Planimals?
Until now, what we most commonly know as a sea anemone has been classified as an animal, but recent research shows that this organism is genetically half animal and half plant. Typically, the two classifications an organism must meet in order to be considered a plant are that they are autotrophic (produce their own food) and have cell walls in addition to cell membranes, as opposed to animals, whose cells are protected only by a single cell membrane. Though sea anemones do not meet either of these requirements, they have another characteristic that allows them to be considered half-plant.
Both plant and animal cells contain many different types of RNA, the genetic sequence used to create proteins through the process of translation. One very important type found in both plants and animals is microRNA, known as miRNA for short. In the simplest terms, miRNA activates and deactivates genes in order to regulate gene expression post-translation; the difference between miRNA in plants and animals lies in the complexity of this process. These miRNAs find certain strands of different RNA and inhibit their processes, in some cases causing the RNA strands to dissociate entirely. In animals, each miRNA can bind a plethora of different RNA’s in a specific sequence; in plants, this process is far more specific.
Plant miRNAs have much higher sequence specificity, allowing them to only bind with a handful of different target RNAs. The entire process itself is more specific and more highly regulated, and this new research show that sea anemones posses all the specific qualities of plants in regards to their miRNA. It also shows that, when comparing the sequences of miRNAs in sea anemones those found in other organisms, there are striking similarities with those of other plants as well as other animals, showing us the first evolutionary link between plants and animals with respect to miRNAs.
This research is important for many reasons. As previously stated, it provides a brand new link between the evolution of plants and animals. It also provides the first example of an organism that can be considered both a plant and an animal. Though the sea anemone contains all the given qualities of an animal, this genetic characteristic definitely allows it to be considered a plant as well. Lastly, this discovery provides insight on how different levels of genetic coding and expression can evolve differently.