Plants genetically modified to produce N-acylhomoserine lactones
communicate with bacteria
Rupert G. Fray1, John P. Throup1, 2, 3, Mavis Daykin2, Andrew Wallace1, Paul Williams2, Gordon S.A.B. Stewart2, 4
& Donald Grierson1
1
School of Biological Sciences, Nottingham University
, Loughborough LE12 5RD, UK.
2
School of Pharmaceutical Sciences, University of Nottingham,
University Park, Nottingham NG7 2RD, UK.
3
Current address: SmithKline Beecham Pharmaceuticals
Research and Development, Collegeville PA
19426.
4
Deceased.
Correspondence should be addressed to Rupert G. Fray rupert.fray@nottingham.ac.ukN-acylhomoserine lactonesplant/microbe interactionsbiocontrolrhizosphere
N-acylhomoserine lactones (AHLs) play a critical role in plant/microbe
interactions. The AHL, N-(3-oxohexanoyl)-L-homoserine lactone (OHHL),
induces exoenzymes that degrade the plant cell wall by the pathogenic bacterium
Erwinia carotovora. Conversely, the antifungal activity of the biocontrol
bacterium Pseudomonas aureofaciens 30−84 is due (at least in
part) to phenazine antibiotics whose synthesis is regulated by N-hexanoylhomoserine
lactone (HHL). Targeting the product of an AHL synthase gene (yenI)
from Yersinia enterocolitica to the chloroplasts of transgenic tobacco
plants caused the synthesis in plants of the cognate AHL signaling molecules
(OHHL and HHL). The AHLs produced by the transgenic plants were sufficient
to induce target gene expression in several recombinant bacterial AHL biosensors
and to restore biocontrol activity to an HHL-deficient P. aureofaciens
strain. In addition, pathogenicity was restored to an E. carotovora
strain rendered avirulent as a consequence of a mutation in the OHHL
synthase gene, carI. The ability to generate bacterial quorum-sensing
signaling molecules in the plant offers novel opportunities for disease control
and for manipulating plant/microbe interactions.
