ARS | Publication request: Nuclear Magnetic Resonance (NMR) studies on the biosynthesis of fusaric acid from Fusarium oxysporum f. sp. vasinfectum

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 16, 2011
Publication Date: April 16, 2011
Citation: Stipanovic, R.D., Wheeler, M.H., Puckhaber, L.S., Liu, J., Bell, A.A., Williams, H.J. 2011. Nuclear Magnetic Resonance (NMR) studies on the biosynthesis of fusaric acid from Fusarium oxysporum f. sp. vasinfectum. Journal of Agricultural and Food Chemistry. 59:5351-5356.

Interpretive Summary: The plant pathogen Fusarium oxysporum f. sp. vasinfectum is a fungus that attacks cotton. A uniquely virulent type of this pathogen was inadvertently introduced into the U.S. on cottonseed imported into California for dairy feed. This imported pathogen produces very high amounts of a chemical that is toxic to cotton. This compound is called fusaric acid. This chemical may play a vital role in the pathogenicity of the fungus. To more fully understand the role this chemical may play in the pathogenicity of the fungus, we investigated how the molecule is assembled by the organism. Our research has shown the probable involvement of two kinds of genes that control its production in the fungus. This may help us to develop new strategies to control this pathogen.

Technical Abstract: Fusarium oxysporum is a fungal pathogen that attacks many economically important plants. Uniquely pathogenic strains of F. oxysporum f. sp. vasinfectum were inadvertently imported into the United States on live cottonseed for dairy cattle feed. These strains produce exceptionally high concentrations of the phytotoxin fusaric acid. Thus, fusaric acid may be a critical component in the pathogenicity of these biotypes. This study investigated the biosynthesis of fusaric acid using 13C-labeled substrates including [1,2-13C-2]-acetate as well as 13C- and 15N-labeled aspartate and 15N-glutamine. The incorporation of labeled substrates is consistent with the biosynthesis of fusaric acid from three acetate units at C5-C6, C7-C8, and C9-C10, with the remaining carbons being derived from aspartate via oxaloacetate and the TCA cycle, the oxaloacetate originates in part by transamination of aspartate, but most of the oxaloacetate is derived by deamination of aspartate to fumarate by aspartase. The nitrogen from glutamine is more readily incorporated into fusaric acid than that from aspartate.