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Abstract: PKZ was the most recently discovered member of eIF2α kinase family in fish. CaPKZ, the first identified fish PKZ, possessed a conserved eIF2α kinase catalytic domain in C-terminal and two Z-DNA binding domains (Zα) in N-terminal. The Zα of CaPKZ closely resembled that of other Z-DNA binding proteins: ADAR1, DLM-1, and E3L. In order to understand more about the function of CaPKZ, we expressed and purified three constructed peptides of CaPKZ (PZα): PZα1Zα2, PZα1Zα1 and P Zα2 Zα2. Moreover, most of the plasmids containing d(GC)n inserts were maintained in the Z-conformation, as confirmed by using inhibition of methylation experiments and anti-Z-DNA antibody. Gel mobility shift assays were then used to examine the affinity of these PZα to the recombinant plasmids. Meanwhile, a competition experiment using PZα1Zα2 and anti-Z-DNA antibody was performed. The results revealed that PZα1Zα2 and PZα1Zα1 were able to bind to the recombinant plasmids with high affinity, whereas P Zα2 Zα2 could not bind to it. In addition, dimerization of PZα1Zα2 indicated the function unit of Zα of CaPKZ would be a dimer. [Copyright &y& Elsevier]

Because of the low host specificity, Ichthyophthirius multifiliis (Ich) can widely cause white spot disease in aquatic animals, which is extremely difficult to treat. Prior research has demonstrated a considerable impact of concentrated mannan-oligosaccharide (cMOS) on the prevention of white spot disease in goldfish, but the specific mechanism is still unknown. In this study, transcriptome sequencing, histological analysis, immunofluorescence analysis, phagocytosis activity assay and qRT-PCR assay were used to systematically reveal the potential mechanism of cMOS in supporting the resistance of goldfish (Carrasius auratus) to Ich invasion. According to the transcriptome analysis, the gill tissue of goldfish receiving the cMOS diet showed greater expression of mannose-receptor (MRC) related genes, higher phagocytosis activity, up-regulated expression of phagocytosis-related genes and inflammatory-related genes compared with the control, indicating that cMOS can have an effect on phagocytosis and non-specific immunity of goldfish. After the Ich challenge, transcriptome analysis revealed that cMOS fed goldfish displayed a higher level of phagocytic response, whereas non-cMOS fed goldfish displayed a greater inflammatory reaction. Besides, after Ich infection, cMOS-fed goldfish displayed greater phagocytosis activity, a stronger MRC positive signal, higher expression of genes associated with phagocytosis (ABCB2 , C3 , MRC), and lower expression of genes associated with inflammation (IL-1β, IL-17, IL-8, TNF-α, NFKB). In conclusion, our experimental results suggest that cMOS may support phagocytosis by binding to MRC on the macrophage cell membrane and change the non-specific immunity of goldfish by stimulating cytokine expression. The results of this study provide new insights for the mechanism of cMOS on parasitic infection, and also suggest phagocytosis-related pathways may be potential targets for prevention of Ich infection. [Display omitted] • The receptor of cMOS on the surface of macrophages may be MRC. • The intake of cMOS stimulates the phagocytosis function of goldfish gill macrophages. • The intake of cMOS promotes the non-specific immunity of goldfish gill macrophages. • cMOS has an alleviating effect on white spot disease (Ichthyophthirius multifiliis) of goldfish. [ABSTRACT FROM AUTHOR]