scholarly journals Biotechnology approaches to enhance phosphorus acquisition of tomato plants

2006 ◽  
Author(s):  
Kashchandra G. Raghothama ◽  
Avner Silber ◽  
Avraham Levy
Keyword(s):  
Protein Phosphatase ◽  
Phosphate Uptake ◽  
Biological Significance ◽  
Phosphate Starvation ◽  
Mycorrhizal Symbiosis ◽  
Phosphate Transporters ◽  
Tomato Plants ◽  
Over Expression ◽  
High Affinity

Abstract: Phosphorus is one of the least available macronutrient in the soil. The high affinity phosphate transporters are known to be associated with phosphate acquisition under natural conditions. Due to unique interactions of phosphate with soil particles, up to 80% of the applied phosphates may be fixed forcing the farmers to apply 4 to 5 times the fertilizers necessary for crop production. Efficient uptake and utilization of this essential nutrient is essential for sustainability and profitability of agriculture. Many predictions point to utilization/exhaustion of high quality phosphate rocks within this century. This calls for efforts to improve the ability of plants to acquire and utilize limiting sources of phosphate in the rhizosphere. Two important molecular and biochemical components associated with phosphate efficiency are phosphate transporters and phosphatases. This research project is aimed at defining molecular determinants of phosphate acquisition and utilization in addition to generating phosphate uptake efficient plants. The main objectives of the project were; Creation and analysis of transgenic tomato plants over-expressing phosphatases and transporters Characterization of the recently identified members (LePT3 and LePT4) of the Pi transporter family Generate molecular tools to study genetic responses of plants to Pi deficiency During the project period we have successfully identified and characterized a novel phosphate transporter associated with mycorrhizal symbiosis. The expression of this transporter increases with mycorrhizal symbiosis. A thorough characterization of mutant tomato lacking the expression of this gene revealed the biological significance of LePT3 and another novel gene LePT4. In addition we have isolated and characterized several phosphate starvation induced genes from tomato using a combination of differential and subtractive mRNA hybridization techniques. One of the genes, LePS2 belongs to the family of phospho-protein phosphatase. The functionality of the recombinant protein was determined using synthetic phosphor-peptides. Over expression of this gene in tomato resulted in significant changes in growth, delay in flowering and senescence. It is anticipated that phospho-protein phosphatase may have regulatory role in phosphate deficiency responses of plants. In addition a novel phosphate starvation induced glycerol 3-phosphate permease gene family was also characterized. Two doctoral research students are continuing the characterization and functional analysis of these genes. Over expression of high affinity phosphate transporters in tobacco showed increased phosphate content under hydroponic conditions. There is growing evidence suggesting that high affinity phosphate transporters are crucial for phosphate acquisition even under phosphate sufficiency conditions. This project has helped train several postdoctoral fellows and graduate students. Further analysis of transgenic plants expressing phosphatases and transporters will not only reveal the biological function of the targeted genes but also result in phosphate uptake and utilization efficient plants.  

scholarly journals Regulation of Cation-Coupled High-Affinity Phosphate Uptake in the Yeast Saccharomyces cerevisiae

2000 ◽  
Vol 182 (17) ◽  
pp. 5017-5019 ◽  
Author(s):  
Johanna Pattison-Granberg ◽  
Bengt L. Persson
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Growth Phase ◽  
Phosphate Uptake ◽  
Phosphate Starvation ◽  
Fine Tuning ◽  
Yeast Saccharomyces Cerevisiae ◽  
Phosphate Transporters ◽  
High Affinity ◽  
Mutant Strains ◽  
Uptake Process

ABSTRACT Studies of the high-affinity phosphate transporters in the yeastSaccharomyces cerevisiae using mutant strains lacking either the Pho84 or the Pho89 permease revealed that the transporters are differentially regulated. Although both genes are induced by phosphate starvation, activation of the Pho89 transporter precedes that of the Pho84 transporter early in the growth phase in a way which may possibly reflect a fine tuning of the phosphate uptake process relative to the availability of external phosphate.

scholarly journals Disruption of Histone Deacetylase Gene RPD3 Accelerates PHO5 Activation Kinetics through Inappropriate Pho84p Recycling

2005 ◽  
Vol 4 (8) ◽  
pp. 1387-1395 ◽  
Author(s):  
Sriwan Wongwisansri ◽  
Paul J. Laybourn
Keyword(s):  
Histone Deacetylase ◽  
Cytoplasmic Membrane ◽  
Phosphate Uptake ◽  
Transcriptional Repressor ◽  
Phosphate Starvation ◽  
Phosphate Transporter ◽  
Regulatory Pathway ◽  
Activation Kinetics ◽  
High Affinity ◽  
Negative Role

ABSTRACT The histone deacetylase Rpd3p functions as a transcriptional repressor of a diverse set of genes, including PHO5. Here we describe a novel role for RPD3 in the regulation of phosphate transporter Pho84p retention in the cytoplasmic membrane. We show that under repressing conditions (with Pi), PHO5 expression is increased in a pho4Δ rpd3Δ strain, demonstrating PHO regulatory pathway independence. However, the effect of RPD3 disruption on PHO5 activation kinetics is dependent on the PHO regulatory pathway. Upon switching to activating conditions (without Pi), PHO5 transcripts accumulated more rapidly in rpd3Δ cells. This more rapid response correlates with a defect in phosphate uptake due to premature recycling of Pho84p, the high-affinity H+/PO4 3− symporter. Thus, RPD3 also participates in PHO5 regulation through a previously unidentified effect on maintenance of high-affinity phosphate uptake during phosphate starvation. We propose that Rpd3p has a negative role in the regulation of Pho84p endocytosis.

scholarly journals Phosphate Transport and Sensing in Saccharomyces cerevisiae

Genetics ◽  
2001 ◽  
Vol 159 (4) ◽  
pp. 1491-1499 ◽  
Author(s):  
Dennis D Wykoff ◽  
Erin K O'Shea
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Inorganic Phosphate ◽  
Phosphate Uptake ◽  
Phosphate Starvation ◽  
Phosphate Transport ◽  
Glucose Sensors ◽  
Phosphate Transporters ◽  
Synthetic Lethal ◽  
High Phosphate

Abstract Cellular metabolism depends on the appropriate concentration of intracellular inorganic phosphate; however, little is known about how phosphate concentrations are sensed. The similarity of Pho84p, a high-affinity phosphate transporter in Saccharomyces cerevisiae, to the glucose sensors Snf3p and Rgt2p has led to the hypothesis that Pho84p is an inorganic phosphate sensor. Furthermore, pho84Δ strains have defects in phosphate signaling; they constitutively express PHO5, a phosphate starvation-inducible gene. We began these studies to determine the role of phosphate transporters in signaling phosphate starvation. Previous experiments demonstrated a defect in phosphate uptake in phosphate-starved pho84Δ cells; however, the pho84Δ strain expresses PHO5 constitutively when grown in phosphate-replete media. We determined that pho84Δ cells have a significant defect in phosphate uptake even when grown in high phosphate media. Overexpression of unrelated phosphate transporters or a glycerophosphoinositol transporter in the pho84Δ strain suppresses the PHO5 constitutive phenotype. These data suggest that PHO84 is not required for sensing phosphate. We further characterized putative phosphate transporters, identifying two new phosphate transporters, PHO90 and PHO91. A synthetic lethal phenotype was observed when five phosphate transporters were inactivated, and the contribution of each transporter to uptake in high phosphate conditions was determined. Finally, a PHO84-dependent compensation response was identified; the abundance of Pho84p at the plasma membrane increases in cells that are defective in other phosphate transporters.

Characterization of a Mode of Specific Binding of Fibrin Monomer through its Amino-Terminal Domain by Macrophages and Macrophage Cell-Lines

1990 ◽  
Vol 63 (02) ◽  
pp. 193-203 ◽  
Author(s):  
John R Shainoff ◽  
Deborah J Stearns ◽  
Patricia M DiBello ◽  
Youko Hishikawa-Itoh
Keyword(s):  
Peritoneal Macrophages ◽  
Affinity Binding ◽  
Macrophage Cell ◽  
High Affinity Binding ◽  
Amino Terminal ◽  
High Affinity ◽  
Terminal Domain ◽  
Weak Binding ◽  
Amino Terminal Domain

SummaryThe studies reported here probe the existence of a receptor-mediated mode of fibrin-binding by macrophages that is associated with the chemical change underlying the fibrinogen-fibrin conversion (the release of fibrinopeptides from the amino-terminal domain) without depending on fibrin-aggregation. The question is pursued by 1) characterization of binding in relation to fibrinopeptide content of both the intact protein and the CNBr-fragment comprising the amino-terminal domain known as the NDSK of the protein, 2) tests of competition for binding sites, and 3) photo-affinity labeling of macrophage surface proteins. The binding of intact monomers of types lacking either fibrinopeptide A alone (α-fibrin) or both fibrinopeptides A and B (αβ-fibrin) by peritoneal macrophages is characterized as proceeding through both a fibrin-specific low density/high affinity (BMAX ≃ 200–800 molecules/cell, KD ≃ 10−12 M) interaction that is not duplicated with fibrinogen, and a non-specific high density/low affinity (BMAX ≥ 105 molecules/cell, KD ≥ 10−6 M) interaction equivalent to the weak binding of fibrinogen. Similar binding characteristics are displayed by monocyte/macrophage cell lines (J774A.1 and U937) as well as peritoneal macrophages towards the NDSK preparations of these proteins, except for a slightly weaker (KD ≃ 10−10 M) high-affinity binding. The high affinity binding of intact monomer is inhibitable by fibrin-NDSK, but not fibrinogen-NDSK. This binding appears principally dependent on release of fibrinopeptide-A, because a species of fibrin (β-fibrin) lacking fibrinopeptide-B alone undergoes only weak binding similar to that of fibrinogen. Synthetic Gly-Pro-Arg and Gly-His-Arg-Pro corresponding to the N-termini of to the α- and the β-chains of fibrin both inhibit the high affinity binding of the fibrin-NDSKs, and the cell-adhesion peptide Arg-Gly-Asp does not. Photoaffinity-labeling experiments indicate that polypeptides with elec-trophoretically estimated masses of 124 and 187 kDa are the principal membrane components associated with specifically bound fibrin-NDSK. The binding could not be up-regulated with either phorbol myristyl acetate, interferon gamma or ADP, but was abolished by EDTA and by lipopolysaccharide. Because of the low BMAX, it is suggested that the high-affinity mode of binding characterized here would be too limited to function by itself in scavenging much fibrin, but may act cooperatively with other, less limited modes of fibrin binding.

Acid-Sensing Ion Channels

2020 ◽  
Author(s):  
Stefan Gründer
Keyword(s):  
Nervous System ◽  
Ion Channels ◽  
Excitatory Synapses ◽  
Detailed Characterization ◽  
High Affinity ◽  
Acid Sensing Ion Channels ◽  
Long Time ◽  
Pathological Pain

Acid-sensing ion channels (ASICs) are proton-gated Na+ channels. Being almost ubiquitously present in neurons of the vertebrate nervous system, their precise function remained obscure for a long time. Various animal toxins that bind to ASICs with high affinity and specificity have been tremendously helpful in uncovering the role of ASICs. We now know that they contribute to synaptic transmission at excitatory synapses as well as to sensing metabolic acidosis and nociception. Moreover, detailed characterization of mouse models uncovered an unanticipated role of ASICs in disorders of the nervous system like stroke, multiple sclerosis, and pathological pain. This review provides an overview on the expression, structure, and pharmacology of ASICs plus a summary of what is known and what is still unknown about their physiological functions and their roles in diseases.

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