Insights into food intake response in anadromous Coilia nasus through stomach transcriptome analysis

To understand the molecular basis underlying the response to food intake, RNA sequencing was utilized to analyze the stomach transcriptome of C. nasus with feeding group (CSI) and non-feeding group (CSN). RNA sequencing was utilized to produce two transcriptomes of stomachs from CSI and CSN. A total of 610,640,864 high-quality clean reads were generated using Illumina sequencing technology and assembled into 63,567 unigenes, of which 20,608 were classified into GO enrichment and 12,303 were found in KEGG pathway. Comparative analysis of the gene expression between feeding and non-feeding fish identified 1,968 differentially expressed genes (P<0.05), including up-regulated 1180 genes and down-regulated 788 genes. Our result showed that apart from satiation was evoked by gastric distention, several of the most relevant appetite genes (such as LepR, PI3K, 5-HTR, NUCB2, SS) were involved in the suppression of food intake, resulting in the termination of feeding. Furthermore, dramatic differences were also observed in the genes encoding key enzymes involved in metabolic pathways such as protein digestion and absorption, TCA cycle pathways, fatty acid synthesis and glycolysis, indicating C. nasus can utilize carbohydrate and lipid of food to provide energy for their life activities and spawning migration. Real time qPCR confirmed the differential expression in selected genes.