Submitted to: Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/4/2007
Publication Date: 9/1/2007
Citation: Chen, Z.-Y, Brown, R.L., Damann, K.E., Cleveland, T.E. 2007. Identification of maize kernel endosperm proteins associated with resistance to aflatoxin contamination by Aspergillus flavus. Phytopathology. 97(9):1094-1103. Interpretive Summary: Aflatoxins are poisons produced by the fungus, Aspergillus flavus, after it infects agricultural commodities, such as corn. Since aflatoxins in food and feed are regulated, enhanced ability to control aflatoxin accumulation in corn through increased host resistance against Aspergillus flavus could contribute significantly towards growers producing a safe and more profitable crop. A study conducted by the Food and Feed Safety Research Unit at SRRC identified several proteins that are associated with resistance in certain resistant corn lines and located in the corn kernel endosperm. One particular protein, peroxiredoxin antioxidant (PER 1), was shown to have enzyme activity that could play a role in enhancing plant stress tolerance and resistance. This protein could serve as a marker for corn breeders when breeding resistant corn lines for commercial use. These lines could then be grown to enhance protection of food and feed, as well as to decrease financial losses to growers.
Technical Abstract: Aflatoxins are carcinogens produced mainly by Aspergillus flavus during infection of susceptible crops, such as maize (Zea mays L.). Previously, embryo proteins from maize genotypes resistant or susceptible to A. flavus infection were compared using proteomics and resistance-associated proteins were identified. Here we report the identification of additional resistance associated proteins from maize endosperm using the same approach. Kernel endosperm proteins from five resistant genotypes were compared with those of five susceptible genotypes using large format 2-D gel electrophoresis. Ten protein spots were upregulated 2 fold or higher in resistant lines compared to susceptible ones. Peptide sequencing of these proteins identified them as globulin 2, late embryogenesis abundant proteins (LEA3 and LEA14), a peroxiredoxin antioxidant (PER1), heat shock proteins (HSP17.2), a cold-regulated proteins (COR), and an antifungal trypsin/alpha-amylase inhibitor protein (TI) based on peptide sequences. The gene encoding one such upregulated protein, PER 1, was cloned and over-expressed in Escherichia coli. The over-expressed PER 1 protein demonstrated peroxidase activity in vitro. In addition, per 1 expression was significantly higher in the resistant genotype Mp420 than in the susceptible genotype B73 in the late stage of kernel development, and was significantly induced upon A. flavus infection, suggesting it may play an important role in enhancing kernel stress tolerance and aflatoxin resistance. The significance of other identified proteins to host resistance against fungal infection and stress tolerance is also discussed.