Carnivorous plants repurpose stress genes to digest their prey

Come closer, little insect

Mitsuyasu Hasebe

By Chelsea Whyte

It’s a plant-eat-insect world for pitcher plants. These carnivorous plants have bucket-shaped leaves that hold a pool of fluid to drown and digest unwitting insects that fall in.

Now genetic sequencing of three families of pitcher plants – found in the Americas, tropical Asia and Australia – shows that each plant adapted to its own nutrient-poor habitat using very similar tactics.

“It’s so counterintuitive that a plant would munch on an animal, as opposed to vice versa,” says Victor Albert of the State University of New York at Buffalo, who led the team that sequenced the plant’s genome.

“In order to be a pitcher plant, you need to trap liquid and attract insects, have them fall in and not let them get out, and secrete enzymes that will do the prey digestion for you.”

To find out where carnivorous tendencies in plants come from on a genetic level, Albert and his team analysed proteins found in the plants’ digestive fluid. They found a similar genetic tactic used across the globe.

Each plant repurposed the stress response proteins that are usually produced near cell walls to signal damage from herbivores or the environment.

“These are gene families that have other functions in non-carnivorous relatives or ancestors. In these carnivorous species, they’ve become recruited as part of the system of digestive enzymes and nutrient transporters,” says Tom Givnish of the University of Wisconsin-Madison.

The genes that usually direct the production of stress-signaling proteins are co-opted to make digestive proteins, which sit in fluid at the bottom of a pitcher plant’s leaves and break down insect bodies into usable nutrients.

“It’s a big, complicated series of events at the evolutionary level to become carnivorous,” Albert says, but the fact that these geographically separate plants all did it using the same method suggests there are limited paths for plants to become predators.

There may be other ways for a plant to evolve into a predator, Givnish says, but repurposing stress enzymes may have been the path of least resistance for the pitcher plants.

“Either there may be only a few ways of getting there, or only a few fast ways of getting there,” he says.

Journal reference: Nature, DOI: 10.1038/s41559-016-0059

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