Making plant cells work like miniature factories

Ames Laboratory researchers explore the new frontier of metabolomics

The biotech field of genomics gives scientists genetic roadmaps to link certain genes to diseases. The subsequent study of proteins produced by certain genes spawned the field of proteomics.

Now, a group of researchers at the U.S. Department of Energy’s Ames Laboratory at Iowa State University will use $1.02 million in DOE start-up funding to begin understanding the chemical processes that take place within the cells of plants. This new field, called metabolomics, could result in harnessing plants to efficiently produce biomass for energy production, chemicals and materials for industry or pharmaceuticals, and untold thousands of other uses.

“We know a lot about the genetic make-up of many plants, but we know very little about the chemical changes that take place within plant cells that eventually produce sugars, fibers or waxes,” said Ed Yeung, program director of Chemical and Biological Sciences at Ames Lab and principal investigator on the project. “If we can understand metabolism, then ideally, all the materials a plant produces can be controlled.”

The project, “Mass Spectrometric Imaging of Plant Metabolites,” combines the analytical chemistry expertise of Ames Laboratory with the strength of ISU’s Plant Sciences Institute. Yeung, who is also a distinguished professor of chemistry at ISU, is internationally recognized for his work in developing separation and detection technologies, having won four R&D 100 awards.

Also working on the project are Sam Houk, an Ames Lab senior chemist who specializes in identifying trace elements using inductively couple plasma-mass spectrometry, and associate scientist and ISU chemistry professor Ethan Badman, who specializes in mass spectrometry and gas-phase methods of analysis for biological molecules. Rounding out the team is Basil Nikolau, Director of the Plant Sciences Institute’s Center for Designer Crops and a specialist in biochemistry and functional genomics of plant metabolism.

Funding from the Chemical Sciences, Geosciences and Biosciences Division of the DOE’s Office of Basic Energy Sciences provides $340,000 for operation and equipment this year and another $680,000 in 2006. Additional money is expected in 2007 and could continue if the program receives good marks during a peer review scheduled for 2008.
Before they can study the chemical makeup within plant cells, the team must construct new analytical instruments capable of identifying molecules in such minute quantities.

“Developing the instrumentation is a large part of the proposal and we’re building a special, high-resolution mass spectrometer,” Yeung said, “because there’s nothing available commercially that meets our needs.” He added that the equipment will be housed in the Roy J. Carver Co-Laboratory on the ISU campus.

Mass spectrometry works by measuring the mass of individual ions – molecules that have been electrically charged. Plant material is ionized into a gas, sorted in an analyzer chamber according to the mass-to-charge ratios, and collected by an ion detector. The detector converts ion flux into a proportional electrical current. Finally, the magnitude of the electrical signals is recorded and plotted as a mass spectrum.

The ability to sort and detect these ions at cellular-scale quantities is where the team hopes to fine-tune the instrumentation.

Once the equipment is ready, the team will look at the chemical content in the cells of Arabidopsis thaliana, a small flowering plant that is widely used as a model organism in plant biology. Arabidopsis is a member of the mustard (Brassicaceae) family, which includes cultivated species such as cabbage and radish.

“Arabidopsis is not a major crop like corn and soybeans,” Yeung said, “but because so much is already known about it genetically, we can hopefully begin to draw correlations between the chemical and genetic makeup. We hope that such fundamental research will be applicable to other plants as well.”

Ames Laboratory is operated for the Department of Energy by Iowa State University. The Lab conducts research into various areas of national concern, including energy resources, high-speed computer design, environmental cleanup and restoration, and the synthesis and study of new materials.