Biologists identify genes that control toxic metal accumulation in plants

Biologists at UC San Diego and four other institutions have identified a long-sought after family of genes that controls how yeast and plants accumulate toxic heavy metals and arsenic inside their cells.

Their discovery, published in two separate scientific papers, is a significant advance with the potential to restore environmentally damaged waste sites and protect the food supply from toxic metal contamination.

It could permit scientists to engineer plants capable of removing toxic metals from hazardous waste sites, a process called bioremediation. And it could allow them to improve crops to prevent or minimize their uptake of arsenic, cadmium and other toxic heavy metals in regions of the world where crops are grown in contaminated soil or irrigated with water containing toxic metals.

''Heavy metal and arsenic contamination has become a serious environmental problem that can cause cancer, dementia and other health problems in humans,'' said Julian Schroeder, a professor of biology at UCSD who led one of the research efforts, which identified a key gene in yeast that controls heavy metal tolerance and accumulation. ''By targeting these genes, we may be able to keep heavy metals from accumulating in the edible parts of plants, such as rice grains, and fruits, as well as engineer non-food plants to better accumulate heavy metals in order to remove toxic metals from contaminated sites.''

The discovery by Schroeder and his colleagues, which is detailed in a paper that is now available online and will appear in the December print issue of the Journal of Biological Chemistry, identified the long-sought gene in the genome of fission yeast, whose relatively small genome allows for rapid gene discovery.

The second paper, detailing the discovery of a similar family of genes in the plant Arabidopsis, is being published this week in the early online edition of the journal Proceedings of the National Academy of Sciences, by scientists at the University of Zurich in Switzerland, led by Enrico Martinoia and at POSTECH (Pohang University of Science and Technology) in Korea, led by Youngsook Lee, in collaboration with Schroeder and scientists in Schroeder's laboratory at UCSD.