A Tiny Fern With Towering DNA: The New Record Holder for Largest Genome on Earth

An unassuming little fern found only on the remote Pacific islands of New Caledonia and Vanuatu has shattered the world record for the largest genome of any organism on Earth. The Tmesipteris oblanceolata fern, which grows just 5-10 cm tall, packs an astounding 160.45 billion base pairs (Gbp or gigabases) of DNA into the nucleus of each cell – over 50 times more than the 3.2 billion base pairs in human cells.

If the DNA from a single cell of this fern could be completely unraveled and stretched out, it would extend over 100 meters (328 feet) in length – taller than the Statue of Liberty. In contrast, our human DNA only reaches about 2 meters (6 feet 6 inches)  when unraveled from a cell’s nucleus.

This extraordinary discovery was published on May 31, 2024, in the journal iScience by an international team of plant geneticists led by Pol Fernández and Dr. Jaume Pellicer from the Institut Botànic de Barcelona in Spain. Using a technique called flow cytometry to measure the genome sizes, they confirmed T. oblanceolata had definitively surpassed the previous plant record holder, the Japanese Paris japonica, with its 149 billion base pair genome.

Top 10 of the largest genome size records
Top 10 of the largest genome size records available in eukaryotes. Credit: https://www.cell.com/iscience/fulltext/S2589-0042(24)01111-8

While possessed of this gargantuan genome, T. oblanceolata doesn’t appear exceptional on the surface.

In fact, having such a massive genome may be more of a disadvantage for the fern. Larger cell sizes are required to fit all that DNA, which can impair critical functions like photosynthesis and reproduction.

How does it function? How does it survive with that much DNA in it? While these questions are yet to be answered, the researchers admit much of this excessive DNA may be non-coding “junk,” though its purpose remains unclear.

While T. oblanceolata is the first organism confirmed to exceed 160 billion base pairs, even larger plant genomes may still await discovery in nature’s treasure troves of biodiversity. This record-shattering fern highlights just how much more there is to uncover about the wondrous genetic variety across the tree of life on our planet.

Organism

Genome Size

Notes

Tmesipteris oblanceolata (fork fern)

160.45 Gbp

New record holder as of 2024

Paris japonica (Japanese plant)

149 Gbp

Previous record holder among plants until 2024

Tmesipteris obliqua (fork fern)

147.3 Gbp

Close to record in 2017

Protopterus aethiopicus (marbled lungfish)

129.9 Gbp

Current animal record as of 1972

Viscum album (European mistletoe)

94 Gbp

Largest plant genome sequenced/assembled as of 2022

Neoceratodus forsteri (Australian lungfish)

43 Gbp

Largest sequenced/assembled animal genome as of 2021

Ambystoma mexicanum (axolotl salamander)

32 Gbp

Previous largest sequenced animal genome until 2021

Homo sapiens (humans)

3.2 Gbp

For comparison

Organisms from largest known genome size down to the human genome for reference.

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