It’s known as fight or flight — the message the brain sends your body when it detects something frightening. Something like it happens to plants when they are under attack, too. And then there are fungi — perhaps the most mysterious kingdom of multicellular life.
Fungi too can sense attackers and manufacture powerful weapons to combat them, including the toxins and poisons that can send you to the emergency room if you eat the wrong mushroom.
But little is known about the built-in threat detectors of these limbless, brainless beings. Humans send messages through their nervous systems. A plant’s vascular system is its relay apparatus. But fungi have neither.
Scientists trying to solve this mystery recently grew mushrooms in the lab, unleashed fungi-eating nematodes on them and videotaped the aftermath. They found that the fungi somehow sensed the predators and sent signals to other parts of their bodies. Their findings, published recently in Current Biology, shed new light on how the many cells within even primitive organisms communicate like plants or animals.
“They may appear simple, but they share features that are also known for more complicated organisms,” said Markus Künzler, a microbiologist at ETH Zürich in Switzerland who led the study. “There is internal communication going on that we know very little about.”
What we do know is that fungi-loving nematodes ingest their dinner like creepy, syringe-wielding serial killers. The worm uses a needle on its head to puncture the mushroom’s hyphae — the stringy filaments that make up its mycelium, or vegetative body — and suck out its cellular content.
Under attack, Coprinopsis cinerea, the mushroom commonly known as the “gray shag” or “inky cap” and often used in fungi research, puts up a slow, but steady fight.
Dr. Künzler and his colleagues paired the fungi and nematodes in a lab setting, and also added a dye to the mushrooms that glows under a microscope. They watched the mushroom’s response travel in the form of genes activating, lighting up as its warning message propagated up and down the fungus’s fattest hyphae. It did so every few hours — and it switched directions. As they switched on in succession, the genes produced a nasty toxin the nematodes don’t like.
It makes sense that to survive, a fungus would need to send defense signals throughout its body rather than only at the site of attack. For example, defending its reproductive caps above the soil, even preemptively, would help its legacy continue.
But much remains unknown about the fungus’s signal and how it travels.
“In both plants and animals, electrical and chemical signaling is known,” Dr. Künzler said. “It’s not very clear what happens in the fungus.”
Fungal architecture is quite different from that of plants and animals. It’s possible that the cells within a fungus’s hyphae communicate using chemical or electrical signals, but Dr. Künzler’s results suggest it’s unlikely.
“We think the signal has to travel from one cell to another across the cytoplasm of the cells, which is very special or different from how the signaling is done in a plant or animal body,” he said.
While fungi may be simple compared with animals and plants, they’re multicellular too, and what’s the point of making all those cells stick together if they can’t somehow communicate?