The antiviral immune responses were triggered by the innate immune recognition of viral infection. The type I IFNs (IFN-β and IFN-α) are the key cytokines produced upon viral infection and consequently link innate immunity with adaptive immunity. A main antiviral system in mammals is TRIF-dependent TLRs pathway, but the TRIF-independent RIG-I pathway, has also been discovered recently. In this manuscript, our study focuses on the functional characterization of zebrafish TRIF based on the comparison of its sequence and functional evolution from zebrafish to mammals. Our experimental results show that the full length cDNA of zebrafish TRIF cloned by RACE-PCR approach encodes a protein of 556 amino acids. Luciferase reporter assay confirms that zebrafish TRIF is able to induce the IFN promoter as well as activate NF-κB response promoter. The IFN induction function of zebrafish TRIF is abolished when Ala359 is mutated to Pro or His. Laser confocal microscopy shows that zebrafish TRIF is colocalized with a Golgi apparatus marker, implying its unique subcellular localization in Golgi apparatus. In zebrafish, the mRNA expression of molecules participating in RIG-I pathway are much more sensitive and specific to polyinosine-polycytidylic acid induction compared with those in TRIF-dependent antiviral pathway. The TRIF-dependent TLR4 IFN induction signaling appears not to be functional in zebrafish, since IFN expression cannot be up-regulated by LPS. These two striking findings from de novo ligand induction experiments suggest a novel antiviral mechanism in zebrafish.

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Lipids work as essential energy sources for organisms. However, prawns fed on high-fat diets suffer from oxidative stress, whose potential mechanisms are poorly understood. The present study aimed to explore the regulation mechanism of oxidative stress induced by high fat and the amelioration by vitamin E (VE) of oxidative stress. Macrobrachium rosenbergii were fed with two dietary fat levels (LF 9% and HF 13%) and two VE levels (200 mg/kg and 600 mg/kg) for 8 weeks. The results showed that the HF diet decreased the growth performance, survival rate and antioxidant capacity of M. rosenbergii, as well as inducing hypertrophied lipid droplets, lipophagy and apoptosis. A total of 600 mg/kg of VE in the HF diet alleviated the negative effects induced by HF. In addition, the HF diet suppressed the expression of toll-dorsal and imd-relish signal pathways. After the relish and dorsal pathways were knocked down, the downstream iNOS and NO levels decreased and the MDA level increased. The results indicated that M. rosenbergii fed with a high-fat diet could cause oxidative damage. Its molecular mechanism may be attributed to the fact that high fat suppresses the NF-κB/NO signaling pathway mediating pro-oxidant and antioxidant targets for regulation of oxidative stress. Dietary VE in an HF diet alleviated hepatopancreas oxidative stress and apoptosis.