Carnivorous Plant Throws Out ‘Junk’ DNA

A scanning electron microscope image shows the tiny, 1-millimeter-long bladders used to catch small organisms by Utricularia gibba, the humped bladderwort plant (color added). The submerged growing plant is a voracious carnivore, with its bladders leveraging vacuum pressure to suck in tiny prey at great speed. (Photo: Enrique Ibarra-Laclette and Claudia Anahí Pérez-Torres)
A scanning electron microscope image shows the tiny, 1-millimeter-long bladders used to catch small organisms by Utricularia gibba, the humped bladderwort plant (color added). The submerged growing plant is a voracious carnivore, with its bladders leveraging vacuum pressure to suck in tiny prey at great speed. (Photo: Enrique Ibarra-Laclette and Claudia Anahí Pérez-Torres)

Genes – the bits of DNA that code for proteins – make up about 2 percent of the human genome. The rest consists of a genetic material known as noncoding DNA, and scientists have spent years puzzling over why this material exists in such voluminous quantities.

Now, a new study offers an unexpected insight: The large majority of noncoding DNA, which is abundant in many living things, may not actually be needed for complex life, according to an advance online publication in Nature.

The clues lie in the genome of the carnivorous bladderwort plant, Utricularia gibba.

The U. gibba genome is the smallest ever to be sequenced from a complex, multicellular plant. The researchers who deciphered the DNA say that 97 percent of the genome consists of genes and small pieces of DNA that control those genes.

It appears that the plant has been busy deleting noncoding DNA, sometimes also called "junk" DNA, from its genetic material over many generations, the scientists say. This may explain the difference between bladderworts and species with large amounts of noncoding DNA, like corn and tobacco – and humans.

Eric Lyons, an assistant professor in the School of Plant Sciences at the University of Arizona College of Agriculture and Life Sciences, led the comparative analysis of the bladderwort genome to unravel its complex evolutionary history. His research team provided the analytical software for this task.

The study was directed by Luis Herrera-Estrella, who leads the Laboratorio Nacional de Genómica para la Biodiversidad, or LANGEBIO, in Mexico, and Victor Albert of the University at Buffalo, with contributions from scientists in the United States, Mexico, China, Singapore, Spain and Germany.

"The big story is that only 3 percent of the bladderwort's genetic material is so-called 'junk' DNA," Albert said. "Somehow, this plant has purged most of what makes up plant genomes. What that says is that you can have a perfectly good multicellular plant with lots of different cells, organs, tissue types and flowers, and you can do it without the junk. Junk is not needed."

Noncoding DNA is DNA that doesn't code for any proteins. This includes mobile elements called jumping genes that have the ability to copy (or cut) and paste themselves into new locations of the genome, and thus increase its size.

Scientists have spent countless hours puzzling over why noncoding DNA exists – and in such copious amounts. A recent series of papers from ENCODE, a highly publicized international research project, began to offer an explanation, saying that the majority of noncoding DNA (about 80 percent) appeared to play a role in biochemical functions such as regulation and promotion of DNA conversion into its relative, RNA, which for genes, feeds into the machinery that makes proteins.

Read the rest of this May 13, 2013 UANews article at the link below.

Date released: 
Jun 17 2013
Contact: 
Eric Lyons