Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 8/3/2002
Publication Date: 8/3/2002
Citation: ASHOT, P., NICOLE, P., KOCHIAN, L.V. IDENTIFICATION AND CHARACTERIZATION OF A HEAVY METAL TRANSPORTING P-TYPE ATPASE FROM THE METAL HYPERACCUMULATING PLANT SPECIES, THLASPI CAERULESCENS. PLANT PHYSIOLOGY. 2002. Interpretive Summary:
Technical Abstract: Thlaspi caerulescens is a Zn/Cd-hyperaccumulating plant species that can accumulate and tolerate up to30,000 ppm Zn and 4,000 ppm Cd in the shoots without exhibiting toxicity symptoms. As part of an overall program aimed at elucidating the molecular and physiological mechanisms of heavy metal hyperaccumulation in T. caerulescens, the research described here is focused on identification of genes responsible for the extreme Cd tolerance exhibited by this plant. We have employed yeast functional complementation techniques to identify gene(s) that play a role in Thlaspi Cd tolerance. We found that 100 mM Cd in the growth medium is lethal for our wild type yeast strain. Subsequently, we complemented this yeast strain with a T. caerulescens cDNA library in the yeast expression vector, pFL61, and have identified a number of colonies of transformed yeast that grow well on this restrictive level of Cd. After sequencing the transformants, this information was used for sequence comparisons in Genbank, and several genes were identified that may play a significant role in Cd tolerance mechanisms in T. caerulescens. Among 35 yeast colonies that conformed tolerance to high Cd, 5 were harboring a T. caerulescens cDNA with a high level of similarity to P-type heavy metal transporting ATPases. The T. caerulescens clone was 58% similar to the putative Arabidopsis thaliana P-type ATPase, hma4. Northern blot analysis showed that in T. caerulescens this gene is expressed only in roots and expression level was strongly correlated with Cd treatment. We are in the process of characterizing this ATPase clone in more detail in Thlaspi caerulescens, including a functional characterization of its transport properties in yeast. Supported by NSF Grant # IBN-0129844 to LVK.