R an in Procambarus clarkii : molecular characterization and immune function

As a member of the small G protein superfamily, ras-related nuclear proteins (Ran) mainly function in regulating nucleocytoplasmic transport and microtubule formation. Ran is reported to have an immune function in invertebrate defense against pathogen invasion. This study obtained the full-length sequence of the Ran cDNA ( PcRan ) of Procambarus clarkii and investigated changes in its expression after pathogenic infection and its role in the clearance of pathogenic bacteria. Phylogenetic tree analysis revealed that PcRan and Ran of other crustaceans belong to one branch and have a close genetic relationship. Multiple sequence alignment analyses revealed that PcRan has a highly conserved G domain and contains all the G1–G5 motifs. PcRan expression was widely distributed in various tissues in P. clarkii , with the highest expression levels being found in the muscle and gills. The levels of PcRan expression in several major immune organs, including hepatopancreas, gills, hemocytes, and intestines, were significantly increased after infection with white spot syndrome virus or Aeromonas veronii . After PcRan overexpression, the bacterial clearance ability and survival rate of P. clarkii infected with A. veronii was significantly higher than that of the control group. This study showed that PcRan is involved in the innate immune process of P. clarkii . The results of this study provide theoretical significance and application value for understanding the immune function of Ran after crayfish pathogen infection, and provide guidance for the prevention and control of crayfish diseases.