Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 2/2/2002
Publication Date: 3/25/2002
Citation: KLEIN, M.A., PENCE, N.S., KOCHIAN, L.V. MECHANISMS OF ZINC ACCUMULATION AND TOLERANCE IN THE ZINC/CADMIUM HYPERACCUMULATOR THLASPI CAERULESCENS. AMERICAN SOCIETY OF PLANT BIOLOGISTS ANNUAL MEETING. 2002. Interpretive Summary:
Technical Abstract: Plant acquisition of essential micronutrients requires a well honed regulatory system to take up these relatively scarce metals to levels allowing adequate growth while avoiding phytotoxicity. Additionally, as these micronutrients are also heavy metals, the mechanisms mediating micronutrient accumulation must play a role in heavy metal uptake. Thus, research into micronutrient/heavy metal accumulation and homeostasis shoul provide insights for plant mineral nutrition and the use of plants to remediate heavy metal contaminated soils. To further our understanding of this topic, we are studying the metal uptake & tolerance mechanisms used by the Zn/Cd hyperaccumulator Thlaspi caerulescens. This species accumulates up to 30,000 ppm Zn and 3,000 ppm Cd in the shoots with no visible phytotoxicity symptoms. In an effort to better understand the molecular basis for this dramatic phenotype, we are using two different approaches to oisolate & characterize the genes essential for metal hyperaccumulation. Th first approach is based on our previous observation that expression of a number of micronutrient transport & metabolism genes are up-regulated in T. caerulescens grown on adequate Zn & down-regulated only when plants are grown on very high Zn levels. Thus, we have generated a subtractive cDNA library enriched in genes highly expressed in Zn-adequate T. caerulescens. We have generated high density arrays with this library and are conducting expression profiling to identify candidate hyperaccumulation genes based on gene expression. The second approach uses yeast complementation with a T. caerulescens yeast expression library & screening of the transformed yeast on potentially toxic levels of Zn to identify genes that confer Zn tolerance in T. caerulescens. Supported by USDA NRICGP Grant 98-35100-6105.