Alternative splicing plays key roles in response to stress across different stages of fighting in the fish Betta splendens

Aggression is an evolutionarily conserved behavior critical for animal survival. In the fish Betta splendens, across different stages of fighting interactions, fighting opponents suffer from various stressors, especially from the great demand for oxygen. Using RNA sequencing, we profiled differential alternative splicing (DAS) events in the brains of fish collected before fighting, during fighting, and after fighting to study the involvement of alternative splicing (AS) in the response to stress during the fight. We found that fighting interactions induced the greatest increase in AS in the 'during-fighting' fish, followed by that of the 'after-fighting' fish. Intron retention (IR) was the most enriched type among all the basic AS events. DAS genes were mainly associated with synapse assembly, ion transport, and regulation of protein secretion. We further observed that IR events significantly differentiated between winners and losers for 19 genes, which were associated with messenger RNA biogenesis, DNA repair, and transcription machinery. These genes share many common features, including shorter intron length and higher GC content. This study is the first comprehensive view of AS induced by fighting interactions in a fish species across different stages of those interactions, especially with respect to IR events in winners and losers. Together, these findings facilitate future investigations into transcriptome complexity and AS regulation in response to stress under the context of aggression in vertebrates.