Genes for seeds arose early in plant evolution, ferns reveal

The emergence of seed-producing plants more than 300 million years ago was an evolutionary watershed, opening new environments to plants and ultimately leading to the flowering plants that brighten our world and supply much of our food. But it was less of a leap than it seems, newly published DNA sequences suggest. The genomes, from three fern species and a cycad, one of the oldest kinds of seed-bearing plants, show genes key to making seeds are the same as those in the spore-producing machinery of ferns, which emerged tens of millions of years earlier. They evidently existed in a common ancestor but were recruited into different reproductive functions as plants diverged. The fern and cycad genomes, published in a series of papers over the past several months “fill the gap of the gene flow during plant evolution,” says Shu-Nong Bai, a plant developmental biologist emeritus at Peking University who helped sequence a member of the maidenhair fern genus. “Evolutionary innovation [can] come from the alternative use of existing genes or networks, not new genes.” The genomes also teach a second striking lesson: that plants acquired some of their genes not through mutation and selection, but straight from fungi or other microbes through a controversial process dubbed horizontal gene transfer. Because of the daunting size of most fern genomes and the focus on crops such as rice, wheat, and maize, the majority of the more than 800 plant genomes sequenced so f...
Source: ScienceNOW - Category: Science Source Type: news