Regulatory function of histidine kinase sensor encoding gene barA in bio-control effect of Rahnella aquatilis
Rahnella aquatilis HX2, which was isolated from the vineyard soil, is a gram-negative, plant growth-promoting rhizobacteria. Previous results showed that R. aquatilis HX2 has significant antagonistic effect on certain pathogenic bacteria and fungi including Agrobacterium tumefaciens, Xanthomonas ory...
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| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Zhejiang University Press
2015-01-01
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| Series: | 浙江大学学报. 农业与生命科学版 |
| Subjects: | |
| Online Access: | https://www.academax.com/doi/10.3785/j.issn.1008-9209.2014.03.122 |
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| Summary: | Rahnella aquatilis HX2, which was isolated from the vineyard soil, is a gram-negative, plant growth-promoting rhizobacteria. Previous results showed that R. aquatilis HX2 has significant antagonistic effect on certain pathogenic bacteria and fungi including Agrobacterium tumefaciens, Xanthomonas oryzae, Fusarium oxysporum, Botrytis cinerea, Altemaria solani, etc, and exhibited the potential biocontrol value against rice sheath blight and crown gall of grapevine and sunflower. The completed genomic DNA sequence of R. aquatilis HX2 has been finished.For further discovery of the regulatory systems which regulate its biocontrol and physiological traits, random mutagenesis based on mini-Tn5 transposon was used to investigate the regulatory genes. The candidated genes were focused on the regulatory function in biocontrol-related physiological traits and biocontrol effects. Consequently, a mutant TR57 which had less antagonitic effect against the plant pathogen Agrobacterium vitis K308 was obtained after the random mutagenesis based on mini-Tn5 transposon and antagonitic assay. The DNA sequence flanking the inserted mini-Tn5 transposon was verified as a BarA-liked histidine kinase gene. The putative BarA protein in R. aquatilis HX2 contains HAMP domain, HisKA domain, HATPase_C domain, REC domain and HPT domain. BarA has been reported as the sensor protein of a two-component regulatory system BarA/UvrY in many bacteria, such as Escherichia coli, Pseudomonas spp. and the BarA/UvrY was known as a global regulatory functioning in bacterial survival under the circumstance of pH value and nutrition change. For further investigation of BarA in R. aquatilis HX2, null barA mutant was constructed based on homologous recombination. A vector pSRΔbarA was constructed after inserting the flanking region of barA loci into the suicide vector pSR47S, and transformed into E. coli DH5α (λ-pir). The triparental mating strategy was used to transfer the vector pSRΔbarA into R. aquatilis HX2. After the two-step homologous recombination, the null barA mutant MR57 was obtained consequently. Meanwhile, the complemented vector pRKbarA was constructed after inserting the barA operon into the shuttle vector pRK415G, and then was transformed into MR57.The biocontrol-related physiological traits and biocontrol effect of R. aquatilis HX2 and its derivative strains were compared to valuate the barA regulation function. The experimental results indicated that the mutagenesis of barA caused higher bacterial biofilm formation ability, less swimming and swarming ability. The biocontrol efficiency of barA mutant against A. vitis K308 on grape plants decreased to 26.7%, comparing to 86.2% of the wild type strain. Moreover, the complemented strain could recover all the measured biological characters and bio-control efficiency. Therefore, it was supposed that the histidine kinase gene barA plays the key role in biocontrol function of R. aquatilis HX2.In summary, barA is firstly found as a regulation gene functioning in bacterial biocontrol effect in this study. The results also give us the indication that the modification of bacterial two-component regulation systems would be helpful to facilitate the application of biocontrol bacteria. |
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| ISSN: | 1008-9209 2097-5155 |