title: Proline antagonizes GABA-induced quenching of quorum-sensing in Agrobacterium tumefaciens.
abstract: Plants accumulate free L-proline (Pro) in response to abiotic stresses (drought and salinity) and presence of bacterial pathogens, including the tumor-inducing bacterium Agrobacterium tumefaciens. However, the function of Pro accumulation in host-pathogen interaction is still unclear. Here, we demonstrated that Pro antagonizes plant GABA-defense in the A. tumefaciens C58-induced tumor by interfering with the import of GABA and consequently the GABA-induced degradation of the bacterial quorum-sensing signal, 3-oxo-octanoylhomoserine lactone. We identified a bacterial receptor Atu2422, which is implicated in the uptake of GABA and Pro, suggesting that Pro acts as a natural antagonist of GABA-signaling. The Atu2422 amino acid sequence contains a Venus flytrap domain that is required for trapping GABA in human GABA(B) receptors. A constructed atu2422 mutant was more virulent than the wild type bacterium; moreover, transgenic plants with a low level of Pro exhibited less severe tumor symptoms than did their wild-type parents, revealing a crucial role for Venus flytrap GABA-receptor and relative abundance of GABA and Pro in host-pathogen interaction.
authors.affiliation: Centre National de la Recherche Scientifique, Institut des Sciences du Végétal, Gif-sur-Yvette 91 198, France.
authors.forename: E
authors.initials: E
authors.lastname: Haudecoeur
authors.forename: S
authors.initials: S
authors.lastname: Planamente
authors.forename: A
authors.initials: A
authors.lastname: Cirou
authors.forename: M
authors.initials: M
authors.lastname: Tannières
authors.forename: B J
authors.initials: BJ
authors.lastname: Shelp
authors.forename: S
authors.initials: S
authors.lastname: Moréra
authors.forename: D
authors.initials: D
authors.lastname: Faure
mesh_terms: D016960:Agrobacterium tumefaciens / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D054884:Host-Pathogen Interactions; D018551:Solanum lycopersicum / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D009154:Mutation; D010941:Plant Tumors / Q000382:microbiology; D010944:Plants / Q000378:metabolism / Q000382:microbiology*; D030821:Plants, Genetically Modified; D011392:Proline / Q000378:metabolism / Q000494:pharmacology*; D053038:Quorum Sensing / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D018079:Receptors, GABA / Q000235:genetics* / Q000378:metabolism; D013997:Time Factors; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D014633:Valine / Q000494:pharmacology; D014774:Virulence / Q000235:genetics; D005680:gamma-Aminobutyric Acid / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D001426:Bacterial Proteins; D018079:Receptors, GABA; D005680:gamma-Aminobutyric Acid; D011392:Proline; D014633:Valine
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