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Singh K, Sharmila P, Kumar PA, Pardha-Saradhi P. Successful expression of the synthetic merBps gene in tobacco. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2021; 167:874-883. [PMID: 34537577 DOI: 10.1016/j.plaphy.2021.09.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 09/10/2021] [Accepted: 09/12/2021] [Indexed: 06/13/2023]
Abstract
Organomercury is the most toxic biomagnifiable state of mercury, and to date, no natural organomercurial detoxification mechanism is encountered in plants. Bacterial merB gene encoding organomercury lyase show low expression in transgenic plants. For ideal expression, a synthetic merBps gene possessing143 out of 213 codons discrete from native merB gene from Escherichia. coli was fabricated based on codon usage in tobacco. Through Agrobacterium-mediated transformation, the merBps gene got successfully integrated into tobacco. Of several putative merBps transformants selected with 200 μg ml-1 kanamycin, only ∼45% were PCR positive for both nptII and merBps genes. Healthy and vigorously growing shoots of few PCR-positive putative transgenic lines were multiplied and rooted. After transplantation and acclimatization, the resultant plants flowered and fruited in pots. Southern analysis revealed the presence of a single copy of the merBps gene in four lines. RT-PCR and Western investigations established successful transcription and translation of the merBps gene in these transgenic lines, respectively. Fabrication of fully functional organomercury lyase in merBps transgenic lines was established based on the potential of their (i) seeds to germinate; (ii) shoots to grow and multiply; and (iii) leaf disc to remain green, even in the presence of 4 nmole ml-1 phenylmercuryacetate (PMA) while the wild type was susceptible to even 1 nmole ml-1 PMA. These findings confirmed that the synthetic merBps gene could be effectively expressed in plants and exploited for remediation of organomercurial contaminated sites.
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Affiliation(s)
- Kavita Singh
- Department of Environmental Studies, University of Delhi, Delhi, 110007, India; National Research Center on Plant Biotechnology, Indian Agricultural Research Institute, NewDelhi, 110012, India
| | - Peddisetty Sharmila
- Department of Environmental Studies, University of Delhi, Delhi, 110007, India
| | - P Ananda Kumar
- National Research Center on Plant Biotechnology, Indian Agricultural Research Institute, NewDelhi, 110012, India
| | - P Pardha-Saradhi
- Department of Environmental Studies, University of Delhi, Delhi, 110007, India.
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Rapid antimicrobial susceptibility test for identification of new therapeutics and drug combinations against multidrug-resistant bacteria. Emerg Microbes Infect 2016; 5:e116. [PMID: 27826141 PMCID: PMC5148025 DOI: 10.1038/emi.2016.123] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Revised: 08/28/2016] [Accepted: 08/28/2016] [Indexed: 11/10/2022]
Abstract
Current antimicrobial susceptibility testing has limited screening capability for identifying empirical antibiotic combinations to treat severe bacterial infections with multidrug-resistant (MDR) organisms. We developed a new antimicrobial susceptibility assay using automated ultra-high-throughput screen technology in combination with a simple bacterial growth assay. A rapid screening of 5170 approved drugs and other compounds identified 25 compounds with activities against MDR Klebsiella pneumoniae. To further improve the efficacy and reduce the effective drug concentrations, we applied a targeted drug combination approach that integrates drugs' clinical antimicrobial susceptibility breakpoints, achievable plasma concentrations, clinical toxicities and mechanisms of action to identify optimal drug combinations. Three sets of three-drug combinations were identified with broad-spectrum activities against 10 MDR clinical isolates including K. pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Citrobacter freundii, Enterobacter cloacae and Escherichia coli. Colistin–auranofin–ceftazidime and colistin–auranofin–rifabutin suppressed >80% growth of all 10 MDR strains; while rifabutin–colistin–imipenem inhibited >75% of these strains except two Acinetobacter baumannii isolates. The results demonstrate this new assay has potential as a real-time method to identify new drugs and effective drug combinations to combat severe clinical infections with MDR organisms.
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Zhang R, Wise RR, Struck KR, Sharkey TD. Moderate heat stress of Arabidopsis thaliana leaves causes chloroplast swelling and plastoglobule formation. PHOTOSYNTHESIS RESEARCH 2010; 105:123-134. [PMID: 20563644 DOI: 10.1007/s11120-010-9572-6] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2010] [Accepted: 06/04/2010] [Indexed: 05/28/2023]
Abstract
Photosynthesis is inhibited by heat stress. This inhibition is rapidly reversible when heat stress is moderate but irreversible at higher temperature. Absorbance changes can be used to detect a variety of biophysical parameters in intact leaves. We found that moderate heat stress caused a large reduction of the apparent absorbance of green light in light-adapted, intact Arabidopsis thaliana leaves. Three mechanisms that can affect green light absorbance of leaves, namely, zeaxanthin accumulation (absorbance peak at 505 nm), the electrochromic shift (ECS) of carotenoid absorption spectra (peak at 518 nm), and light scattering (peak at 535 nm) were investigated. The change of green light absorbance caused by heat treatment was not caused by changes of zeaxanthin content nor by the ECS. The formation of non-photochemical quenching (NPQ), chloroplast movements, and chloroplast swelling and shrinkage can all affect light scattering inside leaves. The formation of NPQ under high temperature was not well correlated with the heat-induced absorbance change, and light microscopy revealed no appreciable changes of chloroplast location because of heat treatment. Transmission electron microscopy results showed swollen chloroplasts and increased number of plastoglobules in heat-treated leaves, indicating that the structural changes of chloroplasts and thylakoids are significant results of moderate heat stress and may explain the reduced apparent absorbance of green light under moderately high temperature.
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Affiliation(s)
- Ru Zhang
- Department of Botany, University of Wisconsin-Madison, 430 Lincoln Drive, Madison, WI 53706, USA.
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Hilliard JH, West SH. Starch accumulation associated with growth reduction at low temperatures in a tropical plant. Science 2010; 168:494-6. [PMID: 17838130 DOI: 10.1126/science.168.3930.494] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Growth of Digitaria decumbens is severely reduced by night temperatures of 10 degrees C or below. Ultra-structure of leaves and chemical analyses show a high starch content in chloroplasts of plants illuminated and kept at a temperature of 30 degrees C. This starch disappears after a period in the dark at 30 degrees C, but it remains if the temperature during the dark period is 10 degrees C. The inhibition or slowing of starch translocation out of chloroplasts appears to account for reduced photo-synthesis and growth at low night temperatures.
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Abstract
Light changes the structure of chloroplasts. This effect was investigated by high resolution electron microscopy, photometric methods, and chemical modification. (a) A reversible contraction of chloroplast membrane occurs upon illumination, dark titration with H+, or increasing osmolarity. These gross structural changes arise from a flattening of the thylakoids, with a corresponding decrease in the spacing between membranes. Microdensitometry showed that illumination or dark addition of H+ resulted in a 13–23% decrease in membrane thickness. Osmotically contracted chloroplasts do not show this effect. (b) Rapid glutaraldehyde fixation during actual experiments revealed that transmission changes are closely correlated with the spacing changes and therefore reflect an osmotic mechanism, whereas the light scattering changes have kinetics most similar to changes in membrane thickness or conformation. (c) Kinetic analysis of light scattering and transmission changes with the changes in fluorescence of anilinonaphthalene sulfonic acid bound to membranes revealed that fluorescence preceded light scattering or transmission changes. (d) It is concluded that the temporal sequence of events following illumination probably are protonation, changes in the environment within the membrane, change in membrane thickness, change in internal osmolarity accompanying ion movements with consequent collapse and flattening of thylakoid, change in the gross morphology of the inner chloroplast membrane system, and change in the gross morphology of whole chloroplasts.
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Affiliation(s)
- S Murakami
- Department of Physiology-Anatomy, University of California, Berkeley, California 94720
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Schneider K, Frischknecht K. Orthophosphate influx and efflux rates of Chlorella fusca measured in a continuous turbidostat culture with 32P under various conditions. Arch Microbiol 1977; 115:339-46. [PMID: 603340 DOI: 10.1007/bf00446461] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Metabolic aspects of stomatal opening and ion accumulation by guard cells in Vicia faba. ACTA ACUST UNITED AC 1974. [DOI: 10.1016/s0044-328x(74)80040-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Gross E. Divalent cation binding to chloroplast membranes and its relationship to reversal of quaternary ammonium salt uncoupling of photophosphorylation. Arch Biochem Biophys 1972; 150:324-9. [PMID: 4623865 DOI: 10.1016/0003-9861(72)90042-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Honeycutt RC, Krogmann DW. Inhibition of chloroplast reactions with phenylmercuric acetate. PLANT PHYSIOLOGY 1972; 49:376-80. [PMID: 16657964 PMCID: PMC365968 DOI: 10.1104/pp.49.3.376] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Phenylmercuric acetate is a selective inhibitor of the photosynthetic activities of isolated spinach (Spinacia oleracea) chloroplasts. At 5 mum concentration of phenylmercuric acetate, photophosphorylation is inhibited. At 33 mum phenylmercuric acetate, ferredoxin is inactivated. Ferredoxin-NADP oxidoreductase is 50% inhibited at 100 mum phenylmercuric acetate. Photosystem II reactions are 50% inhibited at 150 mum phenylmercuric acetate and very much higher cooncentrations-500 mum-are needed to approach complete inhibition. Phenylmercuric acetate inhibition of photosystem II appears to be selective, blocking a site between the 3-(3,4-dichlorophenyl)-1,1-dimethyl urea sensitive site and the site inactivated by high concentrations of tris buffer.
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Affiliation(s)
- R C Honeycutt
- Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907
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Seigenthaler PA. Synergetic effect of light and aging on the swelling and photochemical activities of isolated chloroplasts. EXPERIENTIA 1968; 24:1198-9. [PMID: 5703007 DOI: 10.1007/bf02146617] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Horton AA, Packer L. Effect of tetraphenylboron on light-induced uptake of monovalent cations by chloroplasts. Arch Biochem Biophys 1968; 128:820-3. [PMID: 5704314 DOI: 10.1016/0003-9861(68)90093-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Packer L, Allen JM, Starks M. Light-induced ion tranpsort in glutaraldehyde-fixed chloroplasts: studies with nigericin. Arch Biochem Biophys 1968; 128:142-52. [PMID: 5677174 DOI: 10.1016/0003-9861(68)90017-9] [Citation(s) in RCA: 47] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Baddeley MS, Hanson JB. Uncoupling of energy-linked functions of corn mitochondria by linoleic Acid and monomethyldecenylsuccinic Acid. PLANT PHYSIOLOGY 1967; 42:1702-10. [PMID: 16656708 PMCID: PMC1086785 DOI: 10.1104/pp.42.12.1702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Linoleic acid and monomethyldecenylsuccinic acid were tested as uncoupling agents for energy linked functions of corn mitochondria. 2,4-dinitrophenol was used as a standard for comparison. Both compounds uncoupled oxidative phosphorylation, released oligomycin-blocked respiration, and accelerated adenosine triphosphatase. Linoleic acid uncoupled calcium-activated phosphate accumulation and the increase in light scattering that accompanies the accumulation. Unlike dinitrophenol, linoleic acid at 0.1 mm had a destructive effect on membrane semipermeability. Kinetic studies indicated that dinitrophenol and linoleic acid compete with phosphate for active sites in oxidative phosphorylation.Some linoleic acid is taken up by respiring mitochondria and a major share of the uptake is incorporated into phospholipids. Calcium ion and oligomycin promote the uptake, but coenzyme A does not. It is deduced that fatty acid probably attacks the non-phosphorylated intermediate, I approximately X, producing X approximately acyl. Uncoupling results from breakdown of X approximately acyl, but sufficient X approximately acyl is maintained to serve as a source of activated fatty acid.
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Affiliation(s)
- M S Baddeley
- Department of Agronomy, University of Illinois, Urbana, Illinois 61801
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Abstract
Recent reviews have denied the applicability of the classical theory of stomatal movement. The newer explanations are shown to be incorrect, and the major objections to the classical theory invalid. Nevertheless, the classical theory needs to be modified. If the decisive factor is assumed to be carboxylic acid (RCOOH) rather than CO2 concentration, all the known facts can be explained. Two predictions of this modified classical theory were vindicated. The proposed relationship of stomatal opening to RCOOH concentration is illustrated schematically.
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Affiliation(s)
- J Levitt
- University of Missouri, 65202, Columbia, Missouri
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Tweedy JA, Ries SK. Effect of simazine on nitrate reductase activity in corn. PLANT PHYSIOLOGY 1967; 42:280-2. [PMID: 16656504 PMCID: PMC1086525 DOI: 10.1104/pp.42.2.280] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The nutritional and environmental parameters required for eliciting increases in the nitrogen content and growth of corn (Zea mays L.) by non-toxic levels of simazine have been established. Corn seedlings with the endosperm removed 10 days after germination, proved to be a suitable test species. The addition of simazine to the root-zone area of corn plants grown under both sub-optimal temperatures and low nitrate levels, increased the nitrogen content and dry weight of the plants by 20 to 25%. This increase was found to be associated with an effect on nitrate reductase.
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Affiliation(s)
- J A Tweedy
- Department of Horticulture, Michigan State University, East Lansing, Michigan 48823
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Packer L, Barnard AC, Deamer DW. Ultrastructural and Photometric Evidence for Light-Induced Changes in Chloroplast Structure in vivo. PLANT PHYSIOLOGY 1967; 42:283-93. [PMID: 16656505 PMCID: PMC1086526 DOI: 10.1104/pp.42.2.283] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Photometric evidence for a reversible, red-light induced transmission decrease in excised leaf tissue or the thalli of certain marine algae has been obtained under conditions which correspond to the occurrence of a light-induced shrinkage of chloroplasts within the cells. Evidence supporting this conclusion is: A) The kinetics of the nonspecific transmission changes are similar to those observed in chloroplasts in vitro. B) The magnitude of the response is larger than could be accounted for by any known pigment which absorbs at 546 mmu. C) The light-induced transmission changes are optimal at pH 5.5 to 6.5 in the presence of electron flow cofactors and weak acid anions, conditions which are optimal for light-induced chloroplast shrinkage in isolated chloroplasts. D) Examination of chloroplast ultrastructure in dark incubated and illuminated chloroplasts reveals a flattening of the chloroplast structure and shrinkage.
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Affiliation(s)
- L Packer
- Department of Physiology, University of California, Berkeley, California 94720
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Packer L, Siegenthaler PA. Control of chloroplast structure by light. INTERNATIONAL REVIEW OF CYTOLOGY 1966; 20:97-124. [PMID: 5337303 DOI: 10.1016/s0074-7696(08)60798-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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