Transcriptome profiling of farmed rainbow trout (Oncorhynchus mykiss) liver from different sources of dietary zinc

Abstract Dietary zinc as an essential micronutrient plays a major role in controlling the rate of fish performance and reproduction. Given the liver is an important organ for metabolism and some receptors in the liver are critical for maintaining fertility, it has been hypothesized that it may contributes to reproductive indices. In the present work, we investigated the effects of feeding with different sources of zinc supplements on transcriptome profiling of male rainbow trout (Oncorhynchus mykiss) broodstocks fed for 16 weeks on a diet supplemented with 40 mg. kg−1 of mineral zinc supplement (MZ), 40 mg. kg−1 of zinc nanoparticles (ZN) and control diet containing no zinc supplement (CD). Transcriptome sequencing analysis of the liver generated 39 million high-quality reads using an Illumina HiSeq™ 4000 platform, which were de novo assembled into 77,406 unique transcript fragments (unigenes) with mean length of 985 bp across the treatment groups. Subsequent bioinformatics analysis identified 528, 416 and 327 differentially expressed unigenes (DEGs) in liver in response to MZ, ZN and CD diets, respectively. Furthermore, eight immune-related genes were chosen for quantitative real-time PCR analysis to validate the RNA-Seq data and the result shown that one gene was downregulated and seven genes were upregulated, consistent with the results of our RNA-Seq analysis. The results revealed that mineral zinc supplement showed a strong inhibitory effect on the genes of O. mykiss. Dietary zinc in MZ up-regulated 89.4% of DEGs compared to ZN, however, 93.7% of the DEGs in CD were depressed compared to ZN. This transcriptomic research has provided valuable information for understanding the molecular mechanism and potential physiologically pathway of dietary zinc. These findings also provide molecular support to the notion that dietary zinc is useful materials in commercial diets for broodstock rainbow trout.