One Plant's Junk DNA is Another's...? (May 13, 2013)

In the May 12, 2013 issue of Nature, Enrique Ibarra-Laclette, et al. report that the genome of the carnivorous humped bladderwort plant, Utricularia gibba contains only 3% junk DNA.

The Abstract of the paper, "Architecture and evolution of a minute plant genome":

It has been argued that the evolution of plant genome size is principally unidirectional and increasing owing to the varied action of whole-genome duplications (WGDs) and mobile element proliferation. However, extreme genome size reductions have been reported in the angiosperm family tree. Here we report the sequence of the 82-megabase genome of the carnivorous bladderwort plant Utricularia gibba. Despite its tiny size, the U. gibba genome accommodates a typical number of genes for a plant, with the main difference from other plant genomes arising from a drastic reduction in non-genic DNA. Unexpectedly, we identified at least three rounds of WGD in U. gibba since common ancestry with tomato (Solanum) and grape (Vitis). The compressed architecture of the U. gibba genome indicates that a small fraction of intergenic DNA, with few or no active retrotransposons, is sufficient to regulate and integrate all the processes required for the development and reproduction of a complex organism.

So the mystery of the reason for organisms to retain vast amounts of non-coding DNA remains.