March 26, 2023

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This mutant Venus flytrap has mysteriously lost its ability to “count” to 5

Comparison of stimulation of a Venus flytrap and a mutant DYSC. Credit: Ennis Kreuzer, Rainer Heydrich, Swink Scherzer

In 2011, a horticulturist named Matthias Meyer stumbled upon an unusual mutant of a species Venus flytrapIt is a carnivorous plant that traps and feeds on insects. Scientists recently discovered that a typical Venus flytrap can actually “count” to five, which has led to more research into how the plant manages this feat. The mutant flytrap may hold the key. according to new leaf Published in the journal Current Biology, this mutant trap doesn’t close in response to stimulation like typical Venus flytraps.

“This monstrosity obviously forgot how to count, which is why I called it Dyscalculia (DYSC),” said co-author Rainer Heydrich, a biophysicist at Julius-Maximilians-Universität Würzburg (JMU) in Bavaria, Germany. (Formerly called “false”.)

like inform us Previously, the Venus flytrap lured its prey with a pleasant fruity scent. When an insect lands on a leaf, it stimulates the hypersensitive trigger hairs that line the leaf. When the pressure becomes strong enough to bend those hairs, the plant will close its leaves, trapping the insect inside. Long cilia catch the insect and hold it in place, like fingers, as the plant begins to secrete digestive juices. The insect is slowly digested over a period of five to 12 days, after which the trap is reopened, releasing the insect’s dried husk into the wind.

in 2016Heydrich led the team of German scientists Explore this The Venus flytrap can actually “count” the number of times something touches its hair-lined leaves—an ability that helps the plant distinguish the presence of prey from a small acorn or stone, or even a dead insect. The scientists shocked the leaves of the test plants with electromechanical pulses of different intensities and measured the responses. It turns out that the plant detects the first “action effort” but does not close immediately, waiting until the second triggering confirms the presence of actual prey, at which point the trap closes.

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But the Venus flytrap does not close all the way and produces digestive enzymes to devour the prey until the hairs are stimulated three more times (for a total of five stimuli). The German scientists liken this behavior to doing an initial cost-benefit analysis, in which trigger stimuli help a Venus flytrap determine the size and nutritional content of any potential prey that is struggling with whether it is worth the effort. If not, the trap will release whatever is caught within 12 hours or so.

In 2020, Japanese scientists Transgenic a Venus flytrap so that it glows green in response to an external stimulus, giving important clues about how the plant’s short-term “memory” works. They inserted a gene for a calcium-sensing protein called GCaMP6, which glows green whenever it binds to calcium. This green fluorescence allowed the team to visually track changes in calcium concentrations in response to stimulation of the plant’s photosensitive hairs with a needle.

Zoom in / Stimulating the Venus flytrap by touch triggers electrical signals and calcium waves. The calcium signature is decoded; This causes the trap to quickly close. But the DYSC mutant lost the ability to correctly read and decode the calcium signature.

Ennis Kreuzer/University of Würzburg

The results supported the hypothesis that the first stimulus triggers calcium release, but the concentration does not reach the critical threshold that indicates trap closure without a second influx of calcium from the second stimulus. This second stimulus must occur within 30 seconds, because calcium concentrations decrease over time. If it takes more than 30 seconds between the first and second alarms, the trap will not close. So the waxing and waning of calcium concentrations in leaf cells indeed appears to be a kind of short-term memory for the Venus flytrap, although how calcium concentrations work with the plant’s electrical network remains unclear.

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This does not appear to be the case with DYSC, though it is otherwise “essentially indistinguishable” from Venus flytraps in the wild. The DYSC does not shut down in response to two sensory stimuli, nor does it process its prey in response to additional stimuli. Of course, Heydrich et al. I wanted to know why. They purchased wild Venus flytraps and mutant DYSC flytraps and ran parallel experiments: stimulating the plants mechanically and measuring action potentials, spraying the plants with a contact hormone called Jasmine acidwhich is crucial for processing prey.

Heydrich and his team found that the mutation did not appear to affect the action potential or the basic calcium signal in the first two-count phase of the process. Action potentials trigger the firing, but the trap does not close, indicating that tactile activation of calcium signals was suppressed. Moreover, the scientists suspected a defect that affected calcium signal decoding. The use of jasmonic acid did not solve the problem with the failure of rapid closure of the trap, but it did restore the ability to process the prey.

Next, co-author Ines Kreuzer examined patterns of gene expression in the mutated genes to discover any changes that might explain this. She was able to narrow down potential suspects to a few decoding components, which bind to calcium and thus modulate certain effector proteins — most notably an enzyme called LOX3, which plays a vital role in the biosynthesis of jasmine acid. The next step is to look more closely at the modified proteins and alter their activity when prey comes into contact with the DYSC. “In this way, we want to close the circle and see what the factory does to tell the numbers apart, that is, how they are calculated,” Heydrich said.

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DOI: Current Biology, 2023. 10.1016/j.cub.2022.12.058 (About DOIs).

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