Relationship between Energy-dependent Phosphate Uptake and the Electrical Membrane Potential in <i>Lemna gibba</i> G1

Ullrich-Eberius, C. I.; Novacký, A.; Fischer, Eugen; Lüttge, Ulrich

doi:10.1104/pp.67.4.797

Cited by 141 publications

(66 citation statements)

References 15 publications

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“…In the case of alix-1, lower vacuolar Pi levels and missorting of Pi transporters to the tonoplast may suggest that PHT1;1 proteins are exporting Pi out of the vacuole in mutant cells. In this scenario, acidification of the cytosol should be expected, as PHT1 proteins are Pi:H + symporters that cotransport two to four protons along with each Pi ion that is absorbed (Ullrich-Eberius et al, 1981;Sakano, 1990;Nussaume et al, 2011). Such changes in intracellular pH can be registered as variations in NMR spectra.…”

Section: Discussionmentioning

confidence: 99%

ESCRT-III-Associated Protein ALIX Mediates High-Affinity Phosphate Transporter Trafficking to Maintain Phosphate Homeostasis in Arabidopsis

et al. 2015

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ORCID IDs: 0000-0003-2780-4888 (C.R.); 0000-0002-8800-2400 (V.R.)Prior to the release of their cargoes into the vacuolar lumen, sorting endosomes mature into multivesicular bodies (MVBs) through the action of ENDOSOMAL COMPLEX REQUIRED FOR TRANSPORT (ESCRT) protein complexes. MVB-mediated sorting of high-affinity phosphate transporters (PHT1) to the vacuole limits their plasma membrane levels under phosphatesufficient conditions, a process that allows plants to maintain phosphate homeostasis. Here, we describe ALIX, a cytosolic protein that associates with MVB by interacting with ESCRT-III subunit SNF7 and mediates PHT1;1 trafficking to the vacuole in Arabidopsis thaliana. We show that the partial loss-of-function mutant alix-1 displays reduced vacuolar degradation of PHT1;1. ALIX derivatives containing the alix-1 mutation showed reduced interaction with SNF7, providing a simple molecular explanation for impaired cargo trafficking in alix-1 mutants. In fact, the alix-1 mutation also hampered vacuolar sorting of the brassinosteroid receptor BRI1. We also show that alix-1 displays altered vacuole morphogenesis, implying a new role for ALIX proteins in vacuolar biogenesis, likely acting as part of ESCRT-III complexes. In line with a presumed broad target spectrum, the alix-1 mutation is pleiotropic, leading to reduced plant growth and late flowering, with stronger alix mutations being lethal, indicating that ALIX participates in diverse processes in plants essential for their life. INTRODUCTIONTrafficking of cargo proteins coming from the plasma membrane (PM) or the Golgi apparatus (GA) to the vacuole occurs through multivesicular bodies (MVBs) (Winter and Hauser, 2006). These organelles, also termed late endosomes or prevacuolar compartments (PVCs), contain internal vesicles that will be delivered, together with their cargoes, into the lumen of vacuoles/lysosomes upon MVB fusion with the tonoplast (Winter and Hauser, 2006). This process plays a central role in controlling the reutilization, storage, or degradation of membrane components and thus regulates fundamental biological processes including membrane turnover, defense against pathogens, development, hormone transport, nutrient uptake, and cell signaling. In the case of membrane-associated regulatory proteins, the MVB route allows modulation of their function by regulating their abundance at the PM and in other vesicular compartments (e.g., endosomes).The sorting of most integral membrane proteins into intraluminal vesicles (ILVs) is dependent on the attachment of ubiquitin to their cytosolic domains, although ubiquitin-independent sorting mechanisms also exist (McNatt et al., 2007). Selective packaging of protein cargoes into ILVs of MVB is mediated by ESCRT (ENDOSOMAL SORTING COMPLEXES REQUIRED FOR TRANSPORT) protein complexes (Conibear, 2002;Winter and Hauser, 2006;Nickerson et al., 2007;Henne et al., 2011). The latter consist of several cytosolic proteins of the VPS-E (class E Vacuolar Protein Sorting) class that are organized into five complexes: ESCRT-0...

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Section: Discussionmentioning

confidence: 99%

ESCRT-III-Associated Protein ALIX Mediates High-Affinity Phosphate Transporter Trafficking to Maintain Phosphate Homeostasis in Arabidopsis

et al. 2015

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“…For instance, anoxia under floating plant beds may boost the decline of submerged plants. Also, growth of duckweed species can be inhibited at higher pH (33)(34)(35), which may arise from photosynthesis in submerged weed beds. Although these specific mechanisms will tend to enhance rather than weaken the hysteresis, other mechanisms that we did not consider could potentially work the opposite way.…”

Section: Discussionmentioning

confidence: 99%

Floating plant dominance as a stable state

Scheffer

Szabó

Gragnani

et al. 2003

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

343

295

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Invasion by mats of free-floating plants is among the most important threats to the functioning and biodiversity of freshwater ecosystems ranging from temperate ponds and ditches to tropical lakes. Dark, anoxic conditions under thick floating-plant cover leave little opportunity for animal or plant life, and they can have large negative impacts on fisheries and navigation in tropical lakes. Here, we demonstrate that floating-plant dominance can be a self-stabilizing ecosystem state, which may explain its notorious persistence in many situations. Our results, based on experiments, field data, and models, represent evidence for alternative domains of attraction in ecosystems. An implication of our findings is that nutrient enrichment reduces the resilience of freshwater systems against a shift to floating-plant dominance. On the other hand, our results also suggest that a single drastic harvest of floating plants can induce a permanent shift to an alternative state dominated by rooted, submerged growth forms.D ense mats of free-floating plant have an adverse effect on freshwater ecosystems because they create anoxic conditions that strongly reduce animal biomass and diversity (1). Invasions by introduced exotic species are partly responsible for the increase of floating plant dominance. The problems caused by Eichhornia crassipes, Pistia stratiotes, and Salvinia molesta are notorious: they hamper fish production and navigation in tropical regions around the world (2-4). However, eutrophication is likely to have boosted the spread of free-floating plants, too. In temperate climate zones, it is known that dense beds of duckweeds (Lemnaceae) and small, floating water ferns (Azollaceae) are a symptom of high-nutrient loading in small water bodies, such as ponds and canals (5, 6). Just as in the case of tropical plant beds, the dark and anoxic conditions under thick duckweed cover leave little opportunity for animal or plant life (1).The dependence of free-floating plants on high nutrient concentrations in the water is an obvious consequence of their growth form. They have no direct access to the sediment pool of nutrients, and they have a large portion of their leaf surface exposed to the atmosphere rather than to the water, thereby reducing the possibility of taking up nutrients other than carbon through their leaves. By contrast, rooted submerged macrophytes may take up a large part of their nutrients from the sediment (7, 8) and also use their shoots effectively for nutrient uptake from the water column (9, 10). Although floating plants are obviously superior competitors for light, submerged plants may affect the growth of free-floating plants through a reduction of available nutrients in the water column. Competition is likely to be especially strong for nitrogen. Although phosphorus availability in the water column can be reduced because of uptake by submerged macrophytes (11), many studies show unaltered or even increased ortho-P levels after increased macrophyte cover (12-15). By contrast, submerged nitrogen co...

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“…Phosphorus is acquired by the plant roots in an energymediated cotransport process driven by a proton gradient generated by plasma membrane H ϩ -ATPases (5). The kinetic characterization of the P i -uptake system by whole plants and cultured cells indicates a high-affinity transport activity operating at low concentrations (micromolar range) and a lowaffinity activity operating at higher concentrations.…”

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confidence: 99%

Transcriptional regulation of plant phosphate transporters

Muchhal

Raghothama²

1999

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

166

125

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Phosphorus is acquired by plant roots primarily via the high-affinity inorganic phosphate (P i ) transporters. The transcripts for P i transporters are highly inducible upon P i starvation, which also results in enhanced P i uptake when P i is resupplied. Using antibodies specific to one of the tomato P i transporters (encoded by LePT1), we show that an increase in the LePT1 transcript under P i starvation leads to a concurrent increase in the transporter protein, suggesting a transcriptional regulation for P i acquisition. LePT1 protein accumulates rapidly in tomato roots in response to P i starvation. The level of transporter protein accumulation depends on the P i concentration in the medium, and it is reversible upon resupply of P i . LePT1 protein accumulates all along the roots under P i starvation and is localized primarily in the plasma membranes. These results clearly demonstrate that plants increase their capacity for P i uptake during P i starvation by synthesis of additional transporter molecules.Phosphorus availability is considered one of the major factors that limits growth of plants in natural ecosystems. The concentration of available phosphorus is generally in the micromolar range, which is below that of many micronutrients (1). Consequently plants have developed several adaptive mechanisms to overcome P i deficiency. These include changes in root growth and architecture, increased production of phosphatases and RNases, altered activity of several enzymes of the glycolytic pathway (2, 3), and an increased P i uptake rate of roots (4). The ultimate consequences of these modifications are increased P i availability in the rhizosphere and enhanced uptake.Phosphorus is acquired by the plant roots in an energymediated cotransport process driven by a proton gradient generated by plasma membrane H ϩ -ATPases (5). The kinetic characterization of the P i -uptake system by whole plants and cultured cells indicates a high-affinity transport activity operating at low concentrations (micromolar range) and a lowaffinity activity operating at higher concentrations. The very low concentration (micromolar) of P i in soil solution suggests that high-affinity transporters are primarily involved in P i uptake by plants (3). The low-affinity system is apparently expressed constitutively, whereas the high-affinity system is induced under P i deficiency (6). The induction process appears to involve de novo protein synthesis, since inhibitors of protein synthesis drastically reduce the induction of high-affinity P i transport. The increased synthesis of a high-affinity carrier system has been proposed to be responsible for enhanced P i uptake observed under P i -deficiency conditions (6).High-affinity P i transporter genes have been cloned and characterized from fungi and from several plant species, including Arabidopsis, tomato, potato, Medicago, and Catharanthus (7). All the cloned P i transporters are integral membrane proteins containing 12 membrane-spanning regions, separated into two groups of 6 by a lar...

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Relationship between Energy-dependent Phosphate Uptake and the Electrical Membrane Potential in Lemna gibba G1

Cited by 141 publications

References 15 publications

ESCRT-III-Associated Protein ALIX Mediates High-Affinity Phosphate Transporter Trafficking to Maintain Phosphate Homeostasis in Arabidopsis

ESCRT-III-Associated Protein ALIX Mediates High-Affinity Phosphate Transporter Trafficking to Maintain Phosphate Homeostasis in Arabidopsis

Floating plant dominance as a stable state

Transcriptional regulation of plant phosphate transporters

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