A small, seemingly unremarkable fern that grows only on remote islands in the Pacific was named last Friday the Guinness World Record holder for having the largest genome of any organism on Earth.
The New Caledonian fern, Tmesipteris oblanceolata, has more than 50 times more DNA in its cell nucleus than humans.
Unwinding the DNA of one fern cell, which is just a millimeter across, would stretch up to 350 feet, scientists say in a new study.
If erected upright, the DNA would be taller than the tower containing the Statue of Liberty and London's famous Big Ben bell.
The fern's genome weighed a whopping 160 gigabase pairs (Gbp), a measure of DNA length.
This is 7% larger than the previous record holder, the Japanese flowering plant Paris japonica.
The human genome is relatively small at 3.1 Gbps. When our DNA is unpacked, it will be about 6 feet long.
Study co-author Ilia Leitch, a researcher at the Royal Botanic Gardens Kew, told AFP the team was “really surprised to find something bigger than the Paris japonica”.
“We thought we had already reached our biological limits. We are actually pushing the extremes of biology,” she said.
This fern, which grows to 5 to 10 cm tall, is found only in New Caledonia, a French Pacific territory that has recently been experiencing unrest.
Two members of the research team traveled to the main island of Grand Terre in 2023 and collaborated with local scientists to conduct the study, published in the journal iScience.
“A harmless-looking fern.”
Guinness World Records awarded the coveted “largest genome title” to a fern.
“To think that this seemingly harmless fern has 50 times more DNA than a human is a humbling reminder that there is still so much we don't know about the plant world, and that record holders aren't always the most flashy ones on the outside.” It will be.” According to the BBC, World Records editor-in-chief Adam Millward said:
It is estimated that the human body contains more than 30 trillion cells.
Inside each cell is a nucleus that contains DNA, which is like “an instruction book that tells organisms like us how to live and survive,” Leitch explained.
All of the DNA of an organism is called its genome.
So far, scientists have estimated the genome sizes of about 20,000 species of organisms, which is only a fraction of life on Earth.
According to the BBC, some of the largest genomes in the animal kingdom include those of certain lungfish and salamanders, at about 120 billion base pairs.
Plants have the largest genomes, but they can also have incredibly small genomes. The genome of the carnivorous Genlisea aurea is only 0.06 Gbp.
But we humans don't have to feel inadequate compared to the mighty T. oblanceolata.
All the evidence suggests that having a huge genome is a disadvantage, Rich said.
The more DNA there is, the larger the cell must be to fit it all.
For plants, larger cells mean that the pores in the leaves must be larger, which means the leaves can grow more slowly.
It's also trickier to make new copies of all your DNA, which limits your ability to reproduce.
This means that the largest genomes are found in slow-growing perennials that cannot easily adapt to adversity or fight off competition.
Genome size could therefore affect how plants respond to climate change, land-use change and other environmental challenges caused by humans, Leitch said.
“How does it survive with so much DNA in it?”
There may still be larger genomes out there somewhere, but Rich thinks this fern should be close to its limit.
“How does it function? How does it survive with that much DNA?” Rich told the BBC.
Scientists don't know what role most of the DNA plays in such a huge genome, she acknowledged.
Some people say most of it is “junk DNA.”
“But maybe that's our own ignorance. Maybe it has a function and we haven't found it yet,” Leitch said.
Jonathan Wendel, a botanist at Iowa State University who was not involved in the study, agreed that it was “remarkable” how much DNA ferns contain.
But this represents only the first step, he told AFP.
“The big mystery is what all this variation means: how do genomes grow and shrink, and what are the evolutionary causes and consequences of these phenomena?”