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United States Department of Agriculture

Agricultural Research Service

Title: Identification and Characterization of Differentially Expressed Genes in Two Inbred Maize Lines Using Microarray Technology

Authors
item Kelley, Rowena - MSU PLT & SOIL DEPT
item Boykin, Deborah
item Bridges, Susan - MSU DEPT COMP SCI
item Brooks, Thomas
item Williams, William

Submitted to: Multicrop Aflatoxin and Fumonisin Elimination and Fungal Genomics Workshop-The Peanut Foundation
Publication Type: Abstract Only
Publication Acceptance Date: October 12, 2006
Publication Date: October 15, 2006
Citation: Kelley, Rowena Y., Boykin, Debbie L., Bridges, Susan M. Brooks, Thomas D., Williams, W. Paul (2006). Identification and Characterization of Differentially Expressed Genes in Two Inbred Maize Lines Using Microarray Technology. Aflatoxin/Fumonisin, Fungal Genomics Workshop. Hilton Fort Worth, Forth Worth, Texas; October 15-18, 2006.

Interpretive Summary: Aspergillus flavus Link:Fr is a saprophytic fungus that can produce aflatoxin during pathogenesis of maize and other oilseed crops. Aflatoxin B1 is the most potent natural occurring carcinogen known for livestock and humans. Efforts to reduce afaltoxin accumulation have focused on bio-control, agronomic practices, and enhancing host resistance. Though a number of historically important aflatoxin resistant maize lines exist, traditional breeding programs have failed to integrate this resistance into elite lines. Despite a number of Quantitative Trait Loci (QTL) that correspond to resistance having been identified, few individual genes known to contribute to resistance in maize have been characterized. With the availability of maize microarrays we can now begin to identify specific genes within these QTLs that are involved in resistance. Recent microarray studies have identified genes differentially expressed in A. flavus during aflatoxin biosynthesis and during maize acclimation response to ultraviolet radiation. However, no work using microarrays has been done examining gene expression related to A. flavus infection and aflatoxin production. Thus, the objectives of this study were (1) to evaluate differential gene expression levels for resistance to A. flavus kernel infection in susceptible (Va35) and resistant (Mp313E) maize lines using cDNA microarray analysis, (2) to evaluate differences in A. flavus accumulation between the resistant and susceptible maize lines and between inoculation treatments using ears harvested at physiological maturity, and (3) to identify genetic locations of any significantly expressed ESTs. Of the 5065 ESTs represented on the maize microarrays, 234 were found to be significantly up-regulated in response to A. flavus inoculation (P < 0.05). Among these significantly up-regulated genes, 123 were up-regulated in the susceptible line Va35; 95, in the resistant Mp313E; and 16, in both lines. These up-regulated genes were classified into three functional categories: biological process, molecular functions, and cellular components. Using the Maize Genetic and Genomics Database to compare these identified gene sequences with Quantitative Trait Loci (QTL) from Mp313E x B73 and Mp313E x Va35 mapping studies, 64 genes can be mapped to specific locations within the genome. Five of the 64 mapped genes are located on chromosome 1, 3, 4 or 6 and are in close proximity to four previously published QTLs shown to be linked to aflatoxin resistance. As these findings demonstrate, using cDNA microarray experiments and QTL data allows for a more accurate identification of candidate aflatoxin resistant genes in maize. Future coupling of microarray data with available QTL analysis will facilitate understanding of pathways that lead to aflatoxin resistance and identify ESTs/candidate genes that have the largest impact on resistance.

Technical Abstract: Aspergillus flavus Link:Fr is a saprophytic fungus that can produce aflatoxin during pathogenesis of maize and other oilseed crops. Aflatoxin B1 is the most potent natural occurring carcinogen known for livestock and humans. Efforts to reduce afaltoxin accumulation have focused on bio-control, agronomic practices, and enhancing host resistance. Though a number of historically important aflatoxin resistant maize lines exist, traditional breeding programs have failed to integrate this resistance into elite lines. Despite a number of Quantitative Trait Loci (QTL) that correspond to resistance having been identified, few individual genes known to contribute to resistance in maize have been characterized. With the availability of maize microarrays we can now begin to identify specific genes within these QTLs that are involved in resistance. Recent microarray studies have identified genes differentially expressed in A. flavus during aflatoxin biosynthesis and during maize acclimation response to ultraviolet radiation. However, no work using microarrays has been done examining gene expression related to A. flavus infection and aflatoxin production. Thus, the objectives of this study were (1) to evaluate differential gene expression levels for resistance to A. flavus kernel infection in susceptible (Va35) and resistant (Mp313E) maize lines using cDNA microarray analysis, (2) to evaluate differences in A. flavus accumulation between the resistant and susceptible maize lines and between inoculation treatments using ears harvested at physiological maturity, and (3) to identify genetic locations of any significantly expressed ESTs. Of the 5065 ESTs represented on the maize microarrays, 234 were found to be significantly up-regulated in response to A. flavus inoculation (P < 0.05). Among these significantly up-regulated genes, 123 were up-regulated in the susceptible line Va35; 95, in the resistant Mp313E; and 16, in both lines. These up-regulated genes were classified into three functional categories: biological process, molecular functions, and cellular components. Using the Maize Genetic and Genomics Database to compare these identified gene sequences with Quantitative Trait Loci (QTL) from Mp313E x B73 and Mp313E x Va35 mapping studies, 64 genes can be mapped to specific locations within the genome. Five of the 64 mapped genes are located on chromosome 1, 3, 4 or 6 and are in close proximity to four previously published QTLs shown to be linked to aflatoxin resistance. As these findings demonstrate, using cDNA microarray experiments and QTL data allows for a more accurate identification of candidate aflatoxin resistant genes in maize. Future coupling of microarray data with available QTL analysis will facilitate understanding of pathways that lead to aflatoxin resistance and identify ESTs/candidate genes that have the largest impact on resistance.

Last Modified: 7/28/2014
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