High impact information on NHX1

• This salinity tolerance was correlated with higher-than-normal levels of AtNHX1 transcripts, protein, and vacuolar Na+/H+ (sodium/proton) antiport activity [1].
• Taken together, the presence of a vacuolar calmodulin-like protein acting on the vacuolar-localized AtNHX1 C terminus in a Ca(2+)- pH-dependent manner suggests the presence of signaling entities acting within the vacuole [2].
• Arabidopsis thaliana Na(+)/H(+) exchanger 1 (AtNHX1), the most abundant vacuolar Na(+)/H(+) antiporter in A. thaliana, has important roles affecting the maintenance of cellular pH, ion homeostasis, and the regulation of protein trafficking [2].
• The binding of AtCaM15 to AtNHX1 was Ca(2+)- and pH-dependent and decreased with increasing pH values [2].
• Our results also indicate that, whereas the N terminus of AtNHX1 is facing the cytosol, almost the entire C-terminal hydrophilic region resides in the vacuolar lumen [3].

Biological context of NHX1

• Fusion of the SP to At-NHX1 resulted in an increase in the magnitude of Na(+)/H(+) exchange, indicating a role for the SP in protein targeting or regulation [4].
• Hyper-osmotic up-regulation of AtNHX1, 2 or 5 expression is not dependent on the SOS pathway that controls ion homeostasis [5].
• 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 [5].
• 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) [5].
• The majority of exons for Arabidopsis, rice and wheat orthologues of NHX1, NHX5 and SOS1 were conserved except for those at the amino and carboxy terminal ends [6].

Anatomical context of NHX1

• Experiments on vacuolar vesicles isolated from yeast expressing At-NHX1 or NHX1 provided direct evidence for pH-gradient-energized Na(+) accumulation into the vacuole [4].
• To study the ion selectivity of the AtNHX1 protein, we have purified a histidine-tagged version of the protein from yeast microsomes by Ni(2+) affinity chromatography, reconstituted the protein into lipid vesicles, and measured cation-dependent H(+) exchange with the fluorescent pH indicator pyranine [7].
• Strong induction of GUS activity in root hair cells was observed, which suggests a role of AtNHX1 in storing Na+ in the enlarged vacuoles in root hair cells [8].
• The membrane topology of the Arabidopsis thaliana Na(+)/H(+) exchanger isoform 1 (AtNHX1) was investigated by examining the topogenic function of transmembrane (TM) segments using a cell-free system [9].

Associations of NHX1 with chemical compounds

• 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 [5].
• The vacuolar localization of the C terminus of the AtNHX1, taken together with the regulation of the antiporter selectivity by its C terminus, demonstrates the existence of luminal vacuolar regulatory mechanisms of the antiporter activity [3].
• Transgenic Brassica napus plants overexpressing AtNHX1, a vacuolar Na(+)/H(+) antiport from Arabidopsis thaliana, were able to grow, flower, and produce seeds in the presence of 200 mM sodium chloride [10].
• Regulation of expression of the vacuolar Na+/H+ antiporter gene AtNHX1 by salt stress and abscisic acid [8].
• When yeast cells were challenged with lithium, a tracer for sodium, the main effect of the mutations in AtNHX1 was a reduction in the amount of compartmentalized lithium [11].

Other interactions of NHX1

• Similar to AtNHX1, AtNHX2 is localized to the tonoplast of plant cells [5].
• However, additional exons were identified in the predicted NHX1 and SOS1 genes of rice and wheat, as compared with Arabidopsis, indicating gene rearrangement events during evolution from a common ancestor [6].
• We used the T-DNA insertional mutant of AtNHX1 (nhx1 plants) and Affymetrix ATH1 DNA arrays to assess differences in transcriptional profiles and further characterize the roles of a vacuolar cation/proton antiporter [12].
• We cloned wheat orthologs of the Arabidopsis genes AtNHX1 and AVP1 using the polymerase chain reaction and primers corresponding to conserved regions of the respective coding sequences, and a wheat cDNA library as template [13].

Analytical, diagnostic and therapeutic context of NHX1

• DNA array analyses of Arabidopsis thaliana lacking a vacuolar Na+/H+ antiporter: impact of AtNHX1 on gene expression [12].

References