Scientists who sequenced the Amborella genome say its DNA provides conclusive evidence that the ancestor of all flowering plants evolved following a "polyploidy event," during which an organism's entire genome is duplicated. It happened about 200 million years ago, scientists said.

Because redundant copies of genes can evolve to develop new functions, this doubling may be behind "Darwin's abominable mystery" — the apparently abrupt proliferation of new varieties of flowering plants in fossil records dating to the Cretaceous period, about 145 million years ago.

Some duplicated genes were lost over time but others took on new functions, including contributions to the development of floral organs.
Of more than 300,000 flowering plant species alive today, Amborella (Amborella trichopoda) is unique as the sole survivor of an ancient evolutionary lineage that traces back to the last common ancestor of all flowering plants, according to the research team.

The plant is a small understory tree found only on the main island of New Caledonia in the South Pacific. This heritage gives Amborella a special role in the study of flowers, said Victor Albert from the University at Buffalo.
Generations of scientists have worked to solve the puzzle of why flowering plants suddenly proliferated in fossil records, said Claude dePamphilis of Penn State University, another lead investigator.
Though whole genome duplication might sound strange, many species have evidence of doubling in their DNA. The ancient ancestor of all vertebrates — including humans — underwent a polyploidy event, Albert said.
The Amborella genome will provide scientists with a new tool for studying the genetic history of all flowering plants, and how genome duplication may have played a role in the evolution of traits like drought-resistance or fruit maturation.


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