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Understanding Complex Traits in Maize through Structural and Functional Genomics Georgia Davis
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Structural genomics n Science related to discovery of gene order and organization across the genome.
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Structural Genomics n Genetic mapping n Physical mapping n In situ hybridization
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Functional Genomics n Science related to the discovery and definition of the function of genes Whole plantCellular Biochemical RNA C16 C18 C20 C22 C24 C26 AldehydesAlcohols Wax Esters
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Functional Genomics n Trait analysis n Gene disruption strategies –Targeted –Random n DNA microarrays n RNA profiling n Protein chips n Protein prediction algorithms
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Functional Genomics n Insect Resistance –QTL Analysis –Biochemical Pathway Identified. –Major QTL With Unknown Function. n Aflatoxin Reduction –QTL Analysis –Major QTL With Unknown Function. –One Biochemical Pathway Identified.
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Fall armyworm n Present east of Rockies and South of Canada. n Egg adult in 4 weeks n One female lays several hundred eggs. n Broad host range
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Hosts of Fall Armyworm
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Southwestern Corn Borer n Narrow host range. n Mainly in southeastern US.
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Southwestern Corn Borer Hosts
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Germplasm Fall armyworm damage 10 days after infestation with 30 larvae per plant
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Lepidopteran Resistance Beet armyworm European corn borer Corn ear worm Fall armyworm Southwestern corn borer
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Juvenile traits n Dull epicuticular wax layer –Fatty alcohols n No leaf hairs n Adventitious roots present n No buliforme cells n Cells are rounded
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Juvenile vs. Adult Leaves n Leaves maintain their phase status throughout development. n Number of juvenile leaves varies among inbreds. n A number of mutants in juvenile to adult phase change have been identified.
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43% Summary of QTL Study 66% SWCB FAW Juvenility 7% 51% 27% 11%59% 1234 5 678910 gl15
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Gl15 n Apetala2-type transcription factor. n Regulates long-chain wax ester synthesis. n Controls epidermal juvenile to adult phase change.
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Functional Genomics n Insect Resistance –QTL Analysis –Biochemical Pathway Identified. –Major QTL With Unknown Function. n Aflatoxin Reduction –QTL Analysis –Major QTL With Unknown Function. –One Biochemical Pathway Identified.
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Hosts of Aspergillus flavus
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Aspergillus flavus Infection via silk channel wounds in kernels cracks in kernels
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Aflatoxin Aflatoxin B1 Potent carcinogen. Associated with liver cancer in humans.
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Health concerns
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Aflatoxin contamination n Large environmental influence. –Drought stress increases aflatoxin level. n Correct genes in both fungus and host required for high levels of toxin formation. n Synthesis is biochemically similar to anthocyanin biosyntheis in maize.
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Aflatoxin QTL Summary Mp313E favorable allele Va35 favorable allele D A DA
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Anthocyanin vs. aflatoxin a2 bz1 c1-p a1 a1 sh2 a2 bt pr bz2 c1-n c sh wx in1 pr r-g sh bz wx su c2 c2 C2I-df 23X toxin 9X toxin 7X toxin
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Functional Genomics Whole plantCellular Biochemical RNA C16 C18 C20 C22 C24 C26 AldehydesAlcohols Wax Esters
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Summary n Structural genomics provides the tools needed to support functional genomics. n In plants, future technological advancements in the areas of protein-protein interactions and site-specific knockouts on a genome- wide scale are needed.
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