Evaluation of qPCR reference genes for taimen (Hucho taimen) under heat stress

As a powerful and attractive method for detecting gene expression, qRT-PCR has been broadly used in aquaculture research. Understanding the biology of taimen (Hucho taimen) has drawn increasing interest because of its ecological and economic value. Stable reference genes are required for the reliable quantification of gene expression, but such genes have not yet been optimized for taimen. In this study, the stability levels of 10 commonly used candidate reference genes were evaluated using geNorm, NormFinder, BestKeeper, and RefFinder. The expression levels of the 10 genes were detected using 240 samples from 48 experimental groups consisting of 40 individuals treated under four heat-stress conditions (18, 20, 22, and 24 °C) for 24 h and 26 °C for 4, 24, 48, and 72 h. Six tissues (blood, heart, brain, gill, skin, and liver) were collected from each individual. Ribosomal protein S29 (RPS29) and ribosomal protein L19 (RPL19) were the most stable genes among all of the samples, whereas 28S ribosomal RNA (28S rRNA), attachment region binding protein (ARBP), and 18S ribosomal RNA (18S rRNA) were the least stable. These results were verified by an expression analysis of taimen heat-stress genes (heat shock protein 60, hsp60, and heat shock protein 70, hsp70). In conclusion, RPS29 and RPL19 are the optimal reference genes for qRT-PCR analyses of taimen, irrespective of the tissue and experimental conditions. These results allow the reliable study of gene expression in taimen.