A high-quality blue whale genome, segmental duplications, and historical demography

Abstract

Abstract BackgroundThe blue whale, Balaenoptera musculus , is the largest animal known to have ever existed. Body size is tightly coupled to cell metabolism and environmental adaptations. A high-quality genome assembly of this magnificent animal will aid our understanding of body size regulation and related biological processes.ResultsWe report a reference-quality, long read based assembly of the blue whale genome. We sequenced genomic DNA using PacBio long-read, Illumina short-read, and 10X Genomics synthetic long-read technologies. We also obtained long-range mapping information using Bionano optical mapping and Dovetail Hi-C. Additionally, we sequenced the transcriptome of blue whale fibroblasts using Illumina RNA-seq and PacBio Iso-seq technologies. We also measured genome size using a flow cytometry technique. We report on: (1) comparison of alternative long-read and short-read-based assemblies; (2) segmental duplications within the blue whale genome, which have resulted in dramatic amplifications of several genes; (3) sites in IGF1 gene correlated to body size in cetaceans; and (4) heterozygosity and historical demography of Pacific and Atlantic blue whale populations.ConclusionsThis is one of the first high-quality reference genomes of a cetacean and the first baleen whale sequenced using a long-read technology. A high quality, annotated blue whale genome will serve as an important resource for biology, evolution, and conservation research.