The small fern species on Grand Terre Island set a Guinness World Record on May 31 for having the largest genome among living organisms on Earth.
New Caledonia fern (Tmesipteris oblanceolate) has a nucleus containing DNA that is approximately 50 times greater than that of humans. According to a recent study published in the journal iScience, if the DNA from a tiny cell of this plant were unraveled, it would stretch up to 106 meters. If stood upright, it would surpass the famous Big Ben clock tower in London.
The fern’s genome boasts 160 gigabase pairs (Gbp)—a measure of DNA length. This figure is over 7% larger than the previous “record holder,” the flowering plant Paris japonica from Japan. The human genome is relatively small, at only 3.1 Gbp. If unraveled, human DNA would measure about 2 meters long. Ilia Leitch, a researcher at the Royal Botanic Gardens Kew in the UK and co-author of the new study, expressed astonishment at discovering an even larger genome than that of Paris japonica.
The New Caledonia fern has the largest genome in the world. (Photo: Pol Fernandez/Institut Botanic de Barcelona (CSIC)/AFP).
The New Caledonia fern grows to about 5 – 10 cm in height and is found exclusively in New Caledonia, a French territory in the Pacific. Two members of the research team visited Grand Terre Island in New Caledonia in 2023 and collaborated with local scientists for this study.
It is estimated that there are over 30 trillion cells in the human body. Inside each cell is a nucleus containing DNA, akin to a “manual that tells us how to live and survive,” explained Leitch. The complete set of DNA in an organism is referred to as its genome.
So far, scientists have estimated the genome size of around 20,000 organisms, a small fraction of the life forms on Earth. Among animals, the genome of the marbled lungfish is the largest at 130 Gbp. Plants possess the largest genomes, but there are also species with extremely small genomes. The genome of the carnivorous plant Genlisea aurea is only 0.06 Gbp in size.
Leitch noted that all evidence suggests that having a massive genome is a disadvantage. The more DNA an organism has, the larger its cells must be to accommodate it all. For plants, larger cells mean that features like leaf pores must also be larger. This could slow down the plant’s growth. Additionally, producing new copies of all that DNA becomes more challenging, limiting reproductive capacity.
Thus, the largest genomes are found in perennial, slow-growing plants that cannot easily adapt to harsh conditions or compete effectively. Leitch mentioned that genome size could influence how plants respond to climate change, land use changes, and other environmental challenges posed by humans.
