Low Phosphate Conditions Research Articles

Arsenite: the umpire of arsenate perception and responses in plants.

Arsenite regulates the uptake and detoxification of arsenate in plants under low-phosphate conditions by governing the stability of PHOSPHATE STARVATION RESPONSE 1, as reported in a recent study by Navarro and colleagues. This finding opens new opportunities for research into developing mitigation strategies to deal with arsenic toxicity in plants.

ITRAQ-based proteomic analysis of Bacillus subtilis strain NCD-2 regulated by PhoPR two-component system: A comparative analysis with transcriptomics revealed the regulation for fengycin production by branched chain amino acids

The PhoPR two-component system (TCS) is a signal transduction pathway to regulate the phosphate starvation response in Bacillus subtilis and regulated fengycin production in strain NCD-2 under low phosphate condition. The purpose of this study was to characterize the proteome level responses in the phoP-null mutant (MP) and the phoR-null mutant (MR), and to integrate the proteomics with the transcriptomic data obtained previously. The metabolic pathway for fengycin was predicted based on omics analysis as well as molecular genetics assay. Results showed the proteins and genes associated with biosynthesis of branched chain amino acids (BCAAs) were regulated by PhoPR TCS, and liquid chromatography mass spectrometry (LC-MS) analysis also confirmed that the production of BCAAs was down-regulated in the MP and MR mutants, when compared to wild-type strain NCD-2. Protein network analysis showed that the BCAA metabolism was linked to the biosynthesis of lipopeptides. The MP and MR strains decreased the fengycin production when cultured in modified Landy medium supplied with 0.42 mM phosphate, however, the fengycin production could be restored when the glutamic acid was replaced with BCAAs that were added to modified Landy medium. The lpdV gene, which is responsible for the BCAA degradation process, was deleted in strain NCD-2. Compared with the wild-type strain, the lpdV mutant produced significantly less fengycin in the medium supplied with BCAAs. Considered together, the results of this study indicate that the PhoPR TCS regulates fengycin production by affecting BCAA biosynthesis.

Functional Genomic Analysis of the SPL9 Gene in Arabidopsis thaliana under Low Phosphate Conditions

Functional Genomic Analysis of the SPL9 Gene in Arabidopsis thaliana under Low Phosphate Conditions

Stimulation of Hyphal Ramification and Sporulation in Funneliformis mosseae by Root Extracts Is Host Phosphorous Status-Dependent.

A simulation of the environment inhabited by arbuscular mycorrhizal (AM) fungi could provide clues as to how to cultivate these obligate biotrophs axenically. Host intraradical and rhizospheric environments, root extracts and exudates in particular, would be crucial for AM fungi to complete their life cycles. In this study, we analyzed and compared the effects of root exudates (RE) and root extracts (RET) of white clover (Trifolium repens) on the asymbiotic growth of the AM fungus Funneliformis mosseae in vitro, and furtherly analyzed the chemical components of different RET with the LC-MS/MS technique in order to establish an asymbiotic cultivation system for this important and hardly domesticated AM fungus. RET is superior to RE in stimulating spore germination, hyphal elongation and branching, and secondary spore formation (p < 0.05). RET-induced effects were dependent on phosphate supplement levels, and the RET obtained following the treatment with low levels of phosphorus significantly promoted hyphal growth and sporulation (p < 0.05). A few newly formed secondary spores showed limited colonization of white clover roots. The low phosphorus-induced effects could be ascribed to the metabolic adjustment (mainly lipids and organic acids) of white clover roots under low phosphate conditions. Our findings demonstrate that the low phosphate-induced RET boosts the asymbiotic growth of AM fungus, and thus offers an alternative way to fulfill the life cycle of AM fungi asymbiotically.

Acute Sensitivity of V. cholerae to Phosphate Starvation: A Possible Case of Futile Metabolism.

Multi-nutrient starvation profiles are emerging as an essential feature of human pathogen studies. In the present work, we attempted to understand why V. cholerae cannot survive in the growth media that includes carbon and nitrogen but lacks phosphate. However, it can survive starvation in artificial seawater without all three major nutrients (carbon, nitrogen, and phosphate). V. cholerae survival was critically affected below ten mM of phosphate content in the media. Interestingly, the survival of the bacteria in low phosphate conditions improved when cultured under sub-optimal growth conditions, sub-optimal C: N ratio, non-metabolizable nutrient sources, and activation of stringent response. The phosphate starved cells had low ATP levels and high NADH levels; A quick drop in ATP, coupled with impaired redox potential, may lead to cell death. We also observed the acute sensitivity to phosphate limitation among the other members of the genus Vibrio. Among those, V. vulnificus and V. cholerae showed the highest sensitivity (< 0.1%). Among the members of γ-proteobacteria, E. coli and C. sakazaki and S. Typhimurium showed the lowest sensitivity (10%), and the A. hydrophila and V. harvey showing intermediate (1 - 2%) survival in low phosphate condition. The presence of carbon and nitrogen in the media over-weigh the information about the lack of phosphate that would cause continued but futile metabolism. The current study shows a general lack of coordination between carbon, nitrogen, and phosphate metabolism in V. cholerae.

Auxenochlorella Protothecoides Populations Adapted to Low Phosphate Conditions Accumulated More Non-Phosphorus Glycerolipids and Biomass than Wild Type Progenitors

Auxenochlorella Protothecoides Populations Adapted to Low Phosphate Conditions Accumulated More Non-Phosphorus Glycerolipids and Biomass than Wild Type Progenitors

Functional analysis of a Phytophthora host-translocated effector using the yeast model system.

Background Phytophthora plant pathogens secrete effector proteins that are translocated into host plant cells during infection and collectively contribute to pathogenicity. A subset of these host-translocated effectors can be identified by the amino acid motif RXLR (arginine, any amino acid, leucine, arginine). Bioinformatics analysis has identified hundreds of putative RXLR effector genes in Phytophthora genomes, but the specific molecular function of most remains unknown.MethodsHere we describe initial studies to investigate the use of Saccharomyces cerevisiae as a eukaryotic model to explore the function of Phytophthora RXLR effector proteins.Results and ConclusionsExpression of individual RXLR effectors in yeast inhibited growth, consistent with perturbation of a highly conserved cellular process. Transcriptome analysis of yeast cells expressing the poorly characterized P. sojae RXLR effector Avh110 identified nearly a dozen yeast genes whose expression levels were altered greater than two-fold compared to control cells. All five of the most down-regulated yeast genes are normally induced under low phosphate conditions via the PHO4 transcription factor, indicating that PsAvh110 perturbs the yeast regulatory network essential for phosphate homeostasis and suggesting likely PsAvh110 targets during P. sojae infection of its soybean host.

Overexpression of OsPHR3 improves growth traits and facilitates nitrogen use efficiency under low phosphate condition

Phosphorus (P) and nitrogen (N) are both essential macronutrients for maintaining plant growth and development. In rice (Oryza sativa L.), OsPHR3 is one of the four paralogs of PHR1, which acts as a central regulator of phosphate (Pi) homeostasis, as well being involved in N homeostasis. However, the functions of OsPHR3 in N utilization under different Pi conditions have yet to be fully studied. In this study, we aimed to dissect the effect of OsPHR3-overexpression on N utilization under Pi deficient regimes. Biochemical, molecular and physiological assays were performed to determine the N-influx, translocation, and accumulation in OsPHR3-overexpressing rice lines, grown under Pi-sufficient and -deficient conditions, in both hydroponic and soil systems. Furthermore, important agronomic traits of these plants were also evaluated. The overexpression of OsPHR3 increased N uptake under Pi stress regimes. Increased N uptake also elevated total N concentrations in these plants by inducing N transporter genes expression. Furthermore, overexpression of OsPHR3 increased N use efficiency, 1000-grain weight and grain yield under different Pi conditions. We established new findings that OsPHR3-overexpression facilitates N utilization under Pi deficient conditions. This will help achieving higher yields by coordinating the utilization of N and P.

The Role of Phosphate in Alcohol-Induced Experimental Pancreatitis

Heavy alcohol consumption is a common cause of acute pancreatitis; however, alcohol abuse does not always result in clinical pancreatitis. As a consequence, the factors responsible for alcohol-induced pancreatitis are not well understood. In experimental animals, it has been difficult to produce pancreatitis with alcohol. Clinically, alcohol use predisposes to hypophosphatemia, and hypophosphatemia has been observed in some patients with acute pancreatitis. Because of abundant protein synthesis, the pancreas has high metabolic demands, and reduced mitochondrial function leads to organelle dysfunction and pancreatitis. We proposed, therefore, that phosphate deficiency might limit adenosine triphosphate synthesis and thereby contribute to alcohol-induced pancreatitis. Mice were fed a low-phosphate diet (LPD) before orogastric administration of ethanol. Direct effects of phosphate and ethanol were evaluated invitro in isolated mouse pancreatic acini. LPD reduced serum phosphate levels. Intragastric administration of ethanol to animals maintained on an LPD caused severe pancreatitis that was ameliorated by phosphate repletion. In pancreatic acinar cells, low-phosphate conditions increased susceptibility to ethanol-induced cellular dysfunction through decreased bioenergetic stores, specifically affecting total cellular adenosine triphosphate and mitochondrial function. Phosphate supplementation prevented ethanol-associated cellular injury. Phosphate status plays a critical role in predisposition to and protection from alcohol-induced acinar cell dysfunction and the development of acute alcohol-induced pancreatitis. This finding may explain why pancreatitis develops in only some individuals with heavy alcohol use and suggests a potential novel therapeutic approach to pancreatitis. Finally, an LPD plus ethanol provides a new model for studying alcohol-associated pancreatic injury.

Quantitative Proteomics Reveals that GmENO2 Proteins Are Involved in Response to Phosphate Starvation in the Leaves of Glycine max L.

Soybean (Glycine max L.) is a major crop providing important source for protein and oil for human life. Low phosphate (LP) availability is a critical limiting factor affecting soybean production. Soybean plants develop a series of strategies to adapt to phosphate (Pi) limitation condition. However, the underlying molecular mechanisms responsible for LP stress response remain largely unknown. Here, we performed a label-free quantification (LFQ) analysis of soybean leaves grown under low and high phosphate conditions. We identified 267 induced and 440 reduced differential proteins from phosphate-starved leaves. Almost a quarter of the LP decreased proteins are involved in translation processes, while the LP increased proteins are accumulated in chlorophyll biosynthetic and carbon metabolic processes. Among these induced proteins, an enolase protein, GmENO2a was found to be mostly induced protein. On the transcriptional level, GmENO2a and GmENO2b, but not GmENO2c or GmENO2d, were dramatically induced by phosphate starvation. Among 14 enolase genes, only GmENO2a and GmENO2b genes contain the P1BS motif in their promoter regions. Furthermore, GmENO2b was specifically induced in the GmPHR31 overexpressing soybean plants. Our findings provide molecular insights into how soybean plants tune basic carbon metabolic pathway to adapt to Pi deprivation through the ENO2 enzymes.

Roots primed for better phosphate uptake

Plant Science Phosphate is a key resource for plants, and remediating phosphate deficiency drives considerable fertilizer use. In low-phosphate conditions, roots make more root hairs, which makes them better able to take up what little phosphate can be found. Wendrich et al. performed single-cell transcriptomics on the developing Arabidopsis root and queried the resulting gene-expression atlas for responses related to vascular development. The authors found that signals regulating root hair development began in the inner vasculature of the root with transcription factors that drove the production of the hormone cytokinin. Response cascades identified through the transcriptome database pointed to genes in epidermal cells that regulate root hair development. Science , this issue p. [eaay4970][1] [1]: /lookup/doi/10.1126/science.aay4970

Mutualistic Fungal Endophyte Colletotrichum tofieldiae Ct0861 Colonizes and Increases Growth and Yield of Maize and Tomato Plants

Facing rising global food demand in a sustainable way is a great challenge of modern agriculture. Thus, the increase of crop productivity and resilience in an adverse climate scenario is urgently needed. Fungal endophytes have been described as potential biological tools to improve plant yield and tolerance to biotic and abiotic stresses; however, their application in agriculture needs further research. The fungal endophyte Colletotrichum tofieldiae strain Ct0861 establishes a mutualistic interaction with Arabidopsis thaliana, promoting plant growth and silique production at low phosphate conditions. Until now, its ability to colonize and confer benefits to other plant species remained unexplored. Here, we show that Ct0861 colonizes and promotes growth in vitro of maize (Zea mays L.) and tomato (Solanum lycopersicum L.) seedlings, resulting in significantly larger shoot length and weight. Greenhouse and field experiments in optimal nutritional conditions showed an increase between 12% and 22% of yield in both tomato and maize. The inoculated plants were not suffering from phosphate starvation, which points at different modes of action not elucidated yet. These results indicate that the beneficial effect of Ct0861 may extend to other plant species of economic importance, making Ct0861 a potentially valuable inoculant.

Overexpression of a phosphate transporter gene ZmPt9 from maize influences growth of transgenic Arabidopsis thaliana

Phosphate transporters (PHTs) are well-known for their roles in phosphate uptake in plants. However, their actions in imparting plant growth in plants are still not so clear. In our previous study, we observed that maize PHT1 gene ZmPt9 plays a significant role in phosphate uptake. In this study, we further characterized ZmPt9 in response to low phosphate condition through ZmPt9 promoter inductive analysis by GUS staining and quantification. To elucidate the function of ZmPt9, we generated overexpression plant in Arabidopsis. ZmPt9 overexpressing Arabidopsis plants conferred small leaves and early flowering compared with the wild-type plants. In addition, ZmPt9 can complement the late flowering phenotype of Arabidopsis mutant pht1;2. The qRT-PCR analysis revealed that overexpression of ZmPt9 in Arabidopsis changed expression levels of some flowering-related genes. Further expressed detection of hormone related genes revealed that GA and auxin maybe the main determinant for growth influences of ZmPt9. In conclusion, these results suggest that apart from phosphate transport activity, ZmPt9 can be further exploited for improving crops growth.

Vascular transcription factors guide plant epidermal responses to limiting phosphate conditions.

Optimal plant growth is hampered by deficiency of the essential macronutrient phosphate in most soils. Plant roots can, however, increase their root hair density to efficiently forage the soil for this immobile nutrient. By generating and exploiting a high-resolution single-cell gene expression atlas of Arabidopsis roots, we show an enrichment of TARGET OF MONOPTEROS 5/LONESOME HIGHWAY (TMO5/LHW) target gene responses in root hair cells. The TMO5/LHW heterodimer triggers biosynthesis of mobile cytokinin in vascular cells and increases root hair density during low-phosphate conditions by modifying both the length and cell fate of epidermal cells. Moreover, root hair responses in phosphate-deprived conditions are TMO5- and cytokinin-dependent. Cytokinin signaling links root hair responses in the epidermis to perception of phosphate depletion in vascular cells.

The Plasticity of Root Systems in Response to External Phosphate.

Phosphate is an essential macro-element for plant growth accumulated in the topsoil. The improvement of phosphate uptake efficiency via manually manipulating root system architecture is of vital agronomic importance. This review discusses the molecular mechanisms of root patterning in response to external phosphate availability, which could be applied on the alleviation of phosphate-starvation stress. During the long time evolution, plants have formed sophisticated mechanisms to adapt to environmental phosphate conditions. In terms of root systems, plants would adjust their root system architecture via the regulation of the length of primary root, the length/density of lateral root and root hair and crown root growth angle to cope with different phosphate conditions. Finally, plants develop shallow or deep root system in low or high phosphate conditions, respectively. The plasticity of root system architecture responds to the local phosphate concentrations and this response was regulated by actin filaments, post-translational modification and phytohormones such as auxin, ethylene and cytokinin. This review summarizes the recent progress of adaptive response to external phosphate with focus on integrated physiological, cellular and molecular signaling transduction in rice and Arabidopsis.

Investigating the genetic variability of 12 Vietnamese rice accessions (Oryza sativa L.) in response to phosphorus deficiency

Phosphate is the second major factor limiting on crop productivity and leads to various physiological disorders that would consequently affect plant development. In response to phosphate starvation, plants have to improve their root systems for efficiently acquired phosphate. In Vietnam, rice is one of the most important agricultural crops in which 60% of the rain-fed lowland rice is cultured on soil types, which are low in phosphorus or phosphate fixing. This fact along with the scenario in which phosphate resources are running out in fast pace, highly provoked an indispensible need for developing new rice varieties with high productivity under low phosphate condition. An emerging approach in order to accomplish this goal is through genetic improvement of local rice resources. Taking advantage of that, in this study, out of 182 sequenced Vietnamese rice accessions, 12 representatives from 3 distinguishing rice groups: Indica, Japonica and admix Indica subgroup were chosen. The variation in number of crown root, root length, shoot length, root mass, shoot mass, chlorophyll content and root anatomy were examined as parameters to analyze the effect of phosphorus deficiency (1 µM) compare to full phosphate medium (300 µM). The minimum number of plantlets used for each condition was 15. Each genotype was grown in Yoshida hydroponic medium (changed every 4 days, harvesting was made after 14 days). The experimental results showed a remarkable variation of different rice accessions in response to phosphate deficiency. The starvation of phosphate significantly affected almost all examined traits in which several accessions such as G38, G93, G165, G223, G62 accessions were potential hypersensitive and G11, G177 accessions were potential tolerant to P deficiency. These results are interesting and encouraging to further research for screening our Vietnamese rice collection in order to identify the set of potential genes responsible for tolerance in phosphorus starvation condition.

Phosphate regulates malate/citrate-mediated iron uptake and transport in apple

The accumulation of iron (Fe) in the apical meristem is considered as a critical factor involved in limiting the elongation of roots under low phosphate (Pi) conditions. Furthermore, the antagonism between Fe and Pi largely affects the effective utilization of Fe. Although the lack of Pi serves to increase the effectiveness of Fe in rice under both Fe-sufficient and Fe-deficient conditions, the underlying physiological mechanism governing this phenomenon is still unclear. In this study, we found that low Pi alleviated the Fe-deficiency phenotype in apples. Additionally, low Pi treatments increased ferric-chelated reductase (FCR) activity in the rhizosphere, promoted proton exocytosis, and enhanced the Fe concentration in both the roots and shoots. In contrast, high Pi treatments inhibited this process. Under conditions of low Pi, malate and citrate exudation from apple roots occurred under both Fe-sufficient and Fe-deficient conditions. In addition, treatment with 0.5 mM malate and citrate effectively alleviated the Fe and Pi deficiencies. Taken together, these data support the conclusion that a low Pi supply promotes organic acids exudation and enhances Fe absorption during Fe deficiency in apples.

Epigenomic regulation of OTU5 in Arabidopsis thaliana

Epigenetic regulation by DNA methylation and histone marks is crucial to plant development. In Arabidopsis, the otu5 mutant exhibited altered root phenotypes resembling those of phosphate-deficient plants. In low phosphate (Pi) conditions, altered H3K4 and H3K27 trimethylation were associated with the expression of Pi homeostasis-related genes. However, the genetic effect of OTU5 on the epigenomes was left unexplored. We assessed genome-wide DNA methylation, gene expression and histone modifications of roots from both Col-0 and otu5 mutants. We found that OTU5 altered DNA methylation profile with a context-specific effect through targeting local genomic regions. Our analysis showed that in otu5 the abundance of H3K4me3 was clearly associated with the changes of DNA methylation, leading to the transcriptional difference from wildtype. We concluded that OTU5 induced cross-talks among epigenomes that altogether impacted the regulation of approximately 7060 genes. Of which 186 genes associated with root development were likely to be epigenetically regulated.

Cardiac Autonomic Neuropathy and Hemodynamic Dysfunction as a Consequence of Mild Hypercaloric Intake: Modification by Phosphate Supplementation

Cardiac autonomic neuropathy (CAN) has been linked to negative outcomes in diabetic patients, where it is associated with a high risk of cardiac arrhythmia and sudden death. Our previous research showed that prediabetic rats develop CAN in absence of overt signs of metabolic derangement or change in body weight. This was associated with vascular dysfunction and perivascular adipose tissue (PVAT) inflammation, which preceded inflammatory changes in other adipose pools, possibly linked to increased Uncoupling protein 1 (UCP1) and hypoxia‐inducible factor (HIF1‐a) expression. In parallel, phosphate supplementation is a simple intervention to improve body weight, energy metabolism, and glucose tolerance. Moreover, inorganic phosphate acts as a UCP1 inhibitor. Here, we examined the role of phosphate supplementation in ameliorating the early signs of cardiovascular dysfunction in metabolically challenged rats. Male SD rats (5–6 weeks) were randomly allocated into four groups fed either control diet (group 1) or high‐calorie (HC) diet for 12 weeks with three different levels of dietary phosphate; group 2: low phosphate (LP)‐ 0.37 mg/KCal, group 3: intermediate phosphate (IP)‐0.7 mg/KCal, group 4: high phosphate (HP)‐ 1.5 mg/KCal. Daily food intake, body weight, and body composition were recorded. Serum insulin was measured by ELISA. Invasive hemodynamic measurements were done and baroreceptor sensitivity (BRS) was assessed by the vasoactive method. After sacrifice, organs were collected for immunohistochemistry and western blotting. No changes in caloric intake, body weight, blood pressure, and blood glucose levels were observed. However, rats on HC diet showed an increase in serum insulin level and fat/lean ratio. Consistent with our previous work, HC‐feeding was associated with significant reduction in parasympathetic BRS in both the LP and IP groups. This was also accompanied by a reduced left ventricular systolic function. On the cellular level, Oil Red O stain showed a significant increase in the diameter of PVAT adipocytes in LP condition, together with increased expression of HIF‐1α, IL‐1β and UCP‐1. Of note, inflammatory changes observed in the PVAT were not detected in neither white nor brown adipose tissue. Furthermore, higher macrophage infiltration and total ROS score in the PVAT, heart mid‐section and brainstem were observed in LP when compared to control. Our present results highlight a role of phosphate supplementation in the amelioration of the HC induced parasympathetic dysfunction. This could be due to the reported ability of dietary phosphate to improve the assimilation of fat and reduce adipose tissue hypoxia possibly via UCP1 inhibition.Support or Funding InformationFunded by an AUB CRS grantIL1‐UCP1 for perivascular adipose tissue (PVAT), white adipose tissue (WAT), and brown adipose tissue (BAT)Figure 1

Isoelectric point-amyloid formation of α-synuclein extends the generality of the solubility and supersaturation-limited mechanism.

Proteins in either a native or denatured conformation often aggregate at an isoelectric point (pI), a phenomenon known as pI precipitation. However, only a few studies have addressed the role of pI precipitation in amyloid formation, the crystal-like aggregation of denatured proteins. We found that α-synuclein, an intrinsically disordered protein of 140 amino acid residues associated with Parkinson's disease, formed amyloid fibrils at pI (= 4.7) under the low-sodium phosphate conditions. Although α-synuclein also formed amyloid fibrils at a wide pH range under high concentrations of sodium phosphate, the pI-amyloid formation was characterized by marked amyloid-specific thioflavin T fluorescence and clear fibrillar morphology, indicating highly ordered structures. Analysis by heteronuclear NMR in combination with principal component analysis suggested that amyloid formation under low and high phosphate conditions occurred by distinct mechanisms. The former was likely to be caused by the intermolecular attractive charge-charge interactions, where α-synuclein has +17 and −17 charges even with the zero net charge. On the other hand, the latter was caused by the phosphate-dependent salting-out effects. pI-amyloid formation may play a role in the membrane-dependent amyloid formation of α-synuclein, where the negatively charged membrane surface reduces the local pH to pI and the membrane hydrophobic environment enhances electrostatic interactions. The results extend the supersaturation-limited mechanism of amyloid formation: Amyloid fibrils are formed under a variety of conditions of decreased solubility of denatured proteins triggered by the breakdown of supersaturation.