Unlike proactive predators in the animal kingdom, carnivorous plants like the Venus flytrap (Dionaea muscipula) wait for their insect prey to factually come to them before they can catch the victims. The plants count touches from their wretched prey to craft a predatory response.
Carnivorous plants, such as the Venus flytrap (Dionaea muscipula), depend on an animal diet when grown in nutrient-poor soils.
When an insect visits the trap and tilts the mechanosensors on the inner surface, action potentials (APs) are fired. After a moving object elicits two APs, the trap snaps shut, encaging the victim. Panicking preys repeatedly touch the trigger hairs over the subsequent hours, leading to a hermetically closed trap, which via the gland-based endocrine system is flooded by a prey-decomposing acidic enzyme cocktail.
Here, researchers asked the question as to how many times trigger hairs have to be stimulated (e.g., now many APs are required) for the flytrap to recognize an encaged object as potential food, thus making it worthwhile activating the glands. By applying a series of trigger-hair stimulations, they found that the touch hormone jasmonic acid (JA) signaling pathway is activated after the second stimulus, while more than three APs are required to trigger an expression of genes encoding prey-degrading hydrolases, and that this expression is proportional to the number of mechanical stimulations.
A decomposing animal contains a sodium load, and researchers have found that these sodium ions enter the capture organ via glands. They identified a flytrap sodium channel DmHKT1 as responsible for this sodium acquisition, with the number of transcripts expressed being dependent on the number of mechano-electric stimulations. Hence, the number of APs a victim triggers while trying to break out of the trap identifies the moving prey as a struggling Na+-rich animal and nutrition for the plant.
Highlights of the study were:
Carnivorous Dionaea muscipula captures and processes nutrient- and sodium-rich prey.
Via mechano-sensor stimulation, an animal meal is recognized, captured, and processed.
Mechano-electrical waves induce JA signaling pathways that trigger prey digestion.
Number of stimulations controls the production of digesting enzymes and uptake modules
The Venus flytrap Dionaea muscipula, is a carnivorous plantnative to subtropical wetlands on the East Coast of the United States in North Carolina and South Carolina. It catches its prey, chiefly insects and arachnids, with a trapping structure formed by the terminal portion of each of the plant’s leaves, which is triggered by tiny hairs on their inner surfaces. When an insect or spider crawling along the leaves contacts a hair, the trap closes if a different hair is contacted within twenty seconds of the first strike. The requirement of redundant triggering in this mechanism serves as a safeguard against wasting energy by trapping objects with no nutritional value.
The findings were published online Jan. 21 in the journal Current Biology.