AFLATOXIN CONTROL THROUGH TARGETING MECHANISMS GOVERNING AFLATOXIN BIOSYNTHESIS IN CORN AND COTTONSEED
Location: Food and Feed Safety Research
Title: THE SEC- MUTANT OF ASPERGILLUS PARASITICUS IS ALTERED IN ITS PROFILE OF SECONDARY METABOLITES
Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: April 17, 2006
Publication Date: May 21, 2006
Citation: Glassbrook, N.J., Kale, S.P., Bhatnagar, D., Wilkinson, J.R., Yu, J., Cary, J.W., Cleveland, T.E., Payne, G.A. 2006. The sec- mutant of Aspergillus parasiticus is altered in its profile of secondary metabolites. In: Proceedings of the American Society for Microbiology Annual Meeting, May 21-26, 2006, Orlando, FL. Abstract #O-040, p. 428.
The sec- (secondary metabolite minus) mutant of Aspergillus parasiticus SUI produces fewer conidia on complete and minimum media and fails to produce aflatoxin or to convert labeled aflatoxin pathway precursors into aflatoxin. Transcripts of the aflatoxin pathway genes are barely detectable and transcripts of the pathway regulatory gene aflR are reduced 5-10 fold (Kale et al. 2003. Mycological Research. 107:831). To better characterize the metabolism of this mutant, the wild type (WT) and the sec- mutant were cultured from spore suspensions at 28 degrees C in shake flasks containing a balanced salt solution with glucose as the primary carbon source and ammonia as the sole nitrogen source. Samples were analyzed by liquid chromatography coupled with mass spectrometry (LC/MS) and/or gas chromatography coupled with mass spectrometry. Preliminary comparisons of WT with the sec- mutant by LC/MS confirmed that production of aflatoxin B1 is greatly reduced or eliminated in the sec- mutant. In addition, comparisons of the chromatographic fingerprints of the wild type and sec- mutant revealed large differences in the small molecule compositions of the two strains. Although the sec- mutant appeared to have some unique components when compared to WT, chromatograms of the sec- mutant samples lacked many of the prominent peaks present in WT. Thus the sec- mutant appears to be altered in several pathways of secondary metabolism, not just aflatoxin biosynthesis. These findings suggest that the mutation in the sec- strain may be in a global regulator of secondary metabolism. Further experiments are in progress, using mass spectrometry and pulse/pulse-chase techniques, to identify specific compounds and pathways impacted by the mutation. Additionally, this metabolic profile will be compared with a transcriptional profile (using an EST microarray) to determine the changes in gene expression resulting from the sec- mutation.