Loss of glutamate dehydrogenase in Ralstonia solanacearum alters dehydrogenase activity, extracellular polysaccharide production and bacterial virulence

Wu, Jang‐Yen; Kong, Hyun Gi; Jung, Eun Joo; Choi, Seok Reyol; Lee, Hyoung Ju; Wang, Tao; Chung, Eui-Young; Lee, Seon-Woo

doi:10.1016/j.pmpp.2015.03.003

Cited by 10 publications

(20 citation statements)

References 40 publications

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“…A previously constructed transposon (Tn)-inserted mutant pool of SL341 [ 37 ] was screened to select mutants that produce no or less melanin relative to the wild-type SL341 strain. Mutants grown on MG agar plates were randomly selected and inoculated into 96-well culture plates containing 200 μl of minimal medium supplemented with tyrosine.…”

Section: Methodsmentioning

confidence: 99%

“…The 96-well plates were incubated at 30°C in a shaking incubator at 200 rpm for 48 h. The mutant strains showing a reduced or non-pigmented phenotype relative to the wild type were selected and further confirmed on tyrosine-containing MG medium. The Tn insertion site in each mutant was identified according to a previously described method [ 37 ]. In brief, genomic DNA was extracted from each Tn mutant and randomly digested with Sac1 .…”

Section: Methodsmentioning

confidence: 99%

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Genetic Determinants for Pyomelanin Production and Its Protective Effect against Oxidative Stress in Ralstonia solanacearum

Ahmad

Kong

et al. 2016

PLoS ONE

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Ralstonia solanacearum is a soil-borne plant pathogen that infects more than 200 plant species. Its broad host range and long-term survival under different environmental stress conditions suggest that it uses a variety of mechanisms to protect itself against various types of biotic and abiotic stress. R. solanacearum produces a melanin-like brown pigment in the stationary phase when grown in minimal medium containing tyrosine. To gain deeper insight into the genetic determinants involved in melanin production, transposon-inserted mutants of R. solanacearum strain SL341 were screened for strains with defective melanin-producing capability. In addition to one mutant already known to be involved in pyomelanin production (viz., strain SL341D, with disruption of the hydroxphenylpyruvate dioxygenase gene), we identified three other mutants with disruption in the regulatory genes rpoS, hrpG, and oxyR, respectively. Wild-type SL341 produced pyomelanin in minimal medium containing tyrosine whereas the mutant strains did not. Likewise, homogentisate, a major precursor of pyomelanin, was detected in the culture filtrate of the wild-type strain but not in those of the mutant strains. A gene encoding hydroxyphenylpyruvate dioxygenase exhibited a significant high expression in wild type SL341 compared to other mutant strains, suggesting that pyomelanin production is regulated by three different regulatory proteins. However, analysis of the gene encoding homogentisate dioxygenase revealed no significant difference in its relative expression over time in the wild-type SL341 and mutant strains, except for SL341D, at 72 h incubation. The pigmented SL341 strain also exhibited a high tolerance to hydrogen peroxide stress compared with the non-pigmented SL341D strain. Our study suggests that pyomelanin production is controlled by several regulatory factors in R. solanacearum to confer protection under oxidative stress.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Genetic Determinants for Pyomelanin Production and Its Protective Effect against Oxidative Stress in Ralstonia solanacearum

Ahmad

Kong

et al. 2016

PLoS ONE

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“…A previously constructed transposon insertion mutant library of SL341 [27] was screened to select melanin-overproducing mutants to compare with wild-type strain SL341. Mutants grown on MG agar plates were randomly selected and inoculated on 96-well culture plates containing 200 μl of minimal medium supplemented with 500 μg/ml of tyrosine solution.…”

Section: Screening Of Melanin-overproducing Mutants and Identificatiomentioning

confidence: 99%

“…The 96-well plates were incubated at 30 o C in a shaking incubator at 200 rpm for 48 h. The mutant strain showing a higher pigmented phenotype compared with wild-type SL341 was selected and further confirmed by plating on MG medium containing tyrosine. The transposon insertion site in the selected mutant was identified according to a method described previously [27]. Briefly, genomic DNA was extracted from the transposon mutant and randomly digested with SacI.…”

Section: Screening Of Melanin-overproducing Mutants and Identificatiomentioning

confidence: 99%

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Identification of a Gene Involved in the Negative Regulation of Pyomelanin Production in Ralstonia solanacearum

Ahmad

Lee

Khan

et al. 2017

Journal of Microbiology and Biotechnology

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Ralstonia solanacearum causes bacterial wilt in a wide variety of host plant species and produces a melanin-like blackish-brown pigment in stationary phase when grown in minimal medium supplemented with tyrosine. To study melanin production regulation in R. solanacearum, five mutants exhibiting overproduction of melanin-like pigments were selected from a transposon (Tn) insertion mutant library of R. solanacearum SL341. Most of the mutants, except one (SL341T), were not complemented by the original gene or overproduced melanins. SL341T showed Tn insertion in a gene containing a conserved domain of eukaryotic transcription factor. The gene was annotated as a hypothetical protein, given its weak similarity to any known proteins. Upon complementation with its original gene, the mutant strains reverted to their wild-type phenotype. SL341T produced 3-folds more melanin at 72 h post-incubation compared with wild-type SL341 when grown in minimal medium supplemented with tyrosine. The chemical analysis of SL341T cultural filtrate revealed the accumulation of a higher amount of homogentisate, a major precursor of pyomelanin, and a lower amount of dihydroxyphenylalanine, an intermediate of eumelanin, compared with SL341. The expression study showed a relatively higher expression of hppD (encoding hydroxyphenylpyruvate dioxygenase) and lower expression of hmgA (encoding homogentisate dioxygenase) and nagL (encoding maleylacetoacetate isomerase) in SL341T than in SL341. SL341 showed a significantly higher expression of tyrosinase gene compared with SL341T at 48 h post-incubation. These results indicated that R. solanacearum produced both pyomelanin and eumelanin, and the novel hypothetical protein is involved in the negative regulation of melanin production.

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The inhibitory effects of different types of Brassica seed meals on the virulence of Ralstonia solanacearum

Peng

Liu

Shen

et al. 2021

Pest Management Science

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BACKGROUND Understanding the specific inhibitory effects of different Brassica seed meals (BSMs) on soilborne pathogens is important for their application as biocontrol agents for controlling plant disease. In this study, the seed meals of Brassica napus L. (BnSM), Brassica campestris L. (BcSM), and Brassica juncea L. (BjSM), and the combined seed meal of BcSM and BjSM (CSM, 1:1), were selected for investigation. The inhibitory effects of these seed meals on the plant pathogen Ralstonia solanacearum (Smith) and tomato bacterial wilt, were assessed and compared. RESULTS All the BSMs significantly inhibited the growth of R. solanacearum in vitro. Furthermore, the BSMs could effectively suppress R. solanacearum virulence traits, including motility, exopolysaccharide production, dehydrogenase activity, virulence‐related gene expression, and colonization in the soil. Among them, BjSM showed the best inhibiting effects, and CSM displayed synergic toxicity against R. solanacearum. In addition, the predominant antibacterial compounds in BcSM and BjSM were identified as the volatile compounds, 3‐butenyl isothiocyanate and allyl isothiocyanate, respectively. Finally, pot experiment verified that the control effects of BjSM and CSM on tomato wilt reached more than 90%. CONCLUSION This is the first study to report on the ability of different kinds of BSMs to suppress the virulence of R. solanacearum and biocontrol efficiencies against bacterial wilt in tomato plants. Furtherly, the main antibacterial compounds in the BSMs were identified. The results demonstrated that CSM may possess potential for controlling bacterial wilt caused by R. solanacearum. The results provide a fresh perspective for comprehending the mechanism underlying BSM suppression of pathogens and plant disease.

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Loss of glutamate dehydrogenase in Ralstonia solanacearum alters dehydrogenase activity, extracellular polysaccharide production and bacterial virulence

Cited by 10 publications

References 40 publications

Genetic Determinants for Pyomelanin Production and Its Protective Effect against Oxidative Stress in Ralstonia solanacearum

Genetic Determinants for Pyomelanin Production and Its Protective Effect against Oxidative Stress in Ralstonia solanacearum

Identification of a Gene Involved in the Negative Regulation of Pyomelanin Production in Ralstonia solanacearum

The inhibitory effects of different types of Brassica seed meals on the virulence of Ralstonia solanacearum

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