Abstract
Long-distance transport of nitrate requires xylem loading and unloading, a successive process that determines nitrate distribution and subsequent assimilation efficiency. Here, we report the functional characterization of NRT1.8, a member of the nitrate transporter (NRT1) family in Arabidopsis thaliana. NRT1.8 is upregulated by nitrate. Histochemical analysis using promoter-beta-glucuronidase fusions, as well as in situ hybridization, showed that NRT1.8 is expressed predominantly in xylem parenchyma cells within the vasculature. Transient expression of the NRT1.8:enhanced green fluorescent protein fusion in onion epidermal cells and Arabidopsis protoplasts indicated that NRT1.8 is plasma membrane localized. Electrophysiological and nitrate uptake analyses using Xenopus laevis oocytes showed that NRT1.8 mediates low-affinity nitrate uptake. Functional disruption of NRT1.8 significantly increased the nitrate concentration in xylem sap. These data together suggest that NRT1.8 functions to remove nitrate from xylem vessels. Interestingly, NRT1.8 was the only nitrate assimilatory pathway gene that was strongly upregulated by cadmium (Cd(2+)) stress in roots, and the nrt1.8-1 mutant showed a nitrate-dependent Cd(2+)-sensitive phenotype. Further analyses showed that Cd(2+) stress increases the proportion of nitrate allocated to wild-type roots compared with the nrt1.8-1 mutant. These data suggest that NRT1.8-regulated nitrate distribution plays an important role in Cd(2+) tolerance.
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Claims 10
Claim · model-written summary
Nitrate upregulated NRT1.8.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NRT1.8 is upregulated by nitrate.”
t0“Arabidopsis”
Claim · model-written summary
NRT1.8 expression was predominant in xylem parenchyma cells.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae1 - Organ / stage
- xylem parenchyma cellse0
- Gene
- NRT1.8e0
- Outcome
- expressed predominantlye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NRT1.8 is expressed predominantly in xylem parenchyma cells within the vasculature.”
e1“in Arabidopsis thaliana”
Claim · model-written summary
NRT1.8 was localized to the plasma membrane.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Gene
- NRT1.8e0
- Outcome
- plasma membrane localizede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NRT1.8 is plasma membrane localized.”
e1“in Arabidopsis thaliana”
Claim · model-written summary
NRT1.8 mediated low-affinity nitrate uptake in oocytes.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Gene
- NRT1.8e0
- Outcome
- low-affinity nitrate uptakee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NRT1.8 mediates low-affinity nitrate uptake.”
e1“in Arabidopsis thaliana”
Claim · model-written summary
Disrupting NRT1.8 increased xylem sap nitrate concentration significantly.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- Functional disruption of NRT1.8e0
- Gene
- NRT1.8e0
- Outcome
- nitrate concentration in xylem sape0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Functional disruption of NRT1.8 significantly increased the nitrate concentration in xylem sap.”
e1“in Arabidopsis thaliana”
Claim · model-written summary
NRT1.8 was strongly upregulated by cadmium stress in roots.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Organ / stage
- rootse0
- Treatment
- cadmium (Cd(2+)) stresse0
- Gene
- NRT1.8e0
- Outcome
- NRT1.8e0
- Direction
- upregulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NRT1.8 was the only nitrate assimilatory pathway gene that was strongly upregulated by cadmium (Cd(2+)) stress in roots”
e1“in Arabidopsis thaliana”
Claim · model-written summary
The nrt1.8-1 mutant had a nitrate-dependent cadmium-sensitive phenotype.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Material
- nrt1.8-1 mutante0
- Outcome
- nitrate-dependent Cd(2+)-sensitive phenotypee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the nrt1.8-1 mutant showed a nitrate-dependent Cd(2+)-sensitive phenotype.”
e1“in Arabidopsis thaliana”
Claim · model-written summary
Cadmium stress increased nitrate allocation to wild-type roots relative to nrt1.8-1.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Organ / stage
- rootse0
- Treatment
- Cd(2+) stresse0
- Outcome
- proportion of nitrate allocated to wild-type rootse0
- Direction
- increasese0
- Comparator
- nrt1.8-1 mutante0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Cd(2+) stress increases the proportion of nitrate allocated to wild-type roots compared with the nrt1.8-1 mutant.”
e1“in Arabidopsis thaliana”
Claim · model-written summary
The authors infer that NRT1.8 removes nitrate from xylem vessels.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Gene
- NRT1.8e0
- Outcome
- remove nitrate from xylem vesselse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NRT1.8 functions to remove nitrate from xylem vessels.”
e1“in Arabidopsis thaliana”
Claim · model-written summary
The authors infer an important role for NRT1.8-regulated nitrate distribution in cadmium tolerance.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Gene
- NRT1.8e0
- Outcome
- Cd(2+) tolerancee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NRT1.8-regulated nitrate distribution plays an important role in Cd(2+) tolerance.”
e1“in Arabidopsis thaliana”
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- no effect
- negative
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See all 26 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.