A chromosome-level genome assembly of longnose gar, Lepisosteus osseus

Abstract

Holosteans (gars and bowfins) represent the sister lineage to teleost fishes, the latter being a clade that comprises over half of all living vertebrates and includes important models for comparative genomics and human health. A major distinction between the evolutionary history of teleosts and holosteans is that all teleosts experienced a genome duplication event in their early evolutionary history. As the teleost genome duplication occurred after teleosts diverged from holosteans, holosteans have been heralded as a means to bridge teleost models to other vertebrate genomes. However, only three species of holosteans have been genome-sequenced to date, and sequencing of more species is needed to fill sequence sampling gaps and provide a broader comparative basis for understanding holostean genome evolution. Here we report the first high quality reference genome assembly and annotation of the longnose gar (Lepisosteus osseus). Our final assembly consists of 22,709 scaffolds with a total length of 945 bp with contig N₅₀ of 116.61 kb. Using BRAKER2, we annotated a total of 30,068 genes. Analysis of the repetitive regions of the genome reveals the genome to contain 29.12% transposable elements, and the longnose gar to be the only other known vertebrate outside of the spotted gar and bowfin to contain CR1, L2, Rex1, and Babar. These results highlight the potential utility of holostean genomes for understanding the evolution of vertebrate repetitive elements, and provide a critical reference for comparative genomic studies utilizing ray-finned fish models.