People before Charles Darwin could not believe that there are carnivorous plants. It was against the natural order in which mobile animals eat plants and not the other way around. But in 1875, Darwin published Insectivorous Plants, detailing his discovery after spending 16 years performing meticulous experiments to prove the existence of carnivorous plants.
Then five years later, his myth-busting book The Power of Movement in Plants was published. The publication suggests that plants could move and kill insects. Today, researchers seek to trace the evolution of meat-loving plants and their origins.
A Venus fly trap consumes a dead fly as it sits on display at a presentation of carnivorous plants at the Berlin-Dahlem Botanical Garden on July 20, 2013 in Berlin, Germany
No Evidence That Carnivorous Plants Acquired Beastly Traits From Prey
A 2021 study from German researchers at the University of Würzburg explores the origins of carnivorous plants. Using molecular science to underpin the plant's carnivorous lifestyle, they identified how the Venus flytrap (Dionaea muscipula) snaps so fast and morphs into an insect-juicing stomach and intestine to absorb the remains of their prey.
However, they could not answer how evolution equipped the Venus flytrap with the means to eat meat. More so, fossils have not provided clues that show molecular details of the origins of carnivorous plants. They also did not find evidence that these plants acquired any of their beastly traits from hijacking the genes of their prey.
Instead, the findings suggest that co-option and repurposing of existing genes have age-old functions present among flowering plants. As plant genome biologist Victor Albert says, evolution is sneaky and flexible, but it is simpler to repurpose something than to create something new.
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Repurposing Genes to Provide New Tasks
Previous studies show that digestion and absorption are two elements of carnivorous plants, suggesting that evolution has repurposed some existing genes to put them to work in new places and give others new functions. In many carnivorous plants, they repurposed the same genes that are central to their old system of defense.
According to ARS Technica, scientists in the 1970s discovered that the digestive fluid in Venus flytraps contained enzymes used as weapons against bacteria, fungi, and hungry herbivores. Botanists confirmed that these enzymes are used when carnivorous plants trap and process their prey.
These enzymes include chitinase, which breaks down the exoskeleton, a flesh-dissolving protease that breaks down proteins, and the purple acid phosphatase that extracts phosphorus from the prey's corpse.
The team identified the genes linked to aspects of meat-eating plants, like how they attract prey or make their pitchers too slippery for insects to escape. They found that the origins of digestive enzymes of some carnivorous plants were repurposed genes that came from different lines of carnivores, showing a classic case of convergent evolution. It means that there were limited pathways to becoming a carnivorous plant.
Furthermore, the team found that convergent evolution went beyond co-opting because these enzymes continue to evolve and swap some of their amino acids to improve their performance by prolonging activity.
Researchers noted that trapping and digestion among carnivorous plants are best understood for the Venus flytrap. The plant produces the chemical jasmonates that trap the insect and start to break down the corpse. This jasmonate defense is probably one reason for some plants' meat-eating behavior. However, other carnivorous plants have their own unique way of attacking their prey.
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