Cloning and expression of duck C4BPα and verification of its interaction with Riemerella anatipestifer / 生物工程学报

To study the interaction between C4b-binding protein (C4BP) and Riemerella anatipestifer (RA), we cloned duck C4BPα, conducted prokaryotic expression and prepared the polyclonal antibody by immunizing mice. Then indirect immunofluorescence assay and dot blotting hybridization assay were used to verify the interaction between C4BP and RA. The full length of duck C4BPα nucleotide sequence was 1 230 bp, with the highest similarity to chicken C4BPα (82.1%). Phylogenetic tree analysis showed that duck C4BPα and chicken C4BPα were on the same phylogenetic tree branch and the genetic evolution relationship between them was the closest. C4BPα was efficiently expressed in Escherichia coli BL21 (DE3). The recombinant proteins existed in intracellular soluble form. The titer of polyclonal antibody was more than 1:10 000 and polyclonal antibodies could specifically recognize the recombinant proteins. The results of indirect immunofluorescence assay and dot blot hybridization assay showed that RA could interact with duck C4BP. The results provide a basis to further reveal the pathogenesis of RA.

A two-component signal transduction system contributes to the virulence of Riemerella anatipestifer

Similar to other studies of bacterial pathogens, current studies of the pathogenesis of Riemerella anatipestifer (RA) are focused mainly on in vitro culture conditions. To elucidate further the pathogenesis of RA in vivo, bacterial RNA was extracted from overnight tryptic soy broth cultures (in vitro) and from the blood of infected ducks (in vivo) for comparative RNA sequencing analysis. In total, 682 upregulated genes were identified in vivo. Among the upregulated genes, a signal transduction response regulator (ArsR) and a signal transduction histidine kinase (SthK) were predicted to be located on the same operon. A mutant was constructed by deletion of both of these genes. Duck infection tests showed that genes ArsR and SthK were related to the virulence of the pathogen in vivo. Differentially expressed genes identified by comparison of in vitro and in vivo conditions provided an insight into the physiological process of RA infection and provided an opportunity to identify additional virulence factors.