title: The extraembryonic serosa is a frontier epithelium providing the insect egg with a full-range innate immune response.
abstract: Drosophila larvae and adults possess a potent innate immune response, but the response of Drosophila eggs is poor. In contrast to Drosophila, eggs of the beetle Tribolium are protected by a serosa, an extraembryonic epithelium that is present in all insects except higher flies. In this study, we test a possible immune function of this frontier epithelium using Tc-zen1 RNAi-mediated deletion. First, we show that bacteria propagate twice as fast in serosa-less eggs. Then, we compare the complete transcriptomes of wild-type, control RNAi, and Tc-zen1 RNAi eggs before and after sterile or septic injury. Infection induces genes involved in Toll and IMD-signaling, melanisation, production of reactive oxygen species and antimicrobial peptides in wild-type eggs but not in serosa-less eggs. Finally, we demonstrate constitutive and induced immune gene expression in the serosal epithelium using in situ hybridization. We conclude that the serosa provides insect eggs with a full-range innate immune response.
authors.affiliation: Institute of Biology, Leiden University, Leiden, Netherlands.
authors.forename: Chris G C
authors.initials: CG
authors.lastname: Jacobs
authors.affiliation: Institute of Biology, Leiden University, Leiden, Netherlands.
authors.forename: Herman P
authors.initials: HP
authors.lastname: Spaink
authors.affiliation: Institute of Biology, Leiden University, Leiden, Netherlands.
authors.forename: Maurijn
authors.initials: M
authors.lastname: van der Zee
mesh_terms: D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology; D015169:Colony Count, Microbial; D004848:Epithelium / Q000187:drug effects / Q000196:embryology* / Q000276:immunology; D005321:Extraembryonic Membranes / Q000187:drug effects / Q000276:immunology* / Q000382:microbiology; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D017344:Genes, Insect; D007113:Immunity, Innate / Q000187:drug effects / Q000235:genetics; D017403:In Situ Hybridization; D010063:Ovum / Q000187:drug effects / Q000276:immunology* / Q000382:microbiology; D034622:RNA Interference; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018805:Sepsis / Q000276:immunology / Q000382:microbiology / Q000473:pathology; D017423:Sequence Analysis, RNA; D012704:Serous Membrane / Q000187:drug effects / Q000196:embryology / Q000276:immunology* / Q000382:microbiology; D014231:Tribolium / Q000187:drug effects / Q000196:embryology* / Q000235:genetics / Q000276:immunology*
chemical_list: D023181:Antimicrobial Cationic Peptides
keywords: NF-kappaB; RNA sequencing; Toll; Tribolium castaneum; developmental biology; immunology; innate immunity; serosa; stem cells