Microarray-based screening of differentially expressed genes in peanut in response to Aspergillus parasiticus infection and drought stress

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 Aspergillus 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 pre-harvest aflatoxin contamination, using cDNA microarray containing 384 unigenes selected from two expressed sequenced tag (EST) cDNA libraries challenged by biotic and abiotic stresses. A total of 42 up-regulated genes (log2 ratio > 1) in several functional categories were detected under both A. parasiticus challenge and drought stress. A total of 52 up-regulated genes were detected in response to drought stress alone. There were 25 genes commonly expressed in both treatments. The top 20 up-regulated gene from A. parasiticus challenge and drought stress 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. Although 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.