title: The plant GABA signaling downregulates horizontal transfer of the Agrobacterium tumefaciens virulence plasmid.
abstract: In the tumor-inducing (Ti) Agrobacterium tumefaciens, quorum sensing activates the horizontal transfer of the virulent Ti plasmid. In pure culture, this process can be impaired by the A. tumefaciens BlcC lactonase, whose expression is induced by gamma-aminobutyrate (GABA). It was therefore hypothesized that host GABA content might modulate quorum sensing and virulence gene dissemination during A. tumefaciens infection. We examined GABA metabolism and transport in Arabidopsis thaliana tumors combining transcriptomic, metabolomic and histological approaches. In addition, using genetically modified plants and bacteria, we evaluated the impact of plant host GABA content on Ti plasmid dissemination. The results showed that GABA and free proline, which acts as an antagonist of GABA uptake in A. tumefaciens, accumulated in wild-type tumors relative to uninfected plant tissues. Moreover, comparisons of tumors induced on Col-0 and her1 plants showed that the increase in the plant GABA : proline ratio was associated with both the upregulated expression of the blcC gene and the decreased dissemination of Ti plasmid in tumor-colonizing A. tumefaciens populations. This work demonstrates experimentally that the variation in the GABA content in plant tumors can interfere with the dissemination of A. tumefaciens Ti plasmids, and therefore highlights plant GABA content as an important trait in the struggle against pathogenic bacteria.
authors.affiliation: Institute for Integrative Biology of the Cell (I2BC), CNRS CEA Université Paris-Sud, Université Paris-Saclay, Saclay Plant Sciences, Avenue de la Terrasse, 91198, Gif-sur-Yvette Cedex, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Lang
authors.affiliation: Institute for Integrative Biology of the Cell (I2BC), CNRS CEA Université Paris-Sud, Université Paris-Saclay, Saclay Plant Sciences, Avenue de la Terrasse, 91198, Gif-sur-Yvette Cedex, France.
authors.forename: Almudena
authors.initials: A
authors.lastname: Gonzalez-Mula
authors.affiliation: POPS Transcriptomic Platform - Institute of Plant Sciences Paris-Saclay (IPS2), CNRS, INRA, Université Paris-Sud, Université d'Evry, Université Paris-Diderot, Sorbonne Paris-Cité Université Paris-Saclay, Batiment 630, 91405, Orsay, France.
authors.forename: Ludivine
authors.initials: L
authors.lastname: Taconnat
authors.affiliation: Plateforme de Chimie - Métabolisme, INRA Centre de Versailles-Grignon, Route de Saint-Cyr, 78026, Versailles Cedex, France.
authors.forename: Gilles
authors.initials: G
authors.lastname: Clement
authors.affiliation: Institute for Integrative Biology of the Cell (I2BC), CNRS CEA Université Paris-Sud, Université Paris-Saclay, Saclay Plant Sciences, Avenue de la Terrasse, 91198, Gif-sur-Yvette Cedex, France.
authors.forename: Denis
authors.initials: D
authors.lastname: Faure
mesh_terms: D016960:Agrobacterium tumefaciens / Q000235:genetics* / Q000472:pathogenicity*; D017360:Arabidopsis / Q000235:genetics / Q000382:microbiology*; D001692:Biological Transport / Q000235:genetics; D015536:Down-Regulation / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D018014:Gene Transfer Techniques; D017343:Genes, Plant; D055442:Metabolome; D010941:Plant Tumors / Q000235:genetics; D010957:Plasmids / Q000235:genetics*; D015398:Signal Transduction; D059467:Transcriptome / Q000235:genetics; D014774:Virulence / Q000235:genetics; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D005680:gamma-Aminobutyric Acid
keywords: Agrobacterium tumefaciens; Arabidopsis thaliana; gamma-aminobutyrate (GABA); lactonase; plant pathogen; plant tumor; quorum sensing (QS)