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KMID : 0578320110320040317
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Molecules and Cells
2011 Volume.32 No. 4 p.317 ~ p.323
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Negative Regulation of Pathogenesis in Pseudomonas syringae pv. tabaci 11528 by ATP-Dependent Lon Protease
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Yang Hyun-Ju
Lee Jun-Seung
Cha Ji-Young
Baik Hyung-Suk
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Abstract
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Pseudomonas syringae pv. tabaci causes wildfire disease in tobacco plants. The hrp pathogenicity island (hrp PAI) of P. syringae pv. tabaci encodes a type III secretion system (TTSS) and its regulatory system, which are re-quired for pathogenesis in plants. Three important regulatory proteins-HrpR, HrpS, and HrpL-have been identified to activate hrp PAI gene expression. The bacterial Lon protease regulates the expression of various genes. To investigate the regulatory mechanism of the Lon protease in P. syringae pv. tabaci 11528, we cloned the lon gene, and then a ?lon mutant was generated by allelic exchange. lon mutants showed increased UV sensitivity, which is a typical feature of such mutants. The ?lon mutant produced higher levels of tabtoxin than the wild-type. The lacZ gene was fused with hrpA promoter and activity of ?-galactosidase was measured in hrp-repressing and hrp-inducing media. The Lon protease functioned as a negative regulator of hrp PAI under hrp-repressing conditions. We found that strains with lon disruption elicited the host defense sys-tem more rapidly and strongly than the wild-type strain, suggesting that the Lon protease is essential for systemic pathogenesis.
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KEYWORD
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gene regulation, hrp pathogenicity island, lon mutant, Lon protease
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