As far as plants go, Venus flytraps are pretty hardcore. After attracting its prey with a fruity scent and trapping it inside its leaves, the flytrap slowly digests the insect for 5 to 12 days, releasing the empty husk after its meal. But the exact molecular mechanism behind this behavior had been a mystery to scientists—until now.
In a Nature Communications paper published today, Japanese researchers report that an ion channel at the base of a flytrap’s hairy sensors acts as an amplifier for sounding a plant-wide alarm to shut its trap. To be clear, scientists had a decent idea of how well the Venus flytrap could distinguish between real prey and false signals, as well as the anatomy of the tiny hair sensors detecting these signals. However, it was unclear how a plant with no nervous system could convert a physical stimulus into a biological cue.
The history of flytrap science
Given its strange charisma, it’s not surprising that the Venus flytrap gets special attention from the scientific community. For instance, a 2016 study confirmed that the Venus flytrap “counts” the number of stimulations it receives and only shuts its trap when the stimuli pass a certain threshold. Another paper from 2020 by Hiraku Suda, the new study’s lead author, revealed that the fluctuations in calcium concentrations acted as the plant’s short-term memory bank.
The rich literature helped the researchers identify where scientists were lacking in their understanding of the Venus flytrap. For the new study, the team engineered a flytrap with a fluorescent protein for recording the movement of different signals inside the plant.
When they gently bent the plant, they noticed a spike in the concentration of calcium ions, in addition to a small electrical signal. A stronger push, on the other hand, triggered a larger reaction that transported calcium ions and electrical signals throughout the entire plant, according to the paper.
“Our approach enabled us to visualize the moment a physical stimulus is converted into a biological signal in living plants,” Suda, a biologist from Saitama University in Japan, said in a release.
A delicate system
A closer review of the signals revealed that the sensory hair actually consisted of two different cell types. The indented cells converted physical stimuli into calcium signals, whereas adjacent and surrounding cells carried and propagated these signals throughout the plant—but only if the initial stimulus was strong enough.
To see what would happen without these cells, the researchers destroyed the indented cells on flytrap hairs and compared their responses with those of untouched flytraps. There was some variability in which side of the hair was disabled, but in general, the flytraps with faulty indented cells were less likely to react to stimuli, including a colony of ants the scientists had walk near the flytraps.
The new work demonstrates the sophisticated yet delicate nature of flytrap biology, which detects “even the faintest, barely grazing contacts,” Suda said. What’s more, such mechanosensing systems—a plant’s ability to respond to touch—may be “shared” beyond the flytrap, suggesting that there’s a lot more going on with plants than we could have ever imagined.
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