Plant phosphate nutrition
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Frontiers: Functional Disruption of a Chloroplast Pseudouridine Synthase Desensitizes Arabidopsis Plants to Phosphate Starvation | Plant Science

Phosphate (Pi) deficiency is a common nutritional stress of plants in both agricultural and natural ecosystems. Plants respond to Pi starvation in the environment by triggering a suite of biochemical, physiological, and developmental changes that increase survival and growth. The key factors that determine plant sensitivity to Pi starvation, however, are unclear. In this research, we identified an Arabidopsis mutant, dps1, with greatly reduced sensitivity to Pi starvation. The dps1 phenotypes are caused by a mutation in the previously characterized SVR1 (SUPPRESSION OF VARIAGATION 1) gene, which encodes a chloroplast-localized pseudouridine synthase. The mutation of SVR1 results in defects in chloroplast rRNA biogenesis, which subsequently reduces chloroplast translation. Another mutant, rps5, which contains a mutation in the chloroplast ribosomal protein RPS5 and has reduced chloroplast translation, also displayed decreased sensitivity to Pi starvation. Furthermore, wild type plants treated with lincomycin, a chemical inhibitor of chloroplast translation, showed similar growth phenotypes and Pi starvation responses as dps1 and rps5. These results suggest that impaired chloroplast translation desensitizes plants to Pi starvation. Combined with previously published results showing that enhanced leaf photosynthesis augments plant responses to Pi starvation, we propose that the decrease in responses to Pi starvation in dps1, rps5, and lincomycin-treated plants is due to their reduced demand for Pi input from the environment.

DOI: 10.3389/fpls.2017.01421

Lu S, Li C, Zhang Y, Zheng Z, Liu D

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Insights into plant phosphate sensing and signaling

Insights into plant phosphate sensing and signaling | Plant phosphate nutrition | Scoop.it
Highlights
• Pi stress restricts primary root growth through dual regulatory pathways.
• Vacuolar transporters regulate cytosolic Pi homeostasis.
• InsP interacts with SPX domain to regulate Pi transport and/or signal transduction.
• Phloem delivers Pi signaling RNAs to specific sinks for downstream regulation.
• Phosphate starvation-response (PSR) attenuates plant defenses to allow symbiosis with beneficial microbes.
Phosphorus (P) is a macronutrient essential for plant growth, therefore, soil P level is critical to crop yield potential in agriculture. As Pi levels limit crop yield under many soil conditions, it is crucial to understand the mechanisms by which plants adapt to low-phosphate (Pi) soil conditions and interact with their soil microbiome to improve crop P use efficiency, in order to ensure global food security. Recent advances have been made towards achieving this goal through advancing our understanding of the plant's response to limiting Pi conditions to maintain P homeostasis. In this review, we assess advances made in local and systemic Pi sensing and signaling, and in the molecular events for Pi absorption, redistribution and plant–symbiont interactions. These findings offer important avenues for bio-engineering of agricultural crops with traits for enhanced Pi acquisition and utilization.
Ham BK, Chen J, Yan Y, Lucas WJ
DOI: 10.1016/j.copbio.2017.07.005
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COPB: Food for thought: how nutrients regulate root system architecture

COPB: Food for thought: how nutrients regulate root system architecture | Plant phosphate nutrition | Scoop.it
Highlights • Root system architecture is a precise readout of nutrient signalling. • RSA is regulated by transcriptional, translational, redox and cell-wall processes. • Peptides act as local and systemic signals in N and P signalling. • Crosstalk of nutrient signalling pathways underpins interactive effects. • RSA correlates with nutrient use efficiency and yield in crop genotypes.
Shahzad Z, Amtmann A
DOI: 10.1016/j.pbi.2017.06.008
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Novel signals in the regulation of Pi starvation responses in plants: facts and promises

Novel signals in the regulation of Pi starvation responses in plants: facts and promises | Plant phosphate nutrition | Scoop.it
Highlights • Inositol polyphosphates act as signals in phosphate homeostasis. • ROS signaling is associated to phosphate and iron control of root tip growth. • Thousands of RNAs in the plant transcriptome move among distant organs. • Mobile RNAs might act as systemic signals to control phosphate starvation responses and others.
Puga MI, Rojas-Triana M, de Lorenzo L, Leyva A, Rubio V, Paz-Ares J
DOI:10.1016/j.pbi.2017.05.007
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Sci Rep: Light perception in aerial tissues enhances DWF4 accumulation in root tips and induces root growth

Sci Rep: Light perception in aerial tissues enhances DWF4 accumulation in root tips and induces root growth | Plant phosphate nutrition | Scoop.it

Many attempts have been made to characterize the activities of brassinosteroids (BRs), which are important plant hormones. The crosstalk between light perception and the BR signalling pathway has been extensively studied regarding its effects on photomorphogenesis, especially in elongating etiolated hypocotyls. In contrast, how and where the light induces BR biosynthesis remain uncharacterized. DWF4 is one of the main enzymes involved in the BR biosynthesis pathway in Arabidopsis thaliana. We established DWF4-GUS A. thaliana lines in a homozygous dwf4-102 genetic background, but functionally complemented with a genomic DWF4 sequence fused in-frame with a β-glucuronidase (GUS) marker gene. The DWF4-GUS plants enabled the visualization of the accumulation of DWF4 under different conditions. We investigated the effects of aboveground light on root and hypocotyl growth. We observed that root length increased when shoots were maintained under light irrespective of whether roots were exposed to light. We also determined that light perception in aerial tissues enhanced DWF4 accumulation in the root tips. Overall, our data indicate that BR biosynthesis is promoted in the root tip regions by an unknown mechanism in distantly located shoot tissues exposed to light, leading to increased root growth.

Sakaguchi J, Watanabe Y

DOI: 10.1038/s41598-017-01872-4

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Plant Physiol: Root cell-specific regulators of phosphate-dependent growth

Cellular specialization in abiotic stress responses is an important regulatory feature driving plant acclimation. Our in-silico approach of iterative co-expression, interaction and enrichment analyses predicted root cell-specific regulators of phosphate-starvation-response networks in Arabidopsis thaliana. This included three uncharacterized genes termed Phosphate-starvation-induced (PSI)-gene interacting Root-Cell Enriched (PRCE1,2,3). Root-cell-specific enrichment of twelve candidates was confirmed in promoter-GFP lines. T-DNA insertion lines of eleven genes showed changes in phosphate status and growth responses to phosphate availability compared to wild type. Some mutants (cbl1, cipk2, prce3 and wdd1) displayed strong biomass gain irrespective of phosphate supply, while others (cipk14, mfs1, prce1, prce2 and s6k2) were able to sustain growth under low phosphate supply better than wild type. Notably, root or shoot phosphate accumulation did not strictly correlate with organ growth. Mutant response patterns markedly differed from those of master regulators of phosphate homeostasis, PHOSPHATE STARVATION RESPONSE 1 (PHR1) and PHOSPHATE 2 (PHO2), demonstrating that negative growth responses in the latter can be overcome when cell-specific regulators are targeted. RNA-seq analysis high-lighted the transcriptomic plasticity in these mutants and revealed PHR1-dependent and -independent regulatory circuits with gene co-expression profiles that were highly correlated to the quantified physiological traits. Results demonstrate how in-silico prediction of cell-specific, stress-responsive genes uncovers key regulators and how their manipulation can have positive impacts on plant growth under abiotic stress. Linn J, Ren M, Berkowitz O, Ding W, Van Der Merwe MJ, Whelan J, Jost R DOI: 10.1104/pp.16.01698
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Nature Plants: Shoot-to-root mobile polypeptides involved in systemic regulation of nitrogen acquisition

Nature Plants: Shoot-to-root mobile polypeptides involved in systemic regulation of nitrogen acquisition | Plant phosphate nutrition | Scoop.it
Plants uptake nitrogen (N) from the soil mainly in the form of nitrate. However, nitrate is often distributed heterogeneously in natural soil. Plants, therefore, have a systemic long-distance signalling mechanism by which N starvation on one side of the root leads to a compensatory N uptake on the other N-rich side1,2. This systemic N acquisition response is triggered by a root-to-shoot mobile peptide hormone, C-TERMINALLY ENCODED PEPTIDE (CEP), originating from the N-starved roots3,4, but the molecular nature of the descending shoot-to-root signal remains elusive. Here, we show that phloem-specific polypeptides that are induced in leaves upon perception of root-derived CEP act as descending long-distance mobile signals translocated to each root. These shoot-derived polypeptides, which we named CEP DOWNSTREAM 1 (CEPD1) and CEPD2, upregulate the expression of the nitrate transporter gene NRT2.1 in roots specifically when nitrate is present in the rhizosphere. Arabidopsis plants deficient in this pathway show impaired systemic N acquisition response accompanied with N-deficiency symptoms. These fundamental mechanistic insights should provide a conceptual framework for understanding systemic nutrient acquisition responses in plants. Y Ohkubo, M Tanaka, R Tabata, M Ogawa-Ohnishi, Matsubayashi Y. DOI:10.1038/nplants.2017.29
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New Phytol: Strigolactone biosynthesis is evolutionarily conserved, regulated by phosphate starvation and contributes to resistance against phytopathogenic fungi in a moss, Physcomitrella patens

New Phytol: Strigolactone biosynthesis is evolutionarily conserved, regulated by phosphate starvation and contributes to resistance against phytopathogenic fungi in a moss, Physcomitrella patens | Plant phosphate nutrition | Scoop.it

In seed plants, strigolactones (SLs) regulate architecture and induce mycorrhizal symbiosis in response to environmental cues. SLs are formed by combined activity of the carotenoid cleavage dioxygenases (CCDs) 7 and 8 from 9-cis-β-carotene, leading to carlactone that is converted by cytochromes P450 (clade 711; MAX1 in Arabidopsis) into various SLs. As Physcomitrella patens possesses CCD7 and CCD8 homologs but lacks MAX1, we investigated if PpCCD7 together with PpCCD8 form carlactone and how deletion of these enzymes influences growth and interactions with the environment. We investigated the enzymatic activity of PpCCD7 and PpCCD8 in vitro, identified the formed products by high performance liquid chromatography (HPLC) and LC-MS, and generated and analysed ΔCCD7 and ΔCCD8 mutants. We defined enzymatic activity of PpCCD7 as a stereospecific 9-cis-CCD and PpCCD8 as a carlactone synthase. ΔCCD7 and ΔCCD8 lines showed enhanced caulonema growth, which was revertible by adding the SL analogue GR24 or carlactone. Wild-type (WT) exudates induced seed germination in Orobanche ramosa. This activity was increased upon phosphate starvation and abolished in exudates of both mutants. Furthermore, both mutants showed increased susceptibility to phytopathogenic fungi. Our study reveals the deep evolutionary conservation of SL biosynthesis, SL function, and its regulation by biotic and abiotic cues.

Decker EL, Alder A, Hunn S, Ferguson J, Lehtonen MT, Scheler B, Kerres KL, Wiedemann G, Safavi-Rizi V, Nordzieke S, Balakrishna A, Baz L, Avalos J, Valkonen JP, Reski R, Al-Babili S

DOI: 10.1111/nph.14506.

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BMC Genomics: Transcriptional and physiological analyses of Fe deficiency response in maize reveal the presence of Strategy I components and Fe/P interactions

Under limited iron (Fe) availability maize, a Strategy II plant, improves Fe acquisition through the release of phytosiderophores (PS) into the rhizosphere and the subsequent uptake of Fe-PS complexes into root cells. Occurrence of Strategy-I-like components and interactions with phosphorous (P) nutrition has been hypothesized based on molecular and physiological studies in grasses.
Laura Zanin, Silvia Venuti, Anita Zamboni, Zeno Varanini, Nicola Tomasi and Roberto Pinton
DOI: 10.1186/s12864-016-3478-4
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Node-based transporter: Switching phosphorus distribution

Phosphorus removal during grain harvest creates severe challenges for sustainable agriculture.
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Frontiers | Genome-Wide Identification and Characterization of SPX Domain-Containing Members and Their Responses to Phosphate Deficiency in Brassica napus

The importance of SPX domain-encoding proteins to phosphate (Pi) homeostasis and signaling pathways has been well-documented in rice and Arabidopsis. However, global information and responses of SPX members to P stress in allotetraploid Brassica napus, one of the world’s major oil crops that is sensitive to P deficiency, remain undefined. We identified a total of 69 SPX domain-containing genes in the B. napus genome. Based on the domain organizations, these genes were classified into four distinct subfamilies—SPX (11), SPX-EXS (43), SPX-MFS (8), and SPX-RING (7)—that represented clear orthologous relationships to their family members in Arabidopsis. A cis-element analysis indicated that 2 ∼ 4 P1BS elements were enriched in the promoter of SPX subfamily genes except BnaSPX4s. RNA-Seq analysis showed that BnaSPX genes were differentially expressed in response to Pi deficiency. Furthermore, quantitative real-time reverse transcription PCR revealed that nine SPX subfamily genes were significantly induced by Pi starvation and recovered rapidly after Pi refeeding. A functional analysis of two paralogous BnaSPX1 genes in transgenic Arabidopsis indicated their functional divergence during long-term evolution. This comprehensive study on the abundance, molecular characterization and responses to Pi deficiency of BnaSPX genes provides insights into the structural and functional diversities of these family members in B. napus and provides a solid foundation for future functional studies of BnaSPX genes. Du H, Yang C, Ding G, Shi L, Xu F. DOI: 10.3389/fpls.2017.00035.
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Plant J: Improving phosphorus use efficiency - a complex trait with emerging opportunities

Phosphorus (P) is one of the essential nutrients for plants and indispensable for plant growth and development. P deficiency severely limits crop yield and regular fertilizer applications are required to obtain high yields and prevent soil degradation. To access P from the soil, plants have evolved high and low affinity Pi transporters and the ability to induce root architectural changes to forage P. Also, adjustments of numerous cellular processes are triggered by the P starvation response, a tightly regulated process in plants. With the increasing demand for food due to the growing population, demand for P fertilizer is steadily increasing. Given the high costs of fertilizers and in light of the fact that phosphate rock, the source of P fertilizer, is a finite natural resource, there is a need to enhance P fertilizer use efficiency in agricultural systems and develop plants with enhanced Pi uptake and internal P-use efficiency (PUE). In this review we will provide an overview of ongoing relevant research and highlight different approaches towards developing crops with enhanced PUE. In this context, we will summarize our current understanding of root responses to low phosphorus conditions and emphasize the importance of combining PUE with tolerance of other stresses, such as aluminum toxicity. Of the many genes associated with Pi deficiency, this review will focus on those that hold promise or are already at an advanced stage of testing (OsPSTOL1, AVP1, PHO1, OsPHT1;6). Finally, an update is provided on the progress made exploring alternative technologies, such as phosphite fertilizer. This article is protected by copyright. All rights reserved. Heuer S, Gaxiola R, Schilling R, Herrera-Estrella L, López-Arredondo D, Wissuwa M, Delhaize E, Rouached H. DOI: 10.1111/tpj.13423

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BMC Genomics: Systematic characterization of novel lncRNAs responding to phosphate starvation in Arabidopsis thaliana


Background Previously, several long non-coding RNAs (lncRNAs) were characterized as regulators in phosphate (Pi) starvation responses. However, systematic studies of novel lncRNAs involved in the Pi starvation signaling pathways have not been reported. Results Here, we used a genome-wide sequencing and bioinformatics approach to identify both poly(A) + and poly(A)– lncRNAs that responded to Pi starvation in Arabidopsis thaliana. We sequenced shoot and root transcriptomes of the Arabidopsis seedlings grown under Pi-sufficient and Pi-deficient conditions, and predicted 1212 novel lncRNAs, of which 78 were poly(A)– lncRNAs. By employing strand-specific RNA libraries, we discovered many novel antisense lncRNAs for the first time. We further defined 309 lncRNAs that were differentially expressed between P+ and P– conditions in either shoots or roots. Through Gene Ontology enrichment of the associated protein-coding genes (co-expressed or close on the genome), we found that many lncRNAs were adjacent or co-expressed with the genes involved in several Pi starvation related processes, including cell wall organization and photosynthesis. In total, we identified 104 potential lncRNA targets of PHR1, a key regulator for transcriptional response to Pi starvation. Moreover, we identified 16 candidate lncRNAs as potential targets of miR399, another key regulator of plant Pi homeostasis. Conclusions Altogether, our data provide a rich resource of candidate lncRNAs involved in the Pi starvation regulatory network. Yuan J, Zhang Y, Dong J, Sun Y, Lim BL, Liu D, Lu ZJ. DOI: 10.1186/s12864-016-2929-2


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Plant Cell: Light and Ethylene Coordinately Regulate the Phosphate Starvation Response through Transcriptional Regulation of PHOSPHATE STARVATION RESPONSE1

Plants have evolved an array of adaptive responses to low phosphate (Pi) availability, a process modulated by various external stimuli and endogenous growth regulatory signals. Little is known about how these signaling processes interact to produce an integrated response. Arabidopsis thaliana PHOSPHATE STARVATION RESPONSE1 (PHR1) encodes a conserved MYB type transcription factor that is essential for programming Pi starvation-induced (PSI) gene expression and downstream Pi starvation responses (PSRs). Here, we show that loss-of-function mutations in FHY3 and FAR1, encoding two positive regulators of phytochrome signaling, and in EIN3, encoding a master regulator of ethylene responses, cause attenuated PHR1 expression, whereas mutation in HY5, encoding another positive regulator of light signaling, causes increased PHR1 expression. FHY3, FAR1, HY5 and EIN3 directly bind to the PHR1 promoter through distinct cis-elements. FHY3, FAR1 and EIN3 activate, while HY5 represses, PHR1 expression. FHY3 directly interacts with EIN3, and HY5 suppresses the transcriptional activation activity of FHY3 and EIN3 on PHR1. Finally, both light and ethylene promote FHY3 protein accumulation, and ethylene blocks the light-promoted stabilization of HY5. Our results suggest that light and ethylene coordinately regulate PHR1 expression and PSRs through signaling convergence at the PHR1 promoter.

Liu Y, Xie Y, Wang H, Ma X, Yao W, Wang H

DOI: 10.1105/tpc.17.00268

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Root Cell-Specific Regulators of Phosphate-Dependent Growth

Cellular specialization in abiotic stress responses is an important regulatory feature driving plant acclimation. Our in silico approach of iterative coexpression, interaction, and enrichment analyses predicted root cell-specific regulators of phosphate starvation response networks in Arabidopsis (Arabidopsis thaliana). This included three uncharacterized genes termed Phosphate starvation-induced gene interacting Root Cell Enriched (PRCE1, PRCE2, and PRCE3). Root cell-specific enrichment of 12 candidates was confirmed in promoter-GFP lines. T-DNA insertion lines of 11 genes showed changes in phosphate status and growth responses to phosphate availability compared with the wild type. Some mutants (cbl1, cipk2, prce3, and wdd1) displayed strong biomass gain irrespective of phosphate supply, while others (cipk14, mfs1, prce1, prce2, and s6k2) were able to sustain growth under low phosphate supply better than the wild type. Notably, root or shoot phosphate accumulation did not strictly correlate with organ growth. Mutant response patterns markedly differed from those of master regulators of phosphate homeostasis, PHOSPHATE STARVATION RESPONSE1 (PHR1) and PHOSPHATE2 (PHO2), demonstrating that negative growth responses in the latter can be overcome when cell-specific regulators are targeted. RNA sequencing analysis highlighted the transcriptomic plasticity in these mutants and revealed PHR1-dependent and -independent regulatory circuits with gene coexpression profiles that were highly correlated to the quantified physiological traits. The results demonstrate how in silico prediction of cell-specific, stress-responsive genes uncovers key regulators and how their manipulation can have positive impacts on plant growth under abiotic stress.

Linn J, Ren M, Berkowitz O, Ding W, van der Merwe MJ, Whelan J, Jost R

DOI: 10.1104/pp.16.01698

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COPB: Intracellular transport and compartmentation of phosphate in plants

COPB: Intracellular transport and compartmentation of phosphate in plants | Plant phosphate nutrition | Scoop.it
Highlights
• Multiple intracellular Pi transport systems are present in plant cells.
• Membrane potentials and pH influence Pi transport energetics.
 • Pi compartmentation reflects net Pi import and export processes.
Versaw WK, Garcia LR
DOI: 10.1016/j.pbi.2017.04.015
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Plant Cell Env: Enhanced root growth in phosphate‐starved Arabidopsis by stimulating de novo phospholipid biosynthesis through the overexpression of LYSOPHOSPHATIDIC ACID ACYLTRANSFERASE 2 (LPAT2)

Plant Cell Env: Enhanced root growth in phosphate‐starved Arabidopsis by stimulating de novo phospholipid biosynthesis through the overexpression of LYSOPHOSPHATIDIC ACID ACYLTRANSFERASE 2 (LPAT2) | Plant phosphate nutrition | Scoop.it

Upon phosphate starvation, plants retard shoot growth but promote root development presumably to enhance phosphate assimilation from the ground. Membrane lipid remodeling is a metabolic adaptation that replaces membrane phospholipids by non-phosphorous galactolipids, thereby allowing plants to obtain scarce phosphate yet maintain the membrane structure. However, stoichiometry of this phospholipid-to-galactolipid conversion may not account for the massive demand of membrane lipids that enables active growth of roots under phosphate starvation, thereby suggesting the involvement of de novo phospholipid biosynthesis, which is not represented in the current model. We overexpressed an endoplasmic reticulum-localized lysophosphatidic acid acyltransferase, LPAT2, a key enzyme that catalyzes the last step of de novo phospholipid biosynthesis. Two independent LPAT2 overexpression lines showed no visible phenotype under normal conditions but showed increased root length under phosphate starvation, with no effect on phosphate starvation response including marker gene expression, root hair development, and anthocyanin accumulation. Accompanying membrane glycerolipid profiling of LPAT2-overexpressing plants revealed an increased content of major phospholipid classes and distinct responses to phosphate starvation between shoot and root. The findings propose a revised model of membrane lipid remodeling, in which de novo phospholipid biosynthesis mediated by LPAT2 contributes significantly to root development under phosphate starvation.

Angkawijaya AE, Nguyen VC, Nakamura Y

DOI: 10.1111/pce.12988

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Nature Comm: Low phosphate activates STOP1-ALMT1 to rapidly inhibit root cell elongation

Nature Comm: Low phosphate activates STOP1-ALMT1 to rapidly inhibit root cell elongation | Plant phosphate nutrition | Scoop.it

Environmental cues profoundly modulate cell proliferation and cell elongation to inform and direct plant growth and development. External phosphate (Pi) limitation inhibits primary root growth in many plant species. However, the underlying Pi sensory mechanisms are unknown. Here we genetically uncouple two Pi sensing pathways in the root apex of Arabidopsis thaliana. First, the rapid inhibition of cell elongation in the transition zone is controlled by transcription factor STOP1, by its direct target, ALMT1, encoding a malate channel, and by ferroxidase LPR1, which together mediate Fe and peroxidase-dependent cell wall stiffening. Second, during the subsequent slow inhibition of cell proliferation in the apical meristem, which is mediated by LPR1-dependent, but largely STOP1–ALMT1-independent, Fe and callose accumulate in the stem cell niche, leading to meristem reduction. Our work uncovers STOP1 and ALMT1 as a signalling pathway of low Pi availability and exuded malate as an unexpected apoplastic inhibitor of root cell wall expansion.

Balzergue C, Dartevelle T, Godon C, Laugier E, Meisrimler C, Teulon JM, Creff A, Bissler M, Brouchoud C,Hagege A, Muller J, Chiarenza S, Javot H, Becuwe-Linka N, David P, Peret B, Delannoy E, Thibaud MC, Armengaud J, Abel S, Pellequer JL, Nussaume L, Desnos T. DOI:10.1038/ncomms15300

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The plastid outer membrane localized LPTD1 is important for glycerolipid remodeling under phosphate starvation

The plastid outer membrane localized LPTD1 is important for glycerolipid remodeling under phosphate starvation | Plant phosphate nutrition | Scoop.it

Glycerolipid synthesis in plants is coordinated between plastids and the endoplasmic reticulum (ER). A central step within the glycerolipid synthesis is the transport of phosphatidic acid from ER to chloroplasts. The chloroplast outer envelope protein TGD4 belongs to the LptD family conserved in bacteria and plants and selectively binds and may transports phosphatidic acid. We describe a second LptD-family protein in A. thaliana (atLPTD1; At2g44640) characterized by a barrel domain with an amino acid signature typical for cyanobacterial LptDs. It forms a cation selective channel in vitro with a diameter of about 9 Å. atLPTD1 levels are induced under phosphate starvation. Plants expressing an RNAi construct against atLPTD1 show a growth phenotype under normal conditions. Expressing the RNAi against atLPTD1 in the tgd4-1 background renders the plants more sensitive to light stress or phosphate limitation than the individual mutants. Moreover, lipid analysis revealed that digalactosyldiacylglycerol and sulfoquinovosyldiacylglycerol levels remain constant in the RNAi mutants under phosphate starvation, while these two lipids are enhanced in wild-type. Based on our results we propose a function of atLPTD1 in the transport of lipids from ER to chloroplast under phosphate starvation, which is combinatory with the function of TGD4.

Hsueh YC, Ehmann C, Flinner N, Ladig R, Schleiff E.

DOI: 10.1111/pce.12973.

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Nature: Root microbiota drive direct integration of phosphate stress and immunity

Nature: Root microbiota drive direct integration of phosphate stress and immunity | Plant phosphate nutrition | Scoop.it
Plants live in biogeochemically diverse soils with diverse microbiota. Plant organs associate intimately with a subset of these microbes, and the structure of the microbial community can be altered by soil nutrient content. Plant-associated microbes can compete with the plant and with each other for nutrients, but may also carry traits that increase the productivity of the plant. It is unknown how the plant immune system coordinates microbial recognition with nutritional cues during microbiome assembly. Here we establish that a genetic network controlling the phosphate stress response influences the structure of the root microbiome community, even under non-stress phosphate conditions. We define a molecular mechanism regulating coordination between nutrition and defence in the presence of a synthetic bacterial community. We further demonstrate that the master transcriptional regulators of phosphate stress response in Arabidopsis thaliana also directly repress defence, consistent with plant prioritization of nutritional stress over defence. Our work will further efforts to define and deploy useful microbes to enhance plant performance. Castrillo G, Teixeira PJ, Paredes SH, Law TF, de Lorenzo L, Feltcher ME, Finkel OM, Breakfield NW, Mieczkowski P, Jones CD, Paz-Ares J, Dangl JL DOI: 10.1038/nature21417
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Plant J: OsNLA1, a RING‐type ubiquitin ligase, maintains phosphate homeostasis in Oryza sativa via degradation of phosphate transporters

Inorganic phosphate (Pi) transporters (PTs) play vital roles in Pi uptake and translocation in plants. Under Pi sufficient conditions, PTs are degraded to prevent excess Pi accumulation. The mechanisms targeting PTs for degradation are not fully elucidated. In this study, we found that the Oryza sativa (rice) ortholog of Arabidopsis thaliana Nitrogen Limitation Adaptation (NLA), OsNLA1 protein, a RING-type E3 ubiquitin-ligase, was predominantly localized in the plasma membrane, and could interact with rice phosphate transporters OsPT2 and OsPT8. Mutation of the 265th cysteine residue in OsNLA1 that was required for ubiquitination prevented breakdown of OsPT2/PT8, suggesting OsNLA1 targeted OsPT2/PT8 for degradation. Mutation in OsNLA1 (osnla1) led to significant increase of Pi concentration in leaves in a nitrate-independent manner. Overexpression of OsNLA1 or repression of OsPT2/PT8 restored the high leaf Pi concentration in osnla1 mutants to a level similar to that of wild type plants. In contrast to what has been observed in Arabidopsis, the transcript abundance of OsNLA1 did not decrease under Pi limited conditions or in OsmiR827 (microRNA827)- or OsPHR2 (PHOSPHATE STARVATION RESPONSE 2)-overexpressing transgenic lines. Moreover, there was no interaction of OsNLA1 and OsPHO2, an E2 ubiquitin-conjugase, suggesting that OsPHO2 was not the partner of OsNLA1 involved in ubiquitin-mediated PT degradation. Our results show that OsNLA1 is involved in maintaining phosphate homeostasis in rice by mediating the degradation of OsPT2 and OsPT8, and OsNLA1 differs from the ortholog in Arabidopsis in several aspects. This article is protected by copyright. All rights reserved.
Yue W, Ying Y, Wang C, Zhao Y, Dong C, Whelan J, Shou H.
DOI: 10.1111/tpj.13516.
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Phosphorus: The Underrated Element for Feeding the World

Phosphorus: The Underrated Element for Feeding the World | Plant phosphate nutrition | Scoop.it
Predictions on the lifetime of phosphate (Pi) reserves usually take into account only the need for crop production.
A recent report predicts the global need of chemical Pi fertilizer for sustaining productivity in cropland and grassland.
Here we discuss the implications of these predictions for the lifetime of Pi reserves.
Luis Herrera-Estrella, Damar López-Arredondo
DOI: http://dx.doi.org/10.1016/j.tplants.2016.04.010
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Nature : Reducing phosphorus accumulation in rice grains with an impaired transporter in the node

Phosphorus is an important nutrient for crop productivity. More than 60% of the total phosphorus in cereal crops is finally allocated into the grains and is therefore removed at harvest. This removal accounts for 85% of the phosphorus fertilizers applied to the field each year1, 2. However, because humans and non-ruminants such as poultry, swine and fish cannot digest phytate, the major form of phosphorus in the grains, the excreted phosphorus causes eutrophication of waterways. A reduction in phosphorus accumulation in the grain would contribute to sustainable and environmentally friendly agriculture. Here we describe a rice transporter, SULTR-like phosphorus distribution transporter (SPDT), that controls the allocation of phosphorus to the grain. SPDT is expressed in the xylem region of both enlarged- and diffuse-vascular bundles of the nodes, and encodes a plasma-membrane-localized transporter for phosphorus. Knockout of this gene in rice (Oryza sativa) altered the distribution of phosphorus, with decreased phosphorus in the grains but increased levels in the leaves. Total phosphorus and phytate in the brown de-husked rice were 20–30% lower in the knockout lines, whereas yield, seed germination and seedling vigour were not affected. These results indicate that SPDT functions in the rice node as a switch to allocate phosphorus preferentially to the grains. This finding provides a potential strategy to reduce the removal of phosphorus from the field and lower the risk of eutrophication of waterways. Yamaji N, Takemoto Y, Miyaji T, Mitani-Ueno N, Yoshida KT, Ma JF. DOI:10.1038/nature20610

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Mol Plant: An Arabidopsis ABC transporter mediates phosphate deficiency-induced remodeling of root architecture by modulating iron homeostasis in roots

The remodeling of root architecture is a major developmental response of plants to phosphate (Pi) deficiency and is thought to enhance a plant's ability to forage Pi in topsoil. The underlying mechanism controlling this response, however, is poorly understood. In this work, we identified an Arabidopsis mutant, hps10 (hypersensitive to Pi starvation 10), that is morphologically normal under Pi sufficiency but shows increased inhibition of primary root growth and enhanced production of lateral roots under Pi deficiency. hps10 is a previously identified allele (als3-3) of the ALUMINUM SENSITIVE3 (ALS3) gene, which is involved in plant tolerance to aluminum toxicity. Our results show that ALS3 and its interacting protein AtSTAR1 form an ABC transporter complex in tonoplasts. This protein complex mediates a highly electrogenic transport in Xenopus oocytes. Under Pi deficiency, als3 accumulates higher levels of Fe3+ in its roots than the wild type. In Arabidopsis, LPR1 (LOW PHOSPHATE ROOT1) and LPR2 encode ferroxidase, which when mutated reduces Fe3+ accumulation in roots and causes root growth to be insensitive to Pi deficiency. Here, we provide compelling evidence that ALS3 acts with LPR1/2 to regulate Pi deficiency-induced remodeling of root architecture by modulating Fe homeostasis in roots. Dong J, Piñeros MA, Li X, Yang H, Liu Y, Muphy AS, Kochian LV, Liu D. DOI: 10.1016/j.molp.2016.11.001
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Plant Biotechnology Journal: A phosphate starvation-driven bidirectional promoter as a potential tool for crop improvement and in vitro plant biotechnology

Plant Biotechnology Journal: A phosphate starvation-driven bidirectional promoter as a potential tool for crop improvement and in vitro plant biotechnology | Plant phosphate nutrition | Scoop.it
Phosphate (Pi) deficient soils are a major limitant factor for crop production in many regions in the world. Despite that plants have innovated several developmental and biochemical strategies to deal with this stress, there are still massive extensions of land which combine several abiotic stresses, including phosphate starvation, that limit their use for plant growth and food production. In several plant species a genetic program underlies the biochemical and developmental responses of the organism to cope with low phosphate (Pi) availability. Both protein- and miRNA–coding genes involved in the adaptative response are transcriptionally activated upon Pi starvation. Several of the responsive genes have been identified as transcriptional targets of PHR1, a transcription factor that binds a conserved cis-element called PHR1 Binding Site (P1BS). Our group has previously described and characterized a minimal genetic arrangement that includes two P1BS elements, as a phosphate-responsive enhancer (EZ2). Here we report the engineering and successful use of a phosphate-dependent bidirectional promoter, which has been designed and constructed based on the palindromic sequences of the two P1BS elements present in EZ2. This bidirectional promoter has a potential use in both plant in vitro approaches and in the generation of improved crops adapted to Pi starvation and other abiotic stresses.
Oropeza-Aburto A, Cruz-Ramírez A, Mora-Macías J and Herrera-Estrella L
DOI: 10.1111/pbi.12653
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