What excites the Venus flytrap
A Venus flytrap with its prey (center): When the fly comes close to the sensory hairs, an action potential (AP) is triggered in the Venus flytrap (left). Compared to the animal AP of the fly (right), distinctly different ion fluxes are involved in the different APs. Credit: Sönke Scherzer/Uni Würzburg

The Venus flytrap has to be fast in order to hunt flies. It has created a catching organ that can snap shut in a fraction of a second and is controlled by the fastest signaling networks in plants. The action potential is at the center of the network. The action potential is generated when a fly touches one of the six sensory hairs. The capture organ is triggered by a second potential.

The Venus flytrap is able to catch prey thanks to electrical signals. An issue that was previously unexplored has been explored by a team led by Professor Hedrich. The results of the scientists' work are presented in the current issue of the journal. Their focus is on the action potential of the ion transport proteins.

When the Venus flytrap starts to act crazy.

The team wanted to know when the Venus flytrap's capture organ would become excited. When the trap is fully developed and opens for the first time, it will fire its action potentials.

The electrical voltage between the inside and outside of the cell is called the cell's Membrane Potential. During an action potential, the potential drops quickly during depolarization, only to rise again during repolarization, initially above the original resting value, before slowly approaching its original value again. The Venus flytrap's action potential lasts less than a second.

Plants use calcium waves to serve as secondary messengers for communication between cells, tissues and organs. In order to show that action potentials and calcium signals operate in a coordinated manner, we used flytraps that carried the gene for a calcium ion reporterProtein.

There is a surprising discovery in the genetics.

The team was able to identify the genes that are involved in this signaling pathway. It takes less than half a day to open the Venus flytrap's trapping organ. When the trap enters its excitable stage, we looked at the differential expression of genes.

A surprising observation was made by co-author Manfred Heckmann, chair of physiology at JMU. Humans use lutamate as a neurotransmitter. The calcium ion signal and the action potential must be triggered by stimulation of the plant channels.

The AP model is based on the expression of genes.

The Wrzburg research team has gained new insights that allow them to conclude that the action potential is initiated by the influx of calcium ion. How does the action potential increase?

The team was interested in the potential actors in this process after examining the genes. They were able to describe the process with the help of Professor Ingo Dreyer, who was a JMU fellow.

The igniter is represented by the calcium ion that enters the trap cells. The anion channels are opened as second messengers. The result of anion efflux is depolarization. The repolarization phase is initiated by the opening of the potassium ion channels. The process is returned to its initial state by the protons pump.

The Venus flytrap has a lot of potential.

The Venus flytrap is more complex than its victims. The Venus flytrap has two additional components that make it different from humans and flies.

The action potential in the fly trap needs to be repolarized because of a relative of the fly's potassium channel. Plants don't use sodium channels in their processes. Depolarization of the flytrap action potential is achieved by the concerted action of two channels.

Future research and outlook.

Plants don't have synaptic channels, but they do have some channels. What does the plant need in order to grow? What happens to the glutamate in the resting state after stimulation? The questions will be addressed in upcoming studies. Hedrich says that they will be able to clarify this with the help of plants.

There are more questions than answers regarding the structure, function and regulation of glutamate channels. There is a chance that evolution is showing us the way. In very early land plants, there are only one channel of the glutamatereceptor. Is there a connection between the evolution of these channels and the excitability of plants? That's what we want to know.

More information: Sönke Scherzer et al, A unique inventory of ion transporters poises the Venus flytrap to fast-propagating action potentials and calcium waves, Current Biology (2022). DOI: 10.1016/j.cub.2022.08.051 Journal information: Current Biology