The carnivorous bladderwort (Utricularia gibba) certainly has a menacing name for a plant, but that's not the only interesting thing about it: it's also a genetic oddball. Scientists have been left baffled by the recent discovery that this aquatic plant has a tiny genome compared to other plants, but somehow more genes, reports the Washington Post.
To get a grasp of just how unusual this organism is, consider that it has "only" about 80 million base pairs of DNA. While that might sound like a lot, it's quite small by genome standards. It is six times smaller than the grape's genome, for instance. Even so, the bladderwort has 28,500 genes to the grape's 26,300.
How does this little flesh-eating plant pack so many genes into such a small genome? Scientists aren't entirely sure yet — but a 2013 study by Victor Albert of the University at Buffalo offers some clues. Albert found that Utricularia gibba was severely lacking in what is called "junk DNA," or DNA that does not directly code for proteins. Only 3 percent of the plant's DNA is junk. By comparison, in humans junk DNA may comprise as much as 90 percent of the genome!
Though junk DNA has been found to be anything but junk — it seems to serve a purpose in most organisms — the carnivorous bladderwort has seemingly rid itself of this extra baggage. Why? Does the bladderwort gain some benefit from its ultra-efficient genome?
Albert's study revealed that the bladderwort's genome has duplicated entirely at least three times in its evolutionary history, and each time the redundant genetic material has been left on the cutting room floor, and in dramatic fashion.
"It turned out that those rates of evolutionary turnover -- especially the rate of loss -- was incredibly high compared to other plants," Albert said. "The genome was subjected to some heavy duty deletion mechanisms."
When genes turn over frequently, only those that are most important tend to survive to the next generation. Albert suspects that this is evidence of natural selection at work — because only the most important genes survive, selective pressures must have been high for these traits.
But the real answer as to what has driven this plant to organize its genome in such an efficient manner remains elusive. No other related organisms in the Utricularia genus — of which there are hundreds — have such tiny, tightly-packed genomes. Many of these close relatives encounter similar evolutionary pressures, but only Utricularia gibba has so little junk DNA.
Studies are already planned to investigate the matter further, but for now scientists can only speculate.
"It might just not be as good at repairing its DNA as its close friends are," Albert suggested.
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