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The plant GABA signaling downregulates horizontal transfer of the Agrobacterium tumefaciens virulence plasmid
Author(s) -
Lang Julien,
GonzalezMula Almudena,
Taconnat Ludivine,
Clement Gilles,
Faure Denis
Publication year - 2016
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.13813
Subject(s) - agrobacterium tumefaciens , quorum sensing , virulence , biology , plasmid , ti plasmid , transfer dna , bacteria , mutant , transformation (genetics) , arabidopsis thaliana , microbiology and biotechnology , gene , genetics
Summary 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.