Our fascination with the Venus fly trap (Dionaea muscipula) is undeniable. What's not to love about a plant that eats animals? Our obsession with this species has led to a long history of investigation (as well as deplorable practices like poaching). However, despite our familiarity with the Venus fly trap, we still have much to learn about its biology. For instance, little is known about the origins of the molecular machinery involved in its carnivorous lifestyle. Thanks to a 2016 paper published in Genome Research, we now have some insights.
As you can probably imagine, the Venus fly trap genome has been of interest to science for quite some time. After all, it is likely to harbor the keys to this carnivorous curiosity. However, despite looking, no carnivory-specific genes have ever been found. It's as if this wonder of evolution has no genetic basis. Of course, things are not that simple. A breakthrough was made when a team of researchers based out of Germany and Saudi Arabia decided to take a look at "transcription profiles." Essentially, these are chemical indicators of gene activity. When a gene is activated, it produces a chemical signal that can be easily traced. In doing so, researchers are able to get a clear picture of what is going on at a molecular level when an organism responds to its environment.
What the team discovered is pretty amazing. Instead of a new family of carnivorous genes coming online, they found that the Venus fly trap has retooled a handful of genes that are used by many different plant species for defense. As it turns out, the Venus fly trap has coopted a set of genes that in most plants are activated when the plant becomes damaged. When the traps were stimulated by the insects stuck inside, transcripts for the production of chitinase, which is basically a insect digesting enzyme, became amplified. For non-carnivorous plants, chitinase is usually produced in response to insect attack or fungal infection and is believed to be a defense mechanism. This was not the only gene activity either. When an insect was trapped by the plant, transcripts for jasmonic acid saw an increase. Also, when digestive glands within the trap began to activate, the genes responsible for this were showing an expression pattern akin to that of nutrient transport in roots.
It would seem that the evolution of carnivory in this species did not involve novel genes. Instead, the evolution of the Venus fly traps carnivorous lifestyle involved a reprogramming of sets of genes common to most plant species. In essence, the Venus fly trap has melted its shield to build a sword, only the sword is a trap of exquisite beauty and effectiveness.
Photo Credit: Scott Schiller