A new study has revealed that the same enzyme linked to bad breath in humans is responsible for the powerful stench of certain wild ginger plants. The discovery highlights how tiny genetic changes can turn a detoxifying human enzyme into a scent-producing tool for plants seeking to attract insects.
Scientists from Japan’s National Museum of Nature and Science, led by Dr. Yudai Okuyama, found that small mutations in a gene coding for selenium-binding proteins allow some Asarum species—also known as wild ginger—to emit a rotten, sulfur-like odor. This smell, though unpleasant to humans, helps lure in flies that assist with pollination.
How a Human Breath Enzyme Became a Flower’s Insect Bait
In humans, the enzyme in question normally prevents bad breath by breaking down methanethiol, a sulfur-containing by-product of digesting methionine, an amino acid found in proteins. When not properly broken down, methanethiol builds up and causes halitosis.
However, in the Asarum plants studied, the selenium-binding protein does something very different. A few small amino acid changes transform its function. Instead of breaking down methanethiol, the enzyme converts it into dimethyl disulfide (DMDS), a pungent compound that smells like rotting flesh.
DMDS plays a critical role in helping the plant attract carrion-loving insects, especially flies, which are drawn to the foul odor thinking they’ve found a place to lay eggs. In reality, the plants are just tricking them into helping with pollination.
Confirming the Link Between the Gene and the Smell
To prove the enzyme’s new role, the team fed a special version of methionine—tagged with a heavy carbon isotope (carbon-13)—to Asarum fudsinoi, one of the stinkier species. Later, they detected the isotope in the emitted DMDS, directly linking the plant’s odor to the enzyme activity.
When the researchers compared various Asarum species, they found that those with the most DMDS also had a specific form of the selenium-binding protein gene. Remarkably, just two or three amino acid changes were enough to activate this smelly transformation.
“This is a striking example of how a few molecular tweaks can lead to complex traits like scent production,” said Dr. Okuyama.
Not Just Ginger: The Evolution of Stinky Plants
Interestingly, this sulfur-based trick doesn’t belong to Asarum alone. Other plants, like Eurya and Symplocarpus, have evolved similar gene changes to create strong smells that attract pollinators. However, scientists believe these changes happened independently across species—a process known as convergent evolution.
Some of the most famously stinky plants, such as Amorphophallus titanum, also known as the “corpse flower,” use a completely different biological method to create their odors. These species do not carry the same selenium-binding proteins but still manage to emit intense, rotting scents using other enzymes and pathways.
Why This Matters for Science and Agriculture
Understanding how plants produce odors using enzymes found in animals opens new doors for biotechnology and agriculture. Scientists could one day design plants with custom scents to attract specific insects—or even repel pests.
The research also sheds light on plant evolution, showing how nature can reuse existing proteins in new ways. “This discovery shows how evolution builds on old parts to create new functions,” said Okuyama.
While the smell of rotting meat might not sound appealing, it serves a vital purpose in nature. And now, thanks to this new research, we know that an enzyme once linked to fresh breath in humans plays a surprising role in keeping the wild ginger blooming.