Stephens, Brian W , Cook, Douglas R. , Grusak, Michael A. .
Characterization of ZIP1’s role in zinc homeostasis in the Model Legume Medicago truncatula.
The ZIP family of metal transporters includes members in plant, animal, and microbial species, which have sequence similarity to the ZRT (zinc-regulated transporter) and IRT (iron-regulated transporter) proteins in Saccharomyces cerevisiae. Transporters from this family have been shown to transport several metals including cadmium, copper, iron, manganese and zinc. In Medicago truncatula, seven predicted ZIP proteins have been identified thus far, and efforts are underway to fully characterize their selectivity for different metals. MtZIP1 from this family has previously been shown to complement the yeast mutant ScZHY3 that is defective in two transporters that are required for zinc uptake. Kinetic data determined from ZHY3 transformed with construct pFL61::MtZIP1 indicates that ZIP1 is a low affinity zinc transporter with a Km of 1Î¼M and Vmax of 8pmole/min/106 cells. Zinc transport by MtZIP1 is inhibited by both copper and cadmium in the yeast system. Additionally, a mutation in MtZIP1 was identified using the reverse genetic approach of TILLinG. The effect of the mutation on whole plant partitioning of zinc and cadmium between the roots and vegetative tissues will be presented, and other phenotypic characteristics of the mutant will be compared to those of wildtype. Expression of several ZIP genes also will be presented for plants grown on zinc concentrations maintained at normal levels (1Î¼M) or at concentrations that induce zinc deficiency (0Î¼M) or toxicity (10Î¼M). Finally, a model of how MtZIP1 functions in whole-plant metal homeostasis will be described. This work was funded in part by funds from USDA-ARS under Agreement No. 58-6250-6-001 and the HarvestPlus Project under Agreement No. 58-6250-4-F029 to MAG, and USDA-ARS under Agreement No. 3640-21000-019-02S to
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1 - USDA-ARS Children's Nutrition Research Center, Pediatrics
2 - University of California-Davis, Plant Pathology
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM