The same thing that gives plants the ability to grow constantly damages their DNA.
Rooted in place and unable to flee the very light that feeds them, plants have evolved an intricate molecular diplomacy with damage — one that scientists are only beginning to decipher. Researchers at the Salk Institute have identified YAF9B, a protein that awakens specifically after DNA injury and stands guard over a plant's most consequential cells: the stem tissues from which all future growth unfolds. The discovery, published in June 2026, illuminates how living things that cannot move have nonetheless mastered the art of preservation, and it opens a door toward more precise genetic engineering of the crops that feed the world.
- Every day, sunlight fractures plant DNA — the same energy that drives photosynthesis is also a relentless source of genomic harm that plants cannot escape.
- Stem cells, the origin point of every new root, shoot, and leaf, are especially vulnerable: a single uncorrected error there can cascade into lasting damage across the entire organism.
- YAF9B breaks from its sibling protein YAF9B's broader role by activating only after damage strikes and concentrating precisely where the stakes are highest, steering cells toward slow, accurate repair rather than fast, error-prone patching.
- Current CRISPR editing in plants inadvertently triggers the sloppy repair pathway, making precise gene insertion unreliable — understanding YAF9B could change that calculus entirely.
- The Salk team, now partnering with UCLA researchers, is mapping how YAF9A and YAF9B coordinate repair stages, with the long horizon of making crop genome editing both more accurate and more stable.
Plants cannot run from the sun. Every day, the light that sustains them also fractures their DNA, and yet they grow, reproduce, and pass stable genomes to the next generation with remarkable consistency. How they manage this paradox has long been an open question in plant biology.
Researchers at the Salk Institute have now identified a key part of the answer: a protein called YAF9B that acts as a molecular guardian for the stem-cell tissues responsible for all future plant growth. The discovery, published in the Proceedings of the National Academy of Sciences on June 8, 2026, reveals an evolutionary solution refined over millions of years of unrelenting solar exposure.
Inside plant cells, DNA is wound tightly around proteins called histones and bundled into dense chromatin structures. When damage occurs, the buried breaks are difficult to reach and repair. The YAF9 protein family exists across yeast, animals, and plants to help unwind chromatin and direct repair machinery — but plants evolved a second version. YAF9B activates only after DNA damage occurs and concentrates specifically in the stem-cell-rich zones that generate roots, shoots, and leaves.
When a DNA strand breaks, cells face a choice: a fast but error-prone repair method, or a slower, accurate process that uses an intact DNA copy as a template. YAF9B appears to steer stem cells toward the accurate pathway — critical, because errors in those foundational cells can ripple through the entire organism. Senior author Julie Law describes the challenge simply: the same thing that gives plants the ability to grow is constantly damaging their DNA.
The implications reach into agricultural biotechnology. CRISPR-based gene editing in plants currently tends to trigger the fast, imprecise repair pathway, limiting scientists' ability to insert or replace genes with confidence. If researchers can learn how plants naturally promote high-fidelity repair, they may be able to guide editing tools toward greater precision. Law's team, which includes collaborators from UCLA, plans to investigate how YAF9A and YAF9B coordinate across different stages of the repair process — work that could ultimately make crop improvement through genetic engineering more reliable and more exact.
Plants cannot run from the sun. They cannot hide from drought or radiation or the thousand small stresses that accumulate in soil. Every day, the very thing that sustains them—light—damages their DNA. Yet they survive, grow, and reproduce with remarkable fidelity. How they manage this paradox has long puzzled scientists studying plant biology.
Researchers at the Salk Institute have now identified a key piece of that puzzle: a specialized protein called YAF9B that acts as a molecular guardian, protecting the stem cells responsible for a plant's future growth. The discovery, published in the Proceedings of the National Academy of Sciences on June 8, 2026, reveals an elegant evolutionary solution to a problem that affects all living things but poses a particular challenge to organisms rooted in place.
Inside every plant cell, DNA wraps tightly around proteins called histones, which then bundle together into dense structures known as chromatin. This packaging keeps the genome organized, but it creates a problem: when DNA breaks, the damage becomes difficult to detect and repair because the broken regions are buried deep within the chromatin. Plants have evolved specialized proteins that act like emergency responders, unwinding the tightly packed chromatin, directing repair machinery to the damage, and orchestrating the fix. The YAF9 family of proteins performs this function, and it exists across yeast, animals, and plants. But plants did something different. They evolved a second version, YAF9B, that activates only after DNA damage occurs and concentrates specifically in the stem-cell-rich tissues that generate new roots, shoots, and leaves.
Julie Law, a professor at Salk and senior author of the study, frames the challenge plainly: "Plants are unique because the same thing that gives them the ability to grow—sunlight—is constantly damaging their DNA." The question becomes not whether damage occurs, but how plants manage the repair process with such precision that they maintain genome stability across generations.
When DNA breaks, cells have two main repair options. The first, called non-homologous end joining, works quickly—it seals the broken ends back together like a fast patch job. Speed comes at a cost: this method often introduces errors or mutations. The second approach, homology-directed repair, is slower but far more accurate. The cell uses an intact copy of the DNA sequence as a template, carefully rebuilding the damaged region and preserving the original genetic information. YAF9B appears to guide cells toward this more accurate pathway, particularly in stem cells where mistakes could have cascading consequences for the entire organism.
Neeraja Vegesna, first author of the study and a former graduate student in Law's lab, notes that while YAF9A acts as a broad repair-response protein active throughout the plant, YAF9B functions as a specialized defender. "These stem cells are what generate the rest of the plant," Law explains. "The hypothesis is that the plant produces this factor to help protect those cells and give them a better chance of carrying out highly accurate DNA repair."
The practical implications extend beyond basic science. Current CRISPR-based gene editing in plants often triggers the fast but error-prone repair pathway, limiting scientists' ability to precisely insert or replace genes. If researchers can understand how plants naturally promote high-fidelity repair, they might eventually guide genome editing toward greater accuracy while also improving stability in the tissues most critical for growth. Law and her team, which includes researchers from UCLA, now plan to investigate exactly how YAF9A and YAF9B coordinate different stages of the repair process and what allows YAF9B to function as a specialized damage-response factor. The work is supported by the Rita Allen Foundation, the Hess Corporation, the National Institutes of Health, the Chapman Foundation, and the Helmsley Charitable Trust.
The discovery points toward a future where crop improvement through genetic engineering becomes more precise and reliable—a possibility that hinges on understanding the elegant repair systems plants have perfected over millions of years of exposure to an unchanging, damaging sun.
Notable Quotes
Plants are unique because the same thing that gives them the ability to grow—sunlight—is constantly damaging their DNA.— Julie Law, Salk Institute professor and senior author
If we can understand how plants promote high-fidelity repair, we may eventually be able to improve genome editing technologies in plants.— Julie Law
The Hearth Conversation Another angle on the story
Why does it matter that plants have this special protein? Isn't DNA repair just DNA repair?
Because plants can't move. A human exposed to too much radiation can leave. A plant is stuck there, taking damage every single day from the very light that feeds it. So they've evolved something more sophisticated than animals have—a protein that specifically protects the cells that will become tomorrow's growth.
You said YAF9B is "specialized." What does that mean in practical terms?
It means it only shows up after damage happens, and only in the tissues that matter most—the stem cells. It's like having a security guard who only appears when there's a break-in, and only guards the vault, not the whole building.
The article mentions two repair methods. Why would a plant ever choose the fast, sloppy one?
Speed matters when you're under stress. If a plant is drought-stressed or damaged, it might need to repair DNA quickly enough to survive the immediate crisis, even if it means accepting some mutations. But in stem cells, where mistakes get passed on to every new leaf and root, accuracy is worth the wait.
How does this help with CRISPR?
CRISPR cuts DNA and relies on the cell to repair it. Right now, cells usually use that fast, error-prone repair method, so edits are messy. If we can teach cells to use the accurate method—the way YAF9B does—we could edit crops with surgical precision instead of a sledgehammer.
What's the next step for these researchers?
They want to understand exactly how YAF9B works at the molecular level—what makes it different from its cousin YAF9A, and how it convinces cells to choose accuracy over speed. That's the key to eventually using this knowledge to improve crop engineering.