The Arabidopsis AtOPT3 Protein Functions in Metal Homeostasis and Movement of Iron to Developing Seeds

Abstract

The Arabidopsis thaliana 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 article, we report on the isolation and phenotypic characterization of a second AtOPT3 mutant line, opt3-2, harboring a T-DNA insertion in the 5# untranslated region 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.

Multiple Antibiotic Resistance in Arabidopsis Is Conferred by Mutations in a Chloroplast-Localized Transport Protein

“…We observed a 60% decrease in MAR1 expression after 4 d of growth under iron deficiency (Fig. 9A), along with the expected up-regulation of Iron Regulated Transporter1 (IRT1; which encodes for a major high-affinity iron transporter) under similar conditions (Stacey et al, 2008). We also observed a down-regulation of MAR1 when plants were grown for 2 weeks on plates containing a lower concentration of ferrozine (100 mM; Fig.…”

Iron-Binding E3 Ligase Mediates Iron Response in Plants by Targeting Basic Helix-Loop-Helix Transcription Factors

“…Several reports have indicated the importance of proper loading of metal ions into seeds for successful plant reproduction. The role of YSL (AtYSL1 and AtYSL3) and the oligopeptide transporter (AtOPT3) protein family in iron translocation to developing embryo and into the seed coat is critical for reproductive growth (Le Jean et al, 2005;Stacey et al, 2008;Chu et al, 2010;Mendoza-Cózatl et al, 2014;Zhai et al, 2014). Additionally, the role of Arabidopsis thaliana FERRIC REDICTASE DEFECTIVE3 (AtFRD3) in iron acquisition in reproductive tissues such as pollen grain and embryos suggests a complex mechanism of iron nutrition during embryogenesis (Roschzttardtz et al, 2011b).…”

Influence of Soil Chemistry and Plant Physiology in the Phytoremediation of Cu, Mn, and Zn

“…COPT7 was only found in rice and had relatively high expression levels in leaves; similar responses to OsCOPT5 were observed in both Cu deficiency and overdose environments . Furthermore, the oligopeptide transporter AtOPT3 and its orthologue TcOPT3 seem to participate in the mobilization of Cu (Hu et al, 2012;Stacey et al, 2008).…”

“…In Arabidopsis, AtZIP2 seems to participate in Mn transport into the root vasculature for translocation to the shoot (Milner et al, 2013). The oligopeptide transporter AtOPT3 seems to play an important role in the long-distance transport of Mn (Stacey et al, 2008).…”

“…Moreover, members of the ZIP family are expressed in the vascular bundle, suggesting that they contribute to the distribution of Zn along the plant . AtOPT3 and its orthologue TcOPT3 seem to participate in the long-distance transport of Zn (Hu et al, 2012;Stacey et al, 2008).…”