Largest genome on Earth belongs to … a fern?

Watch a video about the tiny fern that holds the new record for largest genome on Earth. Amazingly, it has 50 times more DNA in its cells than humans have.

Largest genome on Earth belongs to a tiny fern

An international team of researchers said on May 31, 2024, they’ve found a new record holder for the largest genome on Earth. A genome is a complete set of DNA in an organism, stored in every cell. And the new title goes to a tiny fern – by the name of Tmesipteris oblanceolata – that lives in New Caledonia and other South Pacific islands.

So how large is the record-holding genome? This species of fern contains 160 billion base pairs, which are the units that make up a strand of DNA. As an illustration, compare that to a human genome, which consists of about 3 billion base pairs. So, incredibly, the fern’s cell has 50 times the amount as a human cell. Put another way, if you laid the fern’s base pairs of DNA end-to-end, they would cover about 328 feet (100 meters). Whereas a human’s base pairs would stretch about 6.5 feet (2 meters).

The researchers published their peer-reviewed study in the journal iScience on May 31, 2024.

Largest genome: A single fern with stubby projections stands straight up from the forest floor.
This tiny fern – Tmesipteris oblanceolata – grows only on a few South Pacific islands. Now, it’s the new record holder for largest genome on Earth. Image via Pol Fernandez/ Kew Gardens.

A world-record holder

And now, the tiny fern holds three Guinness World Records:

  • Largest plant genome
  • Largest genome
  • The largest fern genome for the amount of DNA in the nucleus

Managing editor of Guinness World Records, Adam Millward, said:

To think this innocuous-looking fern boasts 50 times more DNA than humans is a humbling reminder that there’s still so much about the plant kingdom we don’t know, and that record holders aren’t always the showiest on the outside.

A group of people walking single file through a rainforest with green trees and ferns all around.
Researchers from the Royal Botanic Gardens, Kew and the Institut Botànic de Barcelona did field work in the South Pacific island of New Caledonia. Image via Pol Fernandez/ Kew Gardens.

More about Tmesipteris oblanceolata

The previous record holder for largest genome was the flowering plant Paris japonica. It has 150 billion base pairs of DNA. Scientists weren’t sure that was a record that could be beat. Tmesipteris oblanceolata, however, has more than 10 billion more base pairs. Co-author Jaume Pellicer of the Institut Botànic de Barcelona explained more about this rare, tiny fern:

Tmesipteris is a unique and fascinating small genus of ferns, whose ancestors evolved about 350 million years ago, well before dinosaurs set foot on Earth. It is distinguished by its mainly epiphytic habit [it grows mainly on the trunks and branches of trees] and restricted distribution in Oceania and several Pacific Islands. For a long time, we thought that breaking the previous size record of Paris japonica was going to be an impossible mission, but once again, the limits of biology have surpassed our most optimistic predictions.

Based on our previous research, we anticipated the existence of giant genomes in Tmesipteris. That said, discovering the largest genome of them all is not just a feat of scientific exploration, but the result of an almost 14-year journey into the boundless complexity and diversity of plant genomes.

A man with dark facial hair and black clothes with backpack and camera holds up two small fronds.
A researcher holds up some of the ferns studied in fieldwork in New Caledonia in the South Pacific. Image via Oriane Hidalgo/ Kew Gardens.

Largest genome may not be beneficial

Having such a large genome may not be terribly advantageous. For example, larger amounts of DNA mean this plant is slow growing. In addition, it’s also less efficient at photosynthesis and requires more nutrients to grow. So neighboring plants with smaller amounts of DNA can outcompete this tiny fern. Therefore, the fern – and other plants with large genomes – may have a harder time adapting to climate change.

Co-author Ilia Leitch of Kew Gardens said:

Who would have thought this tiny, unassuming plant that most people would likely walk past without notice, could bear a world-beating record in genome size? Compared to other organisms, plants are incredibly diverse when viewed at the DNA level, and that should make us pause to think about their intrinsic value in the wider 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.

Bottom line: The new record holder for world’s largest genome goes to a tiny fern that grows on a few islands in the South Pacific.

Source: A 160 Gbp fork fern genome shatters size record for eukaryotes

Via Kew Gardens

Via Nature

Read more: Lady Gaga gets 19 species of ferns named for her

June 6, 2024

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