Researchers redrawing the Tree of Life

10/15/04



The digitalis plant (foxglove, or Digitalis purpurea), besides being an ornamental plant, has been very important in herbal medicine and a source of alkaloids currently used in the treatment of heart diseases.
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Blacksburg, Va. – A $3 million National Science Foundation (NSF) Tree of Life grant is enabling researchers from Virginia Tech and six other laboratories to lead the way in reclassifying the 270,000 species of flowering plants that include all our food plants.

The NSF grant allows scientists from seven laboratories--at Virginia Tech, the University of Florida and Florida Museum of Natural History, Yale University, the University of Michigan, the University of California at Davis, the University of Wisconsin at Madison, and the University of Washington--to combine expertise to solve existing classification problems and develop formal regrouping and reclassification of these plants. The areas of expertise include genes and genomes, morphology and anatomy, fossil records, and computer modeling of such things as the time of origin.

Molecular biology and gene sequencing have changed the concept of plant evolution. "We thought for awhile we understood the classification, relationships, and date of origin and divergence of these plants," said Khidir Hilu, professor of biology at Virginia Tech. Formerly, flowering plants, which are the most dominant plant on the surface of the Earth and economically the most important, were classified by flower and leaf as monocots, such as orchids, and dicots, such as tomatoes, oranges, and cotton, Hilu said. Now, based on information from the genes, flowering plants are classified into a basal group that includes both monocots and some dicots such as magnolias and the true dicots, called eudicots. The new system has broken up several traditional groups and shuffled and mixed others, Hilu said.

The problem is that scientists still don't know where some groups fit and have no formal classification of others. In the past, most people suggested magnolias or buttercups were some of the earliest evolving flowering plants, or the base of the flowering plants tree. Now, Hilu said, a small shrub from New Caledonia called an Amborella forms the base, with water lilies coming directly after that. "This indicates a major shift from a shrub of terrestrial habitat to aquatic habitat," Hilu said. "That's a major change in structure and ecology."

Hilu had been researching flowering plants throughout his career with previous NSF grants to Virginia Tech. He also has been working with grasses, the fourth largest flowering plant group, which provides 80 percent of the world's food, such as cereal crops. His lab is one of the leaders in that family. With grants from agencies including the U.S. Agency for International Development and the Jeffress Fund, he has studied crops such as rice, peanut, cowpea, and millets, using biotechnological methods, and focused on outreach programs with Kenya and Morocco.

The Tree of Life laboratories will exchange plant and DNA material and gene sequence data, and some labs will focus on analyzing certain aspects of the project. Each laboratory will depend on results from the others, including Hilu's work on the mat-K gene. Then all the data generated at the seven labs will be combined and computer analyzed, a tree of life for flowering plants developed based on molecular information, and information from fossils, anatomy, and morphology imposed on the tree to confirm the relationships and come up with reliable groupings that will be used as the basis for a system of classification. The eventual goal of these projects is to have all flowering plants, algae, mammals, insects, and others put together in a full tree of life.

There are several benefits for doing so. For example, in plants, chemists and biologists searching for compounds in medicinal plants need to know their relatives and ancestors, since families of plants tend to have similar chemistries. Understanding biodiversity in the frame of patterns of relationships is important in the assessment of vegetation dynamics and species extinction due to climatic changes. The new tree would also help in the study of patterns of gene transfers among plant genomes.

Source: Eurekalert & others

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