Structural And Functional Characterization Of The Nuclear Hormone Receptor Encoding Gene,Hc-daf-12,in Parasitic Nematode Haemonchus Contortus

Haemonchus contortus is a common parasitic nematode that parasitize the stomach of ruminants such as cattles and sheep.Due to absorbing host blood,it caused anemia,weakness,slowly growth and even death of animals especially lambs that lead to significant economic loss of animal husbandry.At present,the prevention and treatment of haemonchosis mainly rely on chemical deworming.However,the abused of chemical drugs lead to the emergence of drug-resistant strains,and drug residues caused different degrees of pollution to the environment.Therefore,it is necessary to find a new effective and environmental methods to control H.contortus.In this study,we found that the free-living stage of parasitic nematodes and the dauer(diapause)of free-living C.elegans were very similar in morphological,developmental and behavioral aspects.The dauer stage is regulated by four signaling pathways,of which the nuclear receptor signaling pathway is most downstream.DAF-12 is the crucial gene on the nuclear receptor signaling pathway,which regulates the growth and development of parasites.In this study,the structure and function of Hc-daf-12 gene were studied by bioinformatics analysis,immunohistochemistry and RNA interference in H.contortus.At the present study,we determined the c DNA,g DNA,amino acids and upstream promoter sequence of Hc-daf-12.Hc-daf-12 was highly homologous to the daf-12 genes family that conserved domains including Ligand Binding Domain and DNA Binding Domain.Hc-daf-12 was transcribed in all stages of H.contortus and had the highest level of transcription in stage L3.Polyclonal antibody,localized in intestine,was obtained by expressing protein Hc-DAF-12-LBD of Hc-DAF-12 truncated protein and purified high specificity protein to immune rabbits.Finally,it was proved that Hc-daf-12 gene played an important role in the growth and development of H.contortus by studying the function using RNAi.To sum up,we obtained the Hc-daf-12 gene of H.contortus,and studied the structure and function of this gene.That will provide theoretical basis for both exploring the diapause mechanism of H.contortus L3 and developing new drugs.