(ORDO NEWS) — In a new study, scientists are trying to understand how the tree fern can accumulate chromosomes.
Ferns are strange plants. They are green and leafy like other woodland plants, but more often reproduce like mushrooms, releasing clouds of spores.
Many species do not require a breeding partner, unlike most of their seed-bearing counterparts. Recent studies estimate that ferns evolved from seed-bearing plants about 400 million years ago.
But the genomes of ferns, as it turned out, are amazingly huge. Despite the unique physiology of ferns and their relationship to seed plants, researchers have largely ignored these strange genomes.
Until recently, only two (relatively small) fern genomes have been fully sequenced compared to over 200 flowering plant genomes.
Now, the first complete genome of the flying spider monkey tree-fern has been successfully sequenced. Its name seems to hint at how these strange plants have accumulated such a huge set of genes.
“If you want to understand the origin of seeds or flowers, then ferns are a very important comparison,” says Fei-Wei Li, a biologist at the Boyce Thompson Institute at Cornell University, who co-authored the new study.
“But what I really want to know is why fern genomes are so huge,” Nature Plants quoted the biologist as saying.
Lee’s team found that the palm-shaped fern contains over 6 billion base pairs of DNA, a billion more than the average flowering plant genome. Humans, for example, have about three billion pairs.
The results of the latest study showed that more than 100 million years ago, the ancestor of this fern completely duplicated its genome. That is, it is most likely a replication error that is common in plants, Lee says.
However, it is not clear why tree ferns retain so much genetic material. Most flowering plants revert to thinner genomes after duplication.
This species is able to accumulate chromosomes. For plants that reproduce asexually, a large genome could add room for beneficial mutations, the biologist says.
Ferns are long-lived plants, so they develop more slowly, which may have contributed to the preservation of their genetic material.
Using the fully sequenced genome, the researchers also discovered which genes create the fern’s unusual stem-like stem.
“This is very valuable information about how key traits evolved in stem plants,” says Jan de Vries, a biologist at the University of Göttingen in Germany.
“Using this knowledge, we can start to remake humans for biological purposes,” he says.
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