Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/1999
Publication Date: N/A
Interpretive Summary: Aspergillus fungi sometimes grow on certain grains or seed, like corn, peanuts and cottonseed. Because these fungi can produce aflatoxin and sterigmatocystin, mycotoxins that are toxic to humans and animals, the presence of Aspergillus causes considerable concern. The present study showed that polyunsaturated fatty acids (pufa) and metabolites of pufa produced by plants are capable of altering the asexual/sexual development of the fungi; whereas, monounsaturated and saturated fatty acids do not. The production of aflatoxin and sterigmatocystin is often correlated with the stage of Aspergillus asexual/sexual development. It has been reported by others that sporulating factors are oxygenated fatty acids derived from pufa. Thus, pufa may have its effect by being a precursor to these sporulating factors. The plant metabolites of pufa are similar in structure to sporulating factors, and thus may serve as competitors or mimics. This work would benefit other scientists, who would be interested in understanding asexual/sexual development of Aspergillus as a method to control aflatoxin and sterigmatocystin production by the fungi.
Technical Abstract: Aspergillus spp. are frequent seed-colonizing fungi that produce carcinogenic mycotoxins, aflatoxin, and sterigmatocystin. The production of Aspergillus mycotoxins is correlated with the ability of the fungi to develop conidiophores (i.e., asexual spores) and overwintering bodies (i.e., sclerotia ascospores contained within cleistothecia). We have found that development of all three of these structures in Aspergillus nidulans, Aspergillus flavus, and Aspergillus parasiticus are statistically affected by linoleic acid and linoleic acid seed derivatives, hydroperoxylinoleic acids, which we have previously shown to regulate aflatoxin and sterigmatocystin production. Specific morphological effects of these fatty acids include inducing precocious and increased asexual spore development in A. flavus and A. parasiticus strains and altered sclerotial production in A. flavus. In A. nidulans, asexual to sexual spore ratio was altered by all three compounds in a manner similar to that of the A. nidulans sporulating factors, psi factors. Other polyunsaturated fatty acids had similar, although lesser, effects on Aspergillus development, whereas saturated and monounsaturated fatty acids did not affect Aspergillus development. Because A. nidulans psi factors are also derived from linoleic acid, our results suggest that seed fatty acids might regulate fungal development by mimicking and/or interfering with fungal sporogenic compounds.