Phosphate transport and homeostasis in Arabidopsis.
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ABSTRACT:
SUBMITTER: Poirier Y
PROVIDER: S-EPMC3243343 | biostudies-literature | 2002
REPOSITORIES: biostudies-literature
Publications
Phosphate transport and homeostasis in Arabidopsis.
Poirier Yves Y Bucher Marcel M
The arabidopsis book 20020930
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Project description:Inorganic phosphate (Pi) is stored in the vacuole, allowing plants to adapt to variable Pi availability in the soil. The transporters that mediate Pi sequestration into vacuole remain unknown, however. Here we report the functional characterization of Vacuolar Phosphate Transporter 1 (VPT1), an SPX domain protein that transports Pi into the vacuole in Arabidopsis. The vpt1 mutant plants were stunted and consistently retained less Pi than wild type plants, especially when grown in medium containing high levels of Pi. In seedlings, VPT1 was expressed primarily in younger tissues under normal conditions, but was strongly induced by high-Pi conditions in older tissues, suggesting that VPT1 functions in Pi storage in young tissues and in detoxification of high Pi in older tissues. As a result, disruption of VPT1 rendered plants hypersensitive to both low-Pi and high-Pi conditions, reducing the adaptability of plants to changing Pi availability. Patch-clamp analysis of isolated vacuoles showed that the Pi influx current was severely reduced in vpt1 compared with wild type plants. When ectopically expressed in Nicotiana benthamiana mesophyll cells, VPT1 mediates vacuolar influx of anions, including Pi, SO4(2-), NO3(-), Cl(-), and malate with Pi as that preferred anion. The VPT1-mediated Pi current amplitude was dependent on cytosolic phosphate concentration. Single-channel analysis showed that the open probability of VPT1 was increased with the increase in transtonoplast potential. We conclude that VPT1 is a transporter responsible for vacuolar Pi storage and is essential for Pi adaptation in Arabidopsis.
| S-EPMC4664319 | biostudies-literature
Project description:Soil availability of inorganic ortho-phosphate (PO43-, Pi) is a key determinant of plant growth and fitness.1 Plants regulate the capacity of their roots to take up inorganic phosphate by adapting the abundance of H+-coupled phosphate transporters of the PHOSPHATE TRANSPORTER 1 (PHT1) family2 at the plasma membrane (PM) through transcriptional and post-translational changes driven by the genetic network of the phosphate starvation response (PSR).3-8 Increasing evidence also shows that plants integrate immune responses to alleviate phosphate starvation stress through the association with beneficial microbes.9-11 Whether and how such phosphate transport is regulated upon activation of immune responses is yet uncharacterized. To address this question, we first developed quantitative assays based on changes in the electrical PM potential to measure active Pi transport in roots in real time. By inserting micro-electrodes into bulging root hairs, we were able to determine key characteristics of phosphate transport in intact Arabidopsis thaliana (hereafter Arabidopsis) seedlings. The fast Pi-induced depolarization observed was dependent on the activity of the major phosphate transporter PHT1;4. Notably, we observed that this PHT1;4-mediated phosphate uptake is repressed upon activation of pattern-triggered immunity. This inhibition depended on the receptor-like cytoplasmic kinases BOTRYTIS-INDUCED KINASE 1 (BIK1) and PBS1-LIKE KINASE 1 (PBL1), which both phosphorylated PHT1;4. As a corollary to this negative regulation of phosphate transport by immune signaling, we found that PHT1;4-mediated phosphate uptake normally negatively regulates anti-bacterial immunity in roots. Collectively, our results reveal a mechanism linking plant immunity and phosphate homeostasis, with BIK1/PBL1 providing a molecular integration point between these two important pathways.
| S-EPMC8791604 | biostudies-literature
Project description:The present work describes the effects on iron homeostasis when copper transport was deregulated in Arabidopsis thaliana by overexpressing high affinity copper transporters COPT1 and COPT3 (COPTOE ). A genome-wide analysis conducted on COPT1OE plants, highlighted that iron homeostasis gene expression was affected under both copper deficiency and excess. Among the altered genes were those encoding the iron uptake machinery and their transcriptional regulators. Subsequently, COPTOE seedlings contained less iron and were more sensitive than controls to iron deficiency. The deregulation of copper (I) uptake hindered the transcriptional activation of the subgroup Ib of basic helix-loop-helix (bHLH-Ib) factors under copper deficiency. Oppositely, copper excess inhibited the expression of the master regulator FIT but activated bHLH-Ib expression in COPTOE plants, in both cases leading to the lack of an adequate iron uptake response. As copper increased in the media, iron (III) was accumulated in roots, and the ratio iron (III)/iron (II) was increased in COPTOE plants. Thus, iron (III) overloading in COPTOE roots inhibited local iron deficiency responses, aimed to metal uptake from soil, leading to a general lower iron content in the COPTOE seedlings. These results emphasized the importance of appropriate spatiotemporal copper uptake for iron homeostasis under non-optimal copper supply. The understanding of the role of copper uptake in iron metabolism could be applied for increasing crops resistance to iron deficiency.
| S-EPMC7390907 | biostudies-literature
Project description:Recent studies have shown various metabolic and transcriptomic interactions between sulfur (S) and phosphorus (P) in plants. However, most studies have focused on the effects of phosphate (Pi) availability and P signaling pathways on S homeostasis, whereas the effects of S availability on P homeostasis remain largely unknown. In this study, we investigated the interactions between S and P from the perspective of S availability. We investigated the effects of S availability on Pi uptake, transport, and accumulation in Arabidopsis thaliana grown under sulfur sufficiency (+S) and deficiency (-S). Total P in shoots was significantly increased under -S owing to higher Pi accumulation. This accumulation was facilitated by increased Pi uptake under -S. In addition, -S increased root-to-shoot Pi transport, which was indicated by the increased Pi levels in xylem sap under -S. The -S-increased Pi level in the xylem sap was diminished in the disruption lines of PHT1;9 and PHO1, which are involved in root-to-shoot Pi transport. Our findings indicate a new aspect of the interaction between S and P by listing the increased Pi accumulation as part of -S responses and by highlighting the effects of -S on Pi uptake, transport, and homeostasis.
| S-EPMC7215917 | biostudies-literature
Project description:Arabidopsis mitochondrial-localized heat shock protein 70-1 (mtHSC70-1) modulates vegetative growth by assisting mitochondrial complex IV assembly and maintaining reactive oxygen species (ROS) homeostasis. In addition, mtHSC70-1 affects embryo development, and this effect is mediated by auxin. However, whether mtHSC70-1 regulates vegetative growth through auxin and knowledge of the link between ROS homeostasis and auxin distribution remain unclear. Here, we found that mtHSC70-1 knockout seedlings (mthsc70-1a) displayed shortened roots, decreased fresh root weight and lateral root number, increased root width and abnormal root morphology. The introduction of the mtHSC70-1 gene into mthsc70-1a restored the growth and development of roots to the level of the wild type. However, sugar and auxin supplementation could not help the mutant roots restore to normal. Moreover, mthsc70-1a seedlings showed a decrease in meristem length and activity, auxin transport carrier (PINs and AUX1) and auxin abundances in root tips. The application of exogenous reducing agents upregulated the levels of PINs in the mutant roots. The introduction of antioxidant enzyme genes (MSD1 or CAT1) into the mthsc70-1a mutant rescued the PIN and local auxin abundances and root growth and development. Taken together, our data suggest that mtHSC70-1 regulates polar auxin transport through ROS homeostasis in Arabidopsis roots.
| S-EPMC9598091 | biostudies-literature
Project description:Plants need abundant nitrogen and phosphorus for higher yield. Improving plant genetics for higher nitrogen and phosphorus use efficiency would save potentially billions of dollars annually on fertilizers and reduce global environmental pollution. This will require knowledge of molecular regulators for maintaining homeostasis of these nutrients in plants. Previously, we reported that the NITROGEN LIMITATION ADAPTATION (NLA) gene is involved in adaptive responses to low-nitrogen conditions in Arabidopsis, where nla mutant plants display abrupt early senescence. To understand the molecular mechanisms underlying NLA function, two suppressors of the nla mutation were isolated that recover the nla mutant phenotype to wild type. Map-based cloning identified these suppressors as the phosphate (Pi) transport-related genes PHF1 and PHT1.1. In addition, NLA expression is shown to be regulated by the low-Pi induced microRNA miR827. Pi analysis revealed that the early senescence in nla mutant plants was due to Pi toxicity. These plants accumulated over five times the normal Pi content in shoots specifically under low nitrate and high Pi but not under high nitrate conditions. Also the Pi overaccumulator pho2 mutant shows Pi toxicity in a nitrate-dependent manner similar to the nla mutant. Further, the nitrate and Pi levels are shown to have an antagonistic crosstalk as displayed by their differential effects on flowering time. The results demonstrate that NLA and miR827 have pivotal roles in regulating Pi homeostasis in plants in a nitrate-dependent fashion.
| S-EPMC3063762 | biostudies-literature
Project description:Iron (Fe) transport and reallocation are essential to Fe homeostasis in plants, but it is unclear how Fe homeostasis is regulated, especially under stress. Here we report that NPF5.9 and its close homolog NPF5.8 redundantly regulate Fe transport and reallocation in Arabidopsis. NPF5.9 is highly upregulated in response to Fe deficiency. NPF5.9 expresses preferentially in vasculature tissues and localizes to the trans-Golgi network, and NPF5.8 showed a similar expression pattern. Long-distance Fe transport and allocation into aerial parts was significantly increased in NPF5.9-overexpressing lines. In the double mutant npf5.8 npf5.9, Fe loading in aerial parts and plant growth were decreased, which were partially rescued by Fe supplementation. Further analysis showed that expression of PYE, the negative regulator for Fe homeostasis, and its downstream target NAS4 were significantly altered in the double mutant. NPF5.9 and NPF5.8 were shown to also mediate nitrate uptake and transport, although nitrate and Fe application did not reciprocally affect each other. Our findings uncovered the novel function of NPF5.9 and NPF5.8 in long-distance Fe transport and homeostasis, and further indicated that they possibly mediate nitrate transport and Fe homeostasis independently in Arabidopsis.
| S-EPMC8577109 | biostudies-literature
Project description:Arabidopsis primary root growth response to phosphate (Pi) deficiency is mainly controlled by changes in apoplastic iron (Fe). Upon Pi deficiency, apoplastic Fe deposition in the root apical meristem activates pathways leading to the arrest of meristem maintenance and inhibition of cell elongation. Here, we report that a member of the uncharacterized cytochrome b561 and DOMON domain (CYBDOM) protein family, named CRR, promotes iron reduction in an ascorbate-dependent manner and controls apoplastic iron deposition. Under low Pi, the crr mutant shows an enhanced reduction of primary root growth associated with increased apoplastic Fe in the root meristem and a reduction in meristematic cell division. Conversely, CRR overexpression abolishes apoplastic Fe deposition rendering primary root growth insensitive to low Pi. The crr single mutant and crr hyp1 double mutant, harboring a null allele in another member of the CYDOM family, shows increased tolerance to high-Fe stress upon germination and seedling growth. Conversely, CRR overexpression is associated with increased uptake and translocation of Fe to the shoot and results in plants highly sensitive to Fe excess. Our results identify a ferric reductase implicated in Fe homeostasis and developmental responses to abiotic stress, and reveal a biological role for CYBDOM proteins in plants.
| S-EPMC10784552 | biostudies-literature
Project description:The xylulose 5-phosphate/phosphate translocator (PTs) (XPT) represents a link between the plastidial and extraplastidial branches of the oxidative pentose phosphate pathway. Its role is to retrieve pentose phosphates from the extraplastidial space and to make them available to the plastids. However, the XPT transports also triose phosphates and to a lesser extent phosphoenolpyruvate (PEP). Thus, it might support both the triose phosphate/PT (TPT) in the export of photoassimilates from illuminated chloroplasts and the PEP/PT (PPT) in the import of PEP into green or non-green plastids. In mutants defective in the day- and night-path of photoassimilate export from the chloroplasts (i.e., knockout of the TPT [tpt-2] in a starch-free background [adg1-1])the XPT provides a bypass for triose phosphate export and thereby guarantees survival of the adg1-1/tpt-2 double mutant. Here we show that the additional knockout of the XPT in adg1-1/tpt-2/xpt-1 triple mutants results in lethality when the plants were grown in soil. Thus the XPT can functionally support the TPT. The PEP transport capacity of the XPT has been revisited here with a protein heterologously expressed in yeast. PEP transport rates in the proteoliposome system were increased with decreasing pH-values below 7.0. Moreover, PEP transport determined in leaf extracts from wild-type plants showed a similar pH-response, suggesting that in both cases PEP2- is the transported charge-species. Hence, PEP import into illuminated chloroplasts might be unidirectional because of the alkaline pH of the stroma. Here the consequence of a block in PEP transport across the envelope was analyzed in triple mutants defective in both PPTs and the XPT. PPT1 is knocked out in the cue1 mutant. For PPT2 two new mutant alleles were isolated and established as homozygous lines. In contrast to the strong phenotype of cue1, both ppt2 alleles showed only slight growth retardation. As plastidial PEP is required e.g., for the shikimate pathway of aromatic amino acid synthesis, a block in PEP import should result in a lethal phenotype. However, the cue1-6/ppt2-1/ppt2-1 triple mutant was viable and even exhibited residual PEP transport capacity. Hence, alternative ways of PEP transport must exist and are discussed.
| S-EPMC6201195 | biostudies-literature
Project description:Chloride ions can be translocated across cell membranes through Cl(-) channels or Cl(-)/H(+) exchangers. The thylakoid-located member of the Cl(-) channel CLC family in Arabidopsis thaliana (AtCLCe) was hypothesized to play a role in photosynthetic regulation based on the initial photosynthetic characterization of clce mutant lines. The reduced nitrate content of Arabidopsis clce mutants suggested a role in regulation of plant nitrate homeostasis. In this study, we aimed to further investigate the role of AtCLCe in the regulation of ion homeostasis and photosynthetic processes in the thylakoid membrane. We report that the size and composition of proton motive force were mildly altered in two independent Arabidopsis clce mutant lines. Most pronounced effects in the clce mutants were observed on the photosynthetic electron transport of dark-adapted plants, based on the altered shape and associated parameters of the polyphasic OJIP kinetics of chlorophyll a fluorescence induction. Other alterations were found in the kinetics of state transition and in the macro-organization of photosystem II supercomplexes, as indicated by circular dichroism measurements. Pre-treatment with KCl but not with KNO3 restored the wild-type photosynthetic phenotype. Analyses by transmission electron microscopy revealed a bow-like arrangement of the thylakoid network and a large thylakoid-free stromal region in chloroplast sections from the dark-adapted clce plants. Based on these data, we propose that AtCLCe functions in Cl(-) homeostasis after transition from light to dark, which affects chloroplast ultrastructure and regulation of photosynthetic electron transport.
| S-EPMC4746265 | biostudies-literature