A miRNA-mRNA study reveals the reason for quality heterogeneity caused by marbling in triploid rainbow trout (Oncorhynchus mykiss) fillets

Abstract

To investigate the quality heterogeneity caused by marbling and its underlying mechanisms, muscle fiber (MF) and myosepta (MS) were dissected for quality analysis. The results revealed that MS is the primary contributor to fish flavor due to its high content of triglycerides (TG), lysophosphatidylinositol (LPI), ceramide (Cer), phosphatidylcholine (PC), lysophosphatidylserine (LPS), and fatty acid (FA) compositions. To explore the underlying reasons, transcriptome analysis was conducted using miRNA-mRNA sequencing. A total of 100 miRNAs and 4782 mRNAs were differentially expressed (DE) between the MF and MS groups. The targeted DE mRNAs were found to be involved in multiple lipid metabolic pathways. By constructing a DE miRNA–mRNA interaction network, we found that miR-727, miR-133, and miR-210 might play key roles in regulating FA metabolism by targeting genes such as hacd2, fas, and others. Additionally, miR-1 and miR-133 might regulate TG accumulation in MS by targeting lpl and lipin2, among others. Novel-m0348-5p might increase LPS-DHA deposition in MS by targeting the expression of acsl6. Furthermore, miR-206, novel-0031-5p, and novel-0137-5p were found to regulate diacylglycerol and glycerophospholipid metabolism in MS by upregulating genes such as mboat2, dgat2 and others. This study provides new insights into the formation of marbling and the molecular mechanisms underlying quality regulation in fish.