New genetic study helps to solve Darwin's mystery about the ancient evolution of flowering plants

Apr 10, 2011
The evolution and diversification of the more than 300,000 living species of flowering plants may have been "jump started" much earlier than previously calculated, according to a new study led by Penn State University scientist Claude dePamphilis. The study provides a wealth of new genetic data and is expected to change the way biologists view the family trees of plants in general and flowering plants in particular. This image shows the leaves and a flower of the yellow poplar tree (Liriodendron tulipifera), a basal angiosperm included in the study led by Penn State scientist Claude dePamphilis. This plant was included in the Ancestral Angiosperm Genome Project. Credit: Hong Ma Laboratory, Penn State University, Yi Hu

(PhysOrg.com) -- The evolution and diversification of the more than 300,000 living species of flowering plants may have been "jump started" much earlier than previously calculated, a new study indicates. According to Claude dePamphilis, a professor of biology at Penn State University and the lead author of the study, which includes scientists at six universities, two major upheavals in the plant genome occurred hundreds of millions of years ago -- nearly 200 million years earlier than the events that other research groups had described. The research also indicates that these upheavals produced thousands of new genes that may have helped drive the evolutionary explosion that led to the rich diversity of present-day flowering plants.

The study, which provides a wealth of new genetic data and a more precise evolutionary time scale, is expected to change the way biologists view the family trees of plants in general and flowering plants in particular. The research findings will be posted on the early-online website of the journal Nature on 10 April 2011, and later will be published in the journal.

"We began with some intense genomic detective work -- combing through nine previously sequenced plant genomes, plus millions of new that the Ancestral Angiosperm Genome Project (http://ancangio.uga.edu/) had gathered from the earliest surviving lineages of flowering plants," dePamphilis said. "We knew that, at some point in ancient history, one or more important genetic metamorphoses had occurred in the ancestor of flowering plants, and we also knew that these metamorphoses could explain the enormous success of so many species living on the Earth today. Most importantly, we suspected that these important changes had been driven by a common mechanism instead of by many independent events." DePamphilis explained that, after examining volumes of , his team discovered and calculated the dates for two instances of a special kind of -- called a polyploidy event -- that revolutionized the flowering-plant lineage.

Amborella trichopoda, a flowering plant. Amborella trichopoda is a basal angiosperm and the earliest surviving branch of the angiosperm tree of life. This plant was included in the Ancestral Angiosperm Genome Project. Credit: Sangtae Kim

"A polyploidy event is basically the acquisition, through mutation, of a 'double dose' of genetic material," explained Yuannian Jiao, a graduate student at Penn State and the first author of the study. "In vertebrates, although genome duplication is known to occur, it generally is lethal. Plants, on the other hand, often survive and can sometimes benefit from duplicated genomes." Jiao explained that, over the generations, most duplicated genes from polyploidy events simply are lost. However, other genes adopt new functions or, in some instances, subdivide the workload with the genetic segments that were duplicated, thereby cultivating more efficiency and better specialization of tasks for the genome as a whole.

Jiao also explained that, although ancient events of polyploidy have been well documented in plant-genome-sequencing projects, biologists had dated the earliest polyploidy event in flowering plants at around 125 to 150 million years ago. "There were hints that even earlier events had occurred, but no good evidence," Jiao said. "That's what makes our team's findings so exciting. We identified at least two major events -- one occurring in the ancestor of all seed plants about 320 million years ago, and another occurring in the flowering-plant lineage specifically, about 192 to 210 million years ago. That's up to 200 million years earlier than such events were assumed to have taken place."

The evolution and diversification of the more than 300,000 living species of flowering plants may have been "jump started" much earlier than previously calculated, according to a new study led by Penn State Unviersity scientist Claude dePamphilis. The study provides a wealth of new genetic data and is expected to change the way biologists view the family trees of plants in general and flowering plants in particular. This image illustrates the two major upheavals in the plant genome that the dePamphilis study reveals occurred hundreds of millions of years ago -- nearly 200 million years earlier than the events that other research groups had described. Credit: Claude dePamphilis Laboratory, Penn State University

DePamphilis added that such polyploidy events probably set in motion a kind of genomic renaissance, and that present-day varieties now are reaping the rewards. "Thanks to events such as these, where vast stretches of DNA have been duplicated and added to the genome, flowering plants have been able to evolve new and better functions. They have seized on the opportunity to become so diverse, so exquisite, and so prevalent," dePamphilis said. He explained that his team was able to trace the history of some of the major genes that define how flowering plants work. "Some of these new genes led to true innovations and have become vital parts of the genetic toolkit for the regulation of flower development," he said. "In other words, without the genes that these polyploidy events helped to create, flowering plants as we know them today probably would not exist."

DePamphilis also said that, thanks to the two polyploidy events that his research team identified, flowering plants may have enjoyed a distinct evolutionary advantage that allowed them to survive harsh climate changes and even mass extinctions. One such extinction that was accompanied by more-recent polyploidy events in several flowering-plant groups was the Cretaceous–Tertiary extinction event (the K-T event) -- a mass extinction of animals and plants that occurred approximately 65.5 million years ago that may have been triggered by a massive asteroid impact.

"Ever since Charles Darwin so famously called the rapid diversification of flowering plants in the fossil record an 'abominable mystery,' generations of scientists have worked to solve this puzzle," dePamphilis said. "We used to say that most of the hundreds of thousands of successful species of flowering plants show genetic traces of ancient polyploidy events. The further we push back the date of when these events happened, the more confidently we can claim that, not most, but all flowering plants are the result of large-scale duplications of the genome. It's possible that the important polyploidy events we've identified were the equivalent of two 'big bangs' for ."

Explore further: Evolution of competitiveness

Related Stories

Darwinian mystery may have been solved

May 11, 2006

U.S. scientists may have solved Charles Darwin's "abominable mystery" of flowering plants' rapid evolution after they appeared 140 million years ago.

How plants learned to respond to changing environments

Jul 12, 2007

A team of John Innes centre scientists lead by Professor Nick Harberd have discovered how plants evolved the ability to adapt to changes in climate and environment. Plants adapt their growth, including key steps in their ...

Unexpected amber find rewrites botanical history

Oct 02, 2009

(PhysOrg.com) -- An unexpected discovery made by Macquarie University PhD student Sargent Bray about the origin and nature of chemical compounds contained in ancient amber has changed our understanding of ...

Recommended for you

Evolution of competitiveness

Oct 29, 2014

Virtually all organisms in the living world compete with members of their own species. However, individuals differ strongly in how much they invest into their competitive ability. Some individuals are highly competitive and ...

Status shift for whale pelvic bones

Oct 29, 2014

For decades, scientists assumed that the relatively small pelvic bones found in whales were simple remnants of their land-dwelling past, "useless vestiges" that served no real purpose, akin to the human appendix ...

Is the outcome of evolution predictable?

Oct 28, 2014

If one would rewind the tape of life, would evolution result in the same outcome? The Harvard evolutionary biologist Stephen Jay Gould came up with this famous thought experiment. He suggested that evolution would not repeat ...

How did complex life evolve? The answer could be inside out

Oct 27, 2014

A new idea about the origin of complex life turns current theories inside out. In the open access journal BMC Biology, cousins Buzz and David Baum explain their 'inside-out' theory of how eukaryotic cells, which all multic ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

sergiosaurio
not rated yet Apr 10, 2011
Argentne geologist and paleontologist Dr. Jorge Calvo proved that huge argentine titanosaurs ate flowers...he proved this years ago.
DavidMcC
not rated yet May 13, 2011
Sergio, that may be true, because they are known to have eaten any and every plant material they could reach:

http://www.absolu...tanosaur

However, it does not affect the validity of this study, because titanosaurs didn't evolve until the cretaceous, something like 100MY after flowers.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.