Plant Physiology

Shrift, Alex; Bechard, Daniel; Harcup, Craig; Fowden, Leslie

doi: 10.1104/pp.58.3.248pmid: 16659657

Abstract An l-cysteinyl-tRNA synthetase (EC 6.1.1.16) from Phaseolus aureus has been purified approximately 200-fold. The enzyme uses selenocysteine as substrate in the ATP-PPi exchange assay; other cysteine analogs were inactive. The molecular weight as determined by Sephadex G-200 column chromatography is about 61,000; sodium dodecyl sulfate and 8 m urea acrylamide gel electrophoresis indicate that the enzyme is a dimer consisting of two identical monomers of molecular weight 30,000. A method for the preparation of selenocysteine from selenocystine is described. 2 Present address: State University of New York Medical Center, Syracuse, New York 13210. 3 Present address: Georgetown University School of Medicine, Washington, D. C. 20007. 1 This research was carried out in part at University College, London, Department of Botany and Microbiology, under tenure of Senior Research Fellowship GM53476 to A. S. from the United States Public Health Service, and in part under United States Public Health Service Grant ES00807. This content is only available as a PDF. © 1976 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Macdowall, Fergus D. H.; Sirois, J. Claude

doi: 10.1104/pp.58.3.253pmid: 16659658

Abstract The elongation phase of growth of plant parts, as 1-cm segments excised from wheat coleoptiles here, is very simply recorded photometrically. One or more aligned segments submerged in aerated buffer pushed an Al foil shutter over a slit of light incident on a photodetector such as a solar or photronic cell, connected directly to a recorder, or a photomultiplier tube in a commercial photometer. Convenient kinetic records were obtained at 5 mm per min chart speed when one segment was combined with a 1-mm long slit, or more segments and longer slits, for which a 1-mm chart unit usually exceeded noise and was equivalent to 4 μm growth per cm coleoptile. In the presence of 10 cm of coleoptile segments no replenishment of solution was necessary during kinetic measurements of response in a 50-ml reservoir of IAA more concentrated than 30 nm. 1 Contribution No. 896. This content is only available as a PDF. © 1976 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Cahen, David; Malkin, Shmuel; Shochat, Susana; Ohad, Itzhak

doi: 10.1104/pp.58.3.257pmid: 16659659

Abstract The relative content of organized pigment, active centers, and acceptor pools of photosystem II and their interconnection during the development of the photosynthetic membranes of Chlamydomonas reinhardi y-1 have been measured using the fluorescence induction technique. The degree of connectivity and efficiency of the developing system has been assessed also from measurements of maximal rates, quantum yield, and flash yield of 2,6-dichlorophenolindophenol photoreduction using H2O as the electron donor. The results obtained indicate that the process of membrane development in this organism consists of two phases: an initial phase of reorganization and connection between pre-existing components, and a second phase of actual accumulation of newly formed, complete, and active units. The ratio of active centers to Chl remains practically constant throughout the process while the degree of connectivity between the active center and the plastoquinone pool was doubled during the early phase of the greening. In addition the degree of connectivity between the plastoquinone pool and the rest of the electron transport chain increases as demonstrated by a 10- to 20-fold rise in the quantum yield and a 10-fold rise in the maximal rate and the flash yield. The ratio of light harvesting Chl to active centers remains apparently constant during the second phase of the greening as indicated by light saturation experiments and by the constancy of the apparent photosynthetic unit size. Electron donation from H2O seems to develop slower than the activity of the rest of the complex as demonstrated by measurements of 2,6-dichlorophenolindophenol photoreduction using 1,5-diphenylcarbazide as the electron donor. The value of all the above parameters which remain constant during the second phase of the greening are comparable to those obtained with membranes of light-grown cells. 1 Max Bogen Research Fellow. 2 Recipient of the United States-Israel Science Foundation Grant 184. This content is only available as a PDF. © 1976 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Beyer, Elmo M.

doi: 10.1104/pp.58.3.268pmid: 16659660

Abstract Ag(I), applied foliarly as AgNO3, effectively blocked the ability of exogenously applied ethylene to elicit the classical “triple” response in intact etiolated peas (Pisum sativum cv. Alaska); stimulate leaf, flower, and fruit abscission in cotton (Gossypium hirsutum cv. Stoneville 213); and induce senescence of orchids (Hybrid white Cattleya, Louise Georgeianna). This property of Ag(I) surpasses that of the well known ethylene antagonist, CO2, and its persistence, specificity, and lack of phytotoxicity at effective concentrations should prove useful in defining further the role of ethylene in plant growth. 1 Contribution No. 2348 from Central Research and Development Department, Experimental Station, E. I. du Pont de Nemours and Company, Wilmington, Delaware 19898. This content is only available as a PDF. © 1976 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Stockman, Daniel R.; Hall, Timothy C.; Ryan, Dale S.

doi: 10.1104/pp.58.3.272pmid: 16659661

Abstract The major globulin of the French bean (Phaseolus vulgaris L.) undergoes a reversible pH-dependent polymerization. At pH values above 6.5, the monomeric form of the protein predominates; and at pH values below 6.5, the protein occurs as a polymer, probably a tetramer. At extremes of pH, the protein dissociates further into peptides. The reversible pH-dependent interaction between globulin subunits is used in this report as the basis for an affinity chromatography procedure for isolation of the globulin. The major globulin from several genetic variants can be obtained in gram quantities and does not indicate the presence of any impurities on discontinuous sodium dodecyl sulfate gel electrophoresis. 1 This work was supported by the Research Division, College of Agricultural and Life Sciences, University of Wisconsin, Madison, and by National Science Foundation Grant PCM74-21675. This content is only available as a PDF. © 1976 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Lin, Willy; Hanson, John B.

doi: 10.1104/pp.58.3.276pmid: 16659662

Abstract Studies were made of the effect of dithioerythritol on net proton flux, potassium influx and efflux, cell potential, and cell resistance in fresh and washed corn (Zea mays L. WF9XM14) root tissue. Dithioerythritol induces equal proton influx and potassium efflux rates, decreases membrane resistance, and hyperpolarizes the cell potential. Greater effects on H+ and K+ fluxes are secured at pH 7 than at pH 5. Other sulfhydryl-protecting reagents produced the same responses. No evidence could be found that dithioerythritol affected energy metabolism or membrane ATPase, and proton influx was induced in the presence of uncoupling agents. We deduce that dithioerythritol activates a passive H+/K+ antiport, driven in these experiments by the outwardly directed electrochemical gradient of K+. The net effect on H+ and K+ fluxes is believed to reside with the combined activity of a polarized H+/K+ exchanging ATPase and the passive H+/K+ antiport. A model is presented to show how the combined system might produce stable potential differences and K+ content. 2 Present address: Department of Biology, Brookhaven National Laboratory, Upton, L. I., N. Y. 11973. 1 Supported by Grant E-(11-1)-790 from the Energy Research and Development Administration, and Grant BG-37509 from the National Science Foundation. This content is only available as a PDF. © 1976 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Gayler, Kenwyn R.; Morgan, Wayne R.

doi: 10.1104/pp.58.3.283pmid: 16659663

Abstract NADP-dependent glutamate dehydrogenase was partially purified from extracts of the marine siphonous green alga Caulerpa simpliciuscula. The enzyme had an apparent Km NH4+ of 0.4 to 0.7 mm and was highly specific for NADPH, α-ketoglutarate, and ammonium ions. The bulk of the NADP-glutamate dehydrogenase was isolated with the chloroplast fraction in cell-free preparations of this alga and was released from these “chloroplast fractions” as a soluble enzyme on gentle lysis of chloroplast membranes. 1 This work was supported by the Australian Research Grants Committee. This content is only available as a PDF. © 1976 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Dittrich, Peter

doi: 10.1104/pp.58.3.288pmid: 16659664

Abstract In vitro studies of dark 14CO2 fixation with isolated cell aggregates of Kalanchoë fedtschenkoi showed that malate synthesized after 20 sec is predominantly (85 to 92%) labeled at carbon 4, while after 20 min only 65 to 69% of the radioactivity was located in this position. The intramolecular labeling pattern of malate could not be changed by supplementing the cells with carboxylation reaction substrates such as ribulose diphosphate or phosphoenolpyruvate. The kinetic decline of label at carbon 4 of malate occurs independently of CO2 fixation, since 4-14C-labeled aspartate fed to the cells gave rise to malate labeled 62% at carbon 4 after 20 min. Furthermore, the cells were capable of converting fed malate to fumarate. It is concluded that synthesis of malate during dark CO2 fixation is accomplished by a single carboxylation step via phosphoenolpyruvate carboxylase and labeling patterns observed in malate are a consequence of the action of fumarase. 1 This paper was supported by Research Grant Di 195/3 from Deutsche Forschungsgemeinschaft. This content is only available as a PDF. © 1976 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Shen, Teh-Chien; Funkhouser, Edward A.; Guerrero, Miguel G.

doi: 10.1104/pp.58.3.292pmid: 16659665

Abstract By use of affinity chromatography on blue dextran-Sepharose, two nitrate reductases from rice (Oryza sativa L.) seedlings, specifically, NADH:nitrate oxidoreductase (EC 1.6.6.1) and NAD(P)-H:nitrate oxidoreductase (EC 1.6.6.2), have been partially separated. Nitrate-induced seedlings contained more NADH-nitrate reductase than NAD(P)H-nitrate reductase, whereas chloramphenicol-induced seedlings contained primarily NAD(P)H-nitrate reductase. NAD(P)H-nitrate reductase was shown to utilize NADPH directly as reductant. This enzyme has a preference for NADPH, but reacts about half as well with NADH. 1 Recipient of Alexander von Humboldt-Stiftung fellowship. Permanent address: Department of Botany, University of Malaya, Kuala Lumpur, Malaysia. This content is only available as a PDF. © 1976 American Society of Plant Biologists This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)