Molecular Plant-Microbe Interactions (2008) 21, 1094-1105

Laura Chalupowicz, Shulamit Manulis-Sasson, Maxim Itkin, Ayelet Sacher, Guido Sessa and Isaac Barash (2008)
Quorum-sensing system affects gall development incited by Pantoea agglomerans pv. gypsophilae
Molecular Plant-Microbe Interactions 21 (8), 1094-1105
Abstract: The quorum-sensing (QS) regulatory system of the gall-forming Pantoea agglomerans pv. gypsophilae was identified. Mass spectral analysis, together with signal-specific biosensors, demonstrated that P. agglomerans pv. gypsophilae produced N-butanoyl-l-homoserine lactone (C₄-HSL) as a major and N-hexanoyl-l-homoserine lactone (C₆-HSL) as a minor QS signal. Homologs of luxI and luxR regulatory genes, pagI and pagR, were characterized in strain P. agglomerans pv. gypsophilae Pag824-1 and shown to be convergently transcribed and separated by 14 bp. The deduced PagI (23.8 kDa) and PagR (26.9 kDa) show high similarity with SmaI (41% identity) and SmaR (43% identity), respectively, of Serratia sp. American Type Culture Collection 39006. PagR possesses characteristic autoinducer binding and a helix-turn-helix DNA-binding domain. Gall formation by P. agglomerans pv. gypsophilae depends on a plasmid-borne hrp/hrc gene cluster, type III effectors, and phytohormones. Disruption of pagI, pagR, or both genes simultaneously in Pag824-1 reduced gall size in gypsophila cuttings by 50 to 55% when plants were inoculated with 10⁶ CFU/ml. Higher reductions in gall size (70 to 90%) were achieved by overexpression of pagI or addition of exogenous C₄-HSL. Expression of the hrp/hrc regulatory gene hrpL and the type III effector pthG in the pagI mutant, as measured with quantitative reverse-transcriptase polymerase chain reaction, was reduced by 5.8 and 6.6, respectively, compared with the wild type, suggesting an effect of the QS system on the Hrp regulon.
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Link to article at publishers website
Database assignments for author(s): Shulamit Manulis-Sasson, Guido Sessa

Research topic(s) for pests/diseases/weeds:
molecular biology - genes

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Pantoea agglomerans