Submitted to: Journal of Food Protection
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/29/2008
Publication Date: 1/15/2009
Citation: Baker, R.L., Brown, R.L., Chen, Z.Y., Cleveland, T.E., Fakhoury, A.M. 2009. A maize trypsin inhibitor (ZmTIp) with limited activity against Aspergillus flavus. Journal of Food Protection. 72:185-188. Interpretive Summary: The fungus named Aspergillus flavus produces a poison called aflatoxin when it infects corn kernels. Aflatoxin prevents the corn from being used commercially. The best strategy for controlling this problem is to develop corn that is resistant to aflatoxin contamination. Towards this aim, we isolated and identified, through comparisons of resistant with susceptible corn lines, proteins that are produced in relatively higher amounts in the resistant lines. One of these proteins was identified as a trypsin inhibitor. The gene corresponding to trypsin inhibitor was cloned and the gene and protein studied to identify properties that may be related to aflatoxin-resistance. We discovered that this trypsin inhibitor had fungal inhibitory properties and inhibited growth to a limited degree of Aspergillus flavus. Further studies are needed to determine if this protein can serve as a marker for aflatoxin-resistance in commercial corn breeding programs and/or is useful in controlling other mycotoxigenic or ear rotting fungi. This could lead to future savings of millions of dollars to growers, as a result of the elimination of aflatoxin contamination of corn.
Technical Abstract: Infection of maize both pre- and post-harvest by Aspergillus flavus is a severe agricultural problem in the Southern United States. Aflatoxins are secondary metabolites produced by A. flavus and are carcinogenic to humans and animals upon ingestion. Extensive research has been conducted to identify sources of resistance to A. flavus in maize. It is well documented that some maize genotypes exhibit greater resistance to A. flavus than others. Many research groups have validated the role of plant trypsin inhibitors (TIs) as a means of plant defense against fungal infection. Research consisting of the cloning, expression, and partial characterization of one previously uncharacterized TI protein has been conducted. The over-expressed protein displayed TI activity, as expected, as well as a slight ability to alter germination of A. flavus conidia. This effect on fungal growth, although less than that of previously investigated TIs, marks this protein as a potential source of resistance to aflatoxin accumulation in maize.