The Plant Pathogen Pantoea ananatis Produces N-Acylhomoserine Lactone and Causes Center Rot Disease of Onion by Quorum Sensing

Department of Applied Chemistry, Utsunomiya University, Tochigi 321-8585, Japan.
Journal of bacteriology (Impact Factor: 2.81). 12/2007; 189(22):8333-8. DOI: 10.1128/JB.01054-07
Source: PubMed


A number of gram-negative bacteria have a quorum-sensing system and produce N-acyl-l-homoserine lactone (AHL) that they use them as a quorum-sensing signal molecule. Pantoea ananatis is reported as a common colonist of wheat heads at ripening and causes center rot of onion. In this study, we demonstrated that P. ananatis SK-1 produced two AHLs, N-hexanoyl-l-homoserine lactone (C6-HSL) and N-(3-oxohexanoyl)-l-homoserine lactone (3-oxo-C6-HSL). We cloned the AHL-synthase gene (eanI) and AHL-receptor gene (eanR) and revealed that the deduced amino acid sequence of EanI/EanR showed high identity to those of EsaI/EsaR from P. stewartii. EanR repressed the ean box sequence and the addition of AHLs resulted in derepression of ean box. Inactivation of the chromosomal eanI gene in SK-1 caused disruption of exopolysaccharide (EPS) biosynthesis, biofilm formation, and infection of onion leaves, which were recovered by adding exogenous 3-oxo-C6-HSL. These results demonstrated that the quorum-sensing system involved the biosynthesis of EPS, biofilm formation, and infection of onion leaves in P. ananatis SK-1.

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Available from: Tsukasa Ikeda, Mar 14, 2014
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    • "Therefore, we propose that a complete rhlR/rhlI pair was acquired horizontally with the deletion of rhlI after divergence of Escherichia, Salmonella, and close relatives, from Pantoea and Erwinia. ExpI and PhzI produce oxoC6 [23], [24], an AHL detected with high sensitivity by SdiA [9], which is consistent with ExpI and PhzI representing descendants of the ancient LuxI protein paired with SdiA. "
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    ABSTRACT: SdiA of E. coli and Salmonella is a LuxR homolog that detects N-acyl homoserine lactones (AHLs). Most LuxR homologs function together with a cognate AHL synthase (a LuxI homolog), but SdiA does not. Instead, SdiA detects AHLs produced by other bacterial species. In this report, we performed a phylogenetic analysis of SdiA. The results suggest that one branch of the Enterobacteriaceae obtained a rhlR/rhlI pair by horizontal transfer. The Erwinia and Pantoea branches still contain the complete pair where it is known as expR/expI and phzR/phzI, respectively. A deletion event removed the luxI homolog from the remainder of the group, leaving just the luxR homolog known as sdiA. Thus ExpR and PhzR are SdiA orthologs and ExpI and PhzI are descendants of the long lost cognate signal synthase of SdiA.
    PLoS ONE 10/2012; 7(10):e47720. DOI:10.1371/journal.pone.0047720 · 3.23 Impact Factor
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    • "In particular, it causes center rot disease of onion, which is seed-borne and seed-transmitted in onion (Coutinho and Venter, 2009; Morohoshi et al., 2007). P. ananatis has also been reported to have ice nucleation activity that can be used in the food industry, as well as use a biological control for specific insect pests (Watanabe and Sato, 1999). "
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    ABSTRACT: The bacteria B1-9 that was isolated from the rhizosphere of the green onion could promote growth of pepper, cucumber, tomato, and melon plants. In particular, pepper yield after B1-9 treatment on the seedling was increased about 3 times higher than that of control plants in a field experiment. Partial 16S rDNA sequences revealed that B1-9 belongs to the genus Pantoea ananatis. Pathogenecity tests showed non-pathogenic on kimchi cabbage, carrot, and onion. The functional characterization study demonstrated B1-9's ability to function in phosphate solubilization, sulfur oxidation, nitrogen fixation, and indole-3-acetic acid production. To trace colonization patterns of B1-9 in pepper plant tissues, we used fluorescent dye, which stains the DNAs of bacteria and plant cells. A large number of B1-9 cells were found on the surfaces of roots and stems as well as in guard cells. Furthermore, several colonized B1-9 cells resided in inner cortical plant cells. Treatment of rhizosphere regions with strain B1-9 can result in efficient colonization of plants and promote plant growth from the seedling to mature plant stage. In summary, strain B1-9 can be successfully applied in the pepper plantation because of its high colonization capacity in plant tissues, as well as properties that promote efficient plant growth.
    The plant pathology journal 09/2012; 28(3). DOI:10.5423/PPJ.OA.02.2012.0026 · 0.72 Impact Factor
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    • "stewartii (von Bodman et al., 2003) and has been reported recently in the pathogens P. agglomerans pv. gypsophilae and P. ananatis (Morohoshi et al., 2007; Chalupowicz et al., 2008). Based on the sequence homology to the pagRI genes of P. agglomerans pv. "
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    ABSTRACT: A 530-kb megaplasmid pPag3 contributing 10.8% of the total genome of Pantoea vagans biocontrol strain C9-1 was sequenced. A rare nonpigmented variant C9-1W was obtained and shown to have lost pPag3, but retained all other plasmids (pPag1, pPag2). Phenotypic characterization of the variant confirmed the function of several annotated genes that may influence ecological fitness and efficacy. Metabolic profiling revealed important plasmid-based carbon utilization phenotypes. Plasmid loss resulted in thiamine auxotrophy, absence of carotenoid pigmentation, desferrioxamine diffusible siderophore biosynthesis, inherent ampicillin resistance and expression of AI-1 quorum-sensing signaling. This confirmed the functional expression of the corresponding genes located on pPag3 in P. vagans.
    FEMS Microbiology Letters 07/2010; 308(1):48-54. DOI:10.1111/j.1574-6968.2010.01994.x · 2.12 Impact Factor
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