The “Gatekeeper” Concept: Cell‐Type Specific Molecular Mechanisms of Plant Adaptation to Abiotic Stress

Henderson, Sam W.; Gilliham, Matthew

doi:10.1002/9781118860526.ch4

Cited by 20 publications

(19 citation statements)

References 165 publications

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“…Overexpression data from plants should be treated with caution due to common pleiotropic responses-see below, but the fact that both over-expression lines had a Cl − accumulation phenotype in the shoot over the null segregant lines further (Figure 8B) indicates that NPF2.5 is likely to have a role in Cl − transport in planta . To understand the physiological role of a particular transporter protein, it is best practice to manipulate its expression specifically in the cells in which it is ordinarily expressed (Møller et al, 2009; Plett et al, 2010; Henderson and Gilliham, 2015). For example, manipulation of the expression of AtHKT1.1 , a gene encoding a protein that is important for retrieving Na + from the root xylem, results in very different phenotypes depending on the cells in which the expression of the transporter is manipulated (Sunarpi et al, 2005; Møller et al, 2009; Plett et al, 2010).…”

Section: Discussionmentioning

confidence: 99%

AtNPF2.5 Modulates Chloride (Cl−) Efflux from Roots of Arabidopsis thaliana

Qiu

Jayakannan

et al. 2017

Front. Plant Sci.

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The accumulation of high concentrations of chloride (Cl−) in leaves can adversely affect plant growth. When comparing different varieties of the same Cl− sensitive plant species those that exclude relatively more Cl− from their shoots tend to perform better under saline conditions; however, the molecular mechanisms involved in maintaining low shoot Cl− remain largely undefined. Recently, it was shown that the NRT1/PTR Family 2.4 protein (NPF2.4) loads Cl− into the root xylem, which affects the accumulation of Cl− in Arabidopsis shoots. Here we characterize NPF2.5, which is the closest homolog to NPF2.4 sharing 83.2% identity at the amino acid level. NPF2.5 is predominantly expressed in root cortical cells and its transcription is induced by salt. Functional characterisation of NPF2.5 via its heterologous expression in yeast (Saccharomyces cerevisiae) and Xenopus laevis oocytes indicated that NPF2.5 is likely to encode a Cl− permeable transporter. Arabidopsis npf2.5 T-DNA knockout mutant plants exhibited a significantly lower Cl− efflux from roots, and a greater Cl− accumulation in shoots compared to salt-treated Col-0 wild-type plants. At the same time, NO3− content in the shoot remained unaffected. Accumulation of Cl− in the shoot increased following (1) amiRNA-induced knockdown of NPF2.5 transcript abundance in the root, and (2) constitutive over-expression of NPF2.5. We suggest that both these findings are consistent with a role for NPF2.5 in modulating Cl− transport. Based on these results, we propose that NPF2.5 functions as a pathway for Cl− efflux from the root, contributing to exclusion of Cl− from the shoot of Arabidopsis.

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Section: Discussionmentioning

confidence: 99%

AtNPF2.5 Modulates Chloride (Cl−) Efflux from Roots of Arabidopsis thaliana

Qiu

Jayakannan

et al. 2017

Front. Plant Sci.

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“…Osakabe et al ., ) and their localization in key cell types underpin plant salinity tolerance. Root xylem parenchyma cells represent ‘gatekeeper’ cell types for shoot NaCl exclusion as they have a physical location and unique protein circuitry primed for this role (Henderson & Gilliham, ). TaHKT1;5‐D is responsible for maintaining high cytosolic K + /Na + ratios in bread wheat shoots; it underpins the Kna1 locus, resides on the plasma membrane (PM) of root xylem parenchyma cells and reduces Na + load in the xylem before entering the shoot (Byrt et al ., ).…”

Section: New Insights Into Salinity Tolerance Mechanismsmentioning

confidence: 99%

Salinity tolerance of crops – what is the cost?

2015

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Contents 668I. 668II. 668III. 670IV. 671V. 672 672 References 672 Summary Soil salinity reduces crop yield. The extent and severity of salt‐affected agricultural land is predicted to worsen as a result of inadequate drainage of irrigated land, rising water tables and global warming. The growth and yield of most plant species are adversely affected by soil salinity, but varied adaptations can allow some crop cultivars to continue to grow and produce a harvestable yield under moderate soil salinity. Significant costs are associated with saline soils: the economic costs to the farming community and the energy costs of plant adaptations. We briefly consider mechanisms of adaptation and highlight recent research examples through a lens of their applicability to improving the energy efficiency of crops under saline field conditions.

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“…Outlined in Figure 1 are major transport steps across cellular membranes that affect nutritive Cluptake, translocation and storage. The key rate-limiting 'gatekeeper' step modulating Claccumulation in the shoot has been shown to be the loading of Clfrom the root stelar symplast into the xylem apoplast, which is regulated following drought and salinity stress via abscisic acid (ABA) [2,[4][5][6][7][8][9][10]. In the root, ABA inhibits xylem loading of Cl -, but ABA has no effect on its uptake [7,9].…”

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Chloride on the Move

Tester

Gilliham

2017

Trends in Plant Science

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Chloride (Cl) is an essential plant nutrient but under saline conditions it can accumulate to toxic levels in leaves; limiting this accumulation improves the salt tolerance of some crops. The rate-limiting step for this process - the transfer of Cl from root symplast to xylem apoplast, which can antagonize delivery of the macronutrient nitrate (NO) to shoots - is regulated by abscisic acid (ABA) and is multigenic. Until recently the molecular mechanisms underpinning this salt-tolerance trait were poorly defined. We discuss here how recent advances highlight the role of newly identified transport proteins, some that directly transfer Cl into the xylem, and others that act on endomembranes in 'gatekeeper' cell types in the root stele to control root-to-shoot delivery of Cl.

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The “Gatekeeper” Concept: Cell‐Type Specific Molecular Mechanisms of Plant Adaptation to Abiotic Stress

Cited by 20 publications

References 165 publications

AtNPF2.5 Modulates Chloride (Cl−) Efflux from Roots of Arabidopsis thaliana

AtNPF2.5 Modulates Chloride (Cl−) Efflux from Roots of Arabidopsis thaliana

Salinity tolerance of crops – what is the cost?

Chloride on the Move

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