title: Transcriptomic immune response of the cotton stainer Dysdercus fasciatus to experimental elimination of vitamin-supplementing intestinal symbionts.
abstract: The acquisition and vertical transmission of bacterial symbionts plays an important role in insect evolution and ecology. However, the molecular mechanisms underlying the stable maintenance and control of mutualistic bacteria remain poorly understood. The cotton stainer Dysdercus fasciatus harbours the actinobacterial symbionts Coriobacterium glomerans and Gordonibacter sp. in its midgut. The symbionts supplement limiting B vitamins and thereby significantly contribute to the host's fitness. In this study, we experimentally disrupted the symbionts' vertical transmission route and performed comparative transcriptomic analyses of genes expressed in the gut of aposymbiotic (symbiont-free) and control individuals to study the host immune response in presence and absence of the mutualists. Annotation of assembled cDNA reads identified a considerable number of genes involved in the innate immune system, including different protein isoforms of several immune effector proteins (specifically i-type lysozyme, defensin, hemiptericin, and pyrrhocoricin), suggesting the possibility for a highly differentiated response towards the complex resident microbial community. Gene expression analyses revealed a constitutive expression of transcripts involved in signal transduction of the main insect immune pathways, but differential expression of certain antimicrobial peptide genes. Specifically, qPCRs confirmed the significant down-regulation of c-type lysozyme and up-regulation of hemiptericin in aposymbiotic individuals. The high expression of c-type lysozyme in symbiont-containing bugs may serve to lyse symbiont cells and thereby harvest B-vitamins that are necessary for subsistence on the deficient diet of Malvales seeds. Our findings suggest a sophisticated host response to perturbation of the symbiotic gut microbiota, indicating that the innate immune system not only plays an important role in combating pathogens, but also serves as a communication interface between host and symbionts.
authors.affiliation: Insect Symbiosis Research Group, Max Planck Institute for Chemical Ecology, Jena, 07745, Germany.
authors.forename: Eugen
authors.initials: E
authors.lastname: Bauer
authors.affiliation: Insect Symbiosis Research Group, Max Planck Institute for Chemical Ecology, Jena, 07745, Germany.
authors.forename: Hassan
authors.initials: H
authors.lastname: Salem
authors.affiliation: Faculty of Mathematics and Computer Science, Friedrich Schiller University, Jena, 07743, Germany.
authors.forename: Manja
authors.initials: M
authors.lastname: Marz
authors.affiliation: Department of Entomology, Max Planck Institute for Chemical Ecology, Jena, 07745, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Vogel
authors.affiliation: Insect Symbiosis Research Group, Max Planck Institute for Chemical Ecology, Jena, 07745, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Kaltenpoth
mesh_terms: D039903:Actinobacteria / Q000502:physiology*; D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D019587:Dietary Supplements; D041981:Gastrointestinal Tract / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology; D020869:Gene Expression Profiling; D007313:Insecta / Q000235:genetics* / Q000276:immunology* / Q000382:microbiology; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000276:immunology* / Q000382:microbiology; D020411:Oligonucleotide Array Sequence Analysis; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013559:Symbiosis / Q000502:physiology*; D014803:Vitamin B Complex
chemical_list: D023181:Antimicrobial Cationic Peptides; D015415:Biomarkers; D012333:RNA, Messenger; D014803:Vitamin B Complex