The TRAF gene family in turbot (Scophthalmus maximus): Identification, characterization, molecular evolution and expression patterns analysis

Tumor necrosis factor receptor-associated factor (TRAF) is an important structural protein, which can bind to TNF receptors and participate in the regulation of TNF signaling pathway. Nonetheless, few studies have been conducted to investigate the systematic identification of TRAF gene family in teleost and role in innate immunity of turbot (Scophthalmus maximus). In this study, eight TRAF genes, namely SmTRAF2aa, SmTRAF2ab, SmTRAF2b, SmTRAF3, SmTRAF4a, SmTRAF5, SmTRAF6 and SmTRAF7, were identified and annotated in turbot by using bioinformatics methods. Analysis of the phylogenetic, syntenic and molecular evolution demonstrated that all SmTRAF members were evolutionarily conserved in teleost. Domain analysis showed all SmTRAF proteins contained a typical conserved N-terminal RING finger domain. Most SmTRAF proteins contained a MATH domain at the C-terminal, while SmTRAF7 contains seven duplicate WD40 domains. In addition, quantitative real-time PCR was performed to detect the expression patterns of SmTRAFs in tissues from healthy and Vibrio anguillarum infected turbots. The results indicated SmTRAFs had diverse tissue expression patterns and the expression of TRAF gene changed significantly after V. anguillarum infection. This study provided a basis for understanding the roles of TRAFs in the innate immune response of turbot.

Shrimp AHPND Causing Vibrio anguillarum Infection: Quantitative Diagnosis and Identifying Antagonistic Bacteria

Acute hepatopancreatic necrosis disease (AHPND) is one of the most common and serious diseases in shrimp aquaculture. Relevant works have focused on the gut microbiota-disease relationship when serious AHPND occurs. In contrast, little is known about how the gut microbiota responds to pathogen infection over AHPND progression, whereas this knowledge is fundamental to uncover the etiology of AHPND. Here, we explored the temporal succession of shrimp gut microbiota during Vibrio anguillarum (a causal pathogen of AHPND) challenge. The successful infection of V. anguillarum was confirmed by linearly increased abundance of the pathogen in the shrimp gut over AHPND progression. V. anguillarum infection caused an irreversible disruption in the shrimp gut microbiota, of which infection and hours post infection (hpi) respectively constrained 6.2% and 10.2% of variation in the data. Furthermore, the predicted functional pathways involved in immunity and metabolism significantly decreased, while those facilitating infectious diseases significantly enriched in the infected shrimp. Intriguingly, after ruling out the effect of background changes in gut microbiota, we identified 20 infection-discriminatory taxa that could be served as independent variables for accurately (89.4%) diagnosing V. anguillarum infection, even at the early infection stage, i.e., 24 hpi. Using a consensus network, we identified several Vibrio and Pseudoalteromonas taxa that directly antagonized V. anguillarum, following the Darwin's niche theory. This is one of the few attempts to identify gut bioindicators for diagnosing pathogen infection. In addition, the antagonistic commensals of V. anguillarum might be the candidate probiotics for preventing AHPND.