Plant Physiology

Shewmaker, Christine K.; Stalker, David M.

doi: 10.1104/pp.100.3.1083pmid: 16653088

Article PDF first page preview Close This content is only available as a PDF. © 1992 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)

Robinson, Sharon A.; Yakir, Dan; Ribas-Carbo, Miquel; Giles, Larry; Osmond, C. Barry; Siedow, James N.; Berry, Joseph A.

doi: 10.1104/pp.100.3.1087pmid: 16653089

Abstract Discrimination against 18O during dark respiration in tissues of Kalanchoë daigremontiana, Medicago sativa, and Glycine max was measured using an on-line system that enabled direct measurements of the oxygen fractionation of samples in a gas-phase leaf disk electrode unit. Discrimination factors for cytochrome pathway respiration were 18.6 to 19.8%o for all tissues. However, discrimination in cyanide-resistant respiration was significantly higher in green tissues (30.4-31.2%o) compared with nongreen tissues (25.3-25.9%o). Using these discrimination factors, the partitioning of electron transport to these pathways was calculated from measurements of discrimination in the absence of inhibitors. Changes in flux through the alternative pathway were measured during the light and dark phases of Crassulacean acid metabolism in leaf disks of K. daigremontiana. The flux of electrons through the alternative pathway was higher during deacidification than during the other phases of Crassulacean acid metabolism. The increase in alternative pathway electron flux accounted for all of the increased respiration in the light phase. Despite this increase, simultaneous measurements of malate concentration and respiratory flux confirm that only a small proportion of the total malate decarboxylation occurs in the mitochondria. 2 Permanent address: Research School of Biological Sciences, The Australian National University, Box 475, Canberra ACT 2601 Australia. 3 Permanent address: Weizmann Institute of Science, Department of Environmental Science and Energy Research, Rehovot, Israel 76100. 4 Permanent address: Department de Fisiologia Vegetal, Facultat de Biologia, Universitat de Barcelona, Barcelona, Spain 08028. 1 This work was supported by National Science Foundation (NSF) grant DCB90-06830 and Department of Energy, Division of Energy Biosciences grant DE-FG05-89 ER 14005 (C.B.O.), Binational Agricultural Research and Development Fund project IS-1344-87 (J.A.B.), Comision Interministerial para la Ciencia y Tecnologia (AGR89-580) (M.R.C.), and NSF grant BSR 87-06429 to the Duke University Phytotron. Carnegie Institution of Washington, Department of Plant Biology Publication No. 1149; Weizmann Institute Department of Environmental Science and Energy Research Publication No. 68. This content is only available as a PDF. © 1992 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)

Schröder, Wolfgang P.; Petit, Patrice X.

doi: 10.1104/pp.100.3.1092pmid: 16653090

Abstract Intact spinach (Spinacia oleracea) chloroplasts, thylakoid membranes, and inside-out or right-side-out thylakoid vesicles have been characterized by flow cytometry with respect to forward angle light scatter, right angle light scatter, and chlorophyll fluorescence. Analysis of intact chloroplasts with respect to forward light scatter and the chlorophyll fluorescence parameter revealed the presence of truly “intact” and “disrupted” chloroplasts. The forward light scatter parameter, normally considered to reflect object size, was instead found to reflect the particle density. One essential advantage of flow cytometry is that additional parameters such as Ricinus communis agglutinin (linked to fluorescein isothiocyanate) fluorescence can be determined through logical conditions placed on bit-maps, amounting to an analytical purification procedure. In the present case, chloroplast subpopulations with fully preserved envelopes, thylakoid membrane, and inside-out or right-side-out thylakoid membranes vesicles can be distinguished. Flow cytometry is also a useful tool to address the question of availability of glycosyl moities on the membrane surfaces if one keeps in mind that organelle-to-organelle interactions could be partially mediated through a recognition process. A high specific binding of R. communis agglutinin and peanut lectin to the chloroplast envelope was detected. This showed that galactose residues were exposed and accessible to specific lectins on the chloroplast surface. No exposed glucose, fucose, or mannose residues could be detected by the appropriate lectins. Ricin binding to the intact chloroplasts caused a strong aggregation. Disruption of these aggregates by resuspension or during passage in the flow cytometer induced partial breakage of the chloroplasts. Only minor binding of R. communis agglutinin and peanut lectin to the purified thylakoid membranes was detected; the binding was found to be low for both inside-out and right-side-out vesicles of the thylakoid membranes. 2 Present address: Arrhenius Laboratories for Natural Sciences, Department of Biochemistry, Stockholm University, S-106 91 Stockholm, Sweden. 1 W.P.S. was supported by the Federation of European Biochemical Societies and the Swedish Institute. This content is only available as a PDF. © 1992 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)

Marano, María Rosa; Carrillo, Néstor

doi: 10.1104/pp.100.3.1103pmid: 16653091

Abstract The size distribution of plastid transcripts during chromoplast differentiation in ripening tomato (Lycopersicon esculentum L.) fruits was determined using northern blot analysis. Hybridization of total cellular RNA from leaves and fruits with several tobacco chloroplast DNA probes showed distinct transcript patterns in chloroplasts and chromoplasts. We also compared transcriptional rates by probing immobilized DNA fragments of small size (representing about 85% of the plastid genome) with run-on transcripts from tomato plastids. The relative rates of transcription of the various DNA regions were very similar in chloro- and chromoplasts. Parallel determination of the steady-state levels of plastid RNA showed no strict correlation between synthesis rate and RNA accumulation. Differences in the relative abundance of transcripts between chloro- and chromoplasts were not very pronounced and were limited to a small number of genes. The results indicate that the conversion of chloroplasts to chromoplasts at the onset of tomato fruit ripening proceeds with no important variations in the relative transcription rates and with only moderate changes in the relative stability of plastid-encoded transcripts. 1 This work was supported by a three-year grant from the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET, Argentina) and grants AC3529 from the International Foundation for Science (Stockholm, Sweden), RG BC 88-88 from the Third World Academy of Sciences (Trieste, Italy), and CRP/ARG 88-15 from the International Centre for Genetic Engineering and Biotechnology (Trieste, Italy). M.R.M. and N.C. are a Fellow and a Career Investigator, respectively, from CONICET. This content is only available as a PDF. © 1992 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)

Yalpani, Nasser; Balke, Nelson E.; Schulz, Margot

doi: 10.1104/pp.100.3.1114pmid: 16653092

Abstract A UDP-glucose:salicylic acid 3-O-glucosyltransferase (EC 2.4.1.35) (GTase) from oat (Avena sativa L. cv Dal) root extracts was assayed in vitro using [14C]salicylic acid (SA) and an ion exchange column to separate SA from β-glucosylsalicylic acid. The GTase, present at a very low constitutive level, was inducible to 23 times the constitutive level. When excised roots were exposed to SA at pH 6.5, the specific activity of the enzyme increased within 1.5 h, peaked after 8 to 10 h, and then declined. The increase in specific activity depended on the concentration of SA in the induction medium. Among 16 phenolics and phenolic derivatives tested, GTase induction showed high specificity toward SA and acetylsalicylic acid. Specific activity of the enzyme was induced to higher levels in roots from 7-d-old seedlings than roots from younger plants. GTase activity was less inducible in basal compared with median or apical root sections. Induction of GTase activity was a result of de novo RNA and protein synthesis. Candidate peptides for the GTase were identified by comparison of two-dimensional electrophoresis gels of proteins labeled with [35S]methionine during incubation of roots in the presence or the absence of SA and a gel of a partially purified GTase preparation. 2 Present address: Center for Agricultural Molecular Biology, Rutgers, The State University of New Jersey, Cook College, P.O. Box 231, New Brunswick, NJ 08903-0231. 3 Present address: Institut fur Landwirtschaftliche Botanik, Meckenheimer Allee 176, D-5300 Bonn, Federal Republic of Germany. 1 Support to N.E.B. by U.S. Department of Agriculture Competitive Research Grants Office grant No. 85-CRCR-1-1572, University of Wisconsin-Madison Graduate School project No. 900317, and the College of Agricultural and Life Sciences, University of Wisconsin-Madison. This content is only available as a PDF. © 1992 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)

Marrè, Maria T.; Venegoni, Alberto; Moroni, Anna

doi: 10.1104/pp.100.3.1120pmid: 16653093

Abstract In Elodea densa leaves, ethanol up to 0.17 m stimulates H+ extrusion activity. This effect is strictly dependent on the presence of K+ in the medium and is suppressed by the presence of the plasmalemma H+-ATPase inhibitor vanadate. Stimulation of H+ extrusion is associated with (a) a decrease in cellular ATP level, (b) a marked hyperpolarization of transmembrane electrical potential, and (c) an increase in net K+ influx. These results suggest that ethanol-induced H+ extrusion is mediated by an activation of the plasma membrane ATP-dependent, electrogenic proton pump. This stimulating effect is associated with an increase of cell sap pH and of the capacity to take up the weak acid 5,5-dimethyloxazolidine-2,4-dione, which is interpretable as due to an increase of cytosolic pH. This indicates that the stimulation of H+ extrusion by ethanol does not depend on a cytosolic acidification by products of ethanol metabolism. The similarity of the effects of ethanol and those of photosynthesis on proton pump activity in E. densa leaves suggests that a common metabolic situation is responsible for the activation of the ATP-dependent H+-extruding mechanism. 1 Research supported by the National Research Council of Italy, Special Project RAISA, Subproject No. 2, Paper No. 383. This content is only available as a PDF. © 1992 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)

Kim, Woo Taek; Yang, Shang Fa

doi: 10.1104/pp.100.3.1126pmid: 16653094

Abstract Ethylene production in plant tissues declines rapidly following induction, and this decline is due to a rapid decrease in the activity of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase, a key enzyme in ethylene biosynthesis. To study the nature of the rapid turnover of ACC synthase in vivo, proteins in wounded ripening tomato (Lycopersicon esculentum) fruit discs were radiolabeled with [35S]methionine, followed by a chase with nonradioactive methionine. Periodically, the radioactive ACC synthase was isolated with an immunoaffinity gel and analyzed. ACC synthase protein decayed rapidly in vivo with an apparent half-life of about 58 min. This value for protein turnover in vivo is similar to that previously reported for activity half-life in vivo and substrate-dependent enzyme inactivation in vitro. Carbonylcyanide-m-chlorophenylhydrazone and 2,4-dinitrophenol, potent uncouplers of oxidative phosphorylation, strongly inhibited the rapid decay of ACC synthase protein in the tissue. Degradation of this enzyme protein was moderately inhibited by the administration of aminooxyacetic acid, a competitive inhibitor of ACC synthase with respect to its substrate S-adenosyl-l-methionine, α,α′-dipyridyl, and phenylmethanesulfonyl fluoride or leupeptin, serine protease inhibitors. These results support the notion that the substrate S-adenosyl-l-methionine participates in the rapid inactivation of the enzyme in vivo and suggest that some ATP-dependent processes, such as the ubiquitin-requiring pathway, are involved in the degradation of ACC synthase proteins. 1 This work was supported by grant No. DCB-9004129 from the National Science Foundation. This content is only available as a PDF. © 1992 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)

Sokol, Roger C.; Stross, Raymond G.

doi: 10.1104/pp.100.3.1132pmid: 16653095

Abstract The light receptor and its mode of operation were studied in photosensitive oospores of Nitella furcata subsp. megacarpa (Allen emend. Wood). Brief pulses of light activated maximal germination of post-secondary dormant oospores removed from lake sediments. Fluence response data at 12 wavelengths were used to construct an action spectrum for germination. The shape of the action spectrum with its maximum at 669 nm provides evidence for the involvement of phytochrome. Germination was induced with photon fluences that established as little as 0.01% of the phytochrome in the far red-absorbing form, which suggests that phytochrome was operating in the very low-fluence response mode. The functioning of phytochrome in the very low-fluence response mode in Nitella is similar to that in higher plants. 1 Present address: Wadsworth Center for Laboratories and Research, New York State Department of Health, Empire State Plaza, Albany, NY 12201-0509. This content is only available as a PDF. © 1992 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)

Pantoja, Omar; Gelli, Angie; Blumwald, Eduardo

doi: 10.1104/pp.100.3.1137pmid: 16653096

Abstract Patch-clamp techniques were employed to study the electrical properties of vacuoles from sugar beet (Beta vulgaris) cell suspensions at physiological concentrations of cytoplasmic Ca2+. Vacuoles exposed to K+ malate revealed the activation of instantaneous and time-dependent outward currents by positive membrane potentials. Negative potentials induced only instantaneous inward currents. The time-dependent outward currents were 10 times more selective for malate than for K+ and were completely blocked by zinc. Vacuoles exposed to KCl developed instantaneous currents when polarized to positive or negative membrane potentials. The time-dependent outward channels could serve as the route for the movement of malate into the vacuole, whereas K+ could move through the time-independent inward and outward channels. 2 Present address: Department of Plant Sciences University of Oxford, South Parks Rd, Oxford OX1 3RB, England. 1 This research was supported by an operating grant of the Natural Sciences and Engineering Council of Canada to E.B. This content is only available as a PDF. © 1992 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)

Cunningham, Francis X.; Vonshak, Avigad; Gantt, Elisabeth

doi: 10.1104/pp.100.3.1142pmid: 16653097

Abstract Acclimation of the photosynthetic apparatus to changes in the light environment was studied in the unicellular red alga Porphyridium cruentum (American Type Culture Collection No. 50161). Absolute or relative amounts of four photosynthetic enzymes and electron carriers were measured, and the data were compared with earlier observations on light-harvesting components (F.X. Cunningham, Jr., R.J. Dennenberg, L. Mustárdy, P.A. Jursinic, E. Gantt [1989] Plant Physiol 91: 1179-1187; F.X. Cunningham, Jr., R.J. Dennenberg, P.A. Jursinic, E. Gantt [1990] Plant Physiol 93: 888-895) and with measurements of photosynthetic capacity. P max, the light-saturated rate of photosynthesis on a chlorophyll (Chl) basis, increased more than 4-fold with increase in growth irradiance from 6 to 280 μeinsteins·m−2·s−1. Amounts of ferredoxin-NADP+ reductase, ribulose-1,5-bisphosphate carboxylase, and cytochrome f increased in parallel with P max, whereas numbers of the light-harvesting complexes (photosystem [PS] I, PSII, and phycobilisomes) changed little, and ATP synthase increased 7-fold relative to Chl. The calculated minimal turnover time for PSII under the highest irradiance, 5 ms, was thus about 4-fold faster than that calculated for cultures grown under the lowest irradiance (19 ms). A change in the spectral composition of the growth light (irradiance kept constant at 15 μeinsteins·m−2·s−1) from green (absorbed predominantly by the phycobilisome antenna of PSII) to red (absorbed primarily by the Chl antenna of PSI) had little effect on the amounts of ribulose-1,5-bisphosphate carboxylase, ATP synthase, and phycobilisomes on a Chl, protein, or thylakoid area basis. However, the number of PSI centers declined by 40%, cytochrome f increased by 40%, and both PSII and ferredoxin-NADP+ reductase increased approximately 3-fold on a thylakoid area basis. The substantial increase in ferredoxin-NADP+ reductase under PSI light is inconsistent with a PSI-mediated reduction of NADP as the sole function of this enzyme. Our results demonstrate a high degree of plasticity in content and composition of thylakoid membranes of P. cruentum. 1 This research was supported in part by grant No. DE-FG05-90ER20007 from the U.S. Department of Energy. This content is only available as a PDF. © 1992 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)