Draft Genome Assembly of the Aral Barbel Luciobarbus brachycephalus Using PacBio Sequencing

Abstract

The endangered Aral barbel Luciobarbus brachycephalus is endemic to the water systems of the Caspian Sea and Aral Sea. Given the scarcity of genetic data for the species, we present a draft assembly based on PacBio long-read sequencing technology. Approximate 299.4 Gb of long reads representing 166× of the estimated genome size were generated, and the final assembly was composed of 653 contigs totaling approximately 1,698.3 Mb, with a contig N50 length of 4.5 Mb. A total of 807.6 Mb represented approximately 47.6% of the assembly and were identified as repeats. Fifty-four thousand and six hundred possible protein genes were predicted, among which 50,727, representing approximately 92.9%, could be annotated by at least one database. Evolutionary analysis showed that L. brachycephalus and Labeo rohita diverged by approximately 42.6 Ma, and the obvious expansion of gene families residing in the L. brachycephalus genome may be attributed to the specific whole-genome duplication of the species. The first genome assembly of L. brachycephalus can not only provide a foundation for genetic conservation and molecular breeding of this species but also contribute to comparative analyses of genome biology and evolution within Cyprinidae.

Keywords: Luciobarbus brachycephalus; PacBio sequencing; de novo assembly; genome annotation; phylogeny.