The Welwitschia plant thrives in the arid Namib Desert, growing only two leaves but is believed to live for up to 3,000 years.
Researchers have explored some genetic mysteries behind the unique shape, extraordinary longevity, and resilience of Welwitschia mirabilis, a plant that grows in the Namib Desert, Africa, as reported by Independent on August 5. The new research was published in the journal Nature Communications.
In Afrikaans, the name for Welwitschia is “tweeblaarkanniedood,” meaning “two leaves that cannot die.” This name is quite fitting as it only grows two leaves throughout its millennia-long life.
Welwitschia, a two-leaved plant growing in the Namib Desert, is believed to live for thousands of years. (Photo: Tao Wan).
“This plant can live for thousands of years and never stops growing. It only stops growing when it dies,” Andrew Leitch, a plant geneticist at Queen Mary University (UK), and a co-author of the study, said. Some of the largest specimens are believed to be over 3,000 years old, with two leaves steadily developing since the beginning of the Iron Age. The long leaves, battered by desert winds and grazed by animals, become fibrous and curl over time, giving Welwitschia an appearance reminiscent of an octopus.
The genetic makeup of Welwitschia reflects its harsh and nutrient-poor environment, and its genetic history seems to correspond with environmental history. Approximately 86 million years ago, after a mistake during cell division, the Welwitschia genome doubled during a period of increasing aridity and prolonged drought. This may also coincide with the formation of the Namib Desert, according to Tao Wan, a botanist at Fairy Lake Botanical Garden (China), the lead author of the study.
Wan noted that “extreme stress” is often associated with such genomic duplications. Leitch added that duplicated genes may also be released from their original functions, potentially acquiring new roles. However, having more genetic material comes with certain costs.
“The most fundamental process for life is DNA duplication, so if there is a larger genome, maintaining life will require more energy, especially in such a harsh environment,” Wan explained. Additionally, a significant portion of the Welwitschia genome consists of “junk” self-replicating DNA sequences known as retrotransposons. “Now that ‘junk’ needs to be duplicated and repaired,” Leitch said.
The research team discovered a burst of activity in retrotransposons from one to two million years ago, likely due to increasing temperature stress. To adapt, the Welwitschia genome underwent epigenetic changes that silenced the “junk” DNA through a process known as DNA methylation. This process, along with other selective pressures, has endowed Welwitschia with an efficient genome.
The new study also identified some peculiarities in the leaves of Welwitschia. Leaves typically grow from the top or apex of the stem and branches. However, the initial apex of Welwitschia dies off, and leaves re-emerge from a vulnerable part of the plant called the meristematic tissue, which supplies new cells for the growing plant. A large number of copies or increased activity of certain genes associated with efficient metabolic mechanisms, cell growth, and resilience may have helped this plant continue to thrive in harsh environments.
As the world warms, lessons from the genome of Welwitschia could help humans develop hardier crops that require less water. “Seeing how Welwitschia can survive in this environment for so long while preserving its DNA and proteins, I truly believe we can find clues on how to improve agriculture,” shared Jim Leebens-Mack, a botanist at the University of Georgia.
