Adaptation of Musca domestica L. Field Population to Laboratory Breeding Causes Transcriptional Alterations

BACKGROUND: The housefly, Musca domestica, has developed resistance to most insecticides applied for its control. Expression of genes coding for detoxification enzymes play a role in the response of the housefly when encountered by a xenobiotic. The highest level of constitutive gene expression of nine P450 genes was previously found in a newly-collected susceptible field population in comparison to three insecticide-resistant laboratory strains and a laboratory reference strain. RESULTS: We compared gene expression of five P450s by qPCR as well as global gene expression by RNAseq in the newly-acquired field population (845b) in generation F(1), F(13) and F(29) to test how gene expression changes following laboratory adaption. Four (CYP6A1, CYP6A36, CYP6D3, CYP6G4) of five investigated P450 genes adapted to breeding by decreasing expression. CYP6D1 showed higher female expression in F(29) than in F(1). For males, about half of the genes accessed in the global gene expression were up-regulated in F(13) and F(29) in comparison with the F(1) population. In females, 60% of the genes were up-regulated in F(13) in comparison with F(1), while 33% were up-regulated in F(29). Forty potential P450 genes were identified. In most cases, P450 gene expression was decreased in F(13) flies in comparison with F(1). Gene expression then increased from F(13) to F(29) in males and decreased further in females. CONCLUSION: The global gene expression changes massively during adaptation to laboratory breeding. In general, global expression decreased as a result of laboratory adaption in males, while female expression was not unidirectional. Expression of P450 genes was in general down-regulated as a result of laboratory adaption. Expression of hexamerin, coding for a storage protein was increased, while gene expression of genes coding for amylases decreased. This suggests a major impact of the surrounding environment on gene response to xenobiotics and genetic composition of housefly strains.