Tae-Hwan Noh

National Academy of Agricultural Science (South Korea), Sŏul, Seoul, South Korea

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Publications (6)11.46 Total impact

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    ABSTRACT: We describe the development of a polymerase chain reaction (PCR) method for the rapid, precise, and specific detection of the Xanthomonas oryzae pv. oryzae (Xoo) K3a race, the bacterial blight pathogen of rice. The specific primer set was designed to amplify a genomic locus derived from an amplified fragment length polymorphism (AFLP) specific for the K3a race. The 1024 bp amplicon was generated from the DNA of 13 isolates of Xoo K3a races out of 120 isolates of other races, pathovars, and Xanthomonas species. The assay does not require isolated bacterial cells or DNA extraction. Moreover, the pathogen was quickly detected in the rice leaf 2 days after inoculation with bacteria and at a distance of 8 cm from the rice leaf 5 days later. The results suggest that this PCR-based assay will be a useful and powerful tool for the detection and identification of the Xoo K3a race in rice plants as well as for early diagnosis of infection in paddy fields.
    Journal of Microbiology and Biotechnology 02/2014; · 1.40 Impact Factor
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    ABSTRACT: Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial blight (BB) in rice. To study its function, a random insertion mutation library of Xoo was constructed using the Tn5 transposon. A mutant strain with decreased virulence against the susceptible rice cultivar IR24 was isolated from the library (aroE mutant), which also had extremely low pigment production. Thermal asymmetric interlaced-polymerase chain reaction (TAIL-PCR) and sequence analysis of the mutant revealed that the transposon was inserted into the aroE gene (encoding shikimate dehydrogenase). To investigate gene expression changes in the pigment- and virulence-deficient mutant, DNA microarray analysis was performed, which showed downregulation of 20 genes involved in the chemotaxis of Xoo. Our findings reveal that mutation of the aroE gene affects virulence and pigment production, as well as expression of genes involved in Xoo chemotaxis.
    Microbiological Research 01/2014; · 1.99 Impact Factor
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    ABSTRACT: Xanthomonas oryzae pv. oryzae causes bacterial blight in rice, and this bacterial blight has been widely found in the major rice-growing areas. We constructed a transposon mutagenesis library of X. oryzae pv. oryzae and identified a mutant strain (KXOM9) that is deficient for pigment production and virulence. Furthermore, the KXOM9 mutant was unable to grow in minimal medium lacking aromatic amino acids. Thermal asymmetric interlaced-PCR and sequence analysis of KXOM9 revealed that the transposon was inserted into the aroC gene, which encodes a chorismate synthase in various bacterial pathogens. In planta growth assays revealed that bacterial growth of the KXOM9 mutant in rice leaves was severely reduced. Genetic complementation of this mutant with a 7.9-kb fragment containing aroC restored virulence, pigmentation, and prototrophy. These results suggest that the aroC gene plays a crucial role in the growth, attenuation of virulence, and pigment production of X. oryzae pv. oryzae.
    Microbiological Research 12/2011; 167(6):326-31. · 1.99 Impact Factor
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    ABSTRACT: Xanthomonas oryzae pathovar oryzae (Xoo) causes bacterial blight disease in rice (Oryza sativa L.). For a study of function, we constructed a random insertion mutant library of Xoo using a Tn5 transposon and isolated the mutant strain (M11; aroK::Tn5) that had extremely low pigment production. In addition, M11 had decreased virulence against the susceptible rice cultivar IR24. Thermal asymmetric interlaced-PCR and sequence analysis of M11 revealed that the transposon was inserted into the aroK gene (which encodes a shikimate kinase). To investigate the expression patterns of the pigment- and virulence-deficient mutant, DNA microarray analysis was performed. In addition, reverse transcriptase-PCR was performed to confirm the expression levels of several genes, including the aro genes of the aroK mutant. Our findings reveal that several crucial genes for virulence, including cellulase and hypersensitive response and pathogenicity (hrp) genes, were regulated by mutations in the aroK gene.
    FEMS Microbiology Letters 12/2009; 301(2):149-55. · 2.05 Impact Factor
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    ABSTRACT: Xanthomonas oryzae pathovar oryzae is the causal agent of rice bacterial blight. The plant pathogenic bacterium X. oryzae pv. oryzae expresses a type III secretion system that is necessary for both the pathogenicity in susceptible hosts and the induction of the hypersensitive response in resistant plants. This specialized protein transport system is encoded by a 32.18kb hrp (hypersensitive response and pathogenicity) gene cluster. The hrp gene cluster is composed of nine hrp, nine hrc (hrp conserved) and eight hpa (hrp-associated) genes and is controlled by HrpG and HrpX, which are known as regulators of the hrp gene cluster. Before mutational analysis of these hrp genes, the transcriptional linkages of the core region of the hrp gene cluster from hpaB to hrcC of the X. oryzae pv. oryzae KACC10859 was determined and the non-polarity of EZTn5 insertional mutagenesis was demonstrated by reverse transcription polymerase chain reaction. Pathogenicity assays of these non-polar hrp mutants were carried out on the susceptible rice cultivar, Milyang-23. According to the results of these assays, all hrp-hrc, except hrpF, and hpaB mutants lost their pathogenicity, which indicates that most hrp-hrc genes encode essential pathogenicity factors. On the other hand, most hpa mutants showed decreased virulence in a different pattern, i.e., hpa genes are not essential but are important for pathogenicity.
    Microbial Pathogenesis 07/2008; 44(6):473-83. · 1.97 Impact Factor
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    ABSTRACT: Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial blight of rice. A random insertional mutant library of Xoo KACC10331 was constructed using a Tn5-derived transposon, and the virulence of the mutants against the susceptible rice cultivar IR24 was assayed. After the virulence assay, the M793 (purD::Tn5) mutant that had reduced virulence against the rice plants was isolated. Thermal asymmetric interlaced-PCR and sequence analysis revealed that the transposon was inserted into the purD gene (encodes a phosphoribosylamine-glycine ligase) of the M793 mutant. The reverse transcriptase-PCR assay revealed that the mutation of the purD gene did not affect the expression of other purine biosynthesis genes. However, the M793 mutant required exogenous purines and thiamine for growth in minimal media. These results indicate that the purD gene plays a crucial role in the growth and virulence of Xoo.
    FEMS Microbiology Letters 12/2007; 276(1):55-9. · 2.05 Impact Factor

Publication Stats

28 Citations
11.46 Total Impact Points

Institutions

  • 2009–2011
    • National Academy of Agricultural Science (South Korea)
      Sŏul, Seoul, South Korea
    • National Institute of Crop Science
      Sŏngnam, Gyeonggi Province, South Korea
  • 2007
    • RURAL DEVELOPMENT ADMINISTRATION
      Seikan-ri, South Chungcheong, South Korea