Analysis of the gacS-gacA regulatory genes of spontaneous mutants of Pseudomonas fluorescens biocontrol strain PfG32R |
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Authors: | W Gusti Ngurah Alit-Susanta Yuichi Takikawa |
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Institution: | (1) Laboratory of Plant Pathology, Faculty of Agriculture, Shizuoka University, 836 Ohya, Shizuoka 422-8529, Japan;(2) The United Graduate School of Agricultural Science, Gifu University, Gifu, Japan;(3) Faculty of Agriculture, Udayana University, Jl. PB. Sudirman, Denpasar, Bali, Indonesia |
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Abstract: | Pseudomonas fluorescens strain PfG32R, a potential biocontrol agent against soilborne pathogens, frequently loses its antifungal activity and ability
to produce enzymes. To characterize genetically the instability of these bacterial functions, we analyzed gacS and gacA genes of PfG32R and three spontaneous mutants of PfG32R (NR1, NR9, and ASW6), which had lost their ability to produce proteases
and antifungal activities. The gacS and gacA sequences of PfG32R had 77%–89% and 78%–87% homology, respectively, with several known gacS and gacA homologues. All three spontaneous mutants were subjected to complementation analysis. Introduction of clones containing an
intact gacS of PfG32R and another P. fluorescens strain Pf-5 as well as strain tea632 of P. syringae pv. theae complemented all three mutants restoring protease and antifungal activities, indicating a mutation in gacS. In sequencing analysis, the mutants had a deletion or change in amino acids in the conserved sensor kinase domains of GacS.
The three mutants maintained both their antibacterial activity against Ralstonia solanacearum and Clavibacter michiganensis ssp. michiganensis and siderophore production, indicating that they are not controlled by the GacS/GacA system.
The sequences reported in this article have been deposited in the DDBJ database under accession numbers AB219364 and AB219365. |
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Keywords: | Pseudomonas fluorescens PfG32R Two-component regulatory system gacS mutants Protease Antifungal activity Antibacterial activity |
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