Submitted to: Biological Control of Fungal and Bacterial Plant Pathogens Working Group
Publication Type: Abstract Only
Publication Acceptance Date: 6/27/2008
Publication Date: 9/12/2008
Citation: Pechy-Tarr, M., Loper, J.E., Mauhofer, M., Keel, C. 2008. Insecticidal activity in root-associated Pseudomonads. International Organization for Biological Control of Fungal and Bacterial Plant Pathogens Working Group Program Book. Interpretive Summary:
Technical Abstract: The development of sustainable, environmentally safe pest management practices is a major agricultural goal worldwide. Microbial biological control agents of insect pests or pathogens have been employed successfully towards this goal, but these agents typically fall in two distinct groups that are effective against plant pathogens or insect pests, but not both. Recently, we found that certain plant-associated strains of Pseudomonas fluorescens, which are known to suppress soil-borne plant diseases, also exhibit potent insecticidal activity due, in part, to their production of a toxin which we termed Fit (for P. fluorescens insecticidal toxin). Fit is related to the insect toxin Mcf (Makes caterpillars floppy) of the entomopathogen Photorhabdus luminescens, a mutualist of insect-invading nematodes. When injected into the hemocoel, even low doses of the Fit producing P. fluorescens strains killed larvae of the tobacco hornworm Manduca sexta and the greater wax moth Galleria mellonella. Mutants with deletions in the Fit toxin gene were significantly less virulent to the larvae. When expressed from an inducible promoter in Escherichia coli, the Fit toxin gene was sufficient to render the bacterium toxic to both insect hosts. Our findings establish the P. fluorescens Fit gene products as potent novel insect toxins that define previously unappreciated insecticidal properties of these plant-colonizing bacteria and highlight new possibilities to employ biocontrol strains to enhance the health and productivity of agricultural crops.