The researchers identified Tmesipteris oblanceolataa fern from New Caledonia that has the largest recorded genome, surpassing the previous record holder Japanese Paris. This discovery, described in detail in iScience Journal, reveals that this fern contains more than 50 times more DNA than humans, highlighting the significant implications of larger genomes for plant biology and adaptation. Credit: SciTechDaily.com
The Tmesipteris oblanceolata fern sets new record for largest genome affecting plant growth and adaptation insights.
- New Caledonian fern species won 3 Guinness World Records titles; The largest plant genome, the largest genome, and the largest fern genome for quantity DNA in the core
- stretched out Tmesipteris oblanceolata genome is taller than Big Ben in London
- Discovery raises new questions about how much DNA can be stored in cells
- The study will help scientists understand how genome size affects species in the face of biodiversity loss and climate change
Record genome
A new record holder for the largest amount of DNA stored in the nucleus of any living organism on the planet has been discovered. The details were given in a new study published in the journal iScience May 31 by researchers from the Royal Botanic Gardens in Kew and the Institut Botànic de Barcelona (IBB-CSIC) in Spain.
In more than 100 meters of untangled DNA, the New Caledonian spiny plant species Tmesipteris oblanceolata was found to contain more than 50 times more DNA than humans, dethroning the Japanese flowering plant species Paris japonica, which has held this record since 2010. In addition, the plant has achieved three Guinness Book titles records for the largest plant genome, the largest genome, and the largest fern genome for the amount of DNA in a nucleus.
The study shows that Tmesipteris oblanceolata has the largest genome, offering new insights into plant evolution and challenges. Credit: Kew
Fern habitat and study methodology
T. oblanceolata is a rare species of fern found on the island nation of New Caledonia, a French overseas territory located in the southwest Pacific, about 750 miles east of Australia and some neighboring islands such as Vanuatu. The genus Tmesipteris is a poorly studied group of plants consisting of about 15 species, most of which are found on a number of Pacific islands and Oceania.
Until now, scientists have only estimated the size of the genomes for two Tmesipteris species— T. tannensis and T. obliqua – both were found to contain gigantic genomes of 73.19 and 147.29 gigabase pairs (Gbp).
In 2023, the main authors Dr. Jaume Pellicer and Dr. Oriane Hidalgo of IBB and formerly of RBG Kew traveled to New Caledonia to collect specimens of Tmesipteris, which were then analyzed to estimate the size of their genomes. This involved isolating the nuclei of thousands of cells, staining them with a dye, and then measuring how much of the dye bound to the DNA in each nucleus—the more dye, the bigger the genome.
Breakthrough insights and comparisons
The analysis revealed the species T. oblanceolata have a record genome size of 160.45 Gbp, about seven percent larger than the genome P. japonica (148.89 Gbps).
Once unraveled, the DNA from each cell of this fern would be taller than the Elizabeth Tower in Westminster, London, which is 96 meters tall and is home to the world-famous Big Ben. By comparison, the human genome contains about 3.1 Gbp distributed over 23 chromosomes, and when stretched out like a ball, the length of DNA in each cell is only about 2 m.
Implications of genome size for plant biology
Dr. Pellicer, a researcher in evolutionary biology, says: “Tmesipteris is a unique and fascinating small genus of ferns, whose ancestors evolved around 350 million years ago – long before the dinosaurs walked the Earth – and are characterized by a predominantly epiphytic habit. [it grows mainly on the trunks and branches of trees] and a limited distribution in Oceania and a few Pacific islands. For a long time, we thought that breaking the previous size record of the Paris japonica would be an impossible mission, but the limits of biology have once again exceeded our most optimistic predictions.
“Based on our previous research, we hypothesized the existence of giant genomes in Tmesipteris. This means that the discovery of the largest genome of all is not just an act of scientific inquiry, but the result of a nearly fourteen-year journey into the infinite complexity and diversity of plant genomes.
To date, scientists worldwide have estimated the genome sizes of more than 20,000 eukaryotic organisms, in the process revealing a wide range of genome sizes across the tree of life. These have been found to have a profound impact not only on their anatomy, as larger genomes need larger cells to house them and take longer to replicate, but also on how they function, develop and where and how they live.
In animals, among the largest genomes is the marbled pufferfish (Protopterus aethiopicus) at 129.90 Gbp and the Neuse River water dog (Necturus lewisi) at 117.47 Gbp. In sharp contrast, the six largest known eukaryotic genomes are held by plants, including European mistletoe (Viscum album) at 100.84 Gbp.
Surprisingly, having a larger genome is usually not an advantage. In the case of plants, species with a large amount of DNA are limited to slow-growing perennials, they are less effective at photosynthesis (the process by which plants convert solar energy into sugars) and require more nutrients (especially nitrogen and phosphate) to grow and compete successfully with their smaller-genome neighbors. These effects may in turn affect the plant’s ability to adapt to climate change and extinction risk.
Genome diversity considerations and future research
Dr. Ilia Leitch, Principal Research Lead – Character Evolution, at RBG Kew, says: “Who would have thought that this tiny, unassuming plant, which most people would probably pass by without noticing, could hold the world record for genome size. Compared to other organisms, plants are incredibly diverse when viewed at the DNA level, and this should make us pause to consider their intrinsic value in the larger view of global biodiversity. This discovery also raises many new and exciting questions about the upper limits of what is biologically possible, and we hope to one day solve these mysteries.”
Adam Millward, Editor-in-Chief of Guinness World Records, says: “To think that this innocuous-looking fern boasts 50 times more DNA than humans is a humbling reminder that there’s still so much we don’t know about the plant kingdom, and that record holders aren’t always the most striking on the outside .”
Reference: “160 Gbp forkhead fern genome breaks size record for eukaryote” by Pol Fernández, Réma Amica, David Bruy, Maarten JM Christenhusz, Ilia J. Leitch, Andrew L. Leitch, Lisa Pokorna, Oriane Hidalgo and Jaume May Pellicer, 2024, iScience.
DOI: 10.1016/j.isci.2024.109889
The study identifying the genome size of Tmesipteris oblanceolata was carried out by an international team of researchers from the Royal Botanic Gardens Kew, Queen Mary University of London, the Herbarium of New Caledonia and the Spanish Research Council (CSIC).