Approximately 86 million years ago, after a mistake in cell division, the entire Weilwichian genome doubled during a period of increased aridity and prolonged drought in the region—perhaps forming the Namib Desert itself, Tao Wan, a botanist at the Fairy Lake Botanical Garden in Shenzhen, China, and lead author of the study. He said that “extreme stress” is often associated with genome duplication events.
Dr. Leech, a co-author on the study, added that the duplicated genes are also released from their original functions, potentially taking on new ones.
However, Dr. Wan said obtaining more genetic material has a cost. “The primary activity of life is DNA replication, so if you have a large genome, it really takes energy to sustain life,” especially in such a harsh environment.
To make matters worse, a large amount of the Willwichia genome are “non-significant” self-replicating DNA sequences called reverse transposons. “Now this junk needs to be replicated and fixed,” Dr. Leech said.
Researchers detected an “explosion” of transposon activity 1 to 2 million years ago, likely due to increased temperature stress. But to counter this, the Willwichia genome has undergone extensive genetic changes that silence unwanted DNA sequences, through a process called DNA methylation.
Dr. Wan said that this process, along with other selective forces, has significantly reduced the volume and cost of active maintenance of the Welwitschia replication DNA library, giving it a “highly efficient, low-cost genome”.
The study also found that wielwichia had other genetic modifications hidden on its leaves.
The average leaf of a plant grows from the tops of the plant, or the tops of its stem and branches. Dr. Wan said that the original end of the growth wieluchia dies off, and the leaves instead flow from a weak area of the plant’s anatomy called the basal tissue, which supplies the plant with new cells. A large number of copies or increased activity of some genes involved in efficient metabolism, cell growth and stress resilience in this region may help this region continue to grow under severe environmental stress. In an increasingly warming world, the genetic lessons provided by Wielwichia may help humans grow crops that are tougher and less thirsty.
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