The technological development of tools that enable the spawning of different native species is paramount to enable ex situ conservation initiatives, as well as providing means for commercial hatchery of threatened fish which, in turn, relieve fisheries pressure over wild stocks. Neotropical migratory freshwater fish depend on hormonal induction for spawning in hatcheries, through expensive methods of limited efficiency. Salminus brasiliensis is one of the largest Neotropical freshwater fish, a piscivorous top-predator, prized in angling, highly valued in the market, and appreciated in gastronomy. Teleost fish have either, two or three GnRH paralogous genes: GnRH1, GnRH2 and the GnRH3. The expression products of these paralogous isoforms consist of a larger prepro-GnRH polypeptide, which undergoes post-translational proteolytic processing to yield the active decapeptide hormone. There is increasing interest in characterizing and understanding these neuropeptides, because of its practical application in hatchery spawning. We present the characterization of GnRH1’s coding sequence for the prepro-GnRH1 polypeptide of S. brasiliensis. An annotation from a genomic assembly was used for searching for GnRH paralogues, based on data from anonymous predicted transcripts. The sequence retrieved for GnRH1 was then used as a query for searching the uncharacterized GnRH paralogues from full genomes of Characiformes deposited at NCBI. The S. brasiliensis GnRH1 gene sequence retrieved was targeted for PCR and submitted to Sanger sequencing, allowing for its confirmation. It spans 423 bp (exon 1: 128 bp; intron: 161 bp; and exon 2: 1134 bp), with open reading frames coding for 264 and 88 amino acids, respectively. The different variants retrieved for the prepro-GnRH (1, 2 and 3) from Characiformes genomes and deposited sequences from NCBI grouped in three distinct clades in a neighbor joining tree, each forming a monophyletic branch and with the S. brasiliensis sequences nested within the expected groups. Here we observed a variation at a proteolytic site (GKR→GRR), reported as highly conserved in vertebrates up to now, that can potentially alter the cleavage site and modify the peptide topology. This work has characterized, for the first time, the sequence of the GnRH1 coding for its prepro-GnRH peptide, for a member of the Charaficormes order. This will help to promote research and development of tools for broodstock spawning and environmental management of S. brasiliensis and related migratory fish.
