Identification and expression analysis of Dicer2 in black tiger shrimp (Penaeus monodon) responses to immune challenges

Abstract

Dicer is a key initiative protein of the RNA interference (RNAi) pathway that produces small interfering RNAs (siRNAs) or micro RNAs (miRNA), which then leads to RNA-directed gene regulation or viral immunity. In the present study, we identified and characterized a Dicer2 cDNA from black tiger shrimp Penaeus monodon (designated as PmDcr2). The full length cDNA of PmDcr2 contains a 5′ untranslated region (UTR) of 109 bp, an open reading frame (ORF) of 4509 bp and a 3′ UTR of 842 bp. The molecular weight (MW) of predicted PmDcr2 protein is 171.7 KDa with the theoretical isoelectric point of 6.23. PmDcr2 amino acid shared the highest similarity of 91.8% and 90.7% with Dicer2 of Litopenaeus vannamei and Marsupenaeus japonicas, respectively. Phylogenic analysis showed PmDcr2 was clustering with shrimp Dicer2, and closed to the insect group including Tribolium castaneum Dicer2. Real-time quantitative PCR showed that PmDcr2 was widely expressed in almost all examined tissues except muscle, with high expression in gill, hemocyte and lymph. The expression of PmDcr2 in hepatopancreas was up-regulated by Vibrio vulnificus and White Spot Syndrome Virus (WSSV), but not by Staphylococcus aureus. Furthermore, the viral nucleotide homologue dsRNA poly (I:C) and ssRNA R484 also remarkably induced PmDcr2 mRNA expression more efficient and stronger. These data reflect that PmDcr2 is not only response to the gram negative bacteria infection, but also specially to the viral infection in black tiger shrimp.