Energization of Transport Processes in Plants. Roles of the Plasma Membrane H+-ATPase

Søndergaard, Teis Esben; Schulz, Alexander; Palmgren, Michael G.

doi:10.1104/pp.104.048231

Cited by 291 publications

(180 citation statements)

References 54 publications

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“…This is reminiscent of the P 3A -type H + ATPase AtAHA2, in which the autoinhibitory activity of the C-terminus is relieved by phosphorylation that allows a subsequent interaction with a 14-3-3 protein [78]. A putative 14-3-3 binding motif can be identified in the C-terminal cytosolic domain of AtHMA3 in silico (T. Hoffmann and U. Krämer, unpublished data).…”

Section: Putative Regulatory Domains In Transition Metal Transportersmentioning

confidence: 99%

Transition metal transport

2007

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Transition metal transporters are of central importance in the plant metal homeostasis network which maintains internal metal concentrations within physiological limits. An overview is given of the functions of known transition metal transporters in the context of the unique chemical properties of their substrates. The modifications of the metal homeostasis network associated with the adaptation to an extreme metalliferous environment are illustrated in two Brassicaceae metal hyperaccumulator model plants based on cross-species transcriptomics studies. In a comparison between higher plants and unicellular algae, hypotheses are generated for evolutionary changes in metal transporter complements associated with the transition to multicellularity.

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Section: Putative Regulatory Domains In Transition Metal Transportersmentioning

confidence: 99%

Transition metal transport

2007

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“…In addition to metabolites such as sugars, minerals and salts, such as phosphate, also can use the phloem pathway to be redistributed from old source leaves towards young and expanding sink leaves (Sondergaard et al 2004). Ren et al (2005) proposed a model showing redistribution of cytosolic Na ϩ from mesophyll cells to phloem as an adaptation to maintain cellular K ϩ nutrient status.…”

Section: Excess Cytosolic Namentioning

confidence: 99%

Cellular traits for sodium tolerance in rice (Oryza sativa L.)

Kader

Lindberg

2008

Plant Biotechnology

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“…In one, photoassimilate enters the apoplast and is subsequently loaded into the phloem by specific transport proteins (3,7). The second mechanism appears to be entirely symplastic (by plasmodesmata) (4)(5)(6).…”

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confidence: 99%

Phloem loading in Verbascum phoeniceum L. depends on the synthesis of raffinose-family oligosaccharides

McCaskill

Turgeon

2007

Proc. Natl. Acad. Sci. U.S.A.

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Phloem loading is the initial step in photoassimilate export and the one that creates the driving force for mass flow. It has been proposed that loading occurs symplastically in species that translocate carbohydrate primarily as raffinose family oligosaccharides (RFOs). In these plants, dense fields of plasmodesmata connect bundle sheath cells to specialized companion cells (intermediary cells) in the minor veins. According to the polymer trap model, advanced as a mechanism of symplastic loading, sucrose from the mesophyll diffuses into intermediary cells and is converted there to RFOs. This process keeps the sucrose concentration low and, because of the larger size of the RFOs, prevents back diffusion. To test this model, the RFO pathway was down-regulated in Verbascum phoeniceum L. by suppressing the synthesis of galactinol synthase (GAS), which catalyzes the first committed step in RFO production. Two GAS genes (VpGAS1 and VpGAS2) were cloned and shown to be expressed in intermediary cells. Simultaneous RNAi suppression of both genes resulted in pronounced inhibition of RFO synthesis. Phloem transport was negatively affected, as evidenced by the accumulation of carbohydrate in the lamina and the reduced capacity of leaves to export sugars during a prolonged dark period. In plants with severe down-regulation, additional symptoms of reduced export were obvious, including impaired growth, leaf chlorosis, and necrosis and curling of leaf margins.plasmodesmata ͉ polymer trap ͉ stachyose ͉ galactinol ͉ RNAi U p to 80% of the carbon fixed in mature leaves by photosynthesis is exported to heterotrophic sinks to enable their growth and development. The first step in the transport pathway, and one that is highly regulated (1, 2), is the transfer of photoassimilate from mesophyll cells to the sieve elements (SEs) and companion cells (CCs) of minor veins (3-6). This process, known as phloem loading, creates the positive hydrostatic pressure difference between source and sink phloem that drives the mass flow of solution.Two loading mechanisms have been proposed. In one, photoassimilate enters the apoplast and is subsequently loaded into the phloem by specific transport proteins (3, 7). The second mechanism appears to be entirely symplastic (by plasmodesmata) (4-6). The first hint that loading might take place symplastically came from the discovery, in certain species, of specialized CCs (intermediary cells) in the minor veins, which are linked to bundle sheath cells by extremely high numbers of asymmetrically branched plasmodesmata (5).In all plants with intermediary cells, the phloem sap contains a substantial amount of raffinose family oligosaccharide (RFO), especially the tri-and tetrasaccharides, raffinose, and stachyose. The consistent association of RFOs with intermediary cells suggests that the synthesis of these sugars is an integral part of the phloem-loading mechanism.This reasoning is the basis of the polymer trap model of symplastic loading (8,9). According to the model, sucrose diffuses from bundle sheath cel...

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Energization of Transport Processes in Plants. Roles of the Plasma Membrane H+-ATPase

Cited by 291 publications

References 54 publications

Transition metal transport

Transition metal transport

Cellular traits for sodium tolerance in rice (Oryza sativa L.)

Phloem loading in Verbascum phoeniceum L. depends on the synthesis of raffinose-family oligosaccharides

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