cDNA cloning, characterization, and expression analysis of the Rac1 and Rac2 genes from Cynoglossus semilaevis

Rac1 and Rac2, belonging to the small Rho GTPase family, play an important role during the immune responses. In this study, a Rac1 homolog (CsRac1) and a Rac2 homolog (CsRac2) were cloned from the Cynoglossus semilaevis. The full-length of CsRac1 and CsRac2 cDNA was 1219 bp and 1047 bp, respectively. Both CsRac1 and CsRac2 contain a 579 bp open reading frame (ORF) which encoding a 192 amino acids putative protein. The predicted molecular weight of CsRac1 and CsRac2 was 21.41 kDa and 21.35 kDa, and their theoretical pI was 8.50 and 7.91, respectively. Sequence analysis showed that the conserved RHO domain was detected both from amino acid of CsRac1 and CsRac2. Homologous analysis showed that CsRac1 and CsRac2 share high conservation with other counterparts from different species. The CsRac1 and CsRac2 transcript showed wide tissue distribution, in which CsRac1 and CsRac2 exhibit the highest expression level in liver and gill, respectively. The expression level of CsRac1 and CsRac2 fluctuated in the liver and gill tissues at different time points after challenged by Vibrio harveyi. Specifically, CsRac1 and CsRac2 were significantly up-regulated at 48 h and 96 h post injection. Moreover, the knocking down of CsRac1 and CsRac2 in cell line (TSHKC) reduced the expression of CsPAK1, CsIL1-β and CsTNF-α. The present data suggests that CsRac1 and CsRac2 might play important roles in the innate immunity of half-smooth tongue sole.