Plants genetically modified to produce N-acylhomoserine lactones communicate with bacteria

N-acylhomoserine lactones (AHLs) play a critical role in plant/microbe inte ractions, The AHL, N-(3-oxohexanoyl)-1-homoserine lactone (OHHL), induces e xoenzymes that degrade the plant cell wall by the pathogenic bacterium Erwi nia carotovora. Conversely, the antifungal activity of the biocontrol bacte rium Pseudomonas aureofaciens 30-84 is due (at least in part) to phenazine antibiotics whose synthesis is regulated by N-hexanoylhomoserine lactone (H HL). Targeting the product of an AHL synthase gene (yen1) from Yersinia ent erocolitica to the chloroplasts of transgenic tobacco plants caused the syn thesis in plants of the cognate AHL signaling molecules (OHHL and HHL). The AHLs produced by the transgenic plants were sufficient to induce target ge ne expression in several recombinant bacterial AHL biosensors and to restor e biocontrol activity to an HHL-deficient P. aureofaciens strain. In additi on, pathogenicity was restored to an E. carotovora strain rendered avirulen t as a consequence of a mutation in the OHHL synthase gene, carl. The abili ty to generate bacterial quorum-sensing signaling molecules in the plant of fers novel opportunities for disease control and for manipulating plant/mic robe interactions.