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Proc Natl Acad Sci U S A. 2006 May 9;103(19):7460-4. Epub 2006 Apr 27.

GABA controls the level of quorum-sensing signal in Agrobacterium tumefaciens.

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Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, Avenue de la Terrasse, Gif-sur-Yvette 91 198, France.


The concentration of GABA increases rapidly in wounded plant tissues, but the implication of this GABA pulse for plant-bacteria interactions is not known. Here we reveal that GABA stimulated the inactivation of the N-(3-oxooctanoyl)homoserine lactone (OC8-HSL) quorum-sensing signal (or "quormone") by the Agrobacterium lactonase AttM. GABA induced the expression of the attKLM operon, which was correlated to a decrease in OC8-HSL concentration in Agrobacterium tumefaciens cultures. The Agrobacterium GABA transporter Bra was required for this GABA-signaling pathway. Furthermore, transgenic tobacco plants with elevated GABA levels were less sensitive to A. tumefaciens C58 infection than were wild-type plants. These findings indicate that plant GABA may modulate quorum sensing in A. tumefaciens, thereby affecting its virulence on plants. Whereas GABA is an essential cell-to-cell signal in eukaryotes, here we provide evidence of GABA acting as a signal between eukaryotes and pathogenic bacteria. The GABA signal represents a potential target for the development of a strategy to control the virulence of bacterial pathogens.

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