Pinocytosis in the root cells of a salt-accumulating halophyte Suaeda altissima and its possible involvement in chloride transport

Balnokin, Yu. V.; Kurkova, E. B.; Халилова, Л. А.; Myasoedov, N. A.; Yusufov, A. G.

doi:10.1134/s102144370706012x

Cited by 29 publications

(10 citation statements)

References 13 publications

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“…Similarly, the present observations suggest the operation of an Na + transport mechanism in planta that is different from currently held models, at least in the case of the IR29 cultivar of rice. Such a mechanism could take several possible forms: (i) a system in which active Na + efflux is either energized differently from what is suggested by current models, possibly via its coupling to passive fluxes of ions other than protons (or even to the passive influx of Na + itself); such coupled transporters are common in animal systems, and, interestingly, a sodium–potassium–chloride transporter has recently been discovered in A. thaliana ( Colmenero-Flores et al , 2007 ); (ii) a vesicle-based system, as has been suggested by Amtmann and Gradmann (1994) for Na + fluxes in Acetabularia , and has recently been shown to operate in manganese transport in Arabidopsis and Populus ( Peiter et al , 2007 ), as well as in chloride transport in the halophyte Suaeda altissima ( Balnokin et al , 2007 ); (iii) a silicate-independent apoplastic contribution, that is not easily discernible from plasma membrane contributions. Further, the possible involvement of more Na + -specific transport systems, as are very common in animal systems, should not be entirely discounted, as it may explain the observed recalcitrance of Na + influx to a wide array of externally applied agents in the present study.…”

Section: Resultsmentioning

confidence: 99%

Futile Na+ cycling at the root plasma membrane in rice (Oryza sativa L.): kinetics, energetics, and relationship to salinity tolerance

Malagoli

Britto

Schulze

et al. 2008

Journal of Experimental Botany

110

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Globally, over one-third of irrigated land is affected by salinity, including much of the land under lowland rice cultivation in the tropics, seriously compromising yields of this most important of crop species. However, there remains an insufficient understanding of the cellular basis of salt tolerance in rice. Here, three methods of 24Na+ tracer analysis were used to investigate primary Na+ transport at the root plasma membrane in a salt-tolerant rice cultivar (Pokkali) and a salt-sensitive cultivar (IR29). Futile cycling of Na+ at the plasma membrane of intact roots occurred at both low and elevated levels of steady-state Na+ supply ([Na+]ext=1 mM and 25 mM) in both cultivars. At 25 mM [Na+]ext, a toxic condition for IR29, unidirectional influx and efflux of Na+ in this cultivar, but not in Pokkali, became very high [>100 μmol g (root FW)−1 h−1], demonstrating an inability to restrict sodium fluxes. Current models of sodium transport energetics across the plasma membrane in root cells predict that, if the sodium efflux were mediated by Na+/H+ antiport, this toxic scenario would impose a substantial respiratory cost in IR29. This cost is calculated here, and compared with root respiration, which, however, comprised only ∼50% of what would be required to sustain efflux by the antiporter. This suggests that either the conventional ‘leak-pump’ model of Na+ transport or the energetic model of proton-linked Na+ transport may require some revision. In addition, the lack of suppression of Na+ influx by both K+ and Ca2+, and by the application of the channel inhibitors Cs+, TEA+, and Ba2+, questions the participation of potassium channels and non-selective cation channels in the observed Na+ fluxes.

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Section: Resultsmentioning

confidence: 99%

Futile Na+ cycling at the root plasma membrane in rice (Oryza sativa L.): kinetics, energetics, and relationship to salinity tolerance

Malagoli

Britto

Schulze

et al. 2008

Journal of Experimental Botany

110

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“…Thus, all (or at least most) of the Na + taken up for rapid osmotic adjustment must be efficiently sequestered in vacuoles. The classical view is that vacuolar Na + sequestration is achieved via tonoplast Na + /H + antiporters (Blumwald and Poole, 1985;Barkla et al, 1995;Gaxiola et al, 1999;Apse and Blumwald, 2007), although the role of pinocytosis has also been advocated (Balnokin et al, 2007). Tonoplast Na + /H + exchangers belong to the CPA family of cation/proton antiporters (Apse and Blumwald, 2007;Rodríguez-Rosales et al, 2008).…”

Section: Targeting Internal Na + Sequestration In Vacuolesmentioning

confidence: 99%

Learning from halophytes: physiological basis and strategies to improve abiotic stress tolerance in crops

Shabala¹

2013

Annals of Botany

686

467

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This review argues that learning from halophytes may be a promising way of achieving this goal. The paper is focused around two central questions: what are the key physiological mechanisms conferring salinity tolerance in halophytes that can be introduced into non-halophyte crop species to improve their performance under saline conditions and what specific genes need to be targeted to achieve this goal? The specific traits that are discussed and advocated include: manipulation of trichome shape, size and density to enable their use for external Na(+) sequestration; increasing the efficiency of internal Na(+) sequestration in vacuoles by the orchestrated regulation of tonoplast NHX exchangers and slow and fast vacuolar channels, combined with greater cytosolic K(+) retention; controlling stomata aperture and optimizing water use efficiency by reducing stomatal density; and efficient control of xylem ion loading, enabling rapid shoot osmotic adjustment while preventing prolonged Na(+) transport to the shoot.

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“…Enclosing ions in (pinocytotic) vesicles (e.g. Field et al, 1980;Balnokin et al, 2007) is a way in which metabolic processes could be 'protected' from potentially damaging concentrations of monovalent cations and anions and a means by which the essential symplastic transport of Na þ and Cl À through the cytoplasm is accomplished. Overall, the evidence (metabolic and analytical) is in favour of substantial Although the focus of research has often been on Na þ toxicity, other factors could contribute to the reductions in growth and ultimately death of halophytes when NaCl is progressively increased.…”

Section: Summing Up On the Topic Of Cytoplasmic Ion Concentrationsmentioning

confidence: 99%

Sodium chloride toxicity and the cellular basis of salt tolerance in halophytes

2014

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The data reviewed here suggest that halophytes tolerate cytoplasmic Na(+) and Cl(-) concentrations of 100-200 mm, but whether these ions ever reach toxic concentrations that inhibit metabolism in the cytoplasm or cause death is unknown. Measurements of ion concentrations in the cytosol of various cell types for contrasting species and growth conditions are needed. Future work should also focus on the properties of the tonoplast that enable ion accumulation and prevent ion leakage, such as the special properties of ion transporters and of the lipids that determine membrane permeability.

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Pinocytosis in the root cells of a salt-accumulating halophyte Suaeda altissima and its possible involvement in chloride transport

Cited by 29 publications

References 13 publications

Futile Na+ cycling at the root plasma membrane in rice (Oryza sativa L.): kinetics, energetics, and relationship to salinity tolerance

Futile Na+ cycling at the root plasma membrane in rice (Oryza sativa L.): kinetics, energetics, and relationship to salinity tolerance

Learning from halophytes: physiological basis and strategies to improve abiotic stress tolerance in crops

Sodium chloride toxicity and the cellular basis of salt tolerance in halophytes

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