Population transcriptomics: insights from Drosophila simulans, Drosophila sechellia and their hybrids
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Sequence differentiation has been widely studied between populations and species, whereas interest in expression divergence is relatively recent. Using microarrays, we compared four geographically distinct populations of Drosophila simulans and a population of Drosophila sechellia, and interspecific hybrids. We observed few differences between populations, suggesting a slight population structure in D. simulans. This structure was observed in direct population comparisons, as well as in interspecific comparisons (hybrids vs. parents, D. sechellia vs. D. simulans). Expression variance is higher in the French and Zimbabwean populations than in the populations from the ancestral range of D. simulans (Kenya and Seychelles). This suggests a large scale phenomenon of decanalization following the invasion of a new environment. Comparing D. simulans and D. sechellia, we revealed 304 consistently differentially expressed genes, with striking overrepresentation of genes of the cytochrome P450 family, which could be related to their role in detoxification as well as in hormone regulation. We also revealed differences in genes involved in Juvenile hormone and Dopamine differentiation. We finally observed very few differentially expressed genes between hybrids and parental populations, with an overrepresentation of X-linked genes.
KeywordsExpression differentiation Population structure Ecology CYP450 Hormone regulation Drosophila
FW was supported by a PhD fellowship from the “Institut Ecologie et Environnement” of the “Centre National de la Recherche Scientifique”. The authors wish to thank Dr Wilfried Haerty for advice both during the analysis and about the manuscript. We also would like to thank Dr Amir Yassin and Dr Francesco Catania for fruitful discussions improving this manuscript. We thank Dr Jean-Jacques Daudin for advice in the statistical analysis. We also thank Dr Michel Piovant for giving access to the array platform. We thank people who provided us with the biological material: Dr Bruno Le Rü, Dr Roland Allemand and Dr Daniel Lachaise (deceased in 2006).
Conflict of interest
The authors declare no conflict of interest.
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