Transcriptome analysis reveals the molecular mechanisms of heterosis on thermal resistance in hybrid tilapia (Oreochromi niloticus ♀×Oreochromi aureus ♂)

Heterosis is a widely observed biological phenomenon in fishes, in which hybrids exhibit superior traits to their parents. However, the underlying molecular mechanisms for heterosis are not well understood. Tilapia is an economically important aquaculture resource with high commercial value, and the phenomenon of high temperature tolerance in hybrid tilapia (Oreochromis niloticus ♀ × Oreochromis aureus ♂, AN) has been observed in recent studies. Uncovering the molecular mechanisms underlying this phenomenon could provide theoretical support for heterosis in thermal tolerance. To investigate the gene expression patterns and alternative splicing events associated with heat stress in tilapia, RNA Sequencing was conducted at control temperature (28 °C) and heat stress temperatures (36 °C and 39 °C). A total of 280, 260, and 261 genes with significantly divergent alternative splicing events were identified in O.niloticus (NL), O.aureus (AR), and O. niloticus ♀ × O.aureus ♂ (AN), respectively. In the heat stress groups (39 °C groups), 83.59% (23779 out of 28446) of the expressed genes showed non-additive expression patterns, and the highest proportion (35.14%) of these genes exhibited over-dominance expression patterns. KEGG pathway enrichment analysis showed that the overlapping genes among common differentially expressed genes (DEGs) and non-additively expressed genes (NAGs) were significantly enriched in apoptosis, adipocytokine signaling, and insulin signaling pathways. Furthermore, among these overlapping genes, 32 genes had undergone alternative splicing events in AN, which may play an important role in the thermal resistance of hybrid tilapia. These findings shed light on the physiological regulation mechanisms that allow hybrid tilapia to exhibit better thermal resistance than their parents. They provide important insights into the molecular basis of heterosis in tilapia and have potential implications for improving aquaculture practices.