A Nanopore-only whole-genome assembly of the blue gourami (Trichopodus trichopterus)

The blue gourami (Trichopodus trichopterus), also known as the three-spot gourami, opaline gourami, and gold gourami, is a model species for the Suborder Anabantoidei, also known as labyrinth fishes, distinguished by their possession of a lung-like labyrinth organ, which enables them to breathe air. Although the physiology and endocrinology of this species have been extensively studied, it lacks a reference genome, and its sex determination mechanism and evolutionary history are mostly unknown. We used Oxford Nanopore technology to sequence size-selected HMW DNA of two blue gourami specimens (one male and one female). The resulting reads were assembled using hifiasm. The female assembly had a total length of ~535Mb and consisted of 62 contigs (N50＞22Mb), with 20 contigs containing ＞90% of all sequence length, and one contig identified as mitochondrial. BUSCO completeness analysis using the actinopterygii_odb10 database produced a score of 99.3%, indicating a complete assembly. The male assembly showed similar completeness and size, but was more fragmented (205 contigs). Annotation of the assembly was performed using a previously published whole-brain transcriptome assembled using Illumina reads. To obtain insights into sex determination mechanisms, we assembled a combined pangenome from both male and female reads and assessed read coverage and predicted gene content in the divergent areas. Insights obtained from ongoing analyses will be presented.