Transcription factor pparαb activates fads2s to promote LC-PUFA biosynthesis in the golden pompano Trachinotus ovatus (Linnaeus 1758)

Fatty acyl desaturase 2 (fads2) is a rate-limiting enzyme in long chain polyunsaturated fatty adds (LC-PUFAs) biosynthesis. In mammals, the lipid metabolism is modulated by a transcription factor, peroxisome proliferator-activated receptor alpha beta (ppar alpha beta): however, the detailed mechanism via ppar alpha beta regulates fads2 remains undear in fish. In the present study, we identified the sequence features of Trachinotus ovatus fatty acyl desaturase 2a (Tofads2a) and fatty acyl desaturase 2b (Tofads2b), which both encoded 442 amino acid polypeptides containing cytochrome-b5-like domains and three representative histidine-rich domains. The Phylogenetic and genome organization analyses revealed characteristic phylogeny: the majority of fads2s exhibited a highly conserved exon/intron architecture. Tissue expression patterns by quantitative real-time PCR (qRT-PCR) showed that the two Tofads2s were prominently expressed in the brain. A nutritional study indicated that the transcription of the two Tofads2s was significantly implicated by treatment with a 1: 1 ratio of fish oil: soybean oil (FO:SO) in the liver and brain. Furthermore, functional characterization in yeast demonstrated that both Tofads2a and Tofads2b possessed Delta 4/Delta 5/Delta 8 desaturation activity. Furthermore, promoter activity assays showed that the expressions of the two Tofads2s were actively regulated by pparap. Moreover, mutation analyses showed that the M1 and M4/M5 binding sites of ppar alpha beta were functionally vital for binding to Tofnds2a and Tofads2b promoters, respectively. Transcriptional activities of the two Tofads2s promoters were significantly reduced after targeted mutation of M1 or M4/M5. Electrophoretic mobile shift assays (EMSAs) verified that ppar alpha beta interacted with the M1 binding site in Tofads2a promoter to accommodate Tofads2a transcription. Briefly, ppar alpha beta plays an important role in Tofads2 expression and may promote the LC-PUFAs biosynthesis by regulating the expression of two Tofads2s. (C) 2020 Elsevier B.V. All rights reserved.