Submitted to: Toxicological Sciences
Publication Type: Abstract Only
Publication Acceptance Date: 12/1/2006
Publication Date: 3/25/2007
Citation: Williams, L.D., Glenn, A.E., Bacon, C.W., Smith, M.A., Riley, R.T. 2007. Fumonisin production is necessary for development of the full spectrum of symptoms indicative of Fusarium verticillioides maize-seedling disease and evidence for disruption of sphingolipid metabolism as the proximate cause. Toxicological Sciences. Abst. 550, p. 118. Interpretive Summary: Abstract - no summary required.
Technical Abstract: The fungus Fusarium verticillioides infects maize and produces fumonisins, inhibitors of ceramide synthase. To determine the role of fumonisins in maize seedling disease, seeds were inoculated with fumonisin producing or non-producing strains of F. verticillioides. Seedlings grown from seeds inoculated with the producing strains had detectable fumonisins in roots and soils, and sphingoid bases and sphingoid base 1-phosphates were elevated in roots. Leaf lesions and abnormal leaf developmental were only observed with producing strains and while non-producing strains of F. verticillioides caused reduced root and stalk growth the effect on growth was greatest with producing strains. Leaf lesion incidence and severity of effects on root and stalk growth were significantly correlated with fumonisin in roots and the extent of disruption of sphingolipid metabolism in roots. In a subsequent study with the fumonisin producing strain MRC826, seedlings grown from inoculated seeds were harvested on days 7, 14 and 21. Reduced growth of aerial plant parts and roots were seen in seedling as early as day 7, however, leaf lesions were not apparent until day 14. Fumonisins were detected in the roots of seedlings and was maximal on day 14. There were significant increases in free sphingoid bases on day 7 which were maximal on day 14. There were also significant increases in free sphingoid base 1-phosphates on day 7. However, the level of free sphinganine 1-phosphate decreased significantly after day 7. These results suggest a time-dependent adaptive response to disrupted sphingolipid metabolism after prolonged fumonisin exposure, and also support the hypothesis that fumonisin is necessary and sufficient to produce the full spectrum of symptoms indicative of F. verticillioides-induced maize seedling disease.