Plant Physiology

Keller, Felix; Frehner, Marco; Wiemken, Andres

doi: 10.1104/pp.88.2.239pmid: 16666286

Abstract The exact subcellular location of sucrose synthase (UDP-d-glucose: d-fructose 2-α-d-glucosyltransferase, EC 2.4.1.13) in Helianthus tuberosus tubers was studied by comparison of its activity in protoplasts with that of vacuoles isolated from them. Assuming 100% of the β-N-acetylglucosaminidase activity to be of vacuolar origin, less than 5% of both the sucrose synthase activity and the extravacuolar marker NAD-malate dehydrogenase was detected in the vacuole preparations. Sucrose synthase is therefore an extravacuolar enzyme. Its role in the inulin metabolism of H. tuberosus is discussed. 2 Present address: Swiss Federal Institute of Technology, Department of Plant Science, ETH-Zentrum, CH-8092 Zürich, Switzerland. 3 Present address: University of Basel, Department of Botany, Hebelstr. 1, CH-4056 Basel, Switzerland. 1 This work was supported by the Swiss National Science Foundation. This content is only available as a PDF. © 1988 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)

Rajasekhar, V. K.; Gowri, G.; Campbell, Wilbur H.

doi: 10.1104/pp.88.2.242pmid: 16666287

Abstract In etiolated squash (Cucurbita maxima L.) cotyledons, nitrate-inducible NADH:nitrate reductase activity and protein were increased in darkness by red light pulses with red/far-red photoreversibility. Continuous far-red light also led to increased levels of nitrate reductase activity and protein. Poly(A)+RNA, which hybridizes to squash nitrate reductase cDNA, was also increased by light treatments. Thus, we found that after nitrate triggering, nitrate reductase expression appears to be regulated by light via phytochrome. 2 Present address: Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92717. 1 Supported by Grant 86 CRCR 11289 from the United States Department of Agriculture, Competitive Research Grants Office and Grant DMB 85-02672 from the National Science Foundation. This content is only available as a PDF. © 1988 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)

Chatfield, J. Mark; Armstrong, Donald J.

doi: 10.1104/pp.88.2.245pmid: 16666288

Abstract Cytokinin oxidase activity from Phaseolus vulgaris cv Great Northern callus cultures exhibited affinity for the lectin concanavalin A. Over 80% of the activity extracted from the callus tissue bound to a concanavalin A-Sepharose 4B column. The bound activity was eluted from the column by the addition of methylmannose to the eluting buffer. On the basis of this result, it appears that most of the cyokinin oxidase activity present in Great Northern callus cultures exists in the form of a glycoprotein. The apparent pI of this enzyme, as estimated by chromatofocusing, is approximately 5.0. 2 Present address: USDA/ARS, Department of Agronomy, University of Illinois, Urbana, IL 61801. 1 Supported by the Science and Education Administration of the United States Department of Agriculture under Grant 86-CRCR-1-1988 from the Competitive Research Grants Office. This content is only available as a PDF. © 1988 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)

Komeda, Yoshibumi; Tanaka, Miyako; Nishimune, Takahiro

doi: 10.1104/pp.88.2.248pmid: 16666289

Abstract We have examined the activity of the thiamin phosphate pyrophosphorylase in Arabidopsis thaliana wild type and in a mutant (th-1) which requires exogenous thiamin for growth. Mutant and wild-type plants grown in 1 × 10−7 molar thiamin were used for the examination of the production of thiamin and thiamin monophosphate (TMP) using 4-methyl-5-hydroxyethylthiazole phosphate and 2-methyl-4-amino-5-hydroxymethylpyrimidine pyrophosphate as substrates. While the wild-type strain formed both thiamin and TMP, the th-1 mutant did not. When TMP was added to the extracts, the th-1 mutant, as well as wild type, produced thiamin. Accordingly, it was concluded that the th-1 mutant was defective in the activity of TMP pyrophosphorylase. Some of the characteristics of the enzyme from the wild-type plant were examined. The optimum temperature for the reaction is 45°C, and the Km values for the substrates are 2.7 × 10−6 molar for 4-methyl-5-hydroxyethylthiazole phosphate and 1.8 × 10−6 molar for 2-methyl-4-amino-5-hydroxymethylpyrimidine pyrophosphate. 1 This work was supported in part by a grant-in-aid to Y.K. for scientific research from the Japanese Ministry of Education, Science, and Culture. This content is only available as a PDF. © 1988 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)

De Leon, Jose Luis Diaz; Daie, Jaleh; Wyse, Roger

doi: 10.1104/pp.88.2.251pmid: 16666290

Abstract The mechanism of sucrose transport into vacuoles isolated from leaf tissue has been studied only in barley (Hordeum vulgare) mesophyll cells. In this tissue, sucrose transport was reported to be a facilitated diffusion. We have observed a facilitated diffusion of sucrose into vacuoles isolated from this tissue. However, no pH dependence was observed. Evidence is presented indicating that the pH dependence of sucrose uptake into vacuoles may be an artifact, reflecting tonoplast instability and survival of isolated vacuoles in different buffers. Apparently vacuoles do not withstand exposure to some commonly used buffers. 1 Contribution No. D-15192-1-88 from New Jersey Agriculture Experiment Station. Supported in part by U.S. Department of Agriculture Competitive Research Grants Office grant No. 84-CRCR-1-1465 and by Rutgers University Research Council. This content is only available as a PDF. © 1988 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)

Ernst, Dietrich; Schefbeck, Katja

doi: 10.1104/pp.88.2.255pmid: 16666291

Abstract Rye (Secale cereale cv Halo) seedlings treated with the herbicide Norflurazon SAN 9789 showed a reduced concentration of mRNA for the small subunit of ribulose-1,5-bisphosphate carboxylase and for the light-harvesting chlorophyll a/b protein. The inhibition of mRNA accumulation by Norflurazon occurred only in the presence of high light intensities and only after a period of days. The primary effect was an inhibition of the transcription rate that occurred within 1 day after exposure of the seedlings to light. 1 Supported by the Deutsche Forschungsgemeinschaft (SFB 184). This content is only available as a PDF. © 1988 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)

Preisser, Joachim; Komor, Ewald

doi: 10.1104/pp.88.2.259pmid: 16666292

Abstract Isolated sugarcane (Saccharum spp. hybrid H50-7209) vacuoles incorporate radioactivity during incubation with labeled UDP-glucose by a mechanism which was postulated to be responsible for sucrose storage in the vacuoles (UDP-glucose group translocator). Analysis of the reaction products in the medium revealed that several enzymic processes are going on during incubation with UDP-glucose such as production of hexose phosphates, UMP, and sugars, all of which seem unrelated to the incorporation of radioactivity into vacuoles. The incorporated radioactivity was identified mainly as (1→3)-β-glucan (callose) of polymerization grades up to more than 20. Callose occurs as a contaminant at the surface of isolated vacuoles coming from the plasmalemma. The properties of UDP-glucose incorporation into the vacuolar preparation compared favorably with known properties of callose synthase. The low mol wt glucans that are found are probably degradation products of labeled callose due to hydrolases, which are liberated by centrifugation of vacuoles. The labeled disaccharide, which chromatographically had been formerly identified as sucrose, is laminaribiose. No sucrose (or sucrose phosphate) could be identified in the vacuole preparation after incubation with UDP-glucose. Thus, the mechanism of sucrose storage in sugarcane vacuoles is still open. This content is only available as a PDF. © 1988 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)

Maretzki, Andrew; Thom, Margaret

doi: 10.1104/pp.88.2.266pmid: 16666293

Abstract A reanalysis of products formed after short-term incubation of sugarcane (Saccharum spp. hybrid cv H50-7209) vacuole preparations with uridine diphosphate [14C]glucose was performed. The results indicated that the ethanol-soluble substance previously identified as sucrose did not elute with sucrose when subjected to high performance liquid chromatography but had the same retention time as a disaccharide tentatively identified as laminaribiose. 1 Supported by a National Science Foundation grant (DMB 8613976). Published as Paper No. 649 in the journal series of the Experiment Station, Hawaiian Sugar Planters' Association. This content is only available as a PDF. © 1988 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)

Fink, Werner; Liefland, Mathias; Mendgen, Kurt

doi: 10.1104/pp.88.2.270pmid: 16666294

Abstract To isolate chitinases and β-1,3-glucanases from the intercellular space of oats (Avena sativa L.), primary leaves were infiltrated with buffer and subjected to gentle centrifugation to obtain intercellular washing fluid (IWF). Approximately 5% of the chitinase and 10% of the β-1,3-glucanase activity of the whole leaf were released. Only small amounts (0.01-0.03%) of the intracellular marker malate-dehydrogenase were released into the IWF during infiltration. Activities of chitinase and β-1,3-glucanase in the IWF and in the leaf extract were compared by different chromatographic methods. On Sephadex G-75, chitinase appeared as a single peak (M r 29.8 kD) both in IWF and homogenate. β-1,3-Glucanase, however, showed two peaks in the IWF (M r 52 and 31.3 kD), whereas the elution pattern of the homogenate showed only one major peak at 22 kD. Chromatofocusing indicated that the IWF contained four chitinases and five β-1,3-glucanases. The elution pattern of the homogenate and IWF were similar with regard to the elution pH, but the peak intensities were distinctly different. Our results demonstrate that extracellular β-1,3-glucanases are different from those located intracellularly. Extracellular and intracellular chitinases do not differ in molecular properties, except for one isozyme which seems to be confined to the extracellular space. We suggest that both enzymes might play a special role in pathogenesis during fungal infection. 1 This work was supported by the Deutsche Forschungsgemeinschaft grant Me 523/12. This content is only available as a PDF. © 1988 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)

De Petter, Edwin; Van Wiemeersch, Luc; Rethy, Roger; Dedonder, Andrée; Fredericq, Henri; De Greef, Jan

doi: 10.1104/pp.88.2.276pmid: 16666295

Abstract Germination of Kalanchoë blossfeldiana Poelln. seeds is absolutely light-requiring. Germination of one seed is the result of one out of three reactions, viz. the very low fluence response (VLFR), the low fluence response (LFR) and the high fluence response/high irradiance response. In order to demonstrate the involvement of phytochrome for both photoresponses, i.e. VLFR and LFR, action spectra for induction were determined. Fluence-response data are analyzed by means of probit analysis in order to calculate the seed population parameters, with special attention to μ, or the fluence for half-maximal induction, and B, the slope in the probit diagram. Laser light was used between 620 and 800 nanometers to analyze the VLFR. Phytochrome is responsible for both photoresponses: the VLFR action spectrum demonstrates an exponential decrease in apparent photoconversion cross-section (Pr → Pfr) up to about 800 nanometers. Assuming that Pr:Pfr-X and Pfr:Pfr-X are the effectors for the VLFR and the LFR, respectively, we estimate an average induction threshold of about 0.003% Pr:Pfr for the VLFR and about 1% Pfr:Pfr for the LFR among individuals of the seed population. 1 These investigations were supported by a grant of the Belgian National Science Foundation (F.K.F.O.-2.0083.83). This content is only available as a PDF. © 1988 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)