Transcribed Microsatellites as Engines of Adaptive Change; Testing the "Tuning Knob" Hypothesis in Natural Populations of the Annual Sunflower, Helianthus annuus

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Microsatellites are highly repetitive DNA sequences found throughout organismal genomes. These sequences have very high mutation rates that change the physical length of the microsatellite. After they were first discovered, it was assumed that microsatellites would only be found in nonfunctional regions of genomes because they would likely disrupt normal gene function. In fact, some of the earliest microsatellites described are known to cause neurodegenerative diseases, like Huntington's chorea. However, we now know that many thousands of genes in many species include microsatellites. The prevalence of microsatellites in genes implies that many may be functional. This project focuses on the role microsatellites might play in altering how genes are expressed in sunflowers. The researchers are testing the hypothesis that microsatellite mutations alter gene expression levels in sunflowers, suggesting that this class of microsatellite can facilitate evolutionary change. Given their mutation rates, microsatellites may represent the most rapidly evolving gene regulatory elements in genomes. If this hypothesis is true, then microsatellite lengths should correlate with gene expression levels. Further, if selection is acting on this source of variation, then allele frequencies in natural populations should reflect these processes. Acceptance of these mechanisms would suggest that populations acquire novel and heritable variation at rates much higher than typically assumed.Broader Impacts: This project supports undergraduate student researchers. Senior researchers will expose biology students to advanced computational methods, and computer science majors interested in computational biology will be involved in the collection of data and analysis. In addition, a major focus of student training is the development of their grant writing and data analysis skills, and the presentation of scientific research findings. Students will present their findings at scientific meetings and coauthor research journal articles. Further, Mississippi State University has one of the highest percentages of minorities among research universities in the country, and strategies designed to include minorities in this project are being pursued.