ScienceCast: Flowering Plants and Ancient Gene Duplications

Uploaded by PennStateScience on 12.05.2011

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 Claude
dePamphilis, a professor of biology at Penn State University and the lead author of the
study, 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.
DePamphilis and his team began with some intense genomic detective work -- combing through
nine previously sequenced plant genomes, plus millions of new gene sequences that the Ancestral
Angiosperm Genome Project had gathered from the earliest surviving lineages of flowering
plants. The team knew that, at some point in ancient history, one or more important
genetic metamorphoses had occurred in the ancestor of flowering plants, and that these
metamorphoses could explain the enormous success of so many living flowering-plant species.
Most importantly, the team suspected that these changes had been driven by a common
mechanism instead of by many independent events. After examining volumes of molecular evidence,
DePamphilis and his team discovered and calculated the dates for two instances of a special kind
of DNA mutation -- called a polyploidy event -- that revolutionized the flowering-plant
"A polyploidy event is when all of the DNA in the cell is duplicated. This duplication
also duplicates all the genes in the cell, all the regulatory elements in the cell, everything
in the genome."
Biologists had dated the earliest polyploidy event in flowering plants at around 125 to
150 million years ago. However, DePamphilis and his team found evidence of two, much earlier
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 -- up to 200 million years earlier than such events were assumed to have taken
Such polyploidy events probably set in motion a kind of genomic renaissance. Thanks to these
events, flowering plants have been able to evolve new and better functions, and have
become so diverse, so exquisite, and so prevalent. Without the genes that these polyploidy events
helped to create, flowering plants as we know them today probably would not exist.
"One of the long-standing topics of investigation in plant biology is one that was raised originally
by Charles Darwin, who pointed out that flowering plants increased in diversity very, very rapidly.
He called it an 'abominable mystery' why the flowering plants originated and then exploded
in diversity so quickly."
DePamphilis believes that the polyploidy events his team discovered may be an important part
of that abominable mystery, and that all species of flowering plants today are the result of
large-scale duplications of the ancient genome -- two "big bangs" for flowering plants.
For Science Cast, I'm Katrina Voss.