When humans are attacked, sensory cells transmit signals through our nervous system, spitting out the neurotransmitter–glutamate. Glutamate stimulates our brain’s amygdala and hypothalamus. This triggers the stress hormone–adrenaline–that jolts us into fight or flight mode. Plants don’t have neurotransmitters. They don’t have nervous systems. The don’t have brains. But now, for the first time, scientists are able to observe how a plant responds to an attack with vivid real-time imagery that illuminates the remarkable differences and similarities between plants and humans. Same substance, same results, different anatomy. In the video below, a plant gets chomped on by a caterpillar. At the site of the wound, the plant spills out glutamate–the same chemical as our glutamate neurotransmitter, but not a neurotransmitter. This triggers a calcium wave throughout the plant body, stimulating a plant stress hormone that prepares it for the vegetal version of fight or flight.
To observe what’s happening, scientists sampled a gene from jellyfish that makes them glow green. Then they genetically modified plants to produce a protein that fluoresces around calcium. The results are a blazing calcium wave that undulates through the plant vascular system when it gets bit.
“[For] the first time, it’s been shown that glutamate leakage at a wound site triggers a system-wide wound response, and the first time we’ve been able to visualize this process happening ,” says Simon Gilroy, professor of botany at the Gilroy Lab at the University of Wisconsin-Madison, and senior author on the paper out today in the journal Science.
An incidental breakthrough
The discovery came about via “the classic opportunistic randomness of science,” says Gilroy. The lab wasn’t investigating plant wounds. It was looking at how plants take in and assimilate information. One day, postdoctoral researcher and first author on the paper, Masatsugu Toyota, approached the team: “‘You have to see this. This is amazing,” he said.’ It just played out in front of us,” says Gilroy.