Scientists Gene Edit Venus Flytraps to Study Prey Detection

A familiar news story is that biologists have found the gene for… But sometimes the story is more complicated. Carl Procko and colleagues have used CRISPR gene editing tools to modify Venus Flytrap plants for the first time, as reported in Current Biology. By mutating trigger hair genes, they aimed to unravel how these carnivorous plants sense prey touch to snap their traps shut. Understanding the biology could enable a better understanding of signalling in many plants.

Venus Flytraps have evolved some ingenious biology to turn their leaves into traps for catching insect prey. Trigger hairs protruding from the leaves sense the touch of landing bugs. This initiates electrical signals that make the two lobes close shut around the victim within a fraction of a second.

Procko and colleagues examined two genes called FLYCATCHER 1 and 2. The genes appear to be connected to the Venus Flytrap signalling system. The scientists decided to investigate how the genes contribute to the plant’s senses by knocking them out. Using a method of gene editing, CRISPR-Cas9, they could deactivate the genes and see what happened to the plants.

Initially, they ran into a small problem. They used a pipette connected to a micromanipulator. Using this, they could bend the plant’s trigger hairs between 5° and 30°. They found that they couldn’t spot a difference between the standard plants and mutants without FLYCATCHER 1. This result was a problem. Procko and colleagues write.

The lack of a detectable difference in flyc1 mutant leaves in our harsh touch-based assay may be due to the deflection of the trigger hairs being large enough to overcome any subtle defects in sensory loss. Indeed, the trigger is extremely sensitive and can detect an angular deflection of just a few degrees. As such, to more finely assess the ability of the leaf to respond to mechanical stimulation, we developed a novel ultrasound-based assay. Detached, open traps were placed with one leaf lobe resting on ultrasound gel atop a 2-cm-diameter transducer. Mechanical stimulation was then applied in the form of pulsed, mechanical ultrasound waves of increasing peak negative pressure (PNP) until the trap closed.

Procko et al. 2023

The results showed flytraps with mutated trigger hair genes were still able to close when insects landed on them. However, they needed stronger pulses of ultrasound to snap shut compared to normal plants. This suggests FLYCATCHER genes contribute to, but are not solely responsible for, touch sensation. Rather than FLYCATCHER genes being the genes for the traps’ signals, there seems to be redundancy with other unidentified genes involved. This redundancy is a puzzle, say Procko and colleagues:

Why would the Venus flytrap require multiple mechanosensory ion channels for prey touch detection? Perhaps high levels of redundancy between mechanosensory channels is important for generating a robust sensory system necessary for prey capture. This system is important to support nutrient acquisition in the nutrient-poor soils in which the plant grows. Indeed, the trigger hair is exquisitely sensitive and can respond to the force of very small prey, such as ants.

Procko et al. 2023

These findings not only unravel Venus Flytrap biology but demonstrate the potential to genetically modify these unique carnivores for the first time using CRISPR. It’s unlikely that Procko and colleagues are doing this intending to engineer more effective flytraps in the future – unless they’ve taken a serious dislike to the scientists in the lab next door. However, the extreme reaction time in Venus Flytrap signalling makes it suitable to test how plants react to their surroundings.

READ THE ARTICLE
Procko, C., Wong, W.M., Patel, J., Mousavi, S.A.R., Dabi, T., Duque, M., Baird, L., Chalasani, S.H. and Chory, J. (2023) “Mutational analysis of mechanosensitive ion channels in the carnivorous Venus flytrap plant,” Current Biology, 33(15), pp. 3257-3264.e4. Available at: https://doi.org/10.1016/j.cub.2023.06.048.

Cover: Venus Flytrap. Image: Canva.