(left) Eye of Science/Science Source; (right) Bruce Salmon

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ScienceShot: Carnivorous Plant Ejects Junk DNA

The carnivorous humped bladderwort (Utricularia gibba), found on all continents except Antarctica, is a model of ruthless genetic efficiency. Only 3% of this aquatic plant's DNA is not part of a known gene, new research shows. In contrast, only 2% of human DNA is part of a gene. The bladderwort, named for its water-filled bladders (shown left) that suck in unsuspecting prey, is a relative of the tomato. Since their evolutionary split 87 million years ago, both plants have experienced episodes of genetic duplication where the plants' DNA doubled in size. But while the tomato has held onto a lot of those duplicates, the bladderwort has thrown out anything it doesn't need, and now has a genome only a tenth as long as the tomato's. The finding, published online today in Nature, overturns the notion that this repetitive, non-coding DNA, popularly called "junk" DNA, is necessary for life.

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Correction, 13 May at 10:45 a.m.: The bladderwort and tomato evolutionary split occurred 87 million years ago, not 87,000.