Cell
Volume 184, Issue 5, 4 March 2021, Pages 1362-1376.e18
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African lungfish genome sheds light on the vertebrate water-to-land transition

https://doi.org/10.1016/j.cell.2021.01.047Get rights and content
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Highlights

  • Chromosome-level assembly of the largest vertebrate genome reported to date

  • Continuous expansion of transposons contributed to the huge lungfish genome

  • Genetic changes enhanced respiration, locomotion, and anxiolytic ability

  • Three genetic innovation steps from bony fishes to lungfishes and then tetrapods

Summary

Lungfishes are the closest extant relatives of tetrapods and preserve ancestral traits linked with the water-to-land transition. However, their huge genome sizes have hindered understanding of this key transition in evolution. Here, we report a 40-Gb chromosome-level assembly of the African lungfish (Protopterus annectens) genome, which is the largest genome assembly ever reported and has a contig and chromosome N50 of 1.60 Mb and 2.81 Gb, respectively. The large size of the lungfish genome is due mainly to retrotransposons. Genes with ultra-long length show similar expression levels to other genes, indicating that lungfishes have evolved high transcription efficacy to keep gene expression balanced. Together with transcriptome and experimental data, we identified potential genes and regulatory elements related to such terrestrial adaptation traits as pulmonary surfactant, anxiolytic ability, pentadactyl limbs, and pharyngeal remodeling. Our results provide insights and key resources for understanding the evolutionary pathway leading from fishes to humans.

Keywords

lungfishes
water-to-land transition
huge genome size
ancestral karyotype
pulmonary surfactant
anxiolytic ability
pentadactyl limbs
pharyngeal remodeling
aestivation

Cited by (0)

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These authors contributed equally

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Present address: Northwestern Polytechnical University, Xi’an 710072, China

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