ARS | Publication request: A maize lectin-like protein with antifungal activity against Aspergillus flavus

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 29, 2008
Publication Date: January 15, 2009
Citation: Baker, R.L., Brown, R.L., Chen, Z.Y., Cleveland, T.E., Fakhoury, A.M. 2009. A maize lectin-like protein with antifungal activity against Aspergillus flavus. Journal of Food Protection. 72:120-127.

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 responds to environmental stress and is called a cold-regulated protein (COR). The gene corresponding to COR was cloned and the gene and protein were studied to identify properties that may be related to aflatoxin-resistance. We discovered that COR had properties similar to other proteins called lectins and could be classified as such. We also found that COR inhibited growth of Aspergillus flavus. Further studies may determine this protein to be a marker for resistance and therefore useful to breeders developing aflatoxin-resistant commercial corn. 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: The filamentous fungus, Aspergillus flavus, causes an ear rot on maize and produces a mycotoxin, aflatoxin, in colonized maize kernels. Aflatoxins are carcinogenic to humans and animals upon ingestion. The presence of aflatoxins in food and feed is strictly regulated by several governmental agencies. Regulations allow for the presence of a minimal amount of the toxin in agricultural products intended for consumption; aflatoxin contamination results in a large loss in profits and in marketable yields for farmers each year. Several research groups have worked to pinpoint sources of resistance to A. flavus and the resulting aflatoxin contamination in maize. It is well documented that some maize genotypes exhibit greater resistance than others. A proteomics approach has recently been used to identify endogenous maize proteins with potential involvement in resistance to the fungus. Research consisting of the cloning, expression, and partial characterization of one such protein, which shares sequence similarity to cold-regulated proteins (CORs), has been conducted. The over-expressed ZmCOR protein exhibited lectin-like activity against conidia of A. flavus and also displayed fungicidal characteristics via the prevention of conidial germination. These traits suggest this protein may play an important role in enhancing kernel resistance to A. flavus and aflatoxin accumulation.