Differential gene expression in response to fungal pathogen exposure in the aquatic invertebrate, Daphnia dentifera

• Published in: Ecology and evolution 2023-08, Vol.13 (8), p.e10354-n/a
• Main Authors: Terrill Sondag, Emily E., Stewart Merrill, Tara E., Drnevich, Jenny, Holmes, Jessica R., Fischer, Eva K., Cáceres, Carla E., Strickland, Lynette R.
• Format: Article
• Language: English
• Subjects: Adaptability; Adaptive immunity; Aquatic organisms; Complexity; Crustaceans; Daphnia; Defense mechanisms; Disease Ecology; Disease spread; Ecological Genetics; Epicuticle; Exposure; Fungi; Gene expression; Gene sequencing; Genes; Genomes; Genotypes; Immune response; Immune system; Immunology; Infections; Invertebrate immunity; Invertebrates; Metschnikowia; Metschnikowia bicuspidata; Parasites; pathogen; Pathogens; RNA‐sequencing; Shellfish; Transcriptomics; Vertebrates
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.10354

While vertebrate immune systems are appreciated for their complexity and adaptability, invertebrate immunity is often considered to be less complex. However, immune responses in many invertebrates likely involve sophisticated processes. Interactions between the crustacean host Daphnia dentifera and its fungal pathogen Metschnikowia bicuspidata provide an excellent model for exploring the mechanisms underlying crustacean immunity. To explore the genomic basis of immunity in Daphnia, we used RNA‐sequencing technology to quantify differential gene expression between individuals of a single host genotype exposed or unexposed to M. bicuspidata over 24 h. Transcriptomic analyses showed that the number of differentially expressed genes between the control (unexposed) and experimental (exposed) groups increased over time. Gene ontology enrichment analysis revealed that differentially expressed genes were enriched for immune‐related molecules and processes, such as cuticle development, prostaglandin, and defense response processes. Our findings provide a suite of immunologically relevant genes and suggest the presence of a rapidly upregulated immune response involving the cuticle in Daphnia. Studies involving gene expression responses to pathogen exposure shine a light on the processes occurring during the course of infection. By leveraging knowledge on the genetic basis for immunity, immune mechanisms can be more thoroughly understood to refine our understanding of disease spread within invertebrate populations. Invertebrate immunity is often oversimplified despite the likeliness that complex immune mechanisms exist in this group. We leverage a model host‐pathogen system Daphnia dentifera and Metschnikowia bicuspidata to explore the genetic underpinnings of invertebrate immunity. We found that Daphnia have a very dynamic and rapidly upregulated immune response during the first 24 h following pathogen exposure and lay important groundwork for future invertebrate immunological studies by providing a suite of putative immune‐related transcripts and their current Gene Ontology annotations.