ARS | Publication request: Identification of resistance-associated proteins in closely-related maize lines varying in aflatoxin accumulation

Submitted to: Molecular Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 2011
Publication Date: N/A

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. In order to make this task easier, we used corn lines with genetically similar backgrounds but which differed in aflatoxin accumulation. Proteins identified as higher in amount in resistant lines versus susceptible repeated findings of previous studies: they fell into antifungal, stress-related, storage and a new category not seen in previous studies, regulatory. Further studies may determine which of these proteins would 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: Aspergillus flavus infection of maize and subsequent contamination with carcinogenic aflatoxins poses serious health concerns, especially in developing countries. Maize lines resistant to A. flavus infection have been identified; however, the development of commercially-useful aflatoxin-resistant maize lines has been hindered due to a lack of breeding markers. To identify maize aflatoxin resistance associated proteins (RAPs) as potential markers for breeding, 52 S4 (selfed 4th generation) lines developed from crosses between five African maize inbreds and five temperate aflatoxin resistant lines were screened using the kernel screening assay. Five pairs of closely-related lines that had 75% to 94% genetic similarity within each pair and had a significant difference in aflatoxin accumulation were selected for the study. Kernel embryo and endosperm protein profiles differences within the pair and across pairs were compared using 2 D PAGE. Differentially expressed (is equal to or greater than 1.5 fold) RAPs were identified through LC-MS/MS which include antifungal, stress-related, storage and regulatory proteins. Sequence homology analysis highlighted the potential involvement of several proteins in maize that confer resistance to A. flavus infection and/or aflatoxin production.