Watch Plants Light Up When They Get Attacked

26
Watch Plants Light Up When They Get Attacked

Plants have no eyes, no ears, no mouth and no hands. They do not have a brain or a nervous system. Muscles? Forget them. They’re stuck where they started, soaking up the sun and sucking up nutrients from the soil. And yet, when something comes around to eat them, they sense it. And they fight back. How is this possible? “You’ve got to think like a vegetable now,” says Simon Gilroy , a botanist who studies how plants sense and respond to their environments at the University of Wisconsin-Madison. “Plants are not green animals,” Dr. Gilroy says. “Plants are different, but sometimes they’re remarkably similar to how animals operate.” To reveal the secret workings of a plant’s threat communication system for a study published Thursday in Science , Masatsugu Toyota (now a professor at Saitama University in Japan) and other researchers in Dr. Gilroy’s lab sent in munching caterpillars like in the video above. They also slashed leaves with scissors. In these and about a dozen other videos, they used a glowing, green protein to trace calcium and accompanying chemical and electrical messages in the plant. And they watched beneath a microscope as warnings transited through the leafy green appendages, revealing that plants aren’t as passive as they seem. The messages start at the point of attack, where glutamate initiates a wave of calcium that propagates through the plant’s veins, or plumbing system. The deluge turns on stress hormones and genetic switches that open plant arsenals and prepare the plant to ward off attackers — with no thought or movement. Like animals, plants are eukaryotes — multicellular organisms — that split from a common ancestor called Luca billions of years ago. To survive, we all sense threats, relay messages about them within our bodies or tissues and respond to these challenges. Our actions vary, adapted for the lifestyles we maintain in different environments, but much of our basic cellular machinery is the same. Biology kept it that way: If it ain’t broke, don’t fix it. One mechanism our cells share is fluctuating levels of calcium ions, which carry an electrical charge. In humans, this charge assists in controlling when your neurons fire messages. Changes in calcium ions make your heart beat or your muscles contract so you can get up and leave when something threatens you. Plants, obviously, can’t run away. But researchers knew that genes that make receptors kind of like those for glutamate initiate electrical signals that travel through plants after being wounded. They turn on genes elsewhere in the plant, allowing them to respond. With the help of glutamate, calcium ions can flow, carrying their signal through channels that open like floodgates when glutamate fits into these special receptor spaces, like keys in locks. These channels aren’t quite the same as those in the mammalian nervous system, but they look very similar and probably worked similarly. They led Dr. Gilroy and his team to look into calcium ion flow. To make the action visible, the researchers […]