Hepatopancreas transcriptome analysis reveals the molecular responses to different dietary n-3 PUFA lipid sources in the swimming crab Portunus trituberculatus

Abstract

n-3 LC-PUFA is vital to crustaceans for the growth, molting and development, while the precise molecular mechanism underlying the regulation of n-3 LC-PUFA is poorly investigated. Herein, an 8-week nutritional trial and transcriptome analysis were used to investigate the impacts of dietary n-3 PUFA lipid sources including fish oil (FO), krill oil (KO) and linseed oil (LO) on the transcriptome characteristics in hepatopancreas of swimming crab (Portunus trituberculatus). Crabs fed KO diet had significantly higher percent weight gain (PWG) and molting ratio (MR) than those of crabs fed other diets. The transcriptome analysis reveled that a total of 6567 unigenes were annotated in KEGG database, of which the expression of 1126 significantly altered in the KO vs FO group, while the expression of 921 unigenes changed in the LO vs FO group. The differentially expressed genes (DEGs) in KO vs FO comparison group involved in fat digestion and absorption, ABC transporters, adipocytokine signaling pathway, protein digestion and absorption, glycolysis/gluconeogenesis and HIF-1 signaling pathway. While dietary LO significantly altered the expression levels of genes involved in carbohydrate digestion and absorption, mineral absorption, protein processing in endoplasmic reticulum, glycosphingolipid biosynthesis and insect hormone biosynthesis. In addition, dietary KO significantly up-regulated the expression levels of cyp18a1 (participates in the process of ecdysteroids biosynthesis and further controls the molting of crustaceans), tryp (trypsin-like serine proteinases, resists the pathogen invasion), pla2 (phospholipase A2, regulates different inflammatory processes), ABC transporter (ATP-binding cassette transporter, transports amino acids, lipids and proteins into and out of the cell), cpt1 (carnitine palmitoyltransferase I, the major rate-limiting enzyme of mitochondrial fatty acid β-oxidation) and slc2 (solute carrier 2, mediates bidirectional glucose transport). Meanwhile, dietary LO could significantly down-regulated the expression level of cyp315a1 compared to dietary FO. To sum up, swimming crab fed with dietary krill oil could not only enhance the transport of glucose, lipids, fatty acids and other substrates, but also up-regulate the expression levels of genes related to molting, immunity and energy metabolism to promote molting and growth of swimming crab. The present study revealed the molecular responses of crabs to different dietary n-3 PUFA lipid sources, and further provided important clues with respect to elucidating the molecular mechanisms underlying the regulation of EPA and DHA on the molting and growth of swimming crab.