Dartmouth biologists have found a gene required for both efficient
photosynthesis and for iron metabolism, processes necessary for producing a
healthy plant and a nutritious food source. This research is part of a
larger effort to learn how plants take up essential nutrients from the
environment as they grow.
The research paper, published with colleagues from Colorado State University
and the University of South Carolina, appeared in the early online edition
of the Proceedings of the National Academy of Science during the week of
July 21.

"There's a lot of attention today on global food shortages," says Mary Lou
Guerinot, the principal investigator on the study and one of the authors of
the paper. "We've found a gene that is key for proper chloroplast function.
This finding might some day help scientists develop plants that grow better
and can serve as more nutritious food."

During photosynthesis, chloroplasts are the subcellular compartment used by
plant cells to convert light energy to sugars, fueling the plant. This
process in the chloroplasts requires iron, and up to 90 percent of the iron
in leaf cells is located in chloroplasts. In this study, Guerinot and her
colleagues provide molecular evidence that FRO7, a gene in the FRO family,
is involved in chloroplast iron acquisition and is required for efficient
photosynthesis. The FRO family is a group of proteins that transfers
electrons from ferric iron (Fe3+) to reduce it to another kind of iron
(Fe2+). This same lab showed that this process (reduction of iron) was
essential for plants to take up iron into the roots from the soil in a study
published in 1999 in Nature.

"We have now shown that an analogous process is required for proper
chloroplast function," says Guerinot. "Moreover, without FRO7, plants sown
in iron deficient soil died as young seedlings. Our findings are of
particular interest because how iron gets into chloroplasts has not been
well understood despite the significance of iron in chloroplasts."

Guerinot explains that one-third of the soil worldwide is iron deficient, so
it is important to understand how plants acquire iron, allocate iron to
different parts of the plant and within the cell, and survive under iron
limiting conditions. This is not only critical to improve plant growth and
crop yields but also to improve human nutrition. According to the World
Health Organization, iron deficiency is the most prevalent nutritional
disorder in the world today and most people get their iron from eating
plants.

"Enriching crops with mineral and vitamin nutrients will provide sustainable
solutions to malnutrition," she says.

The work was funded by the National Science Foundation. The title of the
paper is, "Chloroplast Fe(III) chelate reductase activity is essential for
seedling viability under iron limiting conditions." Co-authors on this paper
include Dartmouth graduate student Jeeyon Jeong, with Erin Connolly and
Loubna Kerkeb at the University of South Carolina, and Marinus Pilon and
Chris Cohu at Colorado State University.
www.checkbiotech.org