Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/9/2006
Publication Date: 8/9/2006
Citation: Stephens, B.W., Cook, D.R., Grusak, M.A. 2006. Functional characterization and expression analysis of the ZIP1 metal transporter in Medicago truncatula. In: Plant Biology 2006 Final Program, August 5-9, 2006, Boston, Massachusetts. p. 160.
Technical Abstract: The family of transporters in plants that has sequence similarity to the ZRT and IRT transporters in Saccharomyces cerevisiae is referred to as the ZIP gene family. These genes encode for proteins that have been shown to transport divalent cations such as zinc, iron and manganese. The ZIP1 gene in Medicago truncatula (MtZIP1) can functionally complement the ZHY3 yeast strain that is defective in zinc uptake. Using this system, MtZIP1 was shown to have a Km of 1uM for Zn and a Vmax of 8.4 pmol Zn/min/10^6 cells. Copper inhibits MtZIP1 by affecting both its affinity for zinc and the rate of zinc transport. MtZIP1 does not appear to transport iron or manganese. Several studies have shown that some ZIPs have the capacity to transport cadmium, a common contaminant in amended soils. Therefore, we also studied and will present kinetic data for zinc uptake in the presence of cadmium, as well as direct measures of cadmium uptake by MtZIP1. Expression analyses were conducted to assess mRNA levels for MtZIP1. Data will be presented for plants grown on varying levels of Zn, ranging from 2 µM (Zn sufficiency) to no Zn (Zn deficiency). Additionally, expression data for other MtZIP genes will be presented for tissues collected from an MtZIP1 mutant, identified using the reverse genetic approach of TILLING. The functional and expression results will be used to discuss the probable role of MtZIP1 in the whole plant homeostasis of zinc in Medicago truncatula.