Root high‐affinity K
            +
            and Cs
            +
            uptake and plant fertility in tomato plants are dependent on the activity of the high‐affinity K
            +
            transporter
            SlHAK5

The interaction between tomato and the fungal pathogen Cladosporium fulvum complies with the gene-for-gene system. Strains of C. fulvum that produce race-specific elicitor AVR4 induce a hypersensitive response, leading to resistance, in tomato plants that carry the Cf-4 resistance gene. The mechanism of AVR4 perception was examined by performing binding studies with 125I-AVR4 on microsomal membranes of tomato plants. We identified an AVR4 high-affinity binding site (KD = 0.05 nM) which exhibited all the characteristics expected for ligand-receptor interactions, such as saturability, reversibility, and specificity. Surprisingly, the AVR4 high-affinity binding site appeared to originate from fungi present on infected tomato plants rather than from the tomato plants themselves. Detailed analysis showed that this fungus-derived, AVR4-specific binding site is heat- and proteinase K-resistant. Affinity crosslinking demonstrated that AVR4 specifically binds to a component of approximately 75 kDa that is of fungal origin. Our data suggest that binding of AVR4 to a fungal component or components is related to the intrinsic virulence function of AVR4 for C. fulvum.

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Biotechnology approaches to enhance phosphorus acquisition of tomato plants

10.32747/2006.7586546.bard ◽

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.

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An NH4+-sensitive component dominates high-affinity K+ uptake in tomato plants

Plant Science ◽

10.1016/j.plantsci.2006.09.003 ◽

2007 ◽

Vol 172 (2) ◽

pp. 273-280 ◽

Cited By ~ 76

Author(s):

Manuel Nieves-Cordones ◽

M. Angeles Martínez-Cordero ◽

Vicente Martínez ◽

Francisco Rubio

Keyword(s):

K Uptake ◽

Tomato Plants ◽

High Affinity

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Neuronal and Extraneuronal Uptake of 3H-Norepinephrine in the Heart of the Active Bat: An Electron Microscopic Radioautographic Study

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100073052 ◽

1973 ◽

Vol 31 ◽

pp. 522-523

Author(s):

Martin Hagopian ◽

Michael D. Gershon ◽

Eladio A. Nunez

Keyword(s):

Smooth Muscle ◽

Monoamine Oxidase ◽

Vascular Smooth Muscle ◽

Cardiac Muscle ◽

Maximum Rate ◽

External Medium ◽

Extraneuronal Uptake ◽

Electron Microscopic ◽

Cardiac Tissues ◽

High Affinity

The ability of cardiac tissues to take up norepinephrine from an external medium is well known. Two mechanisms, called Uptake and Uptake respectively by Iversen have been differentiated. Uptake is a high affinity system associated with adrenergic neuronal elements. Uptake is a low affinity system, with a higher maximum rate than that of Uptake. Uptake has been associated with extraneuronal tissues such as cardiac muscle, fibroblasts or vascular smooth muscle. At low perfusion concentrations of norepinephrine most of the amine taken up by Uptake is metabolized. In order to study the localization of sites of norepinephrine storage following its uptake in the active bat heart, tritiated norepinephrine (2.5 mCi; 0.064 mg) was given intravenously to 2 bats. Monoamine oxidase had been inhibited with pheniprazine (10 mg/kg) one hour previously to decrease metabolism of norepinephrine.

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Clinical Application and Results of the Assessment of Coronary Blood Flow by the Regional Precordial Xenon Residue Detection Technique

Nuklearmedizin ◽

10.1055/s-0037-1620686 ◽

1978 ◽

Vol 17 (04) ◽

pp. 161-171

Author(s):

H.-J. Engel ◽

H. Hundeshagen ◽

P. R. Lichtlen

Keyword(s):

Wall Motion ◽

High Flow ◽

Detection Technique ◽

Fatty Tissue ◽

Technical Aspects ◽

Residue Detection ◽

High Affinity ◽

Artery Disease ◽

The Right ◽

Drug Interventions

Methodological and technical aspects as well as application and results of the precordial Xenon-residue-detection technique are critically reviewed. The results concern mainly normal flow in various regions of the heart esp. in the free wall of the right and left ventricle, poststenotic flow in patients with coronary artery disease in relation to the degree of proximal nar-rowings as well as wall motion of the corresponding LV segment, bypassgraft flow and flow after drug interventions esp. nitrates, betablockers, the calcium-antagonist Nifedipine and the coronary dilator Dipyridamole. In spite of its serious limitations (high affinity of Xenon for fatty tissue, geometrical problems in the assessment of flow and its relation to anatomy, gas exchange in situations of high flow etc.), the technique is found to be a usefull investigatory tool. Due to its technical display and the related high costs routine application is, however, prohibitive.

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Binding of 131I-Labeled Tissue-Type Plasminogen Activator on De-Endothelialized Lesions in Rabbits

Nuklearmedizin ◽

10.1055/s-0038-1628893 ◽

1987 ◽

Vol 26 (05) ◽

pp. 224-228 ◽

Cited By ~ 2

Author(s):

Y. Isaka ◽

H. Etani ◽

K. Kimura ◽

S. Yoneda ◽

T. Kamada ◽

...

Keyword(s):

Plasminogen Activator ◽

Abdominal Aorta ◽

Half Life ◽

Balloon Catheter ◽

Biochemical Properties ◽

Tissue Type ◽

Fibrin Deposition ◽

Tissue Type Plasminogen Activator ◽

High Affinity ◽

Type Plasminogen Activator

Tissue-type plasminogen activator (t-PA) which has a high affinity for fibrin in the clot, was labeled with 131I by the iodogen method, and its binding to de-endothelialized lesions in the rabbit was measured to assess the detectability of thrombi. The de-endothelialized lesion was induced in the abdominal aorta with a Fogarty 4F balloon catheter. Two hours after the de-endothelialization, 131I-labeled t-PA (125 ± 46 μCi) was injected intravenously. The initial half-life of the agent in blood (n = 12) was 2.9 ± 0.4 min. The degree of binding of 131I-labeled t-PA to the de-endothelialized lesion was evaluated at 15 min (n = 6) or at 30 min (n = 6) after injection of the agent. In spite of the retention of the biochemical properties of 131I-labeled t-PA and the presence of fibrin deposition at the de-endothelialized lesion, the binding of t-PA to the lesion was not sufficiently strong. Lesion-to-control ratios (cpm/g/cpm/g) were 1.65 ± 0.40 (at 15 min) and 1.39 ± 1.31 (at 30 min), and lesion-to-blood ratios were 1.39 ± 0.32 (at 15 min) and 1.36 ± 0.23 (at 30 min). These results suggest that radiolabeled t-PA may be inappropriate as a radiopharmaceutical for the scintigraphic detection of a pre-existing thrombotic lesion.

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

Thrombosis and Haemostasis ◽

10.1055/s-0038-1645194 ◽

1990 ◽

Vol 63 (02) ◽

pp. 193-203 ◽

Cited By ~ 9

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.

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Protein S and C4b-Binding Protein: Components Involved in the Regulation of the Protein C Anticoagulant System

Thrombosis and Haemostasis ◽

10.1055/s-0038-1646373 ◽

1991 ◽

Vol 66 (01) ◽

pp. 049-061 ◽

Cited By ~ 233

Author(s):

Björn Dahlbäck

Keyword(s):

Vitamin K ◽

Complement System ◽

Protein C ◽

Protein S ◽

High Affinity ◽

Anticoagulant System ◽

Dependent Protein ◽

The Complement System ◽

Β Chain ◽

Dependent Domain

SummaryThe protein C anticoagulant system provides important control of the blood coagulation cascade. The key protein is protein C, a vitamin K-dependent zymogen which is activated to a serine protease by the thrombin-thrombomodulin complex on endothelial cells. Activated protein C functions by degrading the phospholipid-bound coagulation factors Va and VIIIa. Protein S is a cofactor in these reactions. It is a vitamin K-dependent protein with multiple domains. From the N-terminal it contains a vitamin K-dependent domain, a thrombin-sensitive region, four EGF)epidermal growth factor (EGF)-like domains and a C-terminal region homologous to the androgen binding proteins. Three different types of post-translationally modified amino acid residues are found in protein S, 11 γ-carboxy glutamic acid residues in the vitamin K-dependent domain, a β-hydroxylated aspartic acid in the first EGF-like domain and a β-hydroxylated asparagine in each of the other three EGF-like domains. The EGF-like domains contain very high affinity calcium binding sites, and calcium plays a structural and stabilising role. The importance of the anticoagulant properties of protein S is illustrated by the high incidence of thrombo-embolic events in individuals with heterozygous deficiency. Anticoagulation may not be the sole function of protein S, since both in vivo and in vitro, it forms a high affinity non-covalent complex with one of the regulatory proteins in the complement system, the C4b-binding protein (C4BP). The complexed form of protein S has no APC cofactor function. C4BP is a high molecular weight multimeric protein with a unique octopus-like structure. It is composed of seven identical α-chains and one β-chain. The α-and β-chains are linked by disulphide bridges. The cDNA cloning of the β-chain showed the α- and β-chains to be homologous and of common evolutionary origin. Both subunits are composed of multiple 60 amino acid long repeats (short complement or consensus repeats, SCR) and their genes are located in close proximity on chromosome 1, band 1q32. Available experimental data suggest the β-chain to contain the single protein S binding site on C4BP, whereas each of the α-chains contains a binding site for the complement protein, C4b. As C4BP lacking the β-chain is unable to bind protein S, the β-chain is required for protein S binding, but not for the assembly of the α-chains during biosynthesis. Protein S has a high affinity for negatively charged phospholipid membranes, and is instrumental in binding C4BP to negatively charged phospholipid. This constitutes a novel mechanism for control of the complement system on phospholipid surfaces. Recent findings have shown circulating C4BP to be involved in yet another calcium-dependent protein-protein interaction with a protein known as the serum amyloid P-component (SAP). The binding sites on C4BP for protein S and SAP are independent. SAP, which is a normal constituent in plasma and in tissue, is a so-called pentraxin being composed of 5 non-covalently bound 25 kDa subunits. It is homologous to C reactive protein (CRP) but its function is not yet known. The specific high affinity interactions between protein S, C4BP and SAP suggest the regulation of blood coagulation and that of the complement system to be closely linked.

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Antithrombin III Binding to Surface Immobilized Heparin and Its Relation to F Xa Inhibition

Thrombosis and Haemostasis ◽

10.1055/s-0038-1646057 ◽

1987 ◽

Vol 58 (04) ◽

pp. 1064-1067 ◽

Cited By ~ 41

Author(s):

K Kodama ◽

B Pasche ◽

P Olsson ◽

J Swedenborg ◽

L Adolfsson ◽

...

Keyword(s):

Molecular Weight ◽

Ionic Strength ◽

Surface Coating ◽

Antithrombin Iii ◽

Lower Class ◽

Biologically Active ◽

High Affinity ◽

Heparin Coating ◽

Continuous Surface ◽

Approximate Molecular Weight

SummaryThe mode of F Xa inhibition was investigated on a thromboresistant surface with end-point attached partially depoly-merized heparin of an approximate molecular weight of 8000. Affinity chromatography revealed that one fourth of the heparin used in surface coating had high affinity for antithrombin III (AT). The heparin surface adsorbed AT from both human plasma and solutions of purified AT. By increasing the ionic strength in the AT solution the existence of high and low affinity sites could be shown. The uptake of AT was measured and the density of available high and low affinity sites was found to be in the range of 5 HTid 11 pic.omoles/cmf, respectively Thus the estimated density of biologically active high and low ailmity heparm respectively would be 40 and 90 ng/cm2 The heparin coating did not take up or exert F Xa inhibition by itself. With AT adsorbed on both high and low affinity heparin the surface had the capacity to inhibit several consecutive aliquots of F Xa exposed to the surface. When mainly high affinity sites were saturated with AT the inhibition capacity was considerably lower. Tt was demonstrated that the density of AT on both high and low affinity heparin determines the F Xa inhibition capacity whereas the amount of AT on high affinity sites limits the rate of the reaction. This implies that during the inhibition of F Xa there is a continuous surface-diffusion of AT from sites of a lower class to the high affinity sites where the F Xa/AT complex is formed and leaves the surface. The ability of the immobilized heparin to catalyze inhibition of F Xa is likely to be an important component for the thromboresistant properties of a heparin coating with non-compromized AT binding sequences.

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