Abstract
Metal homeostasis is critical for the survival of living organisms, and metal transporters play central roles in maintaining metal homeostasis in the living cells. We have investigated the function of a metal transporter of the NRAMP family, AtNRAMP3, in Arabidopsis thaliana. A previous study showed that AtNRAMP3 expression is upregulated by iron (Fe) starvation and that AtNRAMP3 protein can transport Fe. In the present study, we used AtNRAMP3 promoter beta-glucoronidase (GUS) fusions to show that AtNRAMP3 is expressed in the vascular bundles of roots, stems, and leaves under Fe-sufficient conditions. This suggests a function in long-distance metal transport within the plant. Under Fe-starvation conditions, the GUS activity driven by the AtNRAMP3 promoter is upregulated without any change in the expression pattern. We analyze the impact of AtNRAMP3 disruption and overexpression on metal accumulation in plants. Under Fe-sufficient conditions, AtNRAMP3 overexpression or disruption does not lead to any change in the plant metal content. Upon Fe starvation, AtNRAMP3 disruption leads to increased accumulation of manganese (Mn) and zinc (Zn) in the roots, whereas AtNRAMP3 overexpression downregulates Mn accumulation. In addition, overexpression of AtNRAMP3 downregulates the expression of the primary Fe uptake transporter IRT1 and of the root ferric chelate reductase FRO2. Expression of AtNRAMP3::GFP fusion protein in onion cells or Arabidopsis protoplasts shows that AtNRAMP3 protein localizes to the vacuolar membrane. To account for the results presented, we propose that AtNRAMP3 influences metal accumulation and IRT1 and FRO2 gene expression by mobilizing vacuolar metal pools to the cytosol.
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Claims 11
Claim · model-written summary
AtNRAMP3 was expressed in vascular bundles of roots, stems, and leaves under sufficient iron.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae1 - Organ / stage
- roots, stems, and leavese0
- Gene
- AtNRAMP3e0
- Outcome
- expressed in the vascular bundlese0
- Qualifier
- Fe-sufficient conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“AtNRAMP3 is expressed in the vascular bundles of roots, stems, and leaves under Fe-sufficient conditions.”
e1“Arabidopsis thaliana”
Claim · model-written summary
Iron starvation upregulated AtNRAMP3 promoter activity without altering its expression pattern.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- Fe-starvation conditionse0
- Gene
- AtNRAMP3e0
- Outcome
- GUS activitye0
- Direction
- upregulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under Fe-starvation conditions, the GUS activity driven by the AtNRAMP3 promoter is upregulated without any change in the expression pattern.”
e1“Arabidopsis thaliana”
Claim · model-written summary
AtNRAMP3 overexpression did not change plant metal content under iron sufficient conditions.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- AtNRAMP3 overexpressione0
- Gene
- AtNRAMP3e0
- Outcome
- plant metal contente0
- Direction
- does not lead to any changee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under Fe-sufficient conditions, AtNRAMP3 overexpression or disruption does not lead to any change in the plant metal content.”
e1“Arabidopsis thaliana”
Claim · model-written summary
AtNRAMP3 disruption did not change plant metal content under iron sufficient conditions.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- disruptione0
- Gene
- AtNRAMP3e0
- Outcome
- plant metal contente0
- Direction
- does not lead to any changee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Under Fe-sufficient conditions, AtNRAMP3 overexpression or disruption does not lead to any change in the plant metal content.”
e1“Arabidopsis thaliana”
Claim · model-written summary
Under iron starvation, AtNRAMP3 disruption increased manganese accumulation in roots.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Organ / stage
- rootse0
- Treatment
- AtNRAMP3 disruptione0
- Gene
- AtNRAMP3e0
- Outcome
- accumulation of manganese (Mn)e0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Upon Fe starvation, AtNRAMP3 disruption leads to increased accumulation of manganese (Mn) and zinc (Zn) in the roots, whereas AtNRAMP3 overexpression downregulates Mn accumulation.”
e1“Arabidopsis thaliana”
Claim · model-written summary
Under iron starvation, AtNRAMP3 disruption increased zinc accumulation in roots.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Organ / stage
- rootse0
- Treatment
- AtNRAMP3 disruptione0
- Gene
- AtNRAMP3e0
- Outcome
- zinc (Zn)e0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Upon Fe starvation, AtNRAMP3 disruption leads to increased accumulation of manganese (Mn) and zinc (Zn) in the roots, whereas AtNRAMP3 overexpression downregulates Mn accumulation.”
e1“Arabidopsis thaliana”
Claim · model-written summary
AtNRAMP3 overexpression downregulated manganese accumulation under iron starvation.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- AtNRAMP3 overexpressione0
- Gene
- AtNRAMP3e0
- Outcome
- Mn accumulatione0
- Direction
- downregulatese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Upon Fe starvation, AtNRAMP3 disruption leads to increased accumulation of manganese (Mn) and zinc (Zn) in the roots, whereas AtNRAMP3 overexpression downregulates Mn accumulation.”
e1“Arabidopsis thaliana”
Claim · model-written summary
AtNRAMP3 overexpression downregulated IRT1 expression.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- overexpression of AtNRAMP3e0
- Gene
- IRT1e0
- Outcome
- expression of the primary Fe uptake transporter IRT1e0
- Direction
- downregulatese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“overexpression of AtNRAMP3 downregulates the expression of the primary Fe uptake transporter IRT1 and of the root ferric chelate reductase FRO2.”
e1“Arabidopsis thaliana”
Claim · model-written summary
AtNRAMP3 overexpression downregulated FRO2 expression.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- overexpression of AtNRAMP3e0
- Gene
- FRO2e0
- Outcome
- root ferric chelate reductase FRO2e0
- Direction
- downregulatese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“overexpression of AtNRAMP3 downregulates the expression of the primary Fe uptake transporter IRT1 and of the root ferric chelate reductase FRO2.”
e1“Arabidopsis thaliana”
Claim · model-written summary
AtNRAMP3 protein localized to the vacuolar membrane.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Organ / stage
- vacuolar membranee0
- Gene
- AtNRAMP3e0
- Outcome
- localizes to the vacuolar membranee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“AtNRAMP3 protein localizes to the vacuolar membrane.”
e1“Arabidopsis thaliana”
Claim · model-written summary
The authors propose AtNRAMP3 mobilizes vacuolar metal pools to the cytosol and thereby influences metal accumulation and IRT1/FRO2 expression.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Gene
- AtNRAMP3e0
- Outcome
- metal accumulation and IRT1 and FRO2 gene expressione0
- Qualifier
- mobilizing vacuolar metal pools to the cytosole0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“AtNRAMP3 influences metal accumulation and IRT1 and FRO2 gene expression by mobilizing vacuolar metal pools to the cytosol.”
e1“Arabidopsis thaliana”
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