when our bodies autocorrect--10/7/26
Today's selection -- from Beyond Inheritance by Roxanne Khamsi. In plants, mutations can occur within older parts of the plant that are passed on to that plant’s new, younger growth:
“The strange events in which anomalous branches take over are often seen in special plants, such as those with variegated leaves or dwarfed traits. These ornamental cultivars are the result of a genetic mutation to begin with, and a second, reverse mutation in part of these plants can cause that portion to revert back to normal growth.
“Part of the appeal of studying revertant mutations in trees is that unlike in the human body, where cells grow in squishy tissues or circulate in blood, plants have more static tissue. You can find new genetic changes in one part of the plant and easily follow them as they are passed on to the subsequent branches that sprout off from that point. For example, a group of Swiss scientists at the University of Lausanne examined the famous 234-year-old ‘Napoleon’ oak tree on their campus-so named because it was already growing there when the French general and his troops crossed the grounds-and were able to trace the mutations that were passed from older parts of the plant to its new, younger branches.
“Trees are a magnificent example of how a single organism can accumulate mutations over time. The sheer genetic diversity in a single long-lived tree might surprise you. A group in Canada did a genetic analysis of bark and needle samples from twenty Sitka spruce trees growing on Vancouver Island and estimated that a single tree could have up to one hundred thousand genetic differences between its base and the tip of its crown. Meanwhile, a recent study from another group suggested that, among trees of the same size, older ones have accumulated more mutations per meter than their younger but equally big counterparts. Because of this, the researchers concluded that long-lived trees might possess more genetic adaptations to their environment that boost the chances of their species' survival.
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| Sitka spruce in the Hoh Rainforest in Olympic National Park |
“These findings support a theory that Tom Whitham wrote about in the early 1980s. He contributed to what became known as the ‘genetic mosaic theory’ of plant defense. The idea was basically that trees have the opportunity over many years to collect mutations that protect their newer parts against pests. Whitham gave the example of narrowleaf cottonwood trees, in which acquired genetic variations seemed to confer certain branches safety against invading aphids.
“Less than a decade after Whitham published his ideas about plant defense, Australian scientists discovered a striking case of a beneficial mutation rescuing a tree. The researchers were exploring a section of New South Wales that had experienced a beetle outbreak when they happened upon a strange-looking eucalyptus tree. The tree had been completely decimated by pests, which had eaten all the leaves–save for one section at the top. The immune leaves belonged to a lone branch that reached for the sky. It remained virtually untouched, whereas the other branches were infested with beetles. In the early 2010s, another group of scientists analyzed samples from the tree and found ten specific DNA changes that were present in cells of that special branch but not the rest of the tree. This gave hard evidence that genetic changes were responsible for the branch's resilience.
“Mutations can have miraculous effects. They can help an organism thrive beyond its initial genetic destiny. But they don't just rescue plants. If you look close enough, you can find examples of the phenomenon of revertant mutation happening in other species, including humans.”
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