Comparative transcriptome analysis of Sinonovacula constricta in gills and hepatopancreas in response to Vibrio parahaemolyticus infection.

The razor clam Sinonovacula constricta is an important economic species in China. However, bacterial pathogenic diseases limits S. constricta farming industry for large-scale production. In this study, de novo transcriptome sequencing was performed on S. constricta gills and hepatopancreas under Vibrio parahaemolyticus challenge for 12 h and 48 h, respectively. Transcripts assembly constructed 18,330 sequences, each of which was 500 bp long and functionally annotated, and 1781 and 490 transcripts were differentially expressed in the gills and hepatopancreas, respectively. Host immune factors that respond to Vibrio infection were then identified. These factors included up-regulated transcripts with function in non-self recognition, signal transduction, immune effectors and anti-apoptosis. The comparison between the differentially expressed transcripts of the gills and hepatopancreas indicated that immune responses had tissue specificity. As an important external barrier between the environment and the clam, ATP-binding cassette transporters and other ion transporters contribute to immune response in gills, while, transcripts in complement system, such as complement 1 q protein, IgGFc-binding protein, and low affinity immunoglobulin epsilon Fc receptor, were more active in hepatopancreas and often not expressed in gill tissues. Eleven genes were selected to be validated by qRT-PCR and the expressions were consistent with the results of RNA-seq. Our study is the first attempt to identify molecular features in different tissues of S. constricta in response to V. parahaemolyticus infection. These findings improved our understanding of bivalve immunity and defense mechanisms and revealed more potential immune-related genes.