Submitted to: Journal of Food Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/21/1998
Publication Date: N/A
Citation: Interpretive Summary: Aflatoxins are a major group of toxins produced by the fungi Aspergillus flavus and A. parasiticus. They are of major concern, especially in the Southeastern U.S., because they have been shown to cause cancer of the liver. Thus, the development of strategies to reduce or eliminate aflatoxin contamination in food and fiber is a research priority in ARS. Our efforts on this problem have focused on natural resistance in the host such as corn. This study examined the distribution and localization of two proteins in corn seed that are known to inhibit the growth of the fungi which produce aflatoxins. We isolated and identified the portion of the corn kernel where each protein was produced in the highest concentration. These results further clarify the role of these proteins in inhibiting the growth of these important fungi and suggests that we may be able to develop corn with kernels which produce unique chemicals to fight infection with these pathogens.
Technical Abstract: This study examined the distribution and localization of two antifungal proteins, ribosome-inactivating-protein (RIP) and zeamatin, in maize kernel tissues to better understand their roles in host resistance to the fungal pathogen Aspergillus flavus. Proteins were extracted from endosperm (including aleurone layer) and embryo tissues of imbibed maize kernels and western blot analyses revealed that RIP-like protein was present at higher levels in endosperm than in embryo tissues whereas zeamatin-like protein was more concentrated in embryo tissues than those in endosperm tissues. However, there were three protein bands in the endosperm and two bands in the embryo that reacted to anti-RIP antibody in western blot analyses. Tissue-prints were conducted to localize the antifungal proteins. Imbibed kernels were cut longitudinally and transversely, and blotted onto nitrocellulose membranes. Using antibodies against maize RIP and zeamatin, RIP was found primarily in the aleurone layer of the endosperm and glandular layer of scutellum whereas zeamatin was located mainly in the kernel embryo. These results provide insight into the functions of these antifungal proteins, especially since the presence of RIP and zeamatin within maize kernels uniquely protects kernels from pathogens.