About 86 million years ago, following an error in cell division, Weilwich’s entire genome doubled during a period of increased drought and prolonged drought in the region—perhaps forming the Namib Desert itself, Tao Wan, a botanist at 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 of the study, adds that duplicate genes are also released from their original functions, potentially taking on new functions.
However, Dr. Wan says getting more genetic material costs money. “The main activity of life is DNA replication, so if you have a large genome, it really takes energy to sustain life,” especially in harsh environments.
To make matters worse, much of the Willwichia genome is an “insignificant” self-replicating DNA sequence called a reverse transposon. Now this garbage must be replicated and repaired,” said Dr. Leech.
The researchers detected an “explosion” of transposon activity 1 to 2 million years ago, possibly 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 says that this process, along with other selective powers, has significantly reduced the volume and cost of active maintenance of Welwitschia’s repeating DNA library, giving it a “highly efficient and low-cost genome.”
The study also found that wielwichia has another genetic modification hidden in its leaves.
The average plant leaf grows from the top of the plant, or the top of the stem and branches. Dr Wan said the original tip of the wieluchia growth dies, and the leaves instead drain from a weak area of the plant’s anatomy called basal tissue, which supplies the plant with new cells. A large number of copies or increased activity of several genes involved in efficient metabolism, cell growth and stress resistance in this region can help this region to continue to grow under severe environmental stress. In a warming world, the genetic lessons Wielwichia provides could help humans grow crops that are tougher and less thirsty.
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