Comparative transcriptome sequencing of the hepatopancreas reveals differentially expressed genes in the precocious juvenile Chinese mitten crab,Eriocheir sinensis(Crustacea: Decapoda)

Overnutrition was considered to be the main cause of the precocity in the Chinese mitten crab. Hepatopancreas plays a key role in nutrition metabolism of the crustaceans. However, gene regulation and expression profiles of the hepatopancreas for the precocious crabs still remain ill-defined. Here through de novo sequencing coupled with RNA-Seq (Quantification) analysis, a number of differentially expressed genes (DEGs) in the precocious juvenile crabs were identified. The pooled total RNA from hepatopancreas of the precocious juvenile crabs, normal juvenile crabs and normal matured crabs was used to obtain a reference transcriptome. De novo assembly of the transcriptome revealed 55 561 unigenes with an average length of 1153 bp. Another three cDNA libraries were constructed with the same samples and sequenced separately with the RNA-Seq analysis. A total of 996 DEGs between the precocious and normal juvenile crabs were identified, of which 508 DEGs were upregulated in the precocious juvenile crabs. KEGG enrichment analysis revealed that most enriched DEGs (162, 23.28%) were involved in the metabolic pathways. The expression profiles of 15 DEGs, which includes chitinase, alkaline phosphatase, insulin receptor, juvenile hormone esterase and signal transducer and activator of transcription, were determined by qRT-PCR to confirm the accuracy of the RNA-Seq. These DEGs had already been suggested to be potentially related to the growth and development in crustaceans. Our results, including the assembled transcriptome and the identified DEGs in the precocious juvenile crabs, provide us new resources in the understanding of the functions of the hepatopancreas in the precocity of the Chinese mitten crab.