Identification, evolution, functional characterization and expression pattern of a fatty acyl desaturase (fads1) gene in Chinese sturgeon (Acipenser sinensis)

Fatty acyl desaturases (Fads) are known to play critical roles in the biosynthesis of long-chain polyunsaturated fatty acids (LC-PUFAs) in fish species. To date, research on Fads in fish has predominantly focused on Fads2, while studies on Fads1 have been rarely reported. Acipenseriformes, commonly known as Chondrostei, are an ancient fish lineage with unique evolutionary history. However, the biological roles and evolutionary status of Fads1 in Chondrostei remain unclear, which constrains our understanding of the evolutionary processes shaping LC-PUFA biosynthesis in this lineage. In this study, we identified and characterized a fads1 gene from Chinese sturgeon (Acipenser sinensis), a critically endangered Chondrostei, using molecular cloning and multiple bioinformatic analyses. The spatio-temporal expression patterns, functional characteristics, and transcriptional regulation in response to dietary fatty acids were investigated. The coding sequence of the fads1 gene was 1317 bp in length, encoding a protein of 438 amino acids. Bioinformatic analyses suggested high conservation of fads genes across Chondrostei despite their complex evolutionary history. Functional characterization in yeast showed that Chinese sturgeon Fads1 exhibited Δ5 desaturation activity, efficiently converting 20:3n-6 to arachidonic acid (ARA) and 20:4n-3 to eicosapentaenoic acid (EPA). Fatty acid composition analysis indicated that Chinese sturgeon could biosynthesize LC-PUFAs when they are deficient in their diets. Taken together, these results suggest that fads1 plays a crucial role in LC-PUFA biosynthesis in Chinese sturgeon, which provides solid theoretical basis for dietary LC-PUFA requirement of Chinese sturgeon. Furthermore, our findings provide novel insights into evolutionary diversification of fads genes in fish species.