Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2005
Publication Date: 6/1/2005
Citation: Luo, M., Liang, X.Q., Dang, P.M., Holbrook, Jr., C.C., Bausher, M.G., Lee, R.D., Guo, B. 2005. Microarray-based screening of differentially expressed genes in peanut in response to Aspergillus parasiticus infection and drought stress. Plant Science. 169:695-703. Interpretive Summary: Aspergillus flavus and A. parasiticus can colonize seeds of several agricultural crops including peanut. This can result in contamination of the seeds with toxic fungal metabolite aflatoxins. Aflatoxin contamination is severe in peanut that are grown under drought stressed conditions, and this toxin can cause teratogenic and carcinogenic diseases in animal and human. The development of resistant cultivars can be effective in improving food safety and decreasing production costs. Because of the economic importance of aflatoxin contamination in peanut, it is important to understand peanut resistance at the molecular level and it would be useful to develop markers for use in breeding disease resistant cultivars. In this investigation we report the identification and characterization of specific gene expressions in response to Aspergillus infection and drought stress using new technologies, microarray and real-time PCR. The 384 genes for microarray were selected frp, adversity resistant unique DNA sequences. Some genes identified by microarray analysis were validated by real-time PCR to confirm the gene function and to reduce the false positives. These genes were expressed differentially in different treatments in peanut line A13 which is drought tolerant and has lower aflatoxin contamination. Molecular markers could be developed to more rapidly select for these genes in peanut breeding programs.
Technical Abstract: Aflatoxin contamination caused by Aspergillus fungi is a great concern in peanut production worldwide. Pre-harvest A. parasiticus infection and aflatoxin contamination are usually severe in peanuts that are grown under drought stressed conditions; however, drought tolerant peanut lines have less aflatoxin contamination. The objective of this study was to identify resistance genes in response to A. parasiticus infection under drought stress using microarray and real-time PCR. To identify transcripts involved in the resistance, we studied the gene expression profiles in peanut genotype A13 which is drought tolerant and resistant to preharvest aflatoxin contamination, using cDNA microarray containing 384 unigenes selected from two EST (expressed sequenced tag) cDNA libraries challenged by abiotic and biotic stresses. A total of 83 up-regulated spots (Log2ratio>1) representing 42 genes in several functional categories were detected under both A. parasiticus infection and drought stress. A total of 104 up-regulated spots representing 52 genes were detected in response to drought stress alone. There were forty-nine up-regulated spots (25 genes) commonly expressed in both treatments. The top 20 genes were selected for validation of their expression levels using real-time PCR. A13 was also used to study the functional analysis of these genes and a possible link of these genes to the resistance trait. Microarray technology and real-time PCR were used for comparison of gene expression. The selected genes identified by microarray analysis were validated by real-time PCR. Further investigations are needed to characterize each of these genes. Gene probes could then be developed for application in breeding selection.