|Zimeri, Anne - TMRU/ARS/USDA, ATHENS,GA|
|Williams, Lonnie - TMRU/ARS/USDA, ATHENS,GA|
Submitted to: US-Japan Coop Pgm on Dev and Util of Natural Products Abstracts Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: November 7, 2006
Publication Date: November 8, 2006
Citation: Zimeri, A.M., Williams, L.D., Riley, R.T., Glenn, A.E. 2006. Necessity of fumonisin production by Fusarium verticillioides for Foliar disease on corn seedlings and evaluation of absorption and translocation of the mycotoxin. US-Japan Coop Pgm on Dev and Util of Natural Products Abstracts Proceedings.November 5 - 12, 2006. Washington, DC. Interpretive Summary: Abstract - no summary required.
Technical Abstract: Fusarium verticillioides, the causative agent of corn seedling blight and ear rot, produces the mycotoxin fumonisin B1 (FB1). The toxicity of FB1 is due to its inhibition of ceramide synthase, a key enzyme necessary for sphingolipid metabolism. Such inhibition occurs in both animals and plants. For example, FB1 is known to inhibit ceramide synthase in tomato, causing an increase in free sphinganine, a ceramide precursor, and free phytosphingosine, produced by hydroxylation of sphinganine. We recently reported that roots of corn seedlings inoculated with F. verticillioides had elevated free sphinganine and phytosphingosine as well as their respective 1-phosphates. Thus, FB1 produced by F. verticillioides can inhibit ceramide synthase in corn. Additionally, FB1 production by F. verticillioides strains was tightly linked to their pathogenicity since only FB1 producing strains caused necrotic leaf lesions and developmental abnormalities. Plants exposed to fungal culture extracts containing FB1 exhibited the full suite of symptoms as occurs on plants infected with FB1 producing strains. In addition, we found that aerial portions of such plants contained FB1 (0.0044 ppm), suggesting the metabolite was taken up by roots and translocated. However, active uptake and translocation of FB1 into leaf tissue was minimal (60-90 fold less in leaves than in roots). Accumulation of fumonisin in kernels via translocation was assessed by injecting fungal culture extracts containing FB1 into corn stalks below developing ears prior to pollination. Resulting kernels were collected and sampled for fungal infection and FB1 contamination. Translocation and accumulation of the injected FB1 was not supported. However, the injected fungal extracts appeared to confer resistance because the extract treatments had less F. verticillioides infection and only 0.7 ppm total fumonisin contamination compared to 3.1 ppm in the control kernels. Thus, while FB1 production by F. verticillioides was necessary for development of foliar disease symptoms on seedlings, the mycotoxin apparently was not translocated or accumulated to high levels in the leaves, suggesting the disease development may not involve localized ceramide synthase inhibition in the leaves but may result from another mobile signal or pathway. Furthermore, the apparent lack of FB1 accumulation in the kernels via translocation is encouraging from the standpoint of control strategies, and additional studies are planned to more closely evaluate our initial data on suppression of infection and FB1 contamination of kernels by fungal culture extracts.