In other words, this is how plants manage stress without having a central nervous system.
As opposed to animals, which have long lines of nerve cells to shoot messages across an organism, this discovery suggests that there's a cell-to-cell communication in plants that's just intrinsically a part of all plant tissues.
"Plant cells are not very isolated," said Jose Feijo, a contributor to the study's research team out of Australia and a professor at the University of Maryland. "[The neurotransmitter] is able to shuttle from one cell to another pretty rapidly."
The discovery may lead to medical applications and technology to make crops more resilient, but it also offers insight into how plants have become what they are today. The researchers theorize that plant cells took the neurotransmitter, called gamma-aminobutyric acid or GABA, and "co-opted it" to be a useful communication tool.
"Evolution is a tinkering process — it's not really a design," Feijo said. "From an evolutionary standpoint, this makes sense."
While the compound is exactly the same among plants and animals, the proteins that bind to it are very different within the two kingdoms of life. This means that plants and animals evolved their use of the compound as a messenger separately from one another.
That poses some important questions for further research: How do more ancient plant species, such as ferns, use this compound? And how did this communication system develop?
Scientists suggest that those questions could lead to ways to fight off viruses in plants, helping the efforts against food insecurity. It might also reveal why particular plant-derived drugs that rely on the GABA-signaling system, such as sedatives and anti-epileptics, work in humans.