Every day, plants face an irony: the sunlight that powers their growth is simultaneously damaging their DNA. Yet they cannot escape to shade. Now, scientists at Salk Institute have discovered how plants manage this relentless assault—through a specialized protein called YAF9B that acts as an "extra layer of defense" in the very tissues most critical to survival.
The challenge is fundamental to plant biology. Unlike animals, plants endure constant environmental stress from sunlight, radiation, drought and soil damage—all of which break their genetic code. Inside plant cells, DNA is tightly wrapped around proteins called histones, which pack together into a dense structure called chromatin. This organization keeps the genome orderly but creates a critical problem: broken DNA becomes hidden and difficult to reach, making repairs slower and harder to execute.
The research, published June 8, 2026, in Proceedings of the National Academy of Sciences, reveals that plants evolved a sophisticated solution. "Plants are unique because the same thing that gives them the ability to grow—sunlight—is constantly damaging their DNA," says Julie Law, a professor at Salk and senior author of the study. "The question is, how do they cope with that level of DNA damage?"
The answer lies in two related proteins. The YAF9 family exists across yeast, animals and plants, but plants developed something distinctive: a second version, YAF9B, that activates specifically in response to DNA damage. While YAF9A operates as a broad repair protein throughout the plant, YAF9B concentrates in stem cell-rich tissues that generate new roots, shoots and leaves—the growth centers most vulnerable to genomic instability.
First author Neeraja Vegesna, a former graduate student researcher in Law's lab, explains the significance: "Plants evolved a second version, YAF9B, that is specifically activated after DNA damage occurs." This specialization matters because stem cells are what generate the rest of the plant. By producing YAF9B specifically in these tissues, plants give their most critical growth centers a better chance at highly accurate DNA repair.
When DNA breaks, plants face a choice between speed and accuracy. One repair method, nonhomologous end joining, works fast—like a quick patch job—rapidly sealing broken DNA ends back together. But this approach risks introducing mutations. A second method, homology-directed repair, is slower but far more accurate, carefully rebuilding damaged sequences using an intact DNA copy as a template. YAF9B helps guide cells toward this more precise pathway by opening tightly packed chromatin, directing repair machinery to broken DNA, and coordinating the repair process.
"Accurate DNA repair is essential for maintaining genome stability, but it depends on many proteins working together within chromatin," Law notes. "What's exciting about this study is that we identified YAF9B as a DNA damage-responsive chromatin reader that helps cells carry out high-fidelity DNA repair, revealing a novel innovation used by plants to protect their genomes."
The implications extend beyond pure biology. Current CRISPR-based gene-editing approaches in plants often trigger fast but error-prone repair pathways, limiting scientists' ability to accurately insert or replace genes. By understanding how plants naturally promote precise genome editing, researchers hope future work could guide more accurate gene editing while strengthening genome stability in growth tissues—potentially unlocking new possibilities for improving future crops. Law's next goal is to understand exactly how YAF9B and its relatives coordinate different stages of DNA repair, unraveling the mechanics of nature's own genetic repair masterpiece.