Abstract:The Chinese longsnout catfish (Leiocassis longirostris) is a rare and valuable freshwater fish wildly distributed throughout China. Fish growth is one of the most economically important traits in fish farming. Cultured fish with high growth performance can often bring direct economic benefits while meeting human food demand. The hypothalamus is an important regulatory organ in fish metabolic processes and endocrine activities, directly or indirectly regulating fish growth. Although significant research on L. longirostris has been reported, the molecular mechanisms and key genes involved in its growth are still unclear. Therefore, we performed comparative transcriptomics analysis using Illumina high throughput sequencing technology and analyzed transcript profiles of the brains from fast-growth (FG) with average body mass of (534.02±53.68) g, and slow-growth (SG) with average body mass og (108.41±4.96) g L. longirostris individuals. A total of 267 404 674 clean reads were generated, and 518 differentially expressed genes were identified, of which 412 genes were up-regulated and 106 genes were down-regulated in fast-growth fishes. Then, we subjected all these differentially expressed genes to GO term enrichment and KEGG pathway analysis to find the underlying function annotation. Based on Gene Ontology analysis, plenty of differentially expressed genes were enriched in growth, growth factor activity, and hormone-mediated signaling pathway. KEGG enrichment analysis indicated that some differentially expressed genes involved in MAPK signaling pathway, TGF-beta signaling pathway, calcium signaling pathway, and neuroactive ligand-receptor interaction were enriched. With the differentially expressed genes identified from GO and KEGG enrichment analysis, several key genes related to the growth of L. longirostris were screened, such as gnrh, thr, egr1, fgf18, sst, gipr, cart, and crf. The results of this study enriched the gene resources and provided valuable references for further study on the regulation mechanism of growth of L. longirostris.
