Involvement of gacA Gene in the Suppression of Tomato Bacterial Wilt by Pseudomonas fluorescens FPT9601 |
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Authors: | Liqun ZHANG Qian YANG Yukio TOSA Hitoshi NAKAYASHIKI Shigeyuki MAYAMA |
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Affiliation: | (1) Laboratory of Plant Pathology, Division of Environmental Science of Bioresource Production, Graduate School of Science and Technology, Kobe University, Kobe 657–8501, Japan, JP |
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Abstract: | Pseudomonas fluorescens FPT9601, a plant growth-promoting rhizobacterium (PGPR) isolated from tomato rhizosphere, can protect tomato (Lycopersicon esculentum Mill) from bacterial wilt disease caused by Ralstonia solanacearum. This strain produces antibiotics 2,4-diacetylphloroglucinol (2,4-DAPG) and hydrogen cyanide (HCN). It also produces proteases and uncharacterized siderophores (Sid). A mutant strain SM2214, obtained by Tn5 insertion, did not produce 2,4-DAPG, HCN or proteases, but overproduced Sid. Marker-exchange mutagenesis confirmed that a single transposon insertion caused the multiple phenotypic changes of this mutant. Complementation of the mutant with a 1.3-kb DNA fragment that was amplified from genomic DNA of the wild-type P. fluorescens strain by PCR could restore the lost functions of the mutant strain. Nucleotide sequencing revealed that the fragment contained a 642-bp open reading frame (ORF) highly homologous to the regulator responser gene gacA. The in vitro anti-bacterium test and plant protection experiment under greenhouse conditions indicated that the gacA gene played an important role in the suppression of tomato bacterial wilt disease. Received 20 November 2000/ Accepted in revised form 19 January 2001 |
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Keywords: | : Pseudomonas fluorescens Ralstonia solanacearum two-component regulatory system gacA gene. |
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