The gill transcriptome reveals unique antimicrobial features that protect Nibea albiflora from Cryptocaryon irritans infection

Transcriptomic analysis of large yellow croaker (Larimichthys crocea) reveals the suppression of the inflammatory response from Cryptocaryon irritans infection

Large yellow croaker (Larimichthys crocea) is the most productive marine fish in China. Cryptocaryon irritans is an extremely destructive parasite that causes great economic losses in large yellow croaker aquaculture industry. Therefore, it is very necessary to study the immune response of large yellow croaker in response to C. irritans infection. In this study, the transcriptomic profiles of large yellow croaker were sequenced and analyzed in the brain and head kidney at 72 h after C. irritans infection. Cytokines and chemokines related terms were significantly enriched based on the GO enrichment of down-regulated differentially expressed genes (DEGs) from the head kidney. Meanwhile, cytokine-cytokine receptor interaction was significantly enriched based on the KEGG enrichment of up-regulated DEGs from the brain and down-regulated DEGs from the head kidney, respectively. Moreover, the majority of inflammation-related DEGs were significantly up-regulated in the brain, but distinctly down-regulated in the head kidney. These results showed that the brain and head kidney might play different roles against C. irritans infection, and the inflammatory response of large yellow croaker may be restrained during C. irritans infection. Taken together, the transcriptomic analyses will be helpful to more comprehensively understand the immune mechanism of teleost against C. irritans infection, and provide a theoretical basis for the prevention and treatment of Cryptosporidiosis.

Transcriptomic Variation of Amphiprion Percula (Lacepède, 1802) in Response to Infection with Cryptocaryon Irritans Brown, 1951

Cryptocaryon irritans (Brown 1951) frequently infect the Pomacentridae fishes causing severe economic losses. However, the anti-C. irritans' molecular mechanism in these fishes remains largely unknown. To address this issue, we conducted RNA-Seq for C. irrtians-infected gills of the clownfish Amphiprion percula (Lacepède 1802) at the early (day 1) and late (day 3) stages of infection. A total of 1655 differentially expressed genes (DEGs) were identified. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses of DEGs showed a vast genetic variation related to the following aspects: ECM-receptor interaction, P13K-Akt signalling, cytokine-cytokine receptor interaction, and endocytosis. During the early phase of infection, key genes involved in ATP production, energy homeostasis, and stress control were abruptly increased. In the late phase, however, acute response molecules of the peripheral nervous system (synaptic transmission and local immunity), metabolic system triggering glycogen synthesis, energy maintenance, and osmoregulation were found to be critical. The highest number of upregulated genes (URGs) recovered during the early phase was included under the 'biological process' category, which primarily functions as response to stimuli, signalling, and biological regulation. In the late phase, most of the URGs were related to gene regulation and immune system processes under 'molecular function' category. The immune-related URGs of early infection include major histocompatibility complex (MHC) class-II molecules apparently triggering CD4+ T-cell-activated Th responses, and that of late infection include MHC class-1 molecules for the possible culmination of CD8+ T-cell triggered cytotoxicity. The high level of genic single nucleotide polymorphisms (SNPs) identified during the late phase of infection is likely to influence their susceptibility to secondary infection. In summary, the identified DEGs and their related metabolic and immune-related pathways and the SNPs may provide new insights into coordinating the immunological events and improving resistance in Pomacentridae fishes against C. irritans.

Between-population differences in constitutive and infection-induced gene expression in threespine stickleback

Vertebrate immunity is a complex system consisting of a mix of constitutive and inducible defences. Furthermore, host immunity is subject to selective pressure from a range of parasites and pathogens which can produce variation in these defences across populations. As populations evolve immune responses to parasites, they may adapt via a combination of (1) constitutive differences, (2) shared inducible responses, or (3) divergent inducible responses. Here, we leverage a powerful natural host‐parasite model system (Gasterosteus aculeatus and Schistochephalus solidus) to tease apart the relative contributions of these three types of adaptations to among‐population divergence in response to parasites. Gene expression analyses revealed limited evidence of significant divergence in constitutive expression of immune defence, and strong signatures of conserved inducible responses to the parasite. Furthermore, our results highlight a handful of immune‐related genes which show divergent inducible responses which may contribute disproportionately to functional differences in infection success or failure. In addition to investigating variation in evolutionary adaptation to parasite selection, we also leverage this unique data set to improve understanding of cellular mechanisms underlying a putative resistance phenotype (fibrosis). Combined, our results provide a case study in evolutionary immunology showing that a very small number of genes may contribute to genotype differences in infection response.