De novo transcriptome assembly for the rose spotted snapperLutjanus guttatusand expression analysis of growth/atrophy-related genes

Abstract

The rose spotted snapper is an important fishery resource with potential for farming in several Latin American countries. Since transcriptomic information was not available for this species, we generated a reference transcriptome from eleven tissues (brain, heart, gonad, liver, gut, muscle, white skin, dark skin, and visceral fat) using Illumina HiSeq2000 platform. Transcriptome assembly and annotation were performed with Trinity and Trinotate respectively; 267,601 contigs were assembled, average contig length was 845 bp; 85,677 putative protein sequences were identified. Sixty-six per cent of them showed a significant match to the SwissProt Database. From this assembly, we selected growth/atrophy-related genes to investigate the effect of dietary protein source on gene expression. Pacap expression was measured in the brain; igf1, igf2 and ghr were measured in liver; and mtor, igf1, igf2, myod1, myod2, myogenin, foxo3a, foxo3b, murf1, mafbx, mstn1 and mstn2 were measured in muscle. A feeding trial with juveniles was performed, in which three diets were formulated, a fishmeal-based diet (FM), a terrestrial animal protein diet (PPM) with porcine meat meal and poultry by-products meal, and a vegetable diet (VEG) with a blend of soybean protein concentrate and corn gluten. A reduced expression of somatotropic and myogenic genes in fish fed the VEG diet was observed; however, expression of atrophy genes did not increase with this diet suggesting that atrophy mechanisms were not involved. These results indicate that protein from a vegetable source does not provide proper amino acid requirements to juvenile fish, decreasing expression of myogenic and other growth-related genes.