Two Rab GTPases, EsRab-1 and EsRab-3, involved in anti-bacterial response of Chinese mitten crab Eriocheir sinensis

Rab GTPase is essential for the control of intracellular membrane trafficking in all eukaryotic cells and further affects the ability of phagocytic cells to scavenge pathogen. In the present study, the cDNAs for two crab Rab proteins (EsRab-1 and EsRab-3) were identified from the Chinese mitten crab Eriocheir sinensis by rapid amplification of cDNA ends (RACE) approaches and expressed sequence tag (EST) analysis. The full-length cDNAs of EsRab-1 and EsRab-3 were of 892 bp and 965 bp with ORFs of 615 bp and 630 bp, respectively. The cDNAs encoded two peptides of 204 and 209 amino acid residues with the conserved GTP/Mg2+ binding sites, Switch I region and Switch II region in RAB domains. The mRNA transcripts of EsRab-1 and EsRab-3 were both highest expressed in hepatopancreas, and marginally expressed in other tissues including hemocytes, muscle, gonad, gill and heart. After the crabs were challenged by bacteria Vibrio anguillarum, the expression levels of both EsRab-1 and EsRab-3 in hemocytes were significantly up-regulated, and reached the highest level at 1.5 h post-stimulation, which was 7-fold (P < 0.05) and 6-fold (P < 0.01) of blank group for EsRab-1 and EsRab-3, respectively. No significant change of mRNA expression was detected for either EsRab-1 or EsRab-3 in crabs stimulated by Pichia pastoris. These results clearly suggested the involvement of Rab proteins in crab anti-bacterial immunity.