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Title:   Author  item
                                            Alexander, Nancyitem
                                            McCormick, Susanitem
                                            ZIEGENHORN, SUZANNE - FORMER ARS EMPLOYEE
  Submitted to: National Fusarium Head Blight Forum
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 12/12/2000
                                    Publication  Date: N/A
                                    Citation: N/AInterpretive Summary:
                                Technical Abstract: Fusarium graminearum, the causative agent of wheat head blight, produces the trichothecene deoxynivalenol (DON).  DON acts as a protein synthesis inhibitor and is a significant factor contributing to the disease. However, acetylation of the C-3 hydroxyl group of a number of different trichothecenes reduces the toxicity to yeast as well as to the single-  celled plant, Chlamydomonas, suggesting that the C-3 OH site is critical for toxicity.  Since the TRI101 gene in F. graminearum encodes a 3-O- acetyltransferase, this gene may function for self-protection against DON and its intermediates.  Disruption of the FgTRI101 was done to test if, and to what extent, this gene is involved in self-protection.  The degree of virulence on wheat by mutants deficient in TRI101 activity has also been evaluated.  Fungal disruptants were tested on toxin-containing medium to determine if the mutants were more sensitive than the wild type strain.  They were also analyzed to determine what intermediates in the pathway the synthesized.  TRI101-disrupted mutants in F. graminearum do not accumulate the expected C-3 hydroxylated compound and instead accumulate the C-3,8 hydroxylated compound, which has been shown to be less toxic in our Chlamydomonas toxicity tests.  To test whether FgTRI101 disruptants were less virulent than wild type, wheat virulence testing in the greenhouse showed that the fungal TRI101 disruptants produced far less disease than the wild type.  Our results support the conclusion, that in F. graminearum, FgTRI101 plays a role in self-protection but is not the sole mechanism. Disruption mutants are weakened in their ability to infect and cause disease in wheat, most likely because they do not produce large quantities of a C-3 OH toxic byproduct.


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