The Na+ transporter AtHKT1;1 controls retrieval of Na+ from the xylem in Arabidopsis

Davenport, Romola; Muñoz‐Mayor, Alicia; Jha, Deepa; Essah, Pauline Adobea; Rus, Ana; Tester, Mark

doi:10.1111/j.1365-3040.2007.01637.x

Cited by 427 publications

(403 citation statements)

References 31 publications

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“…A similar mineral distribution mechanism has been reported for the xylem parenchyma cell-localized HKT1 (high-affinity K + transporter 1) and SKC1 (Shoot K + content 1) sodium transporters (Maser et al, 2002;Gong et al, 2004;Ren et al, 2005;Sunarpi et al, 2005). Disruption of these Na + transporters results in overaccumulation of Na + in xylem sap and shoots (Maser et al, 2002;Gong et al, 2004;Ren et al, 2005;Sunarpi et al, 2005;Horie et al, 2006;Davenport et al, 2007;Moller et al, 2009). Here, we observed that in the mutant nrt1.8-1, a greater proportion of nitrate accumulated in shoots under cadmium stress ( Figure 8B).…”

Section: Nrt18 Is An Essential Component Regulating Nitrate Distribusupporting

confidence: 54%

“…It is worth noting that NRT1.8 expression is also induced in shoots under prolonged Cd 2+ treatment ( Figures 6B and 6C), which may contribute to recycling nitrate from shoots to roots. This would partially contribute to increasing the root/shoot nitrate ratio ( Figure 8B), possibly via a similar mechanism proposed for HKT1/SKC1, in which Na + is unloaded from xylem vessels to xylem parenchyma cells, then transported into the phloem and recycled to roots (Maser et al, 2002;Gong et al, 2004;Ren et al, 2005;Sunarpi et al, 2005;Horie et al, 2006;Davenport et al, 2007).…”

Section: Nrt18 Is An Essential Component Regulating Nitrate Distribumentioning

confidence: 99%

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TheArabidopsisNitrate Transporter NRT1.8 Functions in Nitrate Removal from the Xylem Sap and Mediates Cadmium Tolerance

et al. 2010

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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-β-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 (Cd2+) stress in roots, and the nrt1.8-1 mutant showed a nitrate-dependent Cd2+-sensitive phenotype. Further analyses showed that Cd2+ 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 Cd2+ tolerance.

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Section: Nrt18 Is An Essential Component Regulating Nitrate Distribusupporting

confidence: 54%

Section: Nrt18 Is An Essential Component Regulating Nitrate Distribumentioning

confidence: 99%

TheArabidopsisNitrate Transporter NRT1.8 Functions in Nitrate Removal from the Xylem Sap and Mediates Cadmium Tolerance

et al. 2010

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“…Numerous studies have been conducted on the genetic and molecular mechanisms underlying salt tolerance in plants 18,19,30,31 , and have included genomic analyses of the extremophiles Thellungiella parvula 16 and T. salsuginea 43 . However, our current understanding of these aspects of salt tolerance remains limited, especially for woody plants 22,27 .…”

Section: Discussionmentioning

confidence: 99%

Genomic insights into salt adaptation in a desert poplar

et al. 2013

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Despite the high economic and ecological importance of forests, our knowledge of the genomic evolution of trees under salt stress remains very limited. Here we report the genome sequence of the desert poplar, Populus euphratica, which exhibits high tolerance to salt stress. Its genome is very similar and collinear to that of the closely related mesophytic congener, P. trichocarpa. However, we find that several gene families likely to be involved in tolerance to salt stress contain significantly more gene copies within the P. euphratica lineage. Furthermore, genes showing evidence of positive selection are significantly enriched in functional categories related to salt stress. Some of these genes, and others within the same categories, are significantly upregulated under salt stress relative to their expression in another salt-sensitive poplar. Our results provide an important background for understanding tree adaptation to salt stress and facilitating the genetic improvement of cultivated poplars for saline soils.

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“…In theory, the amount of K + and Na + in leaves is determined by several distinct processes: Na + /K + uptake from the soil, longdistance transport to the shoot via the xylem, and redistribution through the phloem. The function of xylem-localized HKT1 in limiting Na + translocation to the shoot has been established (Mä ser et al, 2002;Sunarpi et al, 2005;Rus et al, 2006;Davenport et al, 2007). In hkt1 mutants, xylem Na + concentration is higher than in the wild type (Sunarpi et al, 2005).…”

Section: Phloem and Na + /K + Homeostasismentioning

confidence: 99%

Arabidopsis NPCC6/NaKR1 Is a Phloem Mobile Metal Binding Protein Necessary for Phloem Function and Root Meristem Maintenance

et al. 2010

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SODIUM POTASSIUM ROOT DEFECTIVE1 (NaKR1; previously called NPCC6) encodes a soluble metal binding protein that is specifically expressed in companion cells of the phloem. The nakr1-1 mutant phenotype includes high Na + , K + , Rb + , and starch accumulation in leaves, short roots, late flowering, and decreased long-distance transport of sucrose. Using traditional and DNA microarray-based deletion mapping, a 7-bp deletion was found in an exon of NaKR1 that introduced a premature stop codon. The mutant phenotypes were complemented by transformation with the native gene or NaKR1-GFP (green fluorescent protein) and NaKR1-b-glucuronidase fusions driven by the native promoter. NAKR1-GFP was mobile in the phloem; it moved from companion cells into sieve elements and into a previously undiscovered symplasmic domain in the root meristem. Grafting experiments revealed that the high Na + accumulation was due mainly to loss of NaKR1 function in the leaves. This supports a role for the phloem in recirculating Na + to the roots to limit Na + accumulation in leaves. The onset of root phenotypes coincided with NaKR1 expression after germination. The nakr1-1 short root phenotype was due primarily to a decreased cell division rate in the root meristem, indicating a role in root meristem maintenance for NaKR1 expression in the phloem.

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The Na⁺ transporter AtHKT1;1 controls retrieval of Na⁺ from the xylem in Arabidopsis

Cited by 427 publications

References 31 publications

TheArabidopsisNitrate Transporter NRT1.8 Functions in Nitrate Removal from the Xylem Sap and Mediates Cadmium Tolerance

TheArabidopsisNitrate Transporter NRT1.8 Functions in Nitrate Removal from the Xylem Sap and Mediates Cadmium Tolerance

Genomic insights into salt adaptation in a desert poplar

Arabidopsis NPCC6/NaKR1 Is a Phloem Mobile Metal Binding Protein Necessary for Phloem Function and Root Meristem Maintenance

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