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ARS Home » Midwest Area » West Lafayette, Indiana » Crop Production and Pest Control Research » Research » Publications at this Location » Publication #115742

Title: DIFFERENTIAL SYNTHESIS OF PERITOXIN AND PRECURSORS BY PATHOGENIC STRAINS OF THE FUNGAL PATHOGEN PERICONIA CIRCINATA

Author
item CHURCHILL, A - BOYCE THOMPSON INST
item Dunkle, Larry
item SILBERT, W - BOYCE THOMPSON INST
item MACKO, V - BOYCE THOMPSON INST

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/20/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary: The fungus Periconia circinata causes root rot of sorghum. Only strains that produce secondary metabolites called peritoxins are able to cause disease. Peritoxins are determinants of host-specificity because they are toxic only to sorghum cultivars that are susceptible to the fungus. The biosynthetic pathway leading to production of peritoxins is unknown. Culture fluids from pathogenic and non-pathogenic strains were analyzed directly by sensitive methods incorporating mass spectrometry to identify metabolic intermediates and final products of the pathway and to determine where and how some strains are blocked in the pathway. This approach allowed us to compare in detail the metabolite profiles of the two types of strains and to detect compounds that are common to both phenotypes. Peritoxins A and B and three biologically inactive intermediates were detected only in culture fluids of the pathogenic strains. Therefore, these strains differ from the non-pathogenic strains by several metabolic steps and apparently lack genes that encode the entire peritoxin biosynthetic pathway. This information is important for learning about the ways fungi cause disease, devising novel strategies to control plant diseases, and establishing the molecular and genetic differences between pathogens and non-pathogens.

Technical Abstract: Pathogenic strains of the soilborne fungus Periconia circinata produce peritoxins with host-selective toxicity against susceptible genotypes of sorghum. The peritoxins are low molecular weight, hybrid molecules consisting of a peptide and a chlorinated polyketide. Culture fluids from pathogenic, toxin-producing (Tox+) and non-pathogenic, non-producing (Tox-) strains were analyzed directly by gradient high performance liquid chromatography (HPLC) with photodiode array detection and HPLC-mass spectrometry for intermediates and final products of the biosynthetic pathway. This approach allowed us to compare in detail the metabolite profiles of the Tox+ and Tox- strains and to detect compounds that are common to both phenotypes. Peritoxins A and B and the biologically inactive intermediates N-3-(E-pentenyl)-glutaroyl-aspartate, circinatin and 7-chlorocircinatin were detected only in culture fluids of the Tox+ strains. Thus, the Tox- strains differ from the Tox+ strains by several metabolic steps and may lack genes encoding the entire peritoxin biosynthetic pathway.