Characterization and functional analysis of a clip domain serine protease (MncSP) and its alternative transcript (MncSP-isoform) from Macrobrachium nipponense

The identification of a serpin with immune defense role in oriental river prawn Macrobrachium nipponense

Serpins are a protein superfamily of serine protease inhibitors. One of their functions is to participate in immune responses by inhibiting the activation of prophenoloxidase. To elucidate the immune role of serpin in Macrobrachium nipponense, a serpin gene (Mnserpin) was cloned from M. nipponense in this study. Mnserpin protein has an N-terminal signal peptide and a serpin domain that contains a hinge region, a signature sequence of serpin and a P1(arginine)-P1' scissile bond, and evolutionally closely related to the crustacean serpins. Mnserpin highly expressed in the hepatopancreas and gill. Mnserpin expression increased first and then decreased after Vibrio parahaemolyticus and Aeromonas hydrophila infection, and was knocked down by dsMnserpin injection with a maximum knockdown efficiency of 92 %. Mnserpin knockdown increased the expression of the clip domain serine protease and prophenoloxidase genes and phenoloxidase activity of M. nipponense as well as its mortality rate after V. parahaemolyticus and A. hydrophila infection. The recombinant Mnserpin (rMnserpin) showed bacteria-binding and bacteriostatic activity in vitro. Moreover, rMnserpin injection decreased the bacterial number and the mortality rate of M. nipponense post V. parahaemolyticus and A. hydrophila infection. These results suggested that Mnserpin plays a major role in the innate immune response of M. nipponense.

Full-length transcriptome analysis provides new insights into the diversity of immune-related genes in the threatened freshwater shellfish Solenaia oleivora

Solenaia oleivora, a valuable and rare bivalve endemic to China, is becoming a threatened freshwater sepcies. However, the lack of research on its genome and immune system will hinder advances in its conservation and artificial breeding. In this study, we obtained the full-length transcriptome of S. oleivora using PacBio sequencing. A total of 21,415 transcripts with an average length of 1,726 bp were generated. Among these transcripts, 12,084 had coding sequences (CDS), of which 8,639 were annotated in 6 databases. The structure analysis identified 625 transcript factors (TFs), 8,005 long non-coding RNAs (lncRNAs), and 5,288 simple sequences repeat (SSRs). Meanwhile, massive immune genes were identified from the transcriptome of S. oleivora. In terms of non-self-identification, 97 transcripts of pattern recognition receptors (PRRs) were discovered, including peptidoglycan recognition proteins (PGRPs), gram-negative bacteria binding proteins (GNBPs), toll-like receptors (TLRs), scavenger receptors (SRs), galectins (GALs), C-type lectins (CLTs), and fibrinogen-related protein (FREPs). For pathogen elimination, 7 transcripts related to antimicrobial peptides, lysozymes, and lysosomal enzymes were identified. Moreover, 33 complement-associated transcripts were found. This study enriched the genome resources of S. oleivora and provided new insights for the study of the immune system of S. oleivora.

Application of proteomics and metabolomics to assess ammonia stress response and tolerance mechanisms of juvenile ornate rock lobster Panulirus ornatus

Ammonia is a common pollutant in the aquatic ecosystem and closed aquaculture systems. It may pose a threat to the lobster growth, reproduction and survival. However, there is lack of research of the mechanisms on the toxic effects ammonia at molecular levels. In this work, proteomics and metabolomics were integrated to analyze the proteome and metabolome responses in the ornate spiny lobster Panulirus ornatus treated with ammonia (20 mg L^-1) for 48 h. A total of 199 proteins and 176 metabolites were significantly altered in P. ornatus following ammonia treatment. The responsive proteins and metabolites were predominantly involved in immune response, phase I and phase II biotransformation, carbohydrate metabolism, amino acid metabolism, and lipid metabolism. Furthermore, an increase in urea levels was observed, and amino acid metabolism was induced, indicating that the urea cycle was utilized to biotransform ammonia so as to reduce endogenous ammonia content. Ammonia exposure also affected the antioxidant system and induced cellular apoptosis. Overall, our results provide comprehensive insights into the molecular mechanisms underlying the response of P. ornatus to ammonia stress. We believe that the data reported herein should contribute to the development of novel, efficient methods for P. ornatus aquaculture.