N-ACYL-HOMOSERINE LACTONE-MEDIATED GENE-REGULATION IN BIOLOGICAL-CONTROL BY FLUORESCENT PSEUDOMONADS - CURRENT KNOWLEDGE AND FUTURE WORK

An emerging area within biological control is the role of N-acyl-homos erine lactones (N-acyl-HSL's) in the regulation of competitive fitness and pathogen suppression. N-acyl-HSL regulatory systems utilize two c onserved proteins which belong to the LuxR/LuxI regulatory family: one is a transcriptional regulator and the second produces the N-acyl-HSL signal. These signals regulate the expression of a diverse range of b acterial traits involved in microbe-microbe and host-microbe interacti ons. Several fluorescent pseudomonads important in biological control produce N-acyl-HSL signals which regulate genes that encode products i nvolved in pathogen suppression. In contrast to pathogenic bacteria, l ittle is known regarding N-acyl-HSL-mediated gene regulation in biolog ical control bacteria. This minireview will focus on the current statu s of the role of N-acyl-HSL's in the regulation of phenazine antibioti c and rhamnolipid production in biological control by fluorescent pseu domonads. The potential relevance of this type of regulation in biolog ical control of plant diseases, and areas requiring further research w ill be addressed.