Researchers have identified Tmesipteris oblanceolataa fern from New Caledonia, as it has the largest genome on record, surpassing the previous record Japanese Paris. This discovery, detailed in Science magazine, reveals that this fern contains over 50 times more DNA than humans and highlights the important implications that larger genomes have on plant biology and adaptation. Credit: SciTechDaily.com
of Tmesipteris oblanceolata fern sets new record for largest genome, influencing plant growth and adaptation insights.
- A fern of New Caledonia species has awarded 3 Guinness world record titles; Largest Plant Genome, Largest Genome, and Largest Fern Genome by Quantity of DNA in the core
- Lying down, Tmesipteris oblanceolata The genome is taller than Big Ben in London
- The 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
A record-breaking 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 presented in a new study published in the journal Science on May 31 by researchers from the Royal Botanic Gardens, Kew and the Institut Botànic de Barcelona (IBB-CSIC) in Spain.
Coming in at more than 100 meters of broken down DNA, the New Caledonian fork fern species Tmesipteris oblanceolata was found to contain over 50 times more DNA than humans and dethroned the Japanese flowering plant species Paris japonica, which has held this record since 2010. In addition, the plant has achieved three Guinness World Record titles for the largest plant genome, the largest genome and the largest fern genome for the amount of DNA in the nucleus.
A study reveals that Tmesipteris oblanceolata has the largest genome, offering new perspectives on plant evolution and challenges. Credit: Kew
Fern Natural Habitat and Study Methodology
T. oblanceolata is a rare species of fern found in the island nation of New Caledonia, a French overseas territory located in the Southwest Pacific, about 750 miles east of Australia and some of its neighboring islands such as Vanuatu. The genus Tmesipteris is an understudied group of plants consisting of about 15 species, most of which are found on a number of islands in the Pacific and Oceania.
So far, scientists have only estimated the genome size for two species of Tmesipteris – T. tannensis AND T. obliqua – both were found to contain giant genomes, with 73.19 and 147.29 gigabase pairs (Gbp), respectively.
In 2023, the main authors Dr. Jaume Pellicer and Dr. Oriane Hidalgo, from IBB and previously from RBG Kew, traveled to New Caledonia to collect samples of Tmesipteris, which were then analyzed to estimate their genome size. This involved isolating the nuclei of thousands of cells, staining them with a dye, and then measuring the amount of dye bound to the DNA within each nucleus—the more dye, the larger the genome.
Innovative Findings and Comparisons
The analysis revealed the species T. oblanceolata to have a record genome size of 160.45 Gbp, which is about seven percent larger than that of P. japonica (148.89 Gbps).
When broken down, the DNA from each cell of this fern would stand taller than the Elizabeth Tower in Westminster, London, which is 96 meters tall and home to the world famous Big Ben. By comparison, the human genome contains about 3.1 Gbp spread across 23 chromosomes, and when stretched out like a ball of thread, the length of DNA in each cell is only about 2 m.
Implications of genome size in 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 dinosaurs walked the Earth – and is notable for its habit mainly epiphytic. [it grows mainly on the trunks and branches of trees] and limited distribution in Oceania and some Pacific islands. For a long time, we thought that breaking the previous Paris japonica size record would be an impossible mission, but once again, the limits of biology have exceeded our most optimistic predictions.
“Based on our previous research, we predicted the existence of giant genomes in Tmesipteris. That said, the discovery of the largest genome of all is not just a feat of scientific exploration, but the result of a nearly fourteen-year journey into the limitless complexity and diversity of plant genomes.
To date, scientists around the globe have estimated the genome sizes of over 20,000 eukaryotic organisms, in the process revealing a wide range of genome sizes across the tree of life. These, in turn, 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 reproduce, but also how they function, evolve and where and how they live.
Among animals, some of the largest genomes include the marbled lungfish (Protopterus aethiopicus) at 129.90 Gbp and Neuse River waters (Necturus lewisi) at 117.47 Gbp. In stark contrast, six of the best-known eukaryotic genomes are carried 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 possessing large amounts of DNA are limited to slow-growing perennials, are less efficient at photosynthesis (the process by which plants convert the sun’s energy into sugars) and require more nutrients (especially nitrogen and phosphates) to grow and compete successfully with their smaller-genome neighbors. In turn, such effects can affect a plant’s ability to adapt to climate change and its risk of extinction.
Reflections on genome diversity and future research
Dr. Ilia Leitch, Senior Research Leader – Character Evolution, at RBG Kew, says: “Who would have thought that this small, unassuming plant that most people are likely to pass by without notice could hold a record worldwide in genome size. Compared to other organisms, plants are remarkably diverse when viewed at the DNA level, and this should give us pause to think about their intrinsic value in the larger picture 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 solve these mysteries one day.”
Adam Millward, Managing Editor of Guinness World Records, says: “To think that this innocuous-looking fern boasts 50 times more DNA than humans does is a humbling reminder that there is still much about the plant kingdom that we don’t know and that record holders are not always the most visible from the outside.”
Reference: “A 160 Gbp Fork Fern Genome Breaks the Size Record for Eukaryotes” by Pol Fernández, Rémy Amice, David Bruy, Maarten JM Christenhusz, Ilia J. Leitch, Andrew L. Leitch, Lisa Pokorny, Oriane Hidalgo, and Jaume Pellicer , 2024, Science.
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).