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Title: Fungal endophyte metabolism and allelopathic interactions with host plants

Author
item Glenn, Anthony - Tony
item Zitomer, Nicholas
item Riley, Ronald

Submitted to: International Allelopathy Congress
Publication Type: Abstract Only
Publication Acceptance Date: 6/27/2008
Publication Date: 9/24/2008
Citation: Glenn, A.E., Zitomer, N.C., Riley, R.T. 2008. Fungal endophyte metabolism and allelopathic interactions with host plants. International Allelopathy Congress. September 21-25,2008. Saratoga Springs, NY.

Interpretive Summary: Abstract - no summary required.

Technical Abstract: The maize endophyte Fusarium verticillioides produces the fumonisin mycotoxins, which are of significant concern for their animal toxicity caused by inhibition of ceramide synthase and disruption of sphingolipid metabolism. Fumonisin-producing strains associated with maize cause leaf lesions, developmental abnormalities, stunting, and sometimes death of susceptible corn seedlings. Leaf lesion incidence and severity of effects on root and stalk growth were significantly correlated with fumonisins accumulation and disruption of sphingolipid metabolism in roots. Fumonisins were also detected in leaf tissues, with fumonisin B1 (FB1) preferentially accumulated in leaves over fumonisin B2 and fumonisin B3. Levels of FB1 accumulation in the 1st leaf paralleled the susceptibility of maize lines to F. verticillioides-induced leaf lesions, and the levels of FB1 in all leaves of a susceptible sweet corn were significantly (p<0.001) greater than in the resistant dent corn. For all leaves, plants inoculated with a fumonisin-producing strain had significantly elevated sphingoid bases and their 1-phosphates, indicating disruption of sphingolipid metabolism. Interestingly, a unique population of F. verticillioides pathogenic on banana does not produce fumonisins. Fumonisin-nonproducing banana strains form asymptomatic infections in maize without disruption of sphingolipid metabolism. Molecular analysis of the fumonisin biosynthetic gene cluster showed that essentially the entire cluster was deleted in the banana-associated strains. To further evaluate the impact of fumonisin production on maize seedling disease, a banana strain was cotransformed with two overlapping cosmids containing the full gene cluster. Fumonisin-producing cotransformants were recovered and were pathogenic on sweet corn seedlings, thus supporting the hypothesis that fumonisin production is required for development of foliar disease symptoms. The mechanism of action involves accumulation of FB1 and disruption of sphingolipid metabolism in plant tissues. The significance of maize genotype effects on disease development is being investigated in greater detail, including assessing impacts of fumonisin sensitivity on other maize-associated microbes and metabolic activities.