Putrid plants can reek of hot rotting flesh with one evolutionary trick

Independent genetic changes in one enzyme enabled the same stink of death or dung in many flowers

Three stinky plant flowers that have independently evolved the ability to make the scent of death and dung are shown. On the left, a fly crawls over the small green bell shaped flowers with brown edges of an evergreen shrub Eurya japonica. In the center a large barrel shaped maw of Asarum simile has three large petal-like arm with a red and white ring resembling rows of teeth surrounding a central hole. On the right is Symplocarpus renifolius with a green shoot and a huge red leaf that flops over at the tip and curves to create a cavern from which peeks a spiky, egg-shaped structure.

Some flowers smell like death, and for the same reason. Malodorous members of the Eurya (left, E. japonica pictured), Asarum (A. simile, middle) and Symplocarpus (S. renifolius, right) genera independently evolved changes in an enzyme that help them attract pollinating flies with the unlovely smell of rotting meat.

© 2025 National Museum of Nature and Science

Some plants stink of rotting meat or dung, which helps them attract flies for pollination. How plants make the carrion stench, which is usually produced by bacteria feasting on decaying corpses, has been a mystery until now.

Several types of plants have independently evolved to make the fetid odor thanks to a few tweaks in one gene, researchers report May 8 in Science.

Scientists in Japan used biochemistry and molecular and evolutionary genetics to determine that three unrelated plant lineages hit on the same evolutionary trick to produce the smell. First, a gene called SBP1 was duplicated. (Gene duplication is a pretty common occurrence in the evolution of most organisms, including humans.) Then the extra copy of the gene mutated, swapping a few amino acids in the enzyme it produces.

In a type of wild ginger (Asarum simile) and the East Asian eurya shrub (Eurya japonica), three changes were needed to bring the stink that these plants and some of their relatives share. But the Asian skunk cabbage (Symplocarpus renifolius) needed only two amino acid swaps to become malodorous.

SBP1 makes an enzyme that helps break down a chemical called methanethiol. Methanethiol is pretty smelly itself; it’s the compound that builds up in the mouths of some people with poor dental hygiene and gives them clinically bad breath, or halitosis. The original enzyme made by SBP1 — and related enzymes in humans, animals and plants — breaks methanethiol into hydrogen peroxide, hydrogen sulfide and formaldehyde.

A cartoon of a fly in the upper left corner with a speech bubble showing a fork and knife and a thought bubble showing a rotting animal carcass and animal scat with stink lines and the chemical structure of dimethyl disulfide over it. Three plants that have evolved the ability to make dimethyl disulfide are shown emitting the gut-churning chemical.
Some plants have independently evolved the ability to lure flies for pollination by making a stinky chemical called dimethyl disulfide that smells like rotten animal carcasses or feces. This caricature illustrates how carrion flies looking for dinner may be fooled by plants making the smelly chemical.© 2025 National Museum of Nature and Science, drawn by Yoh Izumori

The tweaked enzymes from the stinky plants instead links two methanethiol molecules into dimethyl disulfide, responsible for the much more putrid scent of rotten meat. (It’s also one of the chemicals hinting at extraterrestrial life that the James Webb Space Telescope detected in the atmosphere of exoplanet K2 18b.)

Among Asarum species, the ability to make dimethyl disulfide was gained and lost more than 18 times, the researchers estimate. There is evidence that plants are under evolutionary pressure to make the foul-smelling molecule, the team found. Those that do may attract more flies to pollinate them.

Imperfect extra copies of genes are often the source of new traits across evolution in many species. Duplicate genes can mutate without harming the function of the original gene, allowing room for innovation. For instance, poppy plants evolved the ability to make morphine by that route.

Tina Hesman Saey is the senior staff writer and reports on molecular biology. She has a Ph.D. in molecular genetics from Washington University in St. Louis and a master’s degree in science journalism from Boston University.