This Mutant Venus Flytrap Mysteriously Lost Its Ability To “Count” To 5

Comparison of stimulation of a Venus flytrap and the DYSC mutant. Credit: Inés Kreuzer, Rainer Hedrich, Soenke Scherzer

In 2011, a horticulturist named Mathias Maier came across an unusual mutant of a venus flytrap, a carnivorous plant that traps and feeds on insects. Scientists recently discovered that the typical Venus flytrap can actually “count” to five, prompting further research into how the plant accomplishes this remarkable feat. The mutant flytrap could hold the key. according to a new paper Published in the journal Current Biology, this mutant flytrap does not close in response to stimulation like typical Venus flytraps.

“This mutant has obviously forgotten how to count, which is why I named it Dyscalculia (DYSC).” said co-author Rainer Hedrich, biophysicist from Julius-Maximilians-Universität Würzburg (JMU) in Bavaria, Germany. (Previously it had been called “ERROR”).

What We have informed formerly, the Venus flytrap lures its prey with a pleasant fruity scent. When an insect lands on a leaf, it stimulates the highly sensitive trigger hairs that line the leaf. When the pressure becomes strong enough to bend those hairs, the plant will close its leaves and trap the insect inside. Long cilia grip and hold the insect in place, much like fingers, as the plant begins to secrete digestive juices. The insect is slowly digested over five to 12 days, after which the trap is reopened, releasing the insect’s dried shell to the wind.

in 2016Hedrich led the team of German scientists who he discovered that Venus flytrap might actually “count” the number of times something touches its hair-covered leaves, an ability that helps the plant distinguish between the presence of prey and a small nut or stone, or even a dead insect. The scientists applied mechanoelectric pulses of different intensities to the leaves of the test plants and measured the responses. It turns out that the plant senses that first “action potential” but doesn’t close immediately, waiting until a second hit confirms the presence of actual prey, at which point the trap closes.

But the Venus flytrap doesn’t shut down all the way, producing digestive enzymes to consume the prey until the hairs fire three more times (for a total of five stimuli). The German scientists compared this behavior to performing a rudimentary cost-benefit analysis, in which trigger stimuli help a Venus flytrap determine the size and nutritional content of any potential prey fighting in its jaws and whether it’s worth it. the effort. If not, the trap will release whatever has been caught in about 12 hours.

In 2020, Japanese scientists genetically altered a Venus flytrap to glow green in response to outside stimulation, yielding important clues about how the plant’s short-term “memory” works. They introduced a gene for a calcium-sensing protein called GCaMP6, which lights up green whenever it binds calcium. That green fluorescence allowed the team to visually track changes in calcium concentrations in response to stimulating the sensitive plant hairs with a needle.

Stimulation of the Venus Flytrap by touch triggers electrical signals and calcium waves.  The calcium signature is decoded;  this causes the trap to close quickly.  But the DYSC mutant has lost the ability to correctly read and decode the calcium signature.
Enlarge / Stimulation of the Venus Flytrap by touch triggers electrical signals and calcium waves. The calcium signature is decoded; this causes the trap to close quickly. But the DYSC mutant has lost the ability to correctly read and decode the calcium signature.

Ines Kreuzer / University of Wurzburg

The results supported the hypothesis that the first stimulus triggers calcium release, but the concentration does not reach the critical threshold indicating that the trap closes without a second influx of calcium from a second stimulus. However, that second stimulus has to occur within 30 seconds, since calcium concentrations decline over time. If more than 30 seconds elapse between the first and second stimulus, the trap will not close. Thus, rising and falling calcium concentrations in leaf cells actually seem to serve as a sort of short-term memory for the Venus flytrap, although how calcium concentrations work with these is not clear. the power grid of the plant.

That does not appear to be the case with DYSC, though it is otherwise “essentially indistinguishable” from Venus flytraps in nature. DYSC does not shut down in response to two sensory stimuli, nor does it process its prey in response to additional stimuli. Naturally, Hedrich et al. she wanted to know why. They purchased wild Venus flytraps and mutant DYSC flytraps and ran parallel experiments: they mechanically stimulated the plants and measured action potentials, and they sprayed the plants with a contact hormone called jasmonic acidwhich is crucial for prey processing.

Hedrich and his team found that the mutation did not appear to affect either the action potential or the underlying calcium signal in the first two-count stage of the process. Action potentials fire, but the trap does not snap, suggesting that tactile activation of calcium signaling is being suppressed. In addition, the scientists suspected a defect that affected the decoding of the calcium signal. The administration of jasmonic acid did not solve the problem of the trap’s rapid closing failure, but it did restore the ability to process prey.

Co-author Ines Kreuzer then examined gene expression patterns in the mutant genes for any changes that might explain this. She was able to narrow down the likely suspects to a few scrambler components, which bind calcium and subsequently modify certain effector proteins, notably an enzyme called LOX3, which plays a vital role in jasmonic acid biosynthesis. The next step is to take a closer look at the modified proteins and change their activity when the prey comes into contact with DYSC. “In this way, we want to come full circle and find out what the plant does to distinguish numbers from each other, that is, how it counts.” hedrich said.

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

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