Venus fly traps’ death-grip trigger discovered

They’re the poster species for carnivorous plants and stuff of nightmares. Venus fly traps (Dionaea muscipula) are only native to North and South Carolina in the United States and can tell the difference between insects that pollinate them and those that make a good meal. Despite not having nerves themselves, they can detect touch from other organisms with highly sensitive sensory hairs. If they are touched twice in quick succession, their leaves will close and capture the prey. However, how the touch sensor of these plants works has been a mystery until now.

The root of this prey-catching technique is a chemical ion channel named DmMSL10 that surrounds the base of a Venus fly trap’s sensory hairs. This membrane allows chemicals to pass through and is the key sensor that detects the very faint touches by prey like flies, according to a study published today in the journal Nature Communications.

To see what is going on at the molecular level of these plants, a team from Japan’s Saitama University and the National Institute for Basic Biology, engineered flytraps that express a specific type of protein called GCaMP6f. They watched as a very gentle bend in the plant’s sensory hairs produced a local change to the electrical charges within the plants. 

By comparison, a stronger bend first creates a larger response from the electrical signal. Like flipping a lightswitch, once that electrical signal in the plant crosses a threshold, an all-or-none large electrical spike occurs alongside a chemical messenger in the plants called a Ca2+ wave.

The electrical signal and Ca2+ wave then travel from the hairy base of the plant up to the leaf blade. According to the team, the mechanism works similarly to an animal nervous system. 

“Our approach enabled us to visualize the moment a physical stimulus is converted into a biological signal in living plants,” study co-author and plant biologist Hiraku Suda said in a statement. 

To look closer at this very tactile sensing system, the team genetically engineered a Venus fly trap that did not have the DmMSL10 ion channel that could pass along the electrical signal that tells the leaves to close. These plants had a much smaller response to stimuli, indicating that DmMSL10 works like an amplifier, boosting that initial small electrical signal until it is strong enough to trigger an action.

A lab-built ecosystem shows how leaf closures work when ants walk on the plants.CREDIT: Masatsugu Toyota/Saitama University

To see how this could work in the wild, the team built a small ecosystem in the lab. Here, ants moved freely and walked over Venus fly traps that had their natural DmMSL10 ion channel and others that did not. In this simulated wild ecosystem, the ants’ touches triggered the reaction across the plants. The plants without the DmMSL10 ion channel had less frequent closures and less bending in the sensory hairs. Those with DmMSL10 closed on the ants more often and their sensory hairs bent more frequently.  

“Our findings show that DmMSL10 is a key mechanosensor for the highly sensitive sensory hairs that enable the detection of touch stimuli from even the faintest, barely grazing contacts,” says Suda. “Many plant responses arise from mechanosensing—the plant’s tactile sense—so the underlying molecular mechanisms may be shared beyond the Venus flytrap.”

 

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