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The Assimilation of γ-Butyrolactone in Agrobacterium tumefaciens C58 Interferes with the Accumulation of the N-Acyl-Homoserine Lactone Signal

September 2004 , Volume 17 , Number  9
Pages  951 - 957

Aurélien Carlier , Romain Chevrot , Yves Dessaux , and Denis Faure

Institut des Sciences du Végétal, UPR2355, Centre National de la Recherche Scientifique, Avenue de la Terrasse, 91198 Gif-sur-Yvette, France

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Accepted 19 April 2004.

Agrobacterium tumefaciens C58 communicates using N-acyl-homoserine lactones (acyl-HSL) and contains two lactonase-encoding genes, attM and aiiB, the products of which are capable of inactivating the acyl-HSL signal. In A. tumefaciens A6, the expression of the attKLM operon is controlled by the transcriptional repressor encoded by an adjacent gene, attJ. An attJ∷Tn5 mutant does not accumulate acyl-HSL because of the constitutive expression of the lactonase AttM, the activity of which inactivates acyl-HSL. In this work, the attKLM operon of A. tumefaciens C58 was shown to be involved in an assimilative pathway of γ-butyrolactone (GBL), γ-hydroxybutyrate (GHB), and succinate semialdehyde (SSA), in which AttM and AttL are key enzymes for GBL and GHB assimilation. The expression of the attKLM promoter was activated in the presence of GBL, GHB, and SSA. Under these conditions, A. tumefaciens C58 did not accumulate the acyl-HSL that it naturally synthesizes, and also became able to inactivate exogenous acyl-HSL signals. Therefore, in A. tumefaciens C58, the assimilative pathway of γ-butyrolactone interferes with the acyl-HSL signaling.

Additional keywords: At plasmid, N-3-oxo-octanoyl-L-homos-erine lactone, quorum sensing, Ti plasmid.

© 2004 The American Phytopathological Society