A small HSP gene of bloody clam (Tegillarca granosa) involved in the immune response against Vibrio parahaemolyticus and lipopolysaccharide

Small heat shock proteins (sHSPs) associate with nuclei, cytoskeleton and membranes, and as molecular chaperones they bind partially denatured proteins, thereby preventing irreversible protein aggregation during stress. In the present study, the small heat shock proteins of Tegillarca granosa (Tg-sHSP) were identified from hemocytes by 3′ and 5′ rapid amplification of cDNA ends (RACE) PCR. The full-length cDNA consisted of 1005 bp with a 594 bp open reading frame encoding 197 amino acids. Sequence comparison showed that Tg-sHSP had low degree of homology to sHSP of other organisms, such as 47.8% similarity with sHSP from Zhikong scallop Chlamys farreri (AAR11780), 34.8% similarity with silkworm Bombyx mori (NP_001036941). A sHSP feature domain Alpha-crystallin domain (ACD) and V/IXI/V motif in the C-terminal extension were identified in Tg-sHSP, indicating that Tg-sHSP should be a new member of sHSP family. Quantitative RT-PCR assay was developed to detect the mRNA expression of Tg-sHSP in five different tissues. Higher-level mRNA expression of Tg-sHSP was detected in the tissues of hemocytes and mantle. The up-regulation of Tg-sHSP after bacteria Vibrio parahaemolyticus and lipopolysaccharide (LPS) challenge showed that sHSPs play a pivotal role in anti-bacterial immunity. These results together indicated that Tg-sHSP would provide candidate promising therapeutic or prophylactic agents in health management and diseases control of clam aquaculture.

Research highlights
► Our study is the first one that cloned small heat shock gene in clam.
► Higher-level mRNA expression of Tg-sHSP was detected in hemocytes.
► Bacterial challenge experiment showed that sHSPs play a pivotal role in immunity.