Characterization of myostatin genes in Black Sea trout, Salmo labrax, and their differential responses to high temperature and starvation stressors

The identification of myostatin (mstn) gene functions in salmonids has been complicated by two whole-gene duplications (WGDs), leading to the presence of up to four mstn genes in their genomes, as opposed to the one or two copies found in other vertebrates. In this research, we molecularly cloned and characterized four mstn genes-Sl-mstna1, Sl-mstna2, Sl-mstnb1, and Sl-mstnb2-in the Black Sea trout (Salmo labrax). We propose that Sl-mstnb2 is a pseudogene due to a nonfunctionalization event, while Sl-mstna1, Sl-mstna2, and Sl-mstnb1 are retained in the Salmo labrax genome due to subfunctionalization. Notably, the expression level of the Sl-mstna1 and Sl-mstna2 genes varied across different tissues, implying divergent regulatory mechanisms. Starvation and high temperature increased mRNA expression of Sl-mstna1 and Sl-mstna2, while Sl-mstnb1 transcription was decreased by both stress factors. The tissue-specific transcription and modulation of Sl-mstnb1 were distinctly different from those of the Sl-mstna duplicates, suggesting functional divergence between the Sl-mstna and Sl-mstnb1 genes.