Scientists achieve precise lifelong protein control in living animals using plant hormone

For decades, biologists have faced a stubborn limitation: they could turn genes on or off, but they couldn't fine-tune the proteins those genes make. They couldn't dial a protein down to half strength in one tissue while leaving it untouched in another. They couldn't watch what happened to an animal's body when a single protein was reduced by a quarter, or a tenth, or held steady for an entire lifetime. This constraint has made it nearly impossible to understand how aging actually works—a process that depends not on single proteins vanishing, but on countless subtle molecular shifts rippling through interconnected tissues over years.

Now researchers at the Center for Genomic Regulation in Barcelona and the University of Cambridge have broken through that wall. They've engineered a system that lets them control protein levels with precision in specific tissues of a living animal, adjusting those levels up or down at will, throughout the creature's entire life. The work, published in Nature Communications, uses an unlikely tool: a plant hormone called auxin, borrowed from the molecular machinery that controls how plants grow.

The team tested their approach in the nematode worm Caenorhabditis elegans, controlling protein levels independently in the intestines and neurons. But the implications reach far beyond worms. "No protein acts alone," explains Dr. Nicholas Stroustrup, senior author of the study. "Our new approach lets us study how multiple proteins in different tissues cooperate to control how the body functions and ages." Until now, researchers lacked the finesse to ask such questions. They had binary tools—on or off—when biology demanded a dimmer switch.

The technique builds on existing technology called the auxin-inducible degron system, or AID, which originated in yeast labs. The basic mechanism is elegant: a target protein gets tagged with a molecular marker called a degron. An enzyme called TIR1 recognizes that tag and destroys the protein, but only when auxin is present. Remove the hormone, and the protein returns. The innovation here was creating what the researchers call a "dual-channel" system by engineering two different versions of TIR1, each triggered by a different auxin compound. By placing these enzymes in different tissues, scientists can now control the same protein independently in multiple locations, or even control two different proteins simultaneously.

The engineering challenge was substantial. The team screened more than one hundred thousand worms, testing different combinations of synthetic switches to find pairs that wouldn't interfere with each other. They also had to solve a problem that had plagued earlier AID systems: the technology often failed in reproductive tissues. By understanding the underlying biology of the germline, they adapted their system to work across the entire body, including cells involved in reproduction.

The practical result is striking. A researcher can now feed auxin-laced food to a worm, and the plant hormone silently activates TIR1 in specific tissues, which recognizes the degron tag and removes just the right amount of protein. The animal continues eating, moving, and growing normally while its molecular composition shifts in precisely controlled ways. "We wanted to be able to control proteins like you turn the volume up or down on a TV," Stroustrup says, "and now we can ask all sorts of new questions."

Those questions matter most for understanding aging and disease. Both are systemic processes—they emerge from constant conversations between different organs, from the way a change in one tissue sends ripples through the whole body. With traditional genetic tools, researchers couldn't separate these effects. They couldn't ask: what if this protein is reduced only in the brain? What if it's reduced only in the gut? What if it's reduced by half in both places? Now they can. They can trace how a small perturbation in one tissue cascades through the organism over time. They can measure how much of a protein is actually needed to maintain health. They can watch aging unfold at the molecular level, with unprecedented control and precision.

Dr. Jeremy Vicencio, a postdoctoral researcher and co-author, notes that the breakthrough opens possibilities that were simply unavailable before. "Now that we've cracked it, we can control two separate proteins simultaneously with incredible precision," he says. "It's a powerful tool that we hope will open up new possibilities for biologists everywhere." The work suggests that the next chapter of aging research—and disease research more broadly—will be written not by turning proteins on and off, but by learning to listen to what happens when you turn them down, just a little, in just the right place, for just the right amount of time.