9318093 Guerinot Iron is an essential nutrient for all higher plants, with iron- containing compounds figuring prominently in the electron transport systems of photosynthesis and respiration. Although iron is abundant in the soil, the acquisition of iron is problematic due to its low solubility at biological pH under aerobic conditions. Iron uptake mechanisms are being studied in the model plant system, Arabidopsis thaliana, using biochemical, genetic and molecular genetic techniques. The focus is on the reduction of ferric iron which takes place at the root surface because ferric reduction is probably the primary factor in making iron available for absorption by plants. The main objective is to identify genes which encode components necessary for ferric reductase activity. Three strategies to identify such genes will be pursued simultaneously: a) use of the FRE1 gene from yeast to identify an Arabidopsis homolog; b) complementation of the fre1-1 yeast mutant to identify an Arabidopsis homolog; and c) identification of Arabidopsis mutants with altered ferric reductase activity and use of such mutants to clone the gene(s) involved in ferric reduction. A study of iron uptake in Arabidopsis should have application to general transmembrance permeation processes and their regulation and may ultimately lead to the construction of iron efficient plant varieties. These studies should also shed light on root specific gene expression and the regulation of gene expression by metals. ***
