The Arabidopsis AtOPT3 protein functions in metal homeostasis and movement of iron to developing seeds.
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.
Stacey
Minviluz G
MG
Division of Plant Sciences, University of Missouri, Columbia, Missouri 65211, USA.
Patel
Ami
A
McClain
William E
WE
Mathieu
Melanie
M
Remley
Melissa
M
Rogers
Elizabeth E
EE
Gassmann
Walter
W
Blevins
Dale G
DG
Stacey
Gary
G
D000483:Alleles; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology*; D035264:Flowers / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D005816:Genetic Complementation Test; D006706:Homeostasis / Q000502:physiology*; D007501:Iron / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008670:Metals / Q000378:metabolism*; D009154:Mutation; D018515:Plant Leaves / Q000166:cytology / Q000378:metabolism; D036226:Seedlings / Q000378:metabolism; D012639:Seeds / Q000254:growth & development*
D029681:Arabidopsis Proteins; D026901:Membrane Transport Proteins; D008670:Metals; C509148:OPT3 protein, Arabidopsis; D007501:Iron