title: An Interspecies Signaling System Mediated by Fusaric Acid Has Parallel Effects on Antifungal Metabolite Production by Pseudomonas protegens Strain Pf-5 and Antibiosis of Fusarium spp.
abstract: Pseudomonas protegens strain Pf-5 is a rhizosphere bacterium that suppresses soilborne plant diseases and produces at least seven different secondary metabolites with antifungal properties. We derived mutants of Pf-5 with single and multiple mutations in biosynthesis genes for seven antifungal metabolites: 2,4-diacetylphoroglucinol (DAPG), pyrrolnitrin, pyoluteorin, hydrogen cyanide, rhizoxin, orfamide A, and toxoflavin. These mutants were tested for inhibition of the pathogens Fusarium verticillioides and Fusarium oxysporum f. sp. pisi. Rhizoxin, pyrrolnitrin, and DAPG were found to be primarily responsible for fungal antagonism by Pf-5. Previously, other workers showed that the mycotoxin fusaric acid, which is produced by many Fusarium species, including F. verticillioides, inhibited the production of DAPG by Pseudomonas spp. In this study, amendment of culture media with fusaric acid decreased DAPG production, increased pyoluteorin production, and had no consistent influence on pyrrolnitrin or orfamide A production by Pf-5. Fusaric acid also altered the transcription of biosynthetic genes, indicating that the mycotoxin influenced antibiotic production by Pf-5 at the transcriptional level. Addition of fusaric acid to the culture medium reduced antibiosis of F. verticillioides by Pf-5 and derivative strains that produce DAPG but had no effect on antibiosis by Pf-5 derivatives that suppressed F. verticillioides due to pyrrolnitrin or rhizoxin production. Our results demonstrated the importance of three compounds, rhizoxin, pyrrolnitrin, and DAPG, in suppression of Fusarium spp. by Pf-5 and confirmed that an interspecies signaling system mediated by fusaric acid had parallel effects on antifungal metabolite production and antibiosis by the bacterial biological control organism.
authors.affiliation: Department of Genetics, College of Agriculture Luiz de Queiroz, ESALQ, University of São Paulo, Piracicaba, São Paulo, Brazil.
authors.forename: Maria Carolina
authors.initials: MC
authors.lastname: Quecine
authors.affiliation: Agricultural Research Service, U.S. Department of Agriculture, Corvallis, Oregon, USA.
authors.forename: Teresa A
authors.initials: TA
authors.lastname: Kidarsa
authors.affiliation: Department of Pharmaceutical Sciences, Oregon State University, Corvallis, Oregon, USA.
authors.forename: Neal C
authors.initials: NC
authors.lastname: Goebel
authors.affiliation: Agricultural Research Service, U.S. Department of Agriculture, Corvallis, Oregon, USA.
authors.forename: Brenda T
authors.initials: BT
authors.lastname: Shaffer
authors.affiliation: Agricultural Research Service, U.S. Department of Agriculture, Corvallis, Oregon, USA.
authors.forename: Marcella D
authors.initials: MD
authors.lastname: Henkels
authors.affiliation: Department of Pharmaceutical Sciences, Oregon State University, Corvallis, Oregon, USA.
authors.forename: T Mark
authors.initials: TM
authors.lastname: Zabriskie
authors.affiliation: Agricultural Research Service, U.S. Department of Agriculture, Corvallis, Oregon, USA loperj@science.oregonstate.edu.|Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, USA.
authors.forename: Joyce E
authors.initials: JE
authors.lastname: Loper
mesh_terms: D000898:Antibiosis; D000935:Antifungal Agents / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D005669:Fusaric Acid / Q000378:metabolism*; D005670:Fusarium / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D053858:Metabolic Networks and Pathways / Q000187:drug effects; D056265:Microbial Interactions; D011549:Pseudomonas / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D015398:Signal Transduction; D014158:Transcription, Genetic
chemical_list: D000935:Antifungal Agents; D003470:Culture Media; D005669:Fusaric Acid