Site-Directed Mutagenesis Study Revealed Three Important Residues in Hc-DAF-22, a Key Enzyme Regulating Diapause of Haemonchus contortus

( ) is one of the most important parasites of small ruminants, especially goats and sheep. The complex life cycle of this nematode is a main obstacle for the control and prevention of haemonchosis. So far, a special form of arrested development called diapause different from the dauer stage in ( ) has been found in many parasitic nematodes. In our previous study, we have characterized a novel gene from sharing high homology with and functional analysis showed this gene has similar biological function with . In this study, mutants were constructed using site-directed mutagenesis, and carried out rescue experiments, RNA interference (RNAi) experiments and enzyme activity analysis with the mutants to further explore the precise function site of Hc-DAF-22. The results showed that mutants could be expressed in the rescued worms and the expression positions were mainly in the intestine which was identical with that of rescued worms. Through lipid staining we found that could rescue mutant ( ) from the fatty acid metabolism deficiency while mutants failed. Brood size and body length analyses in rescue experiment along with body length and life span analyses in RNAi experiment elucidated that resembled in effecting the development and capacity of and mutants impaired the function of . Together with the protease activity assay, this research revealed three important active resides 84C/299H/349H in Hc-DAF-22 by site-directed mutagenesis.