Plants that hoard heavy metals

Researchers interested in understanding the molecular mechanisms that allow plants to hyperaccumulate metals should consider focusing their efforts on the pennycress, Thlaspi caerulescens, according to a new analysis by scientists at Purdue University and Massey University in New Zealand. The study, which was published in the August issue of New Phytologist, is the first step toward finding a model plant species for use in large-scale efforts to uncover the genes involved in metal phytoremediation.

Wendy Ann Peer and colleagues collected different wild metal hyperaccumulators from 20 areas throughout Austria, France, Turkey, and the United States during the spring and summer of 2001. All of the specimens were members of the cabbage family and relatives of Arabidopsis thaliana, a plant whose genes are known and easy to manipulate. The scientists evaluated the plants’ ability to accumulate metals and considered factors that make the plants easy to grow, analyze, and manipulate genetically.

T. caerulescens was the most promising because it grows quickly and easily in the lab, sets several thousand seeds, and is self-fertile. It also has a compact diploid genome and shares about 88% of A. thaliana’s genes, which have already been sequenced.

Peer and colleagues are currently testing another 30 hyperaccumulators and eventually plan to pit T. caerulescens against the winner of the current evaluation. It would be fitting if pennycress comes out on top for genetic studies because it was the first hyperaccumulating plant to be identified in 1885. (New Phytologist 2003, 159, 421–430)