A mutant plant with a counting disability - Phys.org

A mutant plant with a counting disability

January 23 2023, by Robert Emmerich

Stimulation of the Venus flytrap by touch triggers electrical signals and calcium
waves. The calcium signature is decoded; this causes the trap to shut quickly.
The DYSC mutant has lost the ability to read and decode the calcium signature
correctly. Credit: Current Biology (2023). DOI: 10.1016/j.cub.2022.12.058

The newly discovered dyscalculia mutant of the Venus flytrap has lost its
ability to count electrical impulses. Würzburg researchers reveal the
cause of the defect.

The carnivorous Venus flytrap (Dionaea muscipula) can count to five:
This discovery by Würzburg biophysicist Professor Rainer Hedrich

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caused a worldwide excitement in 2016. But how does the plant count?

Hedrich's team from Julius-Maximilians-Universität Würzburg (JMU) in
Bavaria, Germany, has now described the key component in the journal
Current Biology. The researchers found what they were looking for in a
mutant of the Venus flytrap that has lost its counting abilities.

The Venus flytrap counts its prey

The Venus flytrap can survive in its very nutrient-poor home in the
swamps of North and South Carolina because small animals are part of
its prey spectrum. For this purpose, the carnivorous plant has
transformed leaves into snap traps.

Both halves of the trap carry three to four sensory hairs each, which can
sense touch even from very small flies like mosquitoes. However, the
trap does not close at the first touch, but only at the second. So, it has to
remember touch number one and close at lightning speed on "two."

Traps make sense of calcium signals

But that's not all: if the captured prey animal continues to touch the
sensory hairs, a genetically encoded program is gradually called up at the
third, fourth and fifth touch.

In this process, the hormone jasmonic acid is synthesized, the trap is
hermetically sealed and digestive secretions are formed to open up the
animal meal. And transport proteins are put in place. They later absorb
the nutrients released from the prey into the body of the plant.

Each time the sensory hairs are touched, the Venus flytrap fires an
electrical impulse, called an action potential, which spreads over the
entire trap. The action potential is triggered by a calcium signal and

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carried by a calcium wave. "Counting is about measuring the individual
calcium spikes and accounting for them for trap closure and prey
processing," explains Rainer Hedrich.

The Dyscalculia mutant does not count

At a plant fair, Dr. Sönke Scherzer, co-author of the publication in
Current Biology, discovered a Venus flytrap that does not close on "two"
and does not process its prey on further touches. "This mutant has
obviously forgotten how to count, which is why I named it Dyscalculia
(DYSC)," says Hedrich.

In order to find out the cause of the numerical disability, Hedrich's team
examined the mutant's touch-mediated action potential. It turned out that
the touch perception and the associated action potential were unchanged.
Consequently, the calcium signal underlying the action potential could
not be affected by the mutation either.

Thus, the suspicion fell on a defect in the subsequent processes. The
Würzburg researchers were correct in this assumption: after
administration of the contact hormone jasmonic acid, the defect in rapid
trap closure was not cured, but the processing of the prey, which
depends on jasmonic acid, was restored. The DYSC defect was thus to
be found in the decoding of the calcium signal.

Patterns of gene expression analyzed

This is where Dr. Ines Kreuzer came in. The molecular biologist and
DYSC project leader looked for changes in the gene expression patterns
after touch stimulation in the mutant.

"In doing so, we focused on the genes that were no longer correctly

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addressed by touch in the mutant," says the JMU scientist. In this way,
the circle could be narrowed down to a few components operating as
decoders within the calcium signaling pathway.

These potential calcium decoders have calcium-binding domains. After
binding, they modify effector proteins. This includes the enzyme LOX3,
which is important for jasmonic acid biosynthesis. The key component
of the jasmonic acid-independent fast trap closure, on the other hand, is
an anion channel activated by calcium.

The researchers now plan to identify the calcium decoders and their
effector proteins. "To clarify this definitively, we are currently pursuing
two directions," says Hedrich.

His team has analyzed the genome of the Venus flytrap with high
resolution, so that the researchers can look directly for gene
modifications. In the second approach, they are looking at the proteins
that are modified upon prey contact and changed in their activity. "In
this way, we want to close the circle and find out what the plant does to
distinguish numbers from each other, i.e. how it counts."

 More information: Anda-Larisa Iosip et al, DYSCALCULIA, a
Venus flytrap mutant without the ability to count action potentials,
Current Biology (2023). DOI: 10.1016/j.cub.2022.12.058

Provided by University of Würzburg

Citation: A mutant plant with a counting disability (2023, January 23) retrieved 14 May 2024
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