Genome-wide characterization of the Elovl gene family in Gymnocypris przewalskii and their potential roles in adaptation to cold temperature

The elongase of the very long-chain fatty acids (Elovls) gene family in fish has more diversity than in other vertebrates, which plays several critical roles in fatty acid synthesis and low-temperature stress adaptation. Gymnocypris przewalskii settles in plateau lakes with cold and resource-poor settings, and the evolution and function of Elovl genes in this fish are unknown. In the study, to identify the Elovl genes in G. przewalskii, the genome-wide identification and phylogenetic analysis of the gene members have been conducted with the expression profile of different tissues under cold stress. Fatty acid compositions, meanwhile, were detected in both the hepatopancreas and skeletal muscle during cold adaptation. A total of 21 Elovl members have been identified from the genome of G. przewalskii, belonging to Elovl1, Elovl2, Elovl4, Elovl5, Elovl6, Elovl7, and Elovl8 subgroups, with conserved ELO domain and four common motifs. Phylogenetic analysis revealed that subfamilies Elovl1 and Elovl7, Elov2, and Elovl5 have a closer genetic relationship, while the Elovl6 class was classed into an independent clade. Synteny analysis showed that whole-genome duplication, tandem duplicates, and gene conversion could drive the Elovls family expansion in G. przewalskii. The Ka/Ks and RELAX analysis showed distinguishing positive selection traces in ORF sequences of gpElovl2. Transcriptional data showed that different gpElovl subtypes exhibited a tissue-specific expression. Subtypes gpElovl1a, gpElovl2 and gpElovl6l were highly expressed induced by cold stress, as well as fatty acid metabolism-related genes, including Acyl-CoA synthetase long-chain gene (Ascl1a-1) and Stearyl-CoA desaturase gene (Scd1a-1). In addition, monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA) contents of the hepatopancreas and skeletal muscle were significantly increased under 15-day cold stress. These results provide a better understanding of fish Elovl genes and their roles in cold adaptation.

Automated summary

The diversity of the Elovls gene family in fish plays critical roles in fatty acid synthesis and low-temperature stress adaptation. In this study, the Elovl genes in Gymnocypris przewalskii were identified and their expression profiles under cold stress were analyzed. The results revealed that different Elovl subtypes showed tissue-specific expression and some subtypes were highly expressed induced by cold stress. The fatty acid compositions in the hepatopancreas and skeletal muscle also changed significantly during cold adaptation.