Project description:Ayu (Plecoglossus altivelis), an amphidromous fish distributed in East Asia, live in brackish water (BW) during the larval stage and in fresh water (FW) during the adult stage. In this study, we found that ayu larvae of FW acclimation exhibited a slower growth ratio compared with BW acclimation. However, the mechanism underlying FW acclimation on growth suppression is less known. We employed transcriptome analysis to investigate the differential gene expression of FW acclimation by RNA sequencing. We identified 158 up-regulated and 139 down-regulated transcripts in FW acclimated ayu larvae compared with BW acclimated ones. As determined by Gene Ontology annotation and Kyoto Encyclopedia of Genes and Genomes pathway mapping, functional annotation of the genes covered diverse biological functions and processes. They were involved in in neuroendocrinology, osmotic regulation, energy metabolism, and the cytoskeleton. Transcriptional expression of several differentially expressed genes in response to FW acclimation was further confirmed by real-time quantitative PCR. In accordance with the transcriptome analysis, iodothyronine deiodinase (ID), pro-opiomelanocortin (POMC), betaine--homocysteine S-methyltransferase 1 (BHMT), fructose-bisphosphate aldolase B (aldolase B), tyrosine aminotransferase (TAT), and Na+-K+ ATPase (NKA) were up-regulated after FW acclimation. Furthermore, the mRNA expressions of b-type natriuretic peptide (BNP) and transgelin were down-regulated after FW acclimation. In conclusion, our data indicate that FW acclimation reduces the growth rate of ayu larvae, which may result from the expression alteration of genes related to endocrine hormones, energy metabolism, and direct osmoregulation.
