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.
New Caledonian fern, Tmesipteris oblanceolatait has more than 50 times more DNA than humans in the nucleus of its cells.
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 106 meters (350 feet), researchers said in a new study.
Standing upright, DNA would be taller than 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 seven percent larger 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 two meters 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 Japanese Paris“.
“We thought we had already reached the biological limit. We are really pushing the limits of biology,” she said.
The fern, which grows 5 to 10 centimeters tall, 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.
Guinness World Records awarded the fern its coveted “title of largest genome”.
The victory of “this innocuous-looking” fern shows that “record holders are not always the most flamboyant on the outside”, said Guinness World Records editor-in-chief Adam Millward.
What is a genome again?
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.
Among the animals, the marbled platypus has the largest, with 130 Gbp.
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 don’t have to feel inadequate when we compare ourselves to the powerful 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 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.
What’s all that DNA for?
There could still be larger genomes out there somewhere, but Leitch thinks this fern must be close to the limit.
“I can’t understand how an organism with this DNA really works,” she said.
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, a botanist at Iowa State University 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?”
© Agence France-Presse