GSE67861
Expression divergence of chemosensory genes between Drosophila sechellia and its sibling species and its implications for host shift [Dsec JP]
Drosophila sechellia relies exclusively on the fruits of Morinda citrifolia, which are toxic to most insects, including its sibling species D. melanogaster and D. simulans.  Although several odorant binding protein (Obp) genes and olfactory receptor (Or) genes were suggested to be associated with the D. sechellia host shift, a broad view of how chemosensory genes have contributed to this shift is still lacking.  We therefore studied the antennal transcriptomes, the main organ responsible for detecting food resource and oviposition, of D. sechellia and its two sibling species. We wanted to know whether gene expression, particularly chemosensory genes, has diverged between D. sechellia and its two sibling species.  Using a very stringent definition of differential gene expression, we found 147 genes (including 11 chemosensory genes) were up-regulated while only 81 genes (including 5 chemosensory genes) were down-regulated in D. sechellia.  Interestingly, Obp50a exhibited the highest up-regulation, a ~100 fold increase, and Or85c – previously reported to be a larva-specific gene– showed ~20 fold up-regulation in D. sechellia.  Furthermore, Ir84a, proposed to be associated with male courtship behavior, is significantly up-regulated in D. sechellia.  We also found expression divergence in most of the receptor gene families between D. sechellia and the two sibling species.  Our observations suggest that the host shift of D. sechellia is associated with expression profile divergence in all chemosensory gene families and is achieved mostly by up-regulation of chemosensory genes. Overall design: RNAseq experiments in wild type drosophila antennaes. The strain is D. sechellia (k-s10; #14021-0248.25).