Gene expression levels in Drosophila simulans, D. melanogaster, and their female hybrids were compared at the genomic level using microarrays. Dominance of expression levels of one parental species over the other in hybrids is an important factor in determining their overall fertility in that the most fertile hybrids were found to express more of their genes in a paternal pattern even though most genes are initially expressed in a maternal pattern during development. A subset of genes in the hybrids has been selected to explore further the developmental timing of this switch in gene expression. Additionally, expression patterns of hybrids will be examined from crosses between D. melanogaster and two other closely related species to look for general trends in gene expression evolution.
This work will help improve our understanding of speciation through the evolution of gene expression differences involved in hybrid female sterility. Although hybrid sterility commonly arises during speciation, little is know about the actual changes in gene expression that underlie the sterility effect. Understanding more generally how gene expression regulation evolves will also help us understand changes in gene expression in other contexts, such as with cancer development in humans.
