Molecular Mechanisms Controlling Heritable Epigenetic Variation

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This project addresses the nature of cellular processes by which eukaryotic chromosomes generate and maintain heritable variation in gene control without altering DNA sequence. These processes are experimentally simple to study when they operate on, or nearby, genes affecting the production of colorful pigments. Paramutation is a term used to describe one such process in which interactions between parental chromosomes lead to heritable alterations in gene regulation. Examples of paramutation in both plants and animals appear to violate Mendel's first law of genetics that genes remain unchanged following sexual transmission. The paramutation process thus challenges fundamental assumptions of modern biology and presents novel concepts regarding the genesis and maintenance of 'genetic' variation. This project will employ biochemistry, molecular biology, mutational and pedigree analyses to identify specific genomic sequences and associated molecular changes responsible for these dynamic behaviors occurring at the purple plant 1 (pl1) locus in corn. Mutations that functionally define these regions at the pl1 gene as well as mutations that identify at least nine other integral components of the paramutation mechanism will be used to achieve these aims. This research will clarify the types of genome sequences that moderate these dynamic behaviors and reveal the types of chromosome modifications responsible for transmitting heritable, non-DNA encoded, regulatory information. Identification of genomic regions susceptible to paramutation will aid in deciphering important regulatory information of sequenced eukaryotic genomes. Further broader impacts of the project include providing educational and research training outreach in the areas of plant biology, genetics, and chromosome structure/function relationships for both graduate students, underrepresented minority undergraduates and high school students. Understanding this particular mechanism of eukaryotic genetics promises impacts to current research related to fundamental issues of agriculture.