Pht2;1 Encodes a Low-Affinity Phosphate Transporter from Arabidopsis

Daram, Pierre; Brunner, Silvia; Rausch, Christine; Steiner, Cyrill; Amrhein, Nikolaus

doi:10.2307/3871016

Cited by 68 publications

(132 citation statements)

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“…The immunolocalisation of LePT1 has not been reported; however, a comparison of the cellular locations of MtPT1 and LePT1 transcripts reveals that these genes have overlapping but distinct cell-type speci®c expression patterns. In addition to the epidermis and roots hairs, LePT1 transcripts were also detected in root cap, stele and leaf parenchyma cells (Daram et al, 1999;Liu et al, 1998).…”

Section: Discussionmentioning

confidence: 99%

The spatial expression patterns of a phosphate transporter (MtPT1) from Medicago truncatula indicate a role in phosphate transport at the root/soil interface

Chiou¹,

Liu²,

Harrison³

2001

The Plant Journal

183

145

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SummaryThe movement of phosphate from the soil into plant root cells is the ®rst of many crucial transport events required to supply phosphorous (P) to cells throughout the plant. In addition to the ability to acquire phosphate from the soil, the majority of the vascular plants are able to form arbuscular mycorrhizal associations in which phosphate may be delivered to the cortex via a fungus. Previously, we cloned two phosphate transporter genes, MtPT1 and MtPT2 from Medicago truncatula roots. Complementation of a yeast phosphate transport mutant revealed that MtPT1 is a functional phosphate transporter and Northern analyses revealed that MtPT1 is expressed exclusively in roots (Liu et al., 1998, Mol. Plant-Microbe Interact. 11, 14±22). Utilising an antibody speci®c for MtPT1, we have analysed the accumulation and spatial expression patterns of the MtPT1 transporter. MtPT1 transcript and protein levels show close correlation and increase dramatically in the roots in response to phosphate starvation. MtPT1 protein levels decrease in roots during development of a symbiosis with arbuscular mycorrhizal (AM) fungi, indicating that this transporter is not involved in symbiotic phosphate transport. Membrane fractionation and analysis of a MtPT1/GFP fusion protein revealed that MtPT1 is located in the plasma membrane, while in situ hybridisation and immunolocalisation demonstrate the presence of MtPT1 transcripts and protein in the epidermal cells and root hairs of M. truncatula roots. MtPT1 shows expression patterns consistent with a role speci®cally in the acquisition of phosphate from the soil and is distinct from the other phosphate transporter of this class described to date.

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Section: Discussionmentioning

confidence: 99%

The spatial expression patterns of a phosphate transporter (MtPT1) from Medicago truncatula indicate a role in phosphate transport at the root/soil interface

Chiou¹,

Liu²,

Harrison³

2001

The Plant Journal

183

145

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“…11 Functional analyses in yeast, however, suggest that PHT2 proteins catalyze H + -dependent Pi transport. [11][12][13] GFP translational fusions with PHT2 proteins from Arabidopsis, Medicago truncatula, spinach and potato are targeted to the chloroplast envelope, [12][13][14][15] and localization within the inner envelope membrane is supported by subcellular proteomics and membrane fractionation/immunodetection. 14 In addition to a putative role in Pi import into the chloroplast, the presence of PHT2;1 transcripts within the root stele suggests that the encoded protein also functions in a subset of non-photosynthetic plastids.…”

Section: Introductionmentioning

confidence: 99%

Differential expression and phylogenetic analysis suggest specialization of plastid-localized members of the PHT4 phosphate transporter family for photosynthetic and heterotrophic tissues

Guo

Irigoyen

Fowler

et al. 2008

Plant Signaling & Behavior

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Plastids rely on multiple phosphate (Pi) transport activities to support and control a wide range of metabolic processes, including photosynthesis and carbon partitioning. Five of the six members of the PHT4 family of Pi transporters in Arabidopsis thaliana (PHT4;1-PHT4;5) are confirmed or predicted plastid proteins. As a step towards identifying the roles of individual PHT4 Pi transporters in chloroplast and non-photosynthetic plastid Pi dynamics, we used promoter-reporter gene fusions and quantitative RT-PCR studies, respectively, to determine spatial and diurnal gene expression patterns. PHT4;1 and PHT4;4 were both expressed predominantly in photosynthetic tissues, although expression of PHT4;1 was circadian and PHT4;4 was induced by light. PHT4;3 and PHT4;5 were expressed mainly in leaf phloem. PHT4;2 was expressed throughout the root, and exhibited a diurnal pattern with peak transcript levels in the dark. The remaining member of this gene family, PHT4;6, encodes a Golgi-localized protein and was expressed ubiquitously. The overlapping but distinct expression patterns for these genes suggest specialized roles for the encoded transporters in multiple types of differentiated plastids. Phylogenetic analysis revealed conservation of each of the orthologous members of the PHT4 family in Arabidopsis and rice, which is consistent with specialization, and suggests that the individual members of this transporter family diverged prior to the divergence of monocots and dicots. IntroductionDynamic control of stromal inorganic phosphate (Pi) levels is central to the specialized metabolic functions of differentiated plastids. Notably, the concentration of Pi in the chloroplast stroma is tightly coordinated with environmental conditions to modulate both photosynthesis and the subsequent partitioning of fixed carbon. 1,2 Pi concentrations in amyloplasts also are held within a critical limit to prevent inhibition of starch biosynthesis. 3 For each plastid type, Pi concentrations are controlled through a combination of metabolic recycling in the stroma and surrounding cytosol, and the transport of Pi across the plastid limiting membrane. Recent data suggest that similar processes also link the Pi status of the chloroplast stroma and thylakoid lumen. 4 Plastidic Pi transport is generally attributed to members of the plastidic phosphate translocator (pPT) family. 5 These proteins are located in the inner envelope membrane and mediate strict counterexchange of Pi for phosphorylated C3, C5 or C6 compounds. The triose phosphate/Pi translocator (TPT) was the first pPT protein to be identified, and it is expressed almost exclusively in photosynthetic tissues where it catalyzes transport of cytosolic Pi into the chloroplast in exchange for triose phosphates, the end products of photosynthesis. 6 This activity represents the major pathway for carbon allocation to the cytosol during the day as well as the primary route for Pi import into the chloroplast. Related members of the pPT family include the phosphoenolpyruvate/Pi translocator...

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“…pPTs catalyze the exchange of Pi with phosphorylated compounds and therefore would not support net Pi export (Flü gge, 1999;Eicks et al, 2002). In contrast, members of the PHT2 and PHT4 families mediate H + -and/or Na + -dependent Pi transport (Daram et al, 1999;Versaw and Harrison, 2002;Zhao et al, 2003;Guo et al, 2008b;Ruiz Pavó n et al, 2008). The role of these transporters in nonphotosynthetic plastids is unclear.…”

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confidence: 99%

The Sink-Specific Plastidic Phosphate Transporter PHT4;2 Influences Starch Accumulation and Leaf Size in Arabidopsis

et al. 2011

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Nonphotosynthetic plastids are important sites for the biosynthesis of starch, fatty acids, and amino acids. The uptake and subsequent use of cytosolic ATP to fuel these and other anabolic processes would lead to the accumulation of inorganic phosphate (Pi) if not balanced by a Pi export activity. However, the identity of the transporter(s) responsible for Pi export is unclear. The plastid-localized Pi transporter PHT4;2 of Arabidopsis (Arabidopsis thaliana) is expressed in multiple sink organs but is nearly restricted to roots during vegetative growth. We identified and used pht4;2 null mutants to confirm that PHT4;2 contributes to Pi transport in isolated root plastids. Starch accumulation was limited in pht4;2 roots, which is consistent with the inhibition of starch synthesis by excess Pi as a result of a defect in Pi export. Reduced starch accumulation in leaves and altered expression patterns for starch synthesis genes and other plastid transporter genes suggest metabolic adaptation to the defect in roots. Moreover, pht4;2 rosettes, but not roots, were significantly larger than those of the wild type, with 40% greater leaf area and twice the biomass when plants were grown with a short (8-h) photoperiod. Increased cell proliferation accounted for the larger leaf size and biomass, as no changes were detected in mature cell size, specific leaf area, or relative photosynthetic electron transport activity. These data suggest novel signaling between roots and leaves that contributes to the regulation of leaf size.

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Pht2;1 Encodes a Low-Affinity Phosphate Transporter from Arabidopsis

Cited by 68 publications

References 0 publications

The spatial expression patterns of a phosphate transporter (MtPT1) from Medicago truncatula indicate a role in phosphate transport at the root/soil interface

The spatial expression patterns of a phosphate transporter (MtPT1) from Medicago truncatula indicate a role in phosphate transport at the root/soil interface

Differential expression and phylogenetic analysis suggest specialization of plastid-localized members of the PHT4 phosphate transporter family for photosynthetic and heterotrophic tissues

The Sink-Specific Plastidic Phosphate Transporter PHT4;2 Influences Starch Accumulation and Leaf Size in Arabidopsis

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