New research published this Monday in the journal Nature Ecology and Evolution showed how carnivorous plants present in distinct parts of the world had similar evolution pathways through time.
Since Charles Darwin’s days, the carnivorous plants have always been an enigmatic issue to the scientific community. The development of these plants is beginning to make sense to researchers, as there were found many similarities among distinct types of plants in several areas of Earth. The finding that impacted the most was the fact that the eating method from each plant is practically the same.
Victor Albert, a biologist at the University at Buffalo, described the pathway of evolution for the plants as “restricted.” Albert was part of the investigation team, and he and his colleagues assure that they have found similar genetic changes present in the pitcher plants present in Asia, Australia and North America.
The principal difference between the famous carnivorous plant Venus flytrap and pitcher plants is that the first one has jaws that cut the prey, while the other ones can trap insects by attracting them into its leafs with slippery sides.
In the case of the pitcher plants, once the insect is trapped, it can get out by any means. The plant has a cup-shaped leaf that contains a liquid capable of breaking down the insect’s exoskeleton and flesh. This is what makes possible the survival of the plant, as their habitat is usually reduced regarding feeding sources.
Study findings: How evolution worked?
As it was said before, the explanation for the evolution has been a topic for many studies through the years, as scientists have wondered how is it possible that a plant developed this unique lifestyle. Albert qualifies the fact that a plant uses an animal for feeding as “counterintuitive,” and explains that is common to think that animals are the ones who use plants for surviving.
To find the explanation of this particular evolutive pathway, the team of researchers focused first on the Australian pitcher plant, the Cephalotus follicularis. This particular plant possesses two types of leafs, one that does the photosynthesis process and the other one that is converted into the cup-shaped trap. Then, the team proceeded to sequence the plant’s DNA to understand which genes were activated in each type of leaf.
“What we found is that certain genes are only on in the pitcher leaf, or preferentially on in the pitcher leaf, and that some of these very likely have to do with the trap development,” Albert explained while presenting the study this Monday.
The investigation team also conducted an analysis regarding the plant’s fluid and its components, especially the presence of enzymes and proteins in the liquid. After they had confirmed the composition of the fluid, they compared the results with the other two “unrelated” pitcher plants in Asia and America. They also compared the results with the digestive juices present in other carnivorous plants, to obtain a wider conclusion.
The research team found that even when the three pitcher plants evolved separately one from the other, its fluids were composed by the same types of enzymes. According to Thomas Givnish, who studies plant evolution at the University of Wisconsin, there is evidence that shows how even noncarnivorous plants grabbed the same genes for the developing of carnivorous characteristics.
One of the most remarkable discoveries was the fact that the genes seemed to have mutated with the same orientation in many cases. The team explained that this could be the consequence of every plant using the same method to feed, as Givnish states that these discoveries are “one of its kind.”
“So you’ve got convergence at three levels,” Dr. Albert explains. “You’ve got convergence at the morphological, the physiological level, and then you’ve got convergence in terms of co-option of enzymes, and then you’ve got actual convergence of certain amino acid changes within some of those enzymes. It’s really crazy.”
The scientists in charge of the investigation explained that this enzyme similarity has to do with defense mechanisms present in all three plants. According to the study, these enzymes’ evolution was oriented to the defense of the plants against herbivorous insects, diseases, and other threats.
This explanation makes sense when compared with previous investigations and analysis conducted regarding the Venus flytrap. According to Dr. Rainer Hedrich, a biologist at the University of Würzburg, this plant “rewires plant defense against herbivores into offense,” with the use of a hormone called jasmonate. Those investigations found that this response is due to the harsh environment in which these plants live as they “evolved carnivory as an alternative way to obtain those necessary nutrients.”
The investigation team is looking forward to determining the genetic features of each plant more deeply, to discover if there are similarities in each plant’s roots and pitchers, not only enzymes and proteins.