Identification of Immune Genes of the Agamaki Clam (Sinonovacula constricta) by Sequencing and Bioinformatic Analysis of ESTs

The Agamaki clam (Sinonovacula constricta) is an economically important shellfish in Asia. However, genomic research on this species is still in its infancy, and genomic resources are largely unavailable. The objective of this study was to generate expressed sequence tags (ESTs) from a normalized liver complementary DNA library and to identify genes that function in immune defense. A total of 5,296 ESTs were sequenced, from which 540 contigs and 3,473 singletons were identified. BLAST homology analysis indicated that only 20.7% of these ESTs were homologues of known genes while the remaining 79.3% appeared to be novel sequences. Based on sequence similarities, 43 putative immune genes were identified that encode proteases and protease inhibitors, adhesive proteins, stress proteins, lysosomal enzymes, and signal transduction regulators. Our study thus provides both a large collection of novel transcripts and a detailed annotation of immune genes for an important bivalve species.