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This Mysterious Plant Doesn’t Have Time for Junk DNA

Utricularia gibba has less DNA, but more genes

(Albert Lleal/Minden Pictures/Corbis)
smithsonian.com

In the strange world of flora, there's often more to a plant than meets the eye. Take the “humped bladderwort,” also known as Utricularia gibba. The plant is found hanging out underwater or in aquariums around the world. (It’s even classified as an invasive weed in some countries.) But new research has revealed something strange indeed about these little organisms—though they have a much smaller genome than other well-known plants, they actually contain more genes.

A new study took a deeper look at the carnivorous plant and found some surprising results. Researchers compared bladderwort’s genome to that of other plants like grapes, papaya and coffee and found that though the bladderwort has less DNA, it actually contains more genes than its counterparts. In a release, Victor Albert and his team discussed one example:

A comparison with the grape genome shows U. gibba's genetic opulence clearly: The bladderwort genome, holding roughly 80 million base pairs of DNA, is six times smaller than the grape's. And yet, the bladderwort is the species that has more genes: some 28,500 of them, compared to about 26,300 for the grape.

How is that even possible? The answer likely lies in junk DNA, as Rachel Feltman reports for the Washington Post. The term is used to refer to regions of DNA that don’t actually code proteins, and all organisms have it. For example, the human genome contains up to 98 percent junk DNA. But Feltman notes that bladderwort doesn’t have much junk DNA at all—only three percent:

The new study suggests that the plant may owe its super-compact genome to a long history of rampant DNA editing. Basically, the aquatic, carnivorous little plant is gaining and throwing away DNA at an unusually rapid pace.

The team estimates that the plant has duplicated its genome at least three times, but that it balances out its gene gain by getting rid of the junk quickly. But though their new study reveals that bladderwort just doesn’t have time for junk DNA, they still aren’t sure what purpose the plant’s swift editing process serves.

Albert suggests that it could be related to evolution and survival (and other recent research has shown that organisms like squid can edit their DNA on the fly to gain a survival advantage). However, he also concedes that the plants could just be bad at repairing their own DNA. They’ll continue to explore the whys, but for now the mere fact of the humped bladderwort’s weird genome is food for fascinating thought.

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