Comparative transcriptomics in the Drosophila Auditory Organ

We use closely-related Drosophila species to understand mechanosensation and how hearing as a form of mechanosensation drives reproductive isolation and evolution. In particular, we performed RNA-seq to obtain the Johnston's Organ transcriptomes of six closely-related Drosophila species, namely, D.melanogaster, D.yakuba, D.pseudoobscura and D.persimilis. Application of the Ornstein-Uhlenbeck model identified gene expression changes between the species' auditory structures. Motif discovery ( i-cisTarget and iRegulon) in differentially expressed genes in the oobscura group and melanogaster group on these transcriptomes identified thetranscription factor Hr39 as important for auditory differences among species. Hr39 is a nuclear hormone receptor important in song production and spermathecae development. Futher functional analyses Hr39 and many of its downstream targets are expressed in Johnston's Organ neurons. Hr39 mutants show sexually dimorphic defects in auditory mechanics and compound action potentials. These results indicate that Hr39 and its downstream regulon have a key role in Drosophila courtship behavior as a mechanism of reproductive isolation and evolution. Overall design: RNA-seq in the Johnston's Organ of five Drosophila species, namely D.melanogaster, D.yakuba, D.pseudoobscura, D.simulans and D.persimilis.