Immune genes and divergent antimicrobial peptides in flies of the subgenus Drosophila. Issue 1 (December 2016)

• Record Type: Journal Article
• Authors: Hanson, Mark; Hamilton, Phineas; Perlman, Steve
• Is Part Of: BMC evolutionary biology. Volume 16:Issue 1(2016)
• Page Start: 1
• Page End: 14
• Publication Date: 2016-12
• Subjects: Diptericin -- Drosocin -- Drosophila -- Immunity -- Antimicrobial peptide -- AMP; Evolution (Biology) -- Periodicals; 576.805
• DOI: 10.1186/s12862-016-0805-y
• Languages: English
• ISSNs: 1471-2148

Abstract

Abstract Background Drosophila is an important model for studying the evolution of animal immunity, due to the powerful genetic tools developed forD. melanogaster . However, Drosophila is an incredibly speciose lineage with a wide range of ecologies, natural histories, and diverse natural enemies. Surprisingly little functional work has been done on immune systems of species other thanD. melanogaster . In this study, we examine the evolution of immune genes in the speciose subgenus Drosophila, which diverged from the subgenus Sophophora (that includesD. melanogaster ) approximately 25–40 Mya. We focus onD. neotestacea, a woodland species used to study interactions between insects and parasitic nematodes, and combine recent transcriptomic data with infection experiments to elucidate aspects of host immunity. Results We found that the vast majority of genes involved in theD. melanogaster immune response are conserved inD. neotestacea, with a few interesting exceptions, particularly in antimicrobial peptides (AMPs); until recently, AMPs were not thought to evolve rapidly inDrosophila . Unexpectedly, we found a distinct diptericin in subgenus Drosophila flies that appears to have evolved under diversifying (positive) selection. We also describe the presence of the AMP drosocin, which was previously thought to be restricted to the subgenus Sophophora, in the subgenus Drosophila. We challenged two subgenus Drosophila species, D. neotestacea andD. virilis with bacterial and fungal pathogens and quantified AMP expression. Conclusions While diptericin inD. virilis was induced by exposure to gram-negative bacteria, it was not induced inD. neotestacea, showing that conservation of immune genes does not necessarily imply conservation of the realized immune response. Our study lends support to the idea that invertebrate AMPs evolve rapidly, and thatDrosophila harbor a diverse repertoire of AMPs with potentially important functional consequences.