Altered shoot/root Na+ distribution and bifurcating salt sensitivity in Arabidopsis by genetic disruption of the Na+ transporter AtHKT1

Mäser, Pascal; Eckelman, Brendan P.; Vaidyanathan, Rama; Horie, Tomoaki; Fairbairn, David J.; Kubo, Masahiro; Yamagami, Mutsumi; Yamaguchi, Katsushi; Nishimura, Mikio; Uozumi, Nobuyuki; Robertson, Whitney R.; Sussman, Michael R.; Schroeder, Julian I.

doi:10.1016/s0014-5793(02)03488-9

Cited by 374 publications

(373 citation statements)

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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%

“…Based on the phenotype of Arabidopsis thaliana sodium overaccumulation in shoot2 (sas2 allele of HKT1) mutants, Na + transporter HKT1 was proposed to function in the phloem (Berthomieu et al, 2003). However, the current consensus is that HKT1 mainly functions to remove Na + from the xylem, thus limiting Na + accumulation in leaves (Mä ser et al, 2002;Sunarpi et al, 2005;Rus et al, 2006). The extent and mechanism of Na + translocation in the phloem remains unknown and has been identified as a current research topic that is important for understanding Na + tolerance (Munns and Tester, 2008).…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Phloem and Na + /K + Homeostasismentioning

confidence: 99%

Section: Introductionmentioning

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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“…sas2-1 mutation impaired AtHKT1 and thus its Na + transport activity in Xenopus oocytes (83). T-DNA mutation in the AtHKT1 gene has resulted in higher shoot Na + content and lower root Na + content than that in the wild type (84). Moreover AtHKT1 does not show significant K + transport activity in Xenopus oocytes.…”

Section: Sodium Transport From Shoots To Rootsmentioning

confidence: 99%

Salt Stress Signaling and Mechanisms of Plant Salt Tolerance

Chinnusamy

Zhu

Genetic Engineering: Principles and Methods

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INTRODUCTIONSoil salinity of agricultural land has led to the breakdown of ancient civilizations.Even today it threatens agricultural productivity in 77 mha of agricultural land, of which 45 mha (20% of irrigated area) is irrigated and 32 mha (2.1% of dry land) is unirrigated (1). Salinization is further spreading in irrigated land because of improper management of irrigation and drainage. Rain, cyclones and wind also add NaCl into the coastal agricultural land. Soil salinity often leads to the development of other problems in soils such as soil sodicity and alkalinity. Soil sodicity is the result of the binding of Na + to the negatively charged clay particles, which leads to clay swelling and dispersal. Hydrolysis of the Na-clay complex results in soil alkalinity. Thus, soil salinity is a major factor limiting sustainable agriculture.The USDA salinity laboratory defines saline soil as having electrical conductivity of the saturated paste extract (EC e ) of 4 dS m -1 (1 dS m -1 is approximately equal to 10 mM NaCl) or more. High concentrations of soluble salts such as chlorides of sodium, calcium and magnesium contribute to the high electrical conductivity of saline soils.NaCl contributes to most of the soluble salts in saline soil.The development of salinity-tolerant crops is the need of the hour to sustain agricultural production. Conventional breeding programs aimed at improving crop tolerance to salinity have limited success because of the complexity of the trait (2). Slow progress in breeding for salt-tolerant crops can be attributed to the poor understanding of the molecular mechanisms of salt tolerance. Understanding the molecular basis of plant salt tolerance will also help improve drought and extreme-temperature-stress tolerance, since osmotic and oxidative stresses are common to these abiotic stresses. The salt-2 tolerant mechanisms of plants can be broadly described as ion homeostasis, osmotic homeostasis, stress damage control and repair, and growth regulation (3). This chapter reviews recent progress in understanding salt-stress signaling and breeding/genetic engineering for salt -tolerant crops. EFFECT OF SALINITY ON PLANT DEVELOPMENTSalinity affects almost all aspects of plant development, including germination, vegetative growth and reproductive development. Soil salinity imposes ion toxicity, osmotic stress, nutrient (N, Ca, K, P, Fe, Zn) deficiency and oxidative stress on plants.Salinity also indirectly limits plant productivity through its adverse effects on the growth of beneficial and symbiotic microbes. High salt concentrations in soil impose osmotic stress and thus limit water uptake from soil. Sodium accumulation in cell walls can rapidly lead to osmotic stress and cell death (1). Ion toxicity is the result of replacement of K + by Na + in biochemical reactions, and Na + and Cl --induced conformational changes in proteins. For several enzymes, K + acts as cofactor and cannot be substituted by Na + .High K + concentration is also required for binding tRNA to ribosomes and thus protein synt...

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“…In our research into salinity stress of plants, we have identified a sodium cation transporter family in plants called HKT transporters and using the plant Arabidopsis thaliana showed that the AtHKT1 transporter plays a key role in protecting plant leaves from sodium over-accumulation and salt stress [2]. We found that AtHKT1 protects leaves from sodium accumulation by removing sodium from the xylem sap [3,4].…”

Section: What Is the Main Focus Of Your Studies?mentioning

confidence: 99%

“…We and colleagues are pursuing research to identify the transporters for the vacuolar heavy metal chelating and detoxifying peptides called phytochelatins. These transporters have been sought for some 15 years and are key mechanisms that plants use to withstand toxic heavy metals.In our research into salinity stress of plants, we have identified a sodium cation transporter family in plants called HKT transporters and using the plant Arabidopsis thaliana showed that the AtHKT1 transporter plays a key role in protecting plant leaves from sodium over-accumulation and salt stress [2]. We found that AtHKT1 protects leaves from sodium accumulation by removing sodium from the xylem sap [3,4].…”

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confidence: 99%

Spotlight on… Julian Schroeder

2010

FEBS Letters

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Plant Biology is one of the most successful and well-established fields in FEBS Letters. The high quality of our plant studies is safeguarded by experienced Editors, who are top scientists in the field. Among these, Julian Schroeder is a Distinguished Professor and holder of an endowed chair in the Division of Biological Sciences at the University of California, San Diego. With a charismatic and fair personality, he is an avid supporter of young scientists and has an impressive collection of awards and publications. Among other breakthroughs, his research pioneered the characterization of diverse plant specific ion channel classes and his research led to the model for how these ion channels work together in guard cells to control stomatal movements in plants. Prof I have always liked to read broadly about life sciences and other disciplines. In addition, I like FEBS Letters being a European journal, as I have a strong connection to Europe due to my family origins. I like the culture of FEBS Letters, and the fact that sometimes it captures really exciting findings that authors wanted to get rapidly published, or that didn't make it into one of the top journals. What is the main focus of your studies?We are interested in plant cell signal transduction, particularly in the context of environmental stresses, such as drought, salinity, and also increased CO 2 in the atmosphere. Stomatal pores on the epidermis of the leaves are relevant for adaptation to these changes. Upon drought stress, plants synthesize a hormone called abscisic acid (ABA) to induce the closure of stomata, which slows down water loss and desiccation. Each stomatal pore is surrounded by two guard cells, which mediate the pore closure via ion channels that are regulated by different environmental signals. Guard cells are an excellent working model, and we have used them to identify the functions of plant ion channels and are using them to dissect new signalling cascades and mechanisms in response to environmental signals and stress. In a recent publication, we found that the carbonic anhydrases b-CA1 and b-CA4 function early in the pathway that regulates stomatal closing in response to increasing atmospheric and leaf CO 2 levels. The continuing rise in atmospheric CO 2 causes a narrowing of stomatal pores in plants. These proteins bind CO 2 , catalyze CO 2 conversion and transfer the signal via a presently unknown pathway to anion channels that are drivers of stomatal closing [1].There are also other sources of stress that can come from the soil, such as the presence of toxic heavy metals or high salinity. We are trying to identify genes that mediate heavy metal uptake and salt tolerance. In this direction, three labs, including ours, independently discovered a gene family that encodes proteins that play a major role in heavy metal detoxification in plants. We and colleagues are pursuing research to identify the transporters for the vacuolar heavy metal chelating and detoxifying peptides called phytochelatins. These transporters have been sought for...

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Altered shoot/root Na⁺ distribution and bifurcating salt sensitivity in Arabidopsis by genetic disruption of the Na⁺ transporter AtHKT1

Cited by 374 publications

References 32 publications

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

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

Salt Stress Signaling and Mechanisms of Plant Salt Tolerance

Spotlight on… Julian Schroeder

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