The bladderwort plant may seem simple at first glance, but inside its small structure is a tiny genome packed with more genes than larger, more well-known plants.
A team of scientists at the University of Buffalo recently realized this when studying the genomic structure of the plant, also known as Utricularia gibba.
Scientists have long been fascinated with the bladderwort, which lives in the ocean. It's a plant without roots that floats around with tiny branches and has traps that capture prey for it to consume.
But at the genomic level, the plant is even more fascinating: its genome is small, but it has a lot of genes, even more so than more complex plants, like grapes, coffee and papaya. The bladderwort's genome has about 80 million base pairs of DNA, with 28,500 genes. In comparison, the grape only has about 26,000 genes.
It's the reason for this compact treasure trove of genes, however, that makes this plant so amazing.
"The story is that we can see that throughout its history, the bladderwort has habitually gained and shed oodles of DNA," says University at Buffalo Professor of Biological Sciences Victor Albert. "With a shrunken genome," he adds, "we might expect to see what I would call a minimal DNA complement: a plant that has relatively few genes - only the ones needed to make a simple plant. But that's not what we see."
First, the team noticed that the bladderwort's genome contains very little "junk DNA." These are genes that have no clearly outlined purpose. In comparison, the human body is 90 percent junk DNA.
The team compared the bladderwort genome to other related plants. It noticed that the bladderwort constantly takes on new genes, but also constantly sheds others. In the team's study, it determined that the bladderwort went through three episodes of gene duplication, which gave it multiple copies of every gene. This is a common occurrence with DNA.
However, the difference with the bladderwort is that it quickly deleted much of its redundant DNA, leaving only useful genes in its wake, specifically in genes that control breaking down its food and genes that keep its cell walls strong in its native aquatic environment.
"When you have the kind of rampant DNA deletion that we see in the bladderwort, genes that are less important or redundant are easily lost," says Albert. "The genes that remain - and their functions - are the ones that were able to withstand this deletion pressure, so the selective advantage of having these genes must be pretty high."
