Submitted to: International Symposium of Mycotoxicology Meeting
Publication Type: Proceedings
Publication Acceptance Date: June 20, 2009
Publication Date: September 9, 2009
Citation: Guo, B., Wang, Z., Luo, M., Abbas, H.K., Lee, D., Scully, B.T. 2009. Monitoring the gene expression in developing corn kernels under drought stress using oligo-array corn inbred for resistance to preharvest aflatoxin contamination. Proceedings of the International Symposium of Mycotoxicology Meeting, September 9-11, 2009, Vienna, Austria. Technical Abstract: Drought stress is a major factor known to contribute to preharvest aflatoxin contamination. Recent studies have demonstrated higher concentration of defense or stress-related proteins in maize kernels of resistant genotypes compared with susceptible genotypes, suggesting that preharvest field condition influences gene expression differently in different genotypes. The objectives were to screen germplasm for resistance to mycotoxin (aflatoxin and fumonisin) production and to study gene expression profiles in response to drought stress. Aflatoxins and fumonisin B1 are hepatotoxic and carcinogenic metabolites produced by Aspergillus flavus and Fusarium moniliforme. These fungi are common natural contaminants of corn. We screened 87 inbred and breeding lines in 2005 and 2006 and analyzed the levels of total aflatoxin and fumonisin B1. A correlation between aflatoxin and fumonisin B1 concentrations in each line was not evident. Nonetheless, these data suggested that the genetic resistance is evident and not correlated to both fungi, and demonstrate that exposure to both mycotoxins can occur simultaneously. The gene expression studies were conducted in the field rain-out cages with irrigation system. Drought stress was imposed at 20 days after pollination (DAP). Immature ears were sampled at the 25, 30, 35, 40, 45 DAP under drought stress verse well-watered condition using the 70-mer maize oligonucleotide microarrays. Gene expression analyses of preharvest developing kernels were also studied using oligonucleotide macroarray of genes identified in microarray study. Mature ears were harvested and tested in the laboratory for fungal colonization and aflatoxin production. The data suggest that preharvest drought stress could affect on postharvest contamination in different genotypes. These results indicate that 35 to 45 DAP was a unique time-point when the developing kernels entered a distinct phase related to aflatoxin contamination. The greatest amplitude of gene expression to drought stress appeared at 35 to 40 DAP. The difference in aflatoxin contamination in preharvest kernels among resistant and susceptible lines not only depends on genetics of the inbred, but also on the response of drought stress and defense related genes. Preliminary analysis of these diverse inbreds suggests that preharvest drought stress may affect postharvest aflatoxin contamination, and the intensity of gene expression as identified in microarray analysis.