African lungfish genome

Lungfish are the closest extant relative of tetrapods and preserve ancestral traits linked with the water-to-land transition. However, their huge genome sizes have hindered understanding this key transition in evolution. Here, we report a 40 Gb chromosome-level assembly of the African lungfish genome, which is the largest genome sequence ever reported and has a contig and chromosome N50 of 1.59 Mb and 2.76 Gb, respectively. The large size of the lungfish genome is due mainly to accumulation of transposable elements. Ancestral chromosome reconstruction revealed that the chromosome segments were conserved from the common ancestor of bony fish to that of amniotes. Using the genome together with comprehensive transcriptome data, we identified key genes and regulatory elements related to such terrestrial adaptation traits as pulmonary surfactant, anxiolytic ability, pentadactyl limbs and pharyngeal remodeling. Our results provide novel insights and key resources for understanding the evolutionary pathway leading from fish to humans.