Tiny fern breaks world record for largest genome on Earth – with DNA reaching taller than Statue of Liberty

A small, seemingly nondescript fern that grows only on a remote Pacific island was crowned a Guinness World Record holder on Friday for having the largest genome of any organism on Earth.

The New Caledonian fern, Tmesipteris oblanceolata, has more than 50 times more DNA in the nucleus of its cells than humans.

If the DNA from one of the fern’s cells — which are just a fraction of a millimeter wide — were to unravel, it would stretch 350 feet, researchers report in a new study.

Standing upright, DNA would be taller than the Statue of Liberty and the tower that carries London’s famous Big Ben.

The fern genome weighed a whopping 160 gigabase pairs (Gbp), a measurement of DNA length.

This is 7% more than the previous record holder, the Japanese flowering plant Paris japonica.

The human genome is a relatively tiny 3.1 Gbp. If our DNA was revealed, it would be about six feet long.

Study co-author Ilia Leitch, a researcher at Britain’s Royal Botanic Gardens, Kew, told AFP the team was “really surprised to find something even bigger than Paris japonica”.

“We thought we had already reached the biological limit. We’re really pushing the limits of biology,” she said.

The fern, which grows to a height of 5 to 10 centimeters, is only found in New Caledonia, a French Pacific territory that has recently experienced unrest.

Two members of the research team traveled to the main island, Grand Terre, in 2023 and collaborated with local scientists on a study that was published in the journal iScience.

“Harmless looking fern”

Guinness World Records awarded the fern its coveted “title of largest genome”.

“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 flashiest on the outside,” Guinness said, according to the BBC’s World Editor-in-Chief Records Adam Millward.

It is estimated that humans have more than 30 trillion cells in their bodies.

Inside each of these cells is a nucleus that contains DNA, which is like “an instruction book that tells an organism like us how to live and survive,” Leitch explained.

All the DNA of an organism is called its genome.

So far, scientists have estimated the genome size of around 20,000 organisms, which is only a fraction of life on Earth.

Some of the largest genomes in the animal kingdom include certain platypuses and salamanders, with about 120 billion base pairs, according to the BBC.

While plants have the largest genomes, they can also have incredibly small ones. The genome of the carnivorous Genlisea aurea is only 0.06 Gbp.

But we humans needn’t feel inadequate when we compare ourselves to the mighty T. oblanceolata.

All the evidence suggests that having a huge genome is a disadvantage, Leitch said.

The more DNA you have, the bigger your cells have to be to squeeze it all in.

For plants, larger cells mean that things like leaf pores have to be larger, which can cause them to grow more slowly.

It is also more difficult to make new copies of all the DNA, which limits their reproductive abilities.

This means that the most massive genomes are seen in slow-growing perennial plants that cannot easily adapt to adversity or fight off competition.

Genome size can therefore influence how plants respond to climate change, changing land use and other environmental challenges caused by humans, Leitch said.

“How does it survive with that much DNA?”

There could still be larger genomes out there somewhere, but Leitch thinks this fern must be close to the limit.

“How does it work? How does it survive with that much DNA?” Leitch told the BBC.

Scientists don’t know what most of the DNA does in such huge genomes, she admitted.

Some say most of it is “junk DNA”.

“But that’s probably our own ignorance. Maybe it has a function and we have yet to find it,” Leitch said.

Jonathan Wendel, an Iowa State University botanist who was not involved in the research, agreed that it was “amazing” how much DNA the fern packed.

But that only “represents the first step,” he told AFP.

“The big mystery is the meaning of all this variation—how do genomes grow and shrink, and what are the evolutionary causes and consequences of these phenomena?”