Abstract
The Arabidopsis thaliana vacuolar Na+/H+ antiporter AtNHX1 is a salt tolerance determinant. Predicted amino acid sequence similarity, protein topology and the presence of functional domains conserved in AtNHX1 and prototypical mammalian NHE Na+/H+ exchangers led to the identification of five additional AtNHX genes (AtNHX2-6). The AtNHX1 and AtNHX2 mRNAs are the most prevalent transcripts among this family of genes in seedling shoots and roots. A lower-abundance AtNHX5 mRNA is present in both shoots and roots, whereas AtNHX3 transcript is expressed predominantly in roots. AtNHX4 and AtNHX6 mRNAs were detected only by RT-PCR. AtNHX1, 2 or 5 suppress, with differential efficacy, the Na+/Li+-sensitive phenotype of a yeast mutant that is deficient in the endosomal/vacuolar Na+/H+ antiporter ScNHX1. Ion accumulation data indicate that these AtNHX proteins function to facilitate Na+ ion compartmentalization and maintain intracellular K+ status. Seedling steady-state mRNA levels of AtNHX1 and AtNHX2 increase similarly after treatment with NaCl, an equi-osmolar concentration of sorbitol, or ABA, whereas AtNHX5 transcript abundance increases only in response to salt treatment. Hyper-osmotic up-regulation of AtNHX1, 2 or 5 expression is not dependent on the SOS pathway that controls ion homeostasis. However, steady-state AtNHX1, 2 and 5 transcript abundance is greater in sos1, sos2 and sos3 plants growing in medium that is not supplemented with sorbitol or NaCl, providing evidence that transcription of these genes is negatively affected by the SOS pathway in the absence of stress. AtNHX1 and AtNHX2 transcripts accumulate in response to ABA but not to NaCl in the aba2-1, mutant indicating that the osmotic responsiveness of these genes is ABA-dependent. An as yet undefined stress signal pathway that is ABA- and SOS-independent apparently controls transcriptional up-regulation of AtNHX5 expression by hyper-saline shock. Similar to AtNHX1, AtNHX2 is localized to the tonoplast of plant cells. Together, these results implicate AtNHX2 and 5, together with AtNHX1, as salt tolerance determinants, and indicate that AtNHX2 has a major function in vacuolar compartmentalization of Na+.
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Claims 19
Claim · model-written summary
Sequence similarity, protein topology and conserved functional domains led to identification of five additional AtNHX genes, AtNHX2-6.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianat0 - Gene
- AtNHX2-6e0
- Outcome
- identification of five additional AtNHX genese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“led to the identification of five additional AtNHX genes (AtNHX2-6)”
t0“Arabidopsis thaliana”
Claim · model-written summary
AtNHX1 and AtNHX2 mRNAs are the most prevalent transcripts of this gene family in seedling shoots and roots.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Organ / stage
- seedling shoots and rootse0
- Gene
- AtNHX1 and AtNHX2e0
- Outcome
- most prevalent transcriptse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The AtNHX1 and AtNHX2 mRNAs are the most prevalent transcripts among this family of genes in seedling shoots and roots”
t0“Arabidopsis thaliana”
Claim · model-written summary
A lower-abundance AtNHX5 mRNA is present in both shoots and roots.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Organ / stage
- shoots and rootse0
- Gene
- AtNHX5e0
- Outcome
- lower-abundance AtNHX5 mRNA is presente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A lower-abundance AtNHX5 mRNA is present in both shoots and roots”
t0“Arabidopsis thaliana”
Claim · model-written summary
AtNHX3 transcript is expressed predominantly in roots.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Organ / stage
- rootse0
- Gene
- AtNHX3e0
- Outcome
- expressed predominantlye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“AtNHX3 transcript is expressed predominantly in roots”
t0“Arabidopsis thaliana”
Claim · model-written summary
AtNHX4 and AtNHX6 mRNAs were detected only by RT-PCR.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Gene
- AtNHX4 and AtNHX6e0
- Outcome
- detected only by RT-PCRe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“AtNHX4 and AtNHX6 mRNAs were detected only by RT-PCR”
t0“Arabidopsis thaliana”
Claim · model-written summary
AtNHX1, 2 or 5 suppressed, with differing efficacy, the Na+/Li+-sensitive phenotype of a yeast mutant lacking the antiporter ScNHX1.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Gene
- AtNHX1, 2 or 5e0
- Outcome
- Na+/Li+-sensitive phenotype of a yeast mutante0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“AtNHX1, 2 or 5 suppress, with differential efficacy, the Na+/Li+-sensitive phenotype of a yeast mutant that is deficient in the endosomal/vacuolar Na+/H+ antiporter ScNHX1”
t0“Arabidopsis thaliana”
Claim · model-written summary
Ion accumulation data indicate that AtNHX proteins facilitate Na+ compartmentalization and maintain intracellular K+ status.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Gene
- AtNHX proteinse0
- Outcome
- Na+ ion compartmentalization and maintain intracellular K+ statuse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Ion accumulation data indicate that these AtNHX proteins function to facilitate Na+ ion compartmentalization and maintain intracellular K+ status”
t0“Arabidopsis thaliana”
Claim · model-written summary
Seedling mRNA levels of AtNHX1 and AtNHX2 increased similarly after NaCl, equi-osmolar sorbitol or ABA treatment.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- NaCl, an equi-osmolar concentration of sorbitol, or ABAe0
- Gene
- AtNHX1 and AtNHX2e0
- Outcome
- steady-state mRNA levelse0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seedling steady-state mRNA levels of AtNHX1 and AtNHX2 increase similarly after treatment with NaCl, an equi-osmolar concentration of sorbitol, or ABA”
t0“Arabidopsis thaliana”
Claim · model-written summary
AtNHX5 transcript abundance increased only in response to salt treatment.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- salt treatmente0
- Gene
- AtNHX5e0
- Outcome
- transcript abundancee0
- Direction
- increasese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“AtNHX5 transcript abundance increases only in response to salt treatment”
t0“Arabidopsis thaliana”
Claim · model-written summary
Hyper-osmotic up-regulation of AtNHX1, 2 or 5 expression does not depend on the SOS pathway.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Gene
- AtNHX1, 2 or 5e0
- Outcome
- Hyper-osmotic up-regulatione0
- Qualifier
- not dependent on the SOS pathwaye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Hyper-osmotic up-regulation of AtNHX1, 2 or 5 expression is not dependent on the SOS pathway that controls ion homeostasis”
t0“Arabidopsis thaliana”
Claim · model-written summary
Steady-state AtNHX1, 2 and 5 transcript abundance was greater in sos1, sos2 and sos3 plants grown without sorbitol or NaCl.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Material
- sos1, sos2 and sos3 plantse0
- Gene
- AtNHX1, 2 and 5e0
- Outcome
- transcript abundancee0
- Direction
- greatere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“steady-state AtNHX1, 2 and 5 transcript abundance is greater in sos1, sos2 and sos3 plants growing in medium that is not supplemented with sorbitol or NaCl”
t0“Arabidopsis thaliana”
Claim · model-written summary
The authors infer that transcription of these genes is negatively affected by the SOS pathway in the absence of stress.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Outcome
- transcription of these genese0
- Qualifier
- negatively affected by the SOS pathway in the absence of stresse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“transcription of these genes is negatively affected by the SOS pathway in the absence of stress”
t0“Arabidopsis thaliana”
Claim · model-written summary
In the aba2-1 mutant, AtNHX1 and AtNHX2 transcripts accumulated in response to ABA.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Material
- aba2-1e0
- Treatment
- ABAe0
- Gene
- AtNHX1 and AtNHX2e0
- Outcome
- transcriptse0
- Direction
- accumulatee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“AtNHX1 and AtNHX2 transcripts accumulate in response to ABA but not to NaCl in the aba2-1, mutant”
t0“Arabidopsis thaliana”
Claim · model-written summary
In the aba2-1 mutant, AtNHX1 and AtNHX2 transcripts did not accumulate in response to NaCl.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Material
- aba2-1e0
- Treatment
- NaCle0
- Gene
- AtNHX1 and AtNHX2e0
- Outcome
- transcriptse0
- Direction
- not to NaCle0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“AtNHX1 and AtNHX2 transcripts accumulate in response to ABA but not to NaCl in the aba2-1, mutant”
t0“Arabidopsis thaliana”
Claim · model-written summary
The authors conclude that osmotic responsiveness of these genes is ABA-dependent.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Compound
- ABAe0
- Outcome
- osmotic responsiveness of these genese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the osmotic responsiveness of these genes is ABA-dependent”
t0“Arabidopsis thaliana”
Claim · model-written summary
An undefined ABA- and SOS-independent stress signal pathway apparently controls transcriptional up-regulation of AtNHX5 by hyper-saline shock.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Treatment
- hyper-saline shocke0
- Gene
- AtNHX5e0
- Outcome
- transcriptional up-regulation of AtNHX5 expressione0
- Qualifier
- ABA- and SOS-independente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“An as yet undefined stress signal pathway that is ABA- and SOS-independent apparently controls transcriptional up-regulation of AtNHX5 expression by hyper-saline shock”
t0“Arabidopsis thaliana”
Claim · model-written summary
AtNHX2 is localized to the tonoplast of plant cells, like AtNHX1.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Organ / stage
- tonoplaste0
- Gene
- AtNHX2e0
- Outcome
- localized to the tonoplaste0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Similar to AtNHX1, AtNHX2 is localized to the tonoplast of plant cells”
t0“Arabidopsis thaliana”
Claim · model-written summary
The authors conclude that AtNHX2 and 5, together with AtNHX1, are salt tolerance determinants.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Gene
- AtNHX2 and 5, together with AtNHX1e0
- Outcome
- salt tolerance determinantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“these results implicate AtNHX2 and 5, together with AtNHX1, as salt tolerance determinants”
t0“Arabidopsis thaliana”
Claim · model-written summary
The authors conclude that AtNHX2 has a major function in vacuolar compartmentalization of Na+.
- Taxon
- Arabidopsis thalianaArabidopsis thalianat0
- Gene
- AtNHX2e0
- Outcome
- vacuolar compartmentalization of Na+e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“AtNHX2 has a major function in vacuolar compartmentalization of Na+”
t0“Arabidopsis thaliana”
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