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Molecular analysis of a novel gene cluster encoding an insect toxin in plant‐associated strains of Pseudomonas fluorescens
Author(s) -
PéchyTarr Maria,
Bruck Denny J.,
Maurhofer Monika,
Fischer Esther,
Vogne Christelle,
Henkels Marcella D.,
Donahue Kelly M.,
Grunder Jürg,
Loper Joyce E.,
Keel Christoph
Publication year - 2008
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2008.01662.x
Subject(s) - biology , pseudomonas fluorescens , photorhabdus , manduca sexta , galleria mellonella , photorhabdus luminescens , microbiology and biotechnology , spodoptera littoralis , toxin , insect , pseudomonas syringae , gene , bacteria , virulence , botany , lepidoptera genitalia , noctuidae , genetics , pathogen
Summary Pseudomonas fluorescens CHA0 and the related strain Pf‐5 are well‐characterized representatives of rhizosphere bacteria that have the capacity to protect crop plants from fungal root diseases, mainly by releasing a variety of exoproducts that are toxic to plant pathogenic fungi. Here, we report that the two plant‐beneficial pseudomonads also exhibit potent insecticidal activity. Anti‐insect activity is linked to a novel genomic locus encoding a large protein toxin termed Fit (for P. f luorescens i nsecticidal t oxin) that is related to the insect toxin Mcf ( M akes c aterpillars f loppy) of the entomopathogen Photorhabdus luminescens , a mutualist of insect‐invading nematodes. When injected into the haemocoel, even low doses of P. fluorescens CHA0 or Pf‐5 killed larvae of the tobacco hornworm Manduca sexta and the greater wax moth Galleria mellonella . In contrast, mutants of CHA0 or Pf‐5 with deletions in the Fit toxin gene were significantly less virulent to the larvae. When expressed from an inducible promoter in a non‐toxic Escherichia coli host, the Fit toxin gene was sufficient to render the bacterium toxic to both insect hosts. Our findings establish the Fit gene products of P. fluorescens CHA0 and Pf‐5 as potent insect toxins that define previously unappreciated anti‐insect properties of these plant‐colonizing bacteria.