Submitted to: Great Lakes Regional American Chemical Society Symposium
Publication Type: Abstract Only
Publication Acceptance Date: December 31, 2004
Publication Date: March 15, 2005
Citation: Glenn, A.E., Williams, L.D., Riley, R.T. 2005. Fungal secondary metabolites as fitness and pathogenicity factors: a closer look at fumonisin b1. Great Lakes Regional American Chemical Society Symposium. Interpretive Summary: Abstract of presentation - no interpretive summary required.
Technical Abstract: Fungi produce a vast array of secondary metabolites, often of unknown function but generally believed to enhance fitness and ecological interactions. The fungus Fusarium verticillioides infects and endophytically colonizes corn, forming an association of significant concern due to production of various metabolites, most notably fumonisin B1 (FB1). FB1 is a water soluble mycotoxin causing various species-specific animal diseases, including cancer in experimental rodents. We have examined an apparent seedling pathogenicity factor produced by the fungus that results in necrotic leaf lesions and abnormal leaf development. Genetic analysis indicated a single locus segregated for ability to cause disease. Non-pathogenic strains did not cause any disease symptoms, yet still infected and endophytically colonized the corn seedlings. Some strains that were greatly attenuated in their ability to infect seedlings nonetheless caused severe symptoms, suggesting the pathogenicity factor may be a translocated phytotoxin. FB1 production was assessed among the parental and progeny strains and also was found to segregate as a single locus. Linkage between pathogenicity and FB1 production was supported since only the pathogenic strains produced FB1. The non-producing strains lacked much of the fumonisin biosynthetic gene cluster. Free sphingoid bases were elevated significantly in diseased seedlings inoculated with FB1-producing strains due to disruption of sphingolipid metabolism. Seedlings watered with a 1 ppm solution of FB1 showed a stimulatory effect on growth, yet seedlings watered with 10 ppm and higher concentrations showed dose-dependent toxicity, stunting, and elevated free sphingoid bases. Thus far, data have supported FB1 as the phytotoxin and pathogenicity factor causing the disease symptoms. Disease development was dependent upon corn hybrid, indicating that resistance to FB1 toxicity exists. Resistance to FB1 accumulation in corn remains elusive. Efforts are underway to examine FB1 toxicity and resistance mechanisms in differing hybrids, including evaluation of FB1 translocation and accumulation in corn tissues.