Fungal-associated molecules induce key genes involved in the biosynthesis of the antifungal secondary metabolites nunamycin and nunapeptin in the biocontrol strain Pseudomonas fluorescens In5

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Pseudomonas fluorescens In5 synthesizes the antifungal cyclic lipopeptides (CLPs) nunamycin and nunapeptin, which are similar in structure and genetic organization to the pseudomonas-derived phytotoxins syringomycin and syringopeptin. Regulation of syringomycin and syringopeptin is dependent on the two-component global regulatory system GacS/GacA, and the SalA, SyrF, and SyrG transcription factors, which activate syringomycin synthesis in response to plant signalling molecules. Previously, we demonstrated that a specific transcription factor, NunF, positively regulates the synthesis of nunamycin and nunapeptin in P. fluorescens In5 and that the nunF gene is upregulated by fungal-associated molecules. This study focusses on further unravelling the complex regulation governing CLP synthesis in P. fluorescens In5. Promoter fusions were used to show that the specific activator NunF is dependent on the global regulator of secondary metabolism GacA and is regulated by fungal-associated molecules and low temperatures. In contrast, GacA is stimulated by plant signalling molecules leading to the hypothesis that P. fluorescens is a hyphosphere-associated bacterium encoding transcription factor genes that respond to signals indicating the presence of fungi and oomycetes. Based on these findings, we present a model for how synthesis of nunamycin and nunapeptin is regulated by fungal- and oomycete-associated molecules.
Original languageEnglish
Article numbere01284-20
JournalApplied and Environmental Microbiology
Volume86
Number of pages14
ISSN0099-2240
DOIs
Publication statusPublished - 2020

ID: 247355408