonas syringae pv. syringae, lemA is required for brown spot lesion formation on snap bean and for production of syringomycin and extracellular proteases (. Plant-Microbe Interact. 3:149-156, 1990). The lemA mutant NPS3136 (lemA1::Tn5) was previously found to be indistinguishable from its pathogenic parent B728a in its ability to grow when infiltrated into bean leaves of plants maintained under controlled environmental conditions (Willis et al., Mol. Plant-Microbe Interact. 3:149-156, 1990). We compared population sizes of NPS3136 and B728aN (a Nal r clone of wild-type B728a) in two field experiments to determine the effect of inactivation of lemA on the fitness of P. syringae pv. syringae. In one experiment, the bacterial strains were spray inoculated onto the foliage of 25-day-old bean plants. In the other, seeds were inoculated at the time of planting. In both experiments, the strains were inoculated individually and coinoculated in a 1:1 ratio. NPS3136 and B728aN achieved similar large population sizes on germinating seeds. However, in association with leaves, population sizes of NPS3136 were diminished relative to those of B728aN in both experiments. Thus, lemA contributed significantly to the fitness of P. syringae pv. syringae in association with bean leaves but not on germinating seeds under field conditions. When NPS3136 was coinoculated with B728aN, the mutant behaved as it did when inoculated alone. However, population sizes of B728aN in the coinoculation treatment were much lower than those when it was inoculated alone. Inactivation of the lemA gene appeared to have rendered the mutant suppressive to B728aN.

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Pathovar-specific requirement for the Pseudomonas syringae lemA gene in disease lesion formation

Cited by 39 publications

References 26 publications

Regulation of tabtoxin production by the lemA gene in Pseudomonas syringae

Regulation of tabtoxin production by the lemA gene in Pseudomonas syringae

Swarming by Pseudomonas syringae B728a Requires gacS ( lemA ) and gacA but Not the Acyl-Homoserine Lactone Biosynthetic Gene ahlI

Contribution of the Regulatory Gene lemA to Field Fitness of Pseudomonas syringae pv. syringae

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