Lungfish gets largest genome sequenced
- A Nature study published on August 14, 2024 reported the first genome assemblies for the African and South American lungfishes, with Lepidosiren paradoxa taking the record for the largest animal genome sequenced. - The South American lungfish genome measured about 91 gigabases, roughly 30 times the human genome, and researchers said 18 of its 19 chromosomes were each larger than the full human genome. - The work links that DNA expansion to repeat-heavy noncoding regions and gives scientists a sharper genetic view of the fish lineage closest to land vertebrates. (nature.com)
A genome is an organism’s full DNA instruction set, and scientists have now assembled the biggest animal one on record: the South American lungfish’s. (nature.com) In a Nature paper published August 14, 2024, researchers reported new genome assemblies for the African lungfish, *Protopterus annectens*, and the South American lungfish, *Lepidosiren paradoxa*. (nature.com) (lsu.edu) The South American species came in at about 91 gigabases, or roughly 91 billion DNA letters, making it the largest animal genome sequenced so far. (nature.com) (guinnessworldrecords.com) For scale, that is about 30 times the size of the human genome, and the authors said 18 of the lungfish’s 19 chromosomes are each larger than the entire human genome. (nature.com) (leibniz-lib.de) Most of that extra DNA does not come from vastly more genes. The paper reported about 20,000 protein-coding genes, a count in the same broad range seen in other vertebrates. (nature.com) (sciencealert.com) Instead, the genome swelled through huge stretches between genes and inside genes, packed with repeated sequences; the authors estimated repeat content at about 90%. (nature.com) Lungfish matter because they are the closest living fish relatives of tetrapods, the four-limbed vertebrates that later colonized land. Their genomes offer a genetic reference point for a transition that began in the Devonian period. (nature.com) (smithsonianmag.com) The study also argued that lungfish and land vertebrates share regulatory DNA features tied to breathing air, smelling airborne chemicals, and limb-like development. Those similarities help explain why lungfish have long occupied a key place in vertebrate evolution research. (nature.com) This record did not come out of nowhere. A 2021 Nature paper had already assembled the Australian lungfish genome at about 43 gigabases, which at the time was described as the largest animal genome sequenced. (nature.com) The new result pushed that ceiling much higher and filled in all three living lungfish lineages with genome-scale data. That gives researchers a cleaner way to compare how giant genomes grow, persist, and still run a vertebrate body plan. (nature.com)
