Calmodulin is a stress and immune response gene in Chinese mitten crab Eriocheir sinensis

Calmodulin (CaM) is a multifunctional calcium sensor protein that participates in various cellular processes under normal, stress and pathological conditions. In crabs, however, the involvement of CaM in response to environmental stress and immune challenges has not been revealed yet. In the present study, a CaM cDNA (EsCaM) was identified from Chinese mitten crab Eriocheir sinensis and its mRNA expression patterns in response to ambient (salinity and pH) stress and immune challenges was examined. EsCaM encodes a 149-amino-acid protein with a calculated molecular mass of 16.8 kDa and an isoelectric point of 4.09. In unstimulated healthy E. sinensis, EsCaM mRNA transcript was detected in all tested tissues with predominant expression in hepatopancreas and the lowest expression in haemocytes. Ambient salinity (15‰ and 30‰ salinities) and pH (pH 6 and 8.5) stress significantly altered EsCaM mRNA expression in gill, hepatopancreas, haemocytes, intestine and muscle in Chinese mitten crab. In addition, EsCaM gene expression was significantly and rapidly induced as early as 2 h after LPS and Poly(I:C) immune stimulations in haemocytes in vitro. Furthermore, EsCaM expression was significantly up-regulated in E. sinensis haemocytes, gill, hepatopancreas, intestine and muscle in response to Edwardsiella tarda and Vibrio anguillarum challenges. Collectively, our findings suggest that EsCaM is an important stress and immune response gene in Chinese mitten crab.