Cloning, Computational Analysis and Expression Profiling of Steroid 5 Alpha-Reductase 1 (SRD5A1) Gene During Reproductive Phases and Ovatide Stimulation in Endangered Catfish, Clarias Magur

The study successfully cloned and characterized the full coding sequence of the SRD5A1 gene from the endangered catfish Clarias magur, which is crucial for converting testosterone into dihydrotestosterone (DHT), a key hormone in neuroendocrine tissues. The gene's open reading frame (ORF) was 795 base pairs long, encoding a protein of 265 amino acids. The protein was found to be hydrophobic and non-secretory, with seven transmembrane helices. Using AlphaFold 2, the 3D structure was predicted, showing high similarity to bacterial and human SRD5A1 proteins, with a large cavity for binding NADPH and steroid hormones. Key residues for enzyme activity were conserved and identified. Expression levels of SRD5A1 varied with reproductive phases; in females, expression was lower during spawning than preparatory phases, but increased after Ovatide (a GnRH analogue) injection. In males, expression was lowest during the preparatory phase and peaked 16 hours post-Ovatide injection. The study provides the first full-length cDNA characterization of SRD5A1 in this species, with implications for understanding its role in fish reproduction.