Plant Physiology Preview
Published on December 14, 2007; 10.1104/pp.107.108183
OPEN ACCESS ARTICLE
Received August 28, 2007
Accepted November 25, 2007
The Arabidopsis AtOPT3 Protein Functions in Metal Homeostasis and Movement of Iron to Developing Seeds
Minviluz G. Stacey , Ami Patel , William E. McClain , Melanie Mathieu , Melissa Remley , Elizabeth E. Rogers , Walter Gassmann , Dale G. Blevins , and Gary Stacey *
Division of Plant Sciences; Division of Biochemistry; Department of Molecular Microbiology and Immunology; National Center for Soybean Biotechnology, Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211
Division of Plant Sciences, 3Division of Biochemistry; Department of Molecular Microbiology and Immunology; National Center for Soybean Biotechnology, Christopher S. Bond Life Sciences Center, University of Missouri, Columbia, Missouri 65211
* Corresponding author; email: staceyg{at}missouri.edu.
The Arabidopsis AtOPT3 belongs to the oligopeptide transporter (OPT) family, a relatively poorly characterized family of peptide/modified peptide transporters found in archebacteria, bacteria, fungi and plants. A null mutation in AtOPT3 resulted in embryo-lethality, indicating an essential role for AtOPT3 in embryo development. In this paper, we report on the isolation and phenotypic characterization of a second AtOPT3 mutant line, opt3-2, harboring a T-DNA insertion in the 5' UTR of AtOPT3. The T-DNA insertion in the AtOPT3 promoter resulted in reduced but sufficient AtOPT3 expression to allow embryo formation in opt3-2 homozygous seeds. Phenotypic analyses of opt3-2 plants revealed three interesting loss-of function phenotypes associated with iron metabolism. First, reduced AtOPT3 expression in opt3-2 plants resulted in the constitutive expression of root iron-deficiency responses regardless of exogenous iron supply. Second, deregulation of root iron uptake processes in opt3-2 roots resulted in the accumulation of very high levels of iron in opt3-2 tissues. Hyperaccumulation of iron in opt3-2 resulted in the formation of brown necrotic areas in opt3-2 leaves and was more pronounced during the seed filling stage. Third, reduced AtOPT3 expression resulted in decreased accumulation of iron in opt3-2 seeds. The reduced accumulation of iron in opt3-2 seeds is especially noteworthy considering the excessively high levels of accumulated iron in other opt3-2 tissues. AtOPT3, therefore, plays a critical role in two important aspects of iron metabolism, namely, maintenance of whole-plant iron homeostasis and iron nutrition of developing seeds.
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