<i>sas1</i>, an Arabidopsis Mutant Overaccumulating Sodium in the Shoot, Shows Deficiency in the Control of the Root Radial Transport of Sodium

Nublat, Aurélie; Desplans, Jérôme; Casse, Francine; Berthomieu, Pierre

doi:10.1105/tpc.13.1.125

Cited by 58 publications

(26 citation statements)

References 45 publications

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“…Plants that are mutated in the sas1 gene, which causes overaccumulation of sodium in the shoots, exhibit a severely repressed growth phenotype (Nublat et al, 2001). However, although the AtRabG3e transgenic plants showed increased sodium content in the shoots (Fig.…”

Section: The Effects Of Atrab7 (Atrabg3e) On Salt Localizationmentioning

confidence: 99%

Induction of Salt and Osmotic Stress Tolerance by Overexpression of an Intracellular Vesicle Trafficking Protein AtRab7 (AtRabG3e)

et al. 2004

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Adaptation to stress requires removal of existing molecules from various cellular compartments and replacing them with new ones. The transport of materials to and from the specific compartments involved in the recycling and deposition of macromolecules is carried out by an intracellular vesicle trafficking system. Here, we report the isolation of a vesicle trafficking-regulating gene, AtRabG3e (formerly AtRab7), from Arabidopsis. The gene was induced during programmed cell death after treatment of intact leaves with superoxide and salicylic acid or infection with necrogenic pathogens. Transgenic plants that expressed the AtRabG3e gene under the constitutive 35S promoter from cauliflower mosaic virus exhibited accelerated endocytosis in roots, leaves, and protoplasts. The transgenic plants accumulated sodium in the vacuoles and had higher amounts of sodium in the shoots. The transgenic plants also showed increased tolerance to salt and osmotic stresses and reduced accumulation of reactive oxygen species during salt stress. These results imply that vesicle trafficking plays an important role in plant adaptation to stress, beyond the housekeeping function in intracellular vesicle trafficking.Plants are constantly exposed to changes in the environment that results in development of stress, compelling them to adjust to the new conditions. The perturbations in the surrounding environmental conditions often cause an oxidative stress. A mild oxidative stress usually induces antioxidant defenses, whereas a severe stress causes rapid necrosis. Intermediate levels of reactive oxygen species (ROS) often trigger a programmed cell death (PCD) cascade, which eliminates the compromised cells (Datt et al., 2003). The induction and execution of PCD are tightly controlled processes and can be modulated by signaling molecules, such as jasmonic acid, salicylic acid (SA), and ethylene (Lam et al., 1999).Little information exists on the role of intracellular vesicle trafficking in resistance to environmental stresses. Endocytosis has been viewed traditionally as a constitutive housekeeping function in both animal and plant cells. Recently, however, a syntaxinrelated protein, NtSyr1, which is one of the central components of the vesicle trafficking machinery in eukaryotes, was implicated in abscisic acid-mediated responses in tobacco (Nicotiana tabacum; Leyman et al., 1999). In yeast (Saccharomyces cerevisiae), we found that vesicle trafficking between cytosol and the plasma membrane was inhibited by oxidative stress. Overexpression of an Arabidopsis synaptobrevin homolog partially restored the traffic and provided tolerance to lethal concentrations of hydrogen peroxide (H 2 O 2 ; Levine et al., 2001). A link between regulation of endocytosis by GDI:Rab5 complex and the p38-dependent stress response was described recently in animal cells (Cavalli et al., 2001).We have shown previously that a low concentration of superoxide in the presence of nontoxic concentration of SA-induced PCD in intact Arabidopsis leaves (Mazel and Levine, 2001)...

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Section: The Effects Of Atrab7 (Atrabg3e) On Salt Localizationmentioning

confidence: 99%

Induction of Salt and Osmotic Stress Tolerance by Overexpression of an Intracellular Vesicle Trafficking Protein AtRab7 (AtRabG3e)

et al. 2004

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“…To examine more directly the role of SOS1 in controlling Na ϩ transport from the root to the shoot, we measured the Na ϩ content in the xylem sap from sos1 mutant and wild-type plants. The method of xylem sap collection was as described by Gaymard et al (1998) and Nublat et al (2001). The Na ϩ concentration in the xylem sap of both sos1 mutant and wild-type plants increased substantially over time in 100 mM NaCl, but the Na ϩ content was always higher for sos1 (Figure 8).…”

Section: Role Of Sos1 In Controlling Long-distance Na ؉ Transportmentioning

confidence: 99%

The Putative Plasma Membrane Na⁺/H⁺ Antiporter SOS1 Controls Long-Distance Na⁺ Transport in Plants

et al. 2002

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The salt tolerance locus SOS1 from Arabidopsis has been shown to encode a putative plasma membrane Na ؉ /H ؉ antiporter. In this study, we examined the tissue-specific pattern of gene expression as well as the Na ؉ transport activity and subcellular localization of SOS1. When expressed in a yeast mutant deficient in endogenous Na ϩ transporters, SOS1 was able to reduce Na ؉ accumulation and improve salt tolerance of the mutant cells. Confocal imaging of a SOS1-green fluorescent protein fusion protein in transgenic Arabidopsis plants indicated that SOS1 is localized in the plasma membrane. Analysis of SOS1 promoter-␤ -glucuronidase transgenic Arabidopsis plants revealed preferential expression of SOS1 in epidermal cells at the root tip and in parenchyma cells at the xylem/symplast boundary of roots, stems, and leaves. Under mild salt stress (25 mM NaCl), sos1 mutant shoot accumulated less Na ؉ than did the wildtype shoot. However, under severe salt stress (100 mM NaCl), sos1 mutant plants accumulated more Na ؉ than did the wild type. There also was greater Na ؉ content in the xylem sap of sos1 mutant plants exposed to 100 mM NaCl. These results suggest that SOS1 is critical for controlling long-distance Na ؉ transport from root to shoot. We present a model in which SOS1 functions in retrieving Na ؉ from the xylem stream under severe salt stress, whereas under mild salt stress it may function in loading Na ؉ into the xylem. INTRODUCTIONPlant growth depends on mineral nutrients absorbed from the soil by roots. Although Na ϩ is a major cation present in soil solutions, Na ϩ is not considered an essential mineral for most plants. In saline soils, high concentrations of Na ϩ disrupt K ϩ and other mineral nutrition, create hyperosmotic stress, and cause secondary problems such as oxidative stress (Zhu, 2001). These adverse effects contribute to plant growth inhibition and even plant death.Many cytosolic enzymes are activated by K ϩ and inhibited by Na ϩ (Flowers et al., 1977). Three mechanisms are available to plant cells to prevent excessive accumulation of Na ϩ in the cytosol (Niu et al., 1995;Blumwald et al., 2000; Zhu, 2001). First, Na ϩ entry to plant cells may be restricted by selective ion uptake. Nonselective cation channels have been proposed to mediate substantial Na ϩ entry into plant roots, but genes encoding these channels have yet to be identified (Amtmann and Sanders, 1999; Tyerman and Skerrett, 1999). The cloned transporters HKT1 and LCT1 have Na ϩ permeability when expressed in yeast or oocytes, suggesting that they also may be candidate Na ϩ influx transporters (Rubio et al., 1995;Schachtman et al., 1997). Recently, studies in yeast demonstrated that the magnitude of the membrane potential affects net Na ϩ influx into cells. Mutations in the yeast PMP3 gene lead to membrane hyperpolarization, increased Na ϩ influx, and salt sensitivity (Navarre and Goffeau, 2000).Second, internalized Na ϩ can be stored in vacuoles. Vacuolar compartmentation is an efficient strategy for plant cells to deal with salt s...

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“…In preliminary experiments (data not presented), we found that plants whose roots were treated with 10 mM TEA 1 and 3 mM Cs 1 wilted, an effect not seen with other inhibitors that we used. So, in the experiments that we report involving TEA 1 and Cs 1 treatments, we reduced transpiration by keeping the plants in a chamber with 100% relative humidity (compare with Nublat et al, 2001;Shi et al, 2002). In these experiments, we added the inhibitors at the same time as the salt; S. maritima is a saltaccumulating plant and has a strong capacity for Na 1 accumulation, so it adjusts very rapidly to increase in external Na 1 concentration (Clipson, 1987).…”

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confidence: 99%

“…Each treatment, which lasted between 48 and 144 h (see figure and table legends or the text for details) under the conditions described above, had eight replicates with three plants per beaker. Where TEA-Cl, CsCl, or BaCl 2 was included in the treatment, the relative humidity of the growth chamber (Sanyo MLR-350HT growth cabinet; Sanyo Electrical and Biomedical; photosynthetically active radiation of 200 mmol m 22 s 21 ) was maintained at 100% to minimize the effect of transpiration on Na 1 accumulation (compare with Nublat et al, 2001;Shi et al, 2002), since these three inhibitors caused plants to wilt. For treatments with BaCl 2 , MgCl 2 (0.5 mM) replaced MgSO 4 (0.5 mM) in the Hoagland nutrient solution.…”

Section: Plant Materials and Treatmentsmentioning

confidence: 99%

Low-Affinity Na+ Uptake in the HalophyteSuaeda maritima

2007

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Na+ uptake by plant roots has largely been explored using species that accumulate little Na+ into their shoots. By way of contrast, the halophyte Suaeda maritima accumulates, without injury, concentrations of the order of 400 mm NaCl in its leaves. Here we report that cAMP and Ca2+ (blockers of nonselective cation channels) and Li+ (a competitive inhibitor of Na+ uptake) did not have any significant effect on the uptake of Na+ by the halophyte S. maritima when plants were in 25 or 150 mm NaCl (150 mm NaCl is near optimal for growth). However, the inhibitors of K+ channels, TEA+ (10 mm), Cs+ (3 mm), and Ba2+ (5 mm), significantly reduced the net uptake of Na+ from 150 mm NaCl over 48 h, by 54%, 24%, and 29%, respectively. TEA+ (10 mm), Cs+ (3 mm), and Ba2+ (1 mm) also significantly reduced 22Na+ influx (measured over 2 min in 150 mm external NaCl) by 47%, 30%, and 31%, respectively. In contrast to the situation in 150 mm NaCl, neither TEA+ (1–10 mm) nor Cs+ (0.5–10 mm) significantly reduced net Na+ uptake or 22Na+ influx in 25 mm NaCl. Ba2+ (at 5 mm) did significantly decrease net Na+ uptake (by 47%) and 22Na+ influx (by 36% with 1 mm Ba2+) in 25 mm NaCl. K+ (10 or 50 mm) had no effect on 22Na+ influx at concentrations below 75 mm NaCl, but the influx of 22Na+ was inhibited by 50 mm K+ when the external concentration of NaCl was above 75 mm. The data suggest that neither nonselective cation channels nor a low-affinity cation transporter are major pathways for Na+ entry into root cells. We propose that two distinct low-affinity Na+ uptake pathways exist in S. maritima: Pathway 1 is insensitive to TEA+ or Cs+, but sensitive to Ba2+ and mediates Na+ uptake under low salinities (25 mm NaCl); pathway 2 is sensitive to TEA+, Cs+, and Ba2+ and mediates Na+ uptake under higher external salt concentrations (150 mm NaCl). Pathway 1 might be mediated by a high-affinity K transporter-type transporter and pathway 2 by an AKT1-type channel.

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sas1, an Arabidopsis Mutant Overaccumulating Sodium in the Shoot, Shows Deficiency in the Control of the Root Radial Transport of Sodium

Cited by 58 publications

References 45 publications

Induction of Salt and Osmotic Stress Tolerance by Overexpression of an Intracellular Vesicle Trafficking Protein AtRab7 (AtRabG3e)

Induction of Salt and Osmotic Stress Tolerance by Overexpression of an Intracellular Vesicle Trafficking Protein AtRab7 (AtRabG3e)

The Putative Plasma Membrane Na⁺/H⁺ Antiporter SOS1 Controls Long-Distance Na⁺ Transport in Plants

Low-Affinity Na+ Uptake in the HalophyteSuaeda maritima

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sas1, an Arabidopsis Mutant Overaccumulating Sodium in the Shoot, Shows Deficiency in the Control of the Root Radial Transport of Sodium

Cited by 58 publications

References 45 publications

Induction of Salt and Osmotic Stress Tolerance by Overexpression of an Intracellular Vesicle Trafficking Protein AtRab7 (AtRabG3e)

Induction of Salt and Osmotic Stress Tolerance by Overexpression of an Intracellular Vesicle Trafficking Protein AtRab7 (AtRabG3e)

The Putative Plasma Membrane Na+/H+ Antiporter SOS1 Controls Long-Distance Na+ Transport in Plants

Low-Affinity Na+ Uptake in the HalophyteSuaeda maritima

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The Putative Plasma Membrane Na⁺/H⁺ Antiporter SOS1 Controls Long-Distance Na⁺ Transport in Plants