Plant Physiology

Allard, Guy; Nelson, Curtis J.

doi: 10.1104/pp.95.3.663pmid: 16668036

Abstract Elongating grass leaves have successive zones of cell division, cell elongation, and cell maturation in the basal portion of the blade and are a strong sink for photosynthate. Our objective was to determine dry matter (DM) deposition and partitioning in basal zones of elongating tall fescue (Festuca arundinacea Schreb.) leaf blades. Vegetative tall fescue plants were grown in continuous light (350 micromoles per square meter per second photosynthetic photon flux density) to obtain a constant spatial distribution of elongation growth with time. Content and net deposition rates of water-soluble carbohydrates (WSC) and DM along elongating leaf blades were determined. These data were compared with accumulation of 14C in the basal zones following leaf-labeling with 14CO2. Net deposition of DM was highest in the active cell elongation zone, due mainly to deposition of WSC. The maturation zone, just distal to the elongation zone, accounted for 22% of total net deposition of DM in elongating leaves. However, the spatial profile of 14C accumulation suggested that the elongation zone and the maturation zone were sinks of equal strength. WSC-free DM accounted for 55% of the total net DM deposition in elongating leaf blades, but only 10% of incoming 14C-photosynthate accumulated in the water-insoluble fraction (WIF ≈ WSC-free DM) after 2 hours. In the maturation zone, more WSC was used for synthesis of WSC-free DM than was imported as recent photosynthate. 2 Present address: Département de Phytologie, Université Laval, Québec, Canada G1K 7P4. 1 Supported by the Natural Sciences and Engineering Research Council of Canada and Université Laval, Québec. This content is only available as a PDF. © 1991 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)

Ricard, Bérénice; Rivoal, Jean; Spiteri, Anne; Pradet, Alain

doi: 10.1104/pp.95.3.669pmid: 16668037

Abstract Sucrose synthase activity increased in 2-day-old rice (Oryza sativa) seedlings submitted to anaerobic stress. Likewise, both denaturing and native Western blot analysis detected a rise in the cellular concentration of sucrose synthase protein. Significantly higher steady-state levels of sucrose synthase mRNA, as determined by Northern blots and by the ability of total RNA to direct in vitro synthesis of sucrose synthase, were also induced by anaerobic treatment. Analysis of run-on transcripts showed increased transcription of sucrose synthase genes as early as 60 minutes after initiation of anaerobic stress. Together, these results indicate that sucrose synthase is a typical anaerobic protein in rice. This content is only available as a PDF. © 1991 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)

Ullrich, Cornelia I.; Novacky, Anton J.

doi: 10.1104/pp.95.3.675pmid: 16668038

Abstract The effect of the purified host-selective toxin victorin C, a cyclized penta peptide, was compared to that of CCCP and vanadate on membrane functions of susceptible leaves, roots, and single root cap cells of Avena sativa with conventional electrophysiology. The plasmalemma depolarized irreversibly by about 80 millivolts and to below the diffusion potential within 1 hour. Concentrations as low as 12.5 picomolar were effective in the susceptible but not the resistant cultivar. Electrical membrane potential difference changes were independent of pH and could not be prevented by fusicoccin or Ca2+. Membranes began to depolarize after a lag phase that never was shorter than 6.5 minutes, even with concentrations as high as 1.25 micromolar. Membrane depolarization was accompanied by a distinct decrease in specific membrane resistance from 4.5 to 1.0 ohm times square meter on average. These changes were followed by K+ and Cl− efflux and extracellular alkalinization. ATP level and O2 uptake did not decrease within 2 hours. It is concluded that the victorin-induced deleterious membrane alterations are not caused by direct interaction with the plasmalemma H+-ATPase, K+ channels, lipid structure, nor energy metabolism, but they seem to be triggered by a cascade of events leading to an unspecific increase in membrane permeability. 1 Supported by the Deutsche Forschungsgemeinschaft (C. U.), by an Alexander von Humboldt Senior U.S. Scientist award, and by the National Science Foundation, DMB-8516038 (A. N.) This content is only available as a PDF. © 1991 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)

Rivoal, Jean; Ricard, Bérénice; Pradet, Alain

doi: 10.1104/pp.95.3.682pmid: 16668039

Abstract A lactate dehydrogenase activity is present in rice (Oryza sativa L.) seedlings and roots. Under aerobic conditions, lactate dehydrogenase activity is barely detectable in rice seedlings and is very low in rice roots. In 30 day old roots, the activity is increased two to three times by an anoxic or hypoxic treatment and can be detected on immunoblots by an antiserum raised against barley lactate dehydrogenase. The activity present in aerobic seedlings was partially purified. The native enzyme has a molecular mass of 160 kilodaltons, and is a tetramer of 2 subunit (38 and 39 kilodaltons) randomly associated. Studies of substrate specificity, native gel electrophoresis, and immunoblot analysis indicate that the partially purified enzyme is a typical lactate dehydrogenase. However, no increase of lactate dehydrogenase activity or protein was observed in seedlings transferred to anoxia. 1 Present address: MSU-DOE Plant Research Laboratory, East Lansing, MI 48824-1312. 2 Present address: ILRAD, P. O. Box 30709, Nairobi, Kenya, Africa. This content is only available as a PDF. © 1991 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)

Czako, Mihaly; An, Gynheung

doi: 10.1104/pp.95.3.687pmid: 16668040

Abstract DNA coding for the enzymatically active subunit A of diphtheria toxin was placed under the control of the cauliflower mosaic virus 35S promoter and the Agrobacterium left transfer-DNA gene 7 polyadenylation signal. Agrobacteria carrying a binary plant vector with the chimeric diphtheria toxin A gene had very low transforming activity in tobacco (Nicotiana tabacum L.), and greatly diminished the recovery of stable transformants when mixed together with agrobacteria which alone transformed plant cells well. The introduction of this chimeric molecule into tobacco cells by electroporation lowered the level of the transient expression of the coelectroporated chloramphenicol acetyltransferase reporter gene indicating that expression of diphtheria toxin chain A in plant cells is toxic. We have developed a binary vector pGA987 which can be used for probing a variety of plant promoters. 1 This work was supported in part by grants from Washington State University and the Rockefeller Foundation. This content is only available as a PDF. © 1991 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)

Norman, Eric G.; Colman, Brian

doi: 10.1104/pp.95.3.693pmid: 16668041

Abstract The properties and role of the enzyme phosphoglycolate phosphatase in the cyanobacterium Coccochloris peniocystis have been investigated. Phosphoglycolate phosphatase was purified 92-fold and had a native molecular mass of approximately 56 kilodaltons. The enzyme demonstrated a broad pH optimum of pH 5.0 to 7.5 and showed a relatively low apparent affinity for substrate (K m = 222 micromolar) when compared to that from higher plants. The enzyme required both an anion and divalent cation for activity. Mn2+ and Mg2+ were effective divalent cations while Cl− was the most effective anion tested. The enzyme was specific for phosphoglycolate and did not show any activity toward a variety of organic phosphate esters. Growth of the cells on high CO2 and transfer to air did not result in any significant change in phosphoglycolate phosphatase activity. Competitive inhibition of C. peniocystis triose phosphate isomerase by phosphoglycolate was demonstrated (K i = 12.9 micromolar). These results indicate the presence of a specific noninducible phosphoglycolate phosphatase whose sole function may be to hydrolyze phosphoglycolate and prevent phosphoglycolate inhibition of triose phosphate isomerase. 1 Supported by grants to B. C. from Natural Sciences and Engineering Research Council of Canada. This content is only available as a PDF. © 1991 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)

Christie, Peter J.; Hahn, Matthias; Walbot, Virginia

doi: 10.1104/pp.95.3.699pmid: 16668042

Abstract Low-temperature stress was shown to cause a rapid increase in steady-state levels of alcohol dehydrogenase-1 message (Adh1) and protein activity (ADH1) in maize (Zea mays) (B37N, A188) and rice (Oryza sativa) (Taipei 309, Calmochi 101) seedlings. Maize roots and rice shoots and roots from 7-day seedlings shifted to low temperature (10°C) contained as much as 15-fold more Adh1 mRNA and 8-fold more ADH1 protein activity than the corresponding tissues from untreated seedlings. Time-course studies showed that these tissues accumulated Adh1 mRNA and ADH1 activity severalfold within 4- to 8-hour, levels plateaued within 20 to 24 hours, and remained elevated at 4 days of cold treatment. Within 24 hours of returning cold-stressed seedlings to ambient temperature, Adh1 mRNA and ADH1 activity decreased to pretreatment levels. Histochemical staining of maize and rice tissue imprints showed that ADH activity was enhanced along the lengths of cold-stressed maize primary roots and rice roots, and along the stems and leaves of rice shoots. Our observations suggest that short-term cold stress induces Adh1 gene expression in certain plant tissues, which, reminiscient of the anaerobic response, may reflect a fundamental shift in energy metabolism to ensure tissue survival during the stress period. 2 Present address: Universität Konstanz, Fakultät Biologie, Lehrstuhl Phytopathologie, D-7750 Konstanz, Federal Republic of Germany. 1 Supported by the Rockefeller Foundation (grant RF 87058/#58). P.J.C. was supported in part by American Cancer Society grant PF2937. M.H. was supported by postdoctoral fellowships from the Deutsche Forschungsgemeinschaft and the Deutscher Akademischer Austauschdienst (Sonderprogramm Gentechnologie). This content is only available as a PDF. © 1991 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)

Brauer, David; Tu, Shu-I

doi: 10.1104/pp.95.3.707pmid: 16668043

Abstract Certain carboxylic acid groups within the primary structure of proton translocating proteins are thought to be involved in the proton pathway. In this report, the effects of a lipophilic carboxylic acid reactive reagent, N-cyclo-N′(4-dimethylamino-α-naphthyl)carbodiimide (NCD-4), on the two types of proton pumps in maize (Zea mays L.) root microsomes were investigated. NCD-4 was found to inhibit the vacuolar-type H+-ATPase in microsomal preparations; however, the plasma membrane-type H+-ATPase was unaffected. The H+-ATPase in highly purified tonoplast vesicles was also inhibited by NCD-4. Inhibition was dependent on the concentration and length of exposure to the reagent. However, there was little, if any, increase in the fluorescence of treated vesicles, indicating few carboxylic acid residues were reacting. Inhibition of the tonoplast H+-ATPase by NCD-4 was examined further with a partially purified preparation. The partially purified H+-ATPase also showed sensitivity to the NCD-4, supporting the hypothesis that this carboxylic acid reagent is an inhibitor of the tonoplast ATPase from maize roots. This content is only available as a PDF. © 1991 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)

Crowell, Dring N.; Amasino, Richard M.

doi: 10.1104/pp.95.3.711pmid: 16668044

Abstract We report the isolation of five cDNA clones whose corresponding mRNAs accumulate in cultured soybean cells (Glycine max cv Mandarin) during cytokinin or auxin starvation. The levels of three of these mRNAs decrease rapidly after addition of 5 micromolar zeatin to cytokinin-starved cells or after addition of 10 micromolar α-naphthaleneacetic acid to auxin-starved cells. These mRNAs also exhibit various patterns of accumulation in the tissues of intact soybean plants. Partial nucleotide sequence analysis demonstrates that one of the cDNAs in the collection, called SAM46, is 46% identical at the amino acid level to the iron superoxide dismutase gene of Escherichia coli. Expression of this cDNA in Escherichia coli cells results in detectable iron superoxide dismutase activity, confirming the identity of the cDNA. 1 This work was supported by grant DCB-8957036 from the National Science Foundation and by the College of Agricultural and Life Sciences, University of Wisconsin-Madison. R.M.A. is a James D. and Dorothy Shaw Scholar. This content is only available as a PDF. © 1991 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)

Hohl, Michael; Schopfer, Peter

doi: 10.1104/pp.95.3.716pmid: 16668045

Abstract Water relations of growing segments of maize (Zea mays L.) coleoptiles were investigated with osmotic methods using either mannitol (MAN) or polyethylene glycol 6000 (PEG) as external osmotica. Segments were incubated in MAN or PEG solutions at 0 to - 15 bar water potential (Ψo) and the effects were compared on elongation growth, osmotic shrinkage, cell sap osmolality (OC), and osmotic pressure (πi). The nonpenetrating osmoticum PEG affects πi in agreement with Boyle-Mariotte's law, i.e. the segments behave in principle as ideal osmometers. There is no osmotic adjustment in the Ψo range permitting growth (0 to −5 bar) nor in the Ψo range inducing osmotic shrinkage (−5 to −10 bar). Promoting growth by auxin (IAA) has no effect on the osmotic behavior of the tissue toward PEG. In contrast to PEG, MAN produces an apparent increase in πi accompanied by anomalous effects on segment elongation and shrinkage leading to a lower value for Ψo which establishes a growth rate of zero and to an apparent recovery from osmotic shrinkage after 2 hours of incubation. These effects can be quantitatively attributed to uptake of MAN into the tissue. MAN is taken up into the apoplastic space and the symplast as revealed by a large temperature-dependent component of MAN uptake. It is concluded that MAN, in contrast to PEG, is unsuitable as an extemal osmoticum for the quantitative determination of water relations of growing maize coleoptiles. 1 Supported by the Deutsche Forschungsgemeinschaft (SFB 206). This content is only available as a PDF. © 1991 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)