| Sumario: | Antimicrobial peptides constitute an important factor inthe defense of plants against pathogens, and bacterial resis-tance to these peptides have previously been shown to bean important virulence factor in Dickeya dadantii, thecausal agent of soft-rot disease of vegetables. In order tounderstand the bacterial response to antimicrobial pep-tides, a transcriptional microarray analysis was performedupon treatment with sub-lethal concentration of thionins, awidespread plant peptide. In all, 36 genes were found to beoverexpressed, and were classified according to their de-duced function as i) transcriptional regulators, ii) trans-port, and iii) modification of the bacterial membrane. Onegene encoding a uricase was found to be repressed. Themajority of these genes are known to be under the controlof the PhoP/PhoQ system. Five genes representing the dif-ferent functions induced were selected for further analysis.The results obtained indicate that the presence of antimi-crobial peptides induces a complex response which includespeptide-specific elements and general stress-response ele-ments contributing differentially to the virulence in differ-ent hosts.
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