Ferns can be weird. Although they look green and leafy, they produce spores like mushrooms. Many species do not require a partner to fertilize unlike their seed-bearing counterparts. Recent studies estimate ferns split from seed-bearing plants about 400 million years ago.
Fern genomes are quite large. Researchers have neglected to study the strange genomes of ferns, despite their unique physiology and relationship with seed plants. Until recently, only two (relatively small) fern genomes were fully sequenced, compared with more than 200 flowering plant genomes. The first complete tree fern genome, that of the flying spider monkey tree fern, has been successfully sequenced. This is a hint at how these unusual plants acquired such a large set of genes.
” “But what I really want to know is why the fern genomes are so damn big.” “But I really want to understand why the fern genomes have this big .”
Li and his team discovered that the palm-tree-shaped fern contains more than six billion DNA base pair pairs, which is more than the average genome of flowering plants. (Humans, however, have only about three billion pairs). The new analysis suggests that more than 100 million years ago, an ancestor of this fern duplicated its whole genome–a replication error that is common in plants, Li says.
But it isn’t clear why tree-ferns keep so much genetic material. Most flowering plants return to smaller genomes after duplications. Li suggests that this species may be hoarding chromosomes. “I call it the Marie Kondo hypothesis.” The chromosomes are a joy to ferns but not for seed plants. He says that a large genome can increase the chances of beneficial mutations while also buffering from unwanted ones. Ferns also live longer, which may have contributed in part to the retention of genetic material.
The researchers used the fully sequenced genome to discover which genes make the fern’s unusual trunk-like stem. This is a valuable insight into how key traits evolved within stemmed plants, according Jan de Vries, a German plant evolutionary biologist who was not involved with the study. “Evolution is a tinkerer. He says that illuminating the molecular programs that have evolved to work biologically tells us what is biologically feasible and where the limitations are.” “Using this knowledge, we can start tinkering ourselves for synthetic biological purposes.”