Evolution of gene expression and gene regulation during head development in Drosophila americana and D. novamexicana

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Understanding the molecular basis of the morphological diversity observed on earth is a major aim of biological research. Natural variation in adult morphology is the result of changes in developmental processes, which are regulated by the action of developmental gene products. Research in evolutionary developmental (Evo-Devo) biology established that variation in developmental gene expression is a major driver of phenotypic diversity. While genetic changes underlying variation in rather simple morphological traits have been revealed, the genetic and developmental basis of complex trait evolution remains largely elusive. Since the insect head is a complex structure comprising major sensory organs it is an excellent model to contribute answers to this question. In recent years, we and others showed that natural variation in adult head shape and eye size is pervasive in Drosophila. Building on our extensive prior morphological and genetic data, I propose two main objectives. First, I will link genetic variants associated with differences in head shape and eye size between D. americana and D. novamexicana to variation in genome wide developmental gene expression (RNAseq) and gene regulation (ATACseq). This analysis will allow revealing high confidence candidate genes for future functional validation experiments. Chromosomal inversions are a special type of genetic variation that has been associated with phenotypic diversity. Various inversions segregate among D. americana populations and some of them are shared with D. novamexicana. Therefore, the second objective is to link the presence of inversions to variation in regulation and expression of developmental genes. Such data will allow testing common hypotheses explaining why inversions raise in frequency in a population. Eventually our data will contribute to a better mechanistic understanding of how inversions impact phenotypic diversity.