Artificial selection on genes for epigenetic regulation in maize [abstract]
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Maize (corn) was domesticated from teosinte through a single domestication event in Mexico about nine thousand years ago. This domestication brought about the original landrace maize varieties that were spread though out the Americas by Native Americans. From the landraces, breeders have selected inbred lines of maize. Both the domestication and crop breeding have led to the selection of specific alleles at genes that control physical traits of maize. While the domestication and selection processes result in reducing the genetic diversity in all genes, the selected genes exhibit greatly reduced genetic diversity. Epigenetics is defined as phenotypic differences that result from changes in the chromatin state of a gene rather than a change in the DNA sequence. In maize more than 300 genes have been identified to encode proteins that modify chromatin structure and affect epigenetic processes. Among these genes are histone acetyltransferases (HACs) and histone deacetylases (HDAs). Histones are important for condensing the chromatin in the nucleus. To retrieve information on the chromatin, histones must perform a conformational change to loosen the chromatin and allow for it to be copied and expressed by the organism. Have the genes that control epigenetic processes in maize been targets of artificial selection in maize? My project has been to determine if HDA and HAC genes show evidence of selection. Through DNA sequencing on sets of genes in panels of inbred and teosinte accessions, we have discovered one gene from the histone deacetylase group, hda108, with strong evidence of selection. By sequencing landrace accessions we will determine if selection in this gene occurred early during domestication or more recently in the selection process. These results suggest that at least one gene controlling chromatin structure has been a target of selection.