This Carnivorous Plant Throws Out Its Junk DNA

The carnivorous bladderwort plant is a small aquatic species with cheery yellow flowers. It uses tiny traps that act like vacuums (the “bladders” in its name) to suck up prey such as water fleas. It’s a complex little plant. But compared to, say, a tomato, the bladderwort has extremely short DNA—just 80 million DNA base pairs to a tomato’s 780 million.

Tomatoes, like humans, have long strands of DNA that don’t do much. Only 2 percent of the human genome codes for genes—the portion of DNA that contains instructions for building proteins and functional RNA chains. The rest is known as noncoding or junk DNA. Researchers still speculate about the role of this genetic matter, which dominates the genome of not only humans but many other organisms, too.

Not the bladderwort, though. The plant’s DNA might be shorter than the tomato’s, but both plants have around 28,500 genes. The bladderwort just doesn’t have the noncoding DNA. Researchers who sequenced the bladderwort’s genome were surprised to find that 97 percent of the plant’s DNA consists of genes and sections of DNA that control those genes. This shows that complex life is possible without all of the junk DNA, they write.

In a paper published in Nature, the researchers hypothesize that—unlike humans and other plants and animals—the bladderwort actively deleted its junk DNA over many years of evolution. Some species, like the bladderwort, may have a built-in mechanism for deleting noncoding DNA, while others, like humans, may favor DNA insertion and duplication, leading to extraneous quantities of junk DNA. Neither mechanism is likely preferable over the other; they simply represent different paths in life.

More from Smithsonian.com:

Junk DNA Isn’t Junk, and That Really Isn’t News 
You Don’t Know As Much As You Think You Do 

Rachel Nuwer | | READ MORE

Rachel Nuwer is a freelance science writer based in Brooklyn.