2012 Annual Report
1a.Objectives (from AD-416):
Characterize the role of maize kernel proteins and corresponding genes in resistance to aflatoxin contamination and aflatoxin-producing fungi. Identify and characterize resistance-associated proteins/genes in soybean that may enhance our understanding of aflatoxin-resistance and that may be exploited through enhancement of homologous genes in maize. Determine the most useful maize resistance markers for breeders to use in transferring resistance to commercially useful germplasm.
1b.Approach (from AD-416):
Characterize resistance-associated proteins (RAP's), e.g., antifungal, stress
responsive, or interfering with toxin signaling pathways, in developing and mature maize kernels identified at SRRC through proteomic comparisons of resistant and susceptible maize inbreds, some with very similar genetic backgrounds. Identify, using proteome analyses, resistance-associated proteins/genes in soybean with efficacy against A. flavus and aflatoxin production. Soybean is an aflatoxin resistant species, therefore, the possibility exists that resistance factors may be identified that could be exploited through enhancement of homologous genes in maize. Characterize function of maize and soybean proteins/genes through molecular and physiological laboratory and greenhouse investigations. Determine role of proteins/genes in aflatoxin-resistance using RNAi gene silencing technology.
Our lab examined differences in gene expression between resistant and susceptible maize lines using microarray analysis (a method for examining hundreds of genes simultaneously). The data indicate that susceptible maize lines were able to induce most of the genes seen in resistant lines upon Aspergillus (A.) flavus infection, but at a slower pace and a smaller magnitude. Our lab also evaluated the five aflatoxin resistant African maize lines (obtained from International Institute of Tropical Agriculture (IITA)-SRRC breeding program) in 2010 and 2011 under Louisiana field conditions and identified at least one line showed high levels of afaltoxin resistance. Two of the six lines were found to have high levels of aflatoxin resistance, comparable to resistant checks used in the study. A drought study is also planned for the coming year to determine their performance under drought conditions, which are known to severely impact aflatoxin production in maize. Our lab partially characterized a newly identified novel antifungal glucanase gene, including comparing the differences in expression pattern, tissue specificity, of this gene in response to biotic and abiotic stresses. A manuscript summarizing this part of research is currently being revised after conducting additional suggested experiments, such as antifungal assays using transgenic Arabidopsis (an experimental laboratory plant) expressing the corn glucanase gene, as well as studies to determine whether this glucanase gene is regulated through salicylic acid signal transduction pathway (a cascade of biochemical reactions possibly leading to resistance). Lastly, a promoter analysis (the part of a gene that initiates expression of a gene) of PR10 antifungal genes was begun to gain insight into how the expression of host resistance related genes is regulated. A manuscript summarizing the results on the maize PR10.1 promoter analysis is being prepared. In this study, we have identified a small region (0.6 kb) of PR10.1 promoter that can drive high levels of target gus gene expression in Arabidopsis; this can be used in the future to enhance host resistance associated genes in corn.