In planta fitness-cost of the Atu4232-regulon encoding for a selective GABA-binding sensor in Agrobacterium

GABA (gamma-aminobutyric acid) mediates cell-to-cell communication in eukaryotes and interspecies communication in host-microbe interactions. Agrobacterium tumefaciens induces the development of plant tumor in which GABA accumulates. Two periplasmic binding proteins Atu2422 and Atu4243 and their appropriate ABC-transporter are involved in the binding and importation of GABA. The structure of the selective GABA-binding Atu4243 reveals a GABA conformation similar to a proposed model of GABA bound to the mammalian GABAC receptor. The A. tumefaciens atu4243 mutant is affected for GABA uptake, aggressiveness on plant host and GABA-induced degradation of the quorum-sensing signal, hence for horizontal transfer of the tumor-inducing plasmid. Here, we report that a de-repression of atu4243 and its co-regulated neighbor genes affect the fitness of A. tumefaciens during tumor colonization. Atu4243-orthologs are present in several species of the Agrobacterium genus. This addendum highlights the recent data on the GABA transport in the A. tumefaciens plant-pathogen.