The Venus flytrap may be named after the Roman goddess of love, but its bite is unforgiving. Now, German and Saudi Arabian scientists reveal how the carnivore flipped the tables on evolution, turning a distress signal into a cunning weapon.
With its sweet smell and floral appearance, it’s no wonder insects are lured to the clam-shaped leaves of the Venus flytrap. But the relationship quickly turns sour as the flytrap snaps these leaves shut to devour its insect prey.
And this carnivore is a calculated hunter.
Tiny sensory hairs on the leaf surface, when bent by a crawling insect, send electric signals which close the trap. Earlier this year, Rainer Hedrich from the University of Würzburg and colleagues revealed that the Venus flytrap counts to two before slamming its trap shut, ensuring it doesn’t waste energy on false alarms.
Now, Hedrich and his team show how parts of the flytrap’s hunting strategy evolved.
They compared genes in Venus flytraps to those of the non-carnivorous thale cress. When wounded by a feeding insect, thale cress produces a stress hormone called jasmonic acid. This hormone activates molecules which block the insect’s digestive enzymes, making it harder for them to absorb the plant’s nutrients.
“In the Venus flytrap, these defensive processes have been reprogrammed during evolution,” Hedrich explained.
A digesting Venus flytrap also releases jasmonic acid, the authors of the current study found, but the hormone affects the plant, triggering production of more plant enzymes to help break down the insect.
Sniffing out the chemical composition of its prey allows the flytrap to fine-tune which digestive juices, and how much of each, to secrete.
The authors also showed that as they digest prey, Venus flytraps pump out molecules called receptor-like kinases, which “smell” different chemicals. One of these molecules senses chitin, which is commonly found in insect exoskeletons.
“Contact with chitin normally means danger for a plant – that insects will eat the plant,” said Hedrich. But the researchers found when they dropped chitin on Venus flytraps already in digestion mode, it boosted production of a chitin-digesting enzyme almost 2,000-fold.
The authors speculate that sniffing out the chemical composition of its prey allows the flytrap to fine-tune which digestive juices, and how much of each, to secrete.
The team also discovered genes switched on in the glands of a digesting trap were similar to those in the plant’s roots. This suggests the Venus flytrap's bug-absorbing genetic program is copied from how the plant absorbs nutrients from the soil.
So why the change in culinary preference?
For the plant it’s all about economics, the authors write: “The carnivorous syndrome not only covers expenses […] but also gains a surplus, allowing the carnivorous plant to afford and grow new capture organs for future hunting cycles.”
The research was published in the journal Genome Research.
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Viviane Richter is a freelance science writer based in Melbourne.
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