Around 86 million years ago, after an error in cell division, the entire Welwitschia genome doubled during a period of increased aridity and prolonged drought in the region – and possibly the formation of the desert. from Namib itself, said Tao Wan, botanist at Fairy Lake Botanical Garden in Shenzhen, China, and lead author of the study. He said “extreme stress” is often associated with such genome duplication events.
Dr Leitch, co-author of the study, added that the duplicated genes are also released from their original functions, potentially taking on new ones.
However, having more genetic material comes at a cost, Dr Wan said. “The most basic activity in life is DNA replication, so if you have a large genome it is really energy intensive to sustain life,” especially in such a harsh environment.
To make matters worse, a large part of Welwitschia’s genome is made up of “unwanted” self-replicating DNA sequences called retrotransposons. “Now this waste needs to be replicated, repaired,” said Dr Leitch.
Researchers detected an “explosion” in retrotransposon activity one to two million years ago, most likely due to increased heat stress. But to counter this, Welwitschia’s genome underwent widespread epigenetic changes that silenced these unwanted DNA sequences, through a process called DNA methylation.
This process, along with other selective forces, dramatically reduced the size and energy maintenance cost of Welwitschia’s duplicate DNA library, Dr. Wan said, giving it “a very efficient and low cost genome.” .
The study also found that Welwitschia had other genetic changes hidden in its leaves.
The average leaf of a plant grows from the tops of the plant or the tops of its stem and branches. But Welwitschia’s original growing tip dies and the leaves pour out in place of a vulnerable area of the plant’s anatomy called the basal meristem, which provides fresh cells to the growing plant, Dr Wan said. Large copy numbers or increased activity of certain genes involved in efficient metabolism, cell growth and stress resilience in this area can help it continue to thrive under extreme environmental stress. In a warming world, the genetic lessons Welwitschia has to offer can help humans produce more resilient, less thirsty crops.