Do you think the organism with the largest genome would be the blue whale, African elephant, or perhaps a giant sequoia? Not even close. man? Wrong again. Instead, that honor goes to a tiny embryo growing in the French overseas territory of New Caledonia, in the southwestern Pacific Ocean.
New investigations revealed that this type of embryo is called Tmesipteris oblanceolataIt has a genome – all of an organism’s genetic information – that is 7% larger than the previous record holder, the Japanese plant Japanese ParisIt is 50 times larger than the human genome.
The measure of genome size was the number of base pairs, the four basic units of DNA found in the nucleus of an organism’s cells. If it were stretched like a ball of string, the length of the DNA in each cell of this embryo would extend to approximately 106 metres, which would be longer than the Statue of Liberty in New York, the Big Ben clock tower in London or the Taj Mahal. Shop in India. The human genome will be only two meters long.
The fern grows mainly on the ground or on fallen tree trunks in New Caledonia (located 1,200 km east of Australia) and neighboring islands such as Vanuatu.
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“We can say that this species is not very showy. It is a small plant, usually 10 to 15 centimeters long, that can pass by without being noticed,” said evolutionary biologist Jaume Pellicer, from the Barcelona Botanical Institute (IBB), and co-author of the book. “It is easily noticed by anyone who is not specifically looking for it,” a study published on Friday In the magazine iScience.
The samples used in the study were collected last year on Grande Terra Island, the largest in the New Caledonia archipelago. Their leaf-like structures are not true leaves, but rather flat stems. It belongs to a family of ferns whose evolutionary lineage separated from other ferns about 350 million years ago, that is, about 120 million years before the appearance of dinosaurs.
A large genome is not useful. “We believe so Tmesipteris oblanceolata Jaume Pellicer explained that this large genome is not due to any evolutionary advantage, but simply because, for a reason we do not yet know, it was not able to sufficiently remove non-functional or redundant DNA sequences over time. .
Multiple consequences
DNA, which carries an organism’s genetic information, consists of two linked strands that wrap around each other in the form of a double helix, similar to a twisted ladder.
Genome size has multiple consequences. For example, larger genomes require more resources to replicate, repair, and copy DNA, a process the cell uses to produce the proteins an organism needs to function.
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“This increase in demand [de mais recursos] It can increase a plant’s energy and nutritional resources, which can be used for growth, reproduction and stress responses. pressureOrian Hidalgo said, Evolutionary biologist from dad And also Co-author to Stady.
Larger genomes require larger cells to house them and take longer to replicate DNA, slowing the cell division that sustains growth. This can reduce the ability of plant species to compete for light, water and nutrients, making them more ecologically constrained, Orian Hidalgo explained.
Scientists have wondered why some organisms have large genomes and others do not. “This is indeed an interesting question. But what is clear is that there is no relationship between genome size and the complexity of the organism,” said plant geneticist and co-author of the study, Elijah Leach, from the Royal Botanic Gardens, Kew, in London.
There is also no relationship between the physical size of an organism and the size of its genome. The size of the small fetus’s genome is about 6,000% larger than the genome of the blue whale, the largest animal on Earth, and about 4,650% larger than the genome of the African elephant, the largest land animal. It is also about 1,500% larger than the giant sequoia, the tallest plant.
Hey Protopterus aethiopicus, a lungfish from Africa, has the largest known animal genome. The fetus becomes approximately 25% larger.
Scientists evaluated the genome size of about 20,000 organisms with clearly defined cell nuclei, with large genomes being the exception rather than the rule.
“Genome size is an important trait of biodiversity, as it has been shown to play a role in influencing how, where and when a plant is able to grow, compete, and respond to environmental challenges such as climate change and pollution,” said Elia. Leach.
Paul Fernandez/IBP
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