Plant Physiology

Rosenthal, Gerald A.

doi: 10.1104/pp.94.1.1pmid: 16667673

Abstract Massive accumulation of l-canavanine, the 2-amino-4-(guanidinooxy)butyric acid structural analog of l-arginine, occurs in many legumes. Accumulation of large amounts of this nonprotein amino acid results in large part from canavanine's protective efficacy; it forms an effective chemical barrier to predation, disease, and even competition with other plants. Diversion of metabolic resources for the synthesis and storage of appreciable canavanine does not place an inordinate burden on the plant. Catabolism of this nonprotein amino acid provides respiratory carbon, generates essential primary metabolites, and ammoniacal nitrogen for the developing plant. This content is only available as a PDF. © 1990 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)

Kowalczyk, Stanislaw; Bandurski, Robert S.

doi: 10.1104/pp.94.1.4pmid: 11537480

Abstract The first compound in the series of reactions leading to the ester conjugates of indole-3-acetic acid (IAA) in kernels of Zea mays sweet corn is the acyl alkyl acetal, 1-O-indol-3-ylacetyl-β-d-glucose (1-O-IAGlu). The enzyme catalyzing the synthesis of this compound is UDP-glucose:indol-3-ylacetate glucosyl-transferase (IAGlu synthase). The IAA moiety of the high energy compound 1-O-IAGlu may be enzymatically transferred to myo-inositol or to glycerol or the 1-O-IAGlu may be enzymatically hydrolyzed. Alternatively, nonenzymatic acyl migration may occur to yield the 2-O, 4-O, and 6-O esters of IAA and glucose. The 4-O and 6-O esters may then be enzymatically hydrolyzed to yield free IAA and glucose. This work reports new enzymatic activities, the transfer of IAA from 1-O-IAGlu to glycerol, and the enzymecatalyzed hydrolysis of 4-O- and 6-O-IAGlu. Data is also presented on the rate of non-enzymatic acyl migration of IAA from the 1-O to the 4-O and 6-O positions of glucose. We also report that enzymes catalyzing the synthesis of 1-O-IAGlu and the hydrolysis of 1-O, 4-O, and 6-O-IAGlu fractionate as a hormone metabolizing complex. The association of synthetic and hydrolytic capabilities in enzymes which cofractionate may have physiological significance. 2 On leave from: Department of Biochemistry, Institute of Biology, Mikolaj Kopernik University, PL 87-100, Torun, Poland. 1 Supported by grants from the Metabolic Biology Section of the National Science Foundation, DCB-8805148; and by the Life Sciences Section of the National Aeronautics and Space Administration, NAGW-97 and NAG2-362. This content is only available as a PDF. © 1990 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)

Schaeffer, Holly J.; Walton, Jonathan D.

doi: 10.1104/pp.94.1.13pmid: 16667679

Abstract Aluminum chloride induced mesophyll protoplasts of oat (Avena sativa) to produce an extracellular polysaccharide (EPS). EPS induced by AlCl3 appeared identical to that produced in response to the phytotoxin victorin (JD Walton, ED Earle [1985] Planta 165: 407-415). Al ions at 1 millimolar were toxic to protoplasts, but maximum EPS production occurred at a sublethal concentration of 200 micromolar, assayed at pH 6.0. As measured by incorporation of [14C]glucose, AlCl3 stimulated EPS production 10- to 15- fold. Pretreatment of protoplasts with cycloheximide prevented EPS production but not cell death in response to AlCl3, indicating that protein synthesis was necessary for EPS production but not for the phytotoxicity of Al ions. The trivalent salts of Y, Yb, Gd, and In also induced EPS production but those of Sc, Fe, Ga, Cr, and La did not. Mesophyll protoplasts from an acid-soil tolerant oat cultivar, Coker 83-23, produced less EPS in response to AlCl3 than the acid-soil sensitive cultivar Fla 501. EPS was also produced by wheat (Triticum aestivum) and barley (Hordeum vulgare) protoplasts in response to AlCl3. An Al-tolerant cultivar of wheat, Atlas, produced less EPS than an Al-sensitive cultivar, Scout, but an Al-tolerant cultivar of barley, Dayton, produced more than the Al-sensitive cultivar Kearney. Therefore, production of EPS by protoplasts in response to Al ions did not appear to be related to Al ion tolerance at the level of whole plants. EPS fluoresced in the presence of Calcofluor and Sirofluor and was degraded by purified laminarinase [(1→3)β-d-glucanase] but not pectinase (polygalacturonase). EPS was composed solely of glucose in 1→3 linkages; hence it is a (1→3)β-d-glucan (callose). 1 Supported by the U.S. Department of Energy under contract DE-AC02-76ER01338. This content is only available as a PDF. © 1990 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)

Zeiher, Carolyn A.; Randall, Douglas D.

doi: 10.1104/pp.94.1.20pmid: 16667687

Abstract Mitochondria from Pisum sativum seedlings purified free of peroxisomal and chlorophyll contamination were examined for acetyl-coenzyme A (CoA) hydrolase activity. Acetyl-CoA hydrolase activity was latent when assayed in isotonic media. The majority of the enzyme activity was found in the soluble matrix of the mitochondria. The products, acetate and CoA, were quantified by two independent methods and verified that the observed activity was an acetyl-CoA hydrolase. The pea mitochondrial acetyl-CoA hydrolase showed a K m for acetyl-CoA of 74 micromolar and a V max of 6.1 nanomoles per minute per milligram protein. CoA was a linear competitive inhibitor of the enzyme with a K is of 16 micromolar. The sensitivity of the enzyme to changes in mole fraction of acetyl-CoA suggested that the changes in the intramitochondrial acetyl-CoA/CoA ratio may be an effective mechanism of control. The widespread distribution of mitochondrial acetyl-CoA hydrolase activity among different plant species indicated that this may be a general mechanism in plants for synthesizing acetate. 2 Present address: Plant Science Department, University of Arizona, Tucson, AZ 85721 1 This research was supported by the Missouri Agricultural Experiment Station and National Science Foundation grant DMB-8506473. This is journal report No. 10,916 from the Missouri Agricultural Experiment Station. This content is only available as a PDF. © 1990 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)

Frehner, Marco; Scalet, Mario; Conn, Eric E.

doi: 10.1104/pp.94.1.28pmid: 16667698

Abstract The absolute cyanide content of developing fruits was determined in Costa Rican wild lima beans (Phaseolus lunatus), oil flax (Linum usitatissimum), and bitter almonds (Prunus amygdalus). The cyanide potential (HCN-p) of the lima bean and the almond fruit began to increase shortly after anthesis and then stopped before fruit maturity. In contrast, the flax inflorescence had a higher HCN-p in absolute terms than the mature flax fruit. At all times of its development the bean fruit contained the monoglucosides linamarin and lotaustralin. The almond and the flax fruits contained, at anthesis, the monoglucosides prunasin, and linamarin and lotaustralin, respectively, while, at maturity, only the corresponding diglucosides amygdalin, and linustatin and neolinustatin, respectively, were present. 2 Permanent address: Swiss Federal Institute of Technology, Institute of Plant Science, Universitätstrasse 2, CH-8092 Zürich, Switzerland. 3 Permanent address: University of Udine, Institute of Plant Defense, Piazzale Kolbe 4, I-33100 Udine, Italy. 1 This work has been supported in part by the Swiss National Science Foundation (Fellowship in 1986 to M. F.) and in part by National Science Foundation grant DMB 8517190. This content is only available as a PDF. © 1990 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)

Badger, Murray R.; Price, G. Dean

doi: 10.1104/pp.94.1.35pmid: 16667708

Abstract Carbon oxysulfide (COS) was reinvestigated as an inhibitor of active inorganic carbon transport in cells of Synechococcus PCC7942 adapted to growth at low inorganic carbon. COS inhibited both CO2 and HCO3− transport processes in a reversible (in the short term) and mixed competitive manner. The inhibition of COS was established using both silicone oil centrifugation experiments and O2-evolution studies. The K i for COS inhibition was 29 micromolar for CO2 transport and 110 micromolar for HCO3− transport. These results support a model of inorganic carbon transport with a central CO2 pump and an inducible HCO3− utilizing accessory protein which supplies CO2 to the primary pump. This content is only available as a PDF. © 1990 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)

Suh, Sang-Gon; Peterson, Jon E.; Stiekema, Willem J.; Hannapel, David J.

doi: 10.1104/pp.94.1.40pmid: 16667716

Abstract Three abundant proteins of approximate molecular masses of 22, 23, and 24 kilodaltons were purified from potato (Solanum tuberosum L.) tubers by DEAE cellulose and CM-52 cellulose ion exchange column chromatography, electroelution, and high-pressure liquid chromatography (HPLC). Antibodies specific to the gel-purified 22-kilodalton protein were prepared. Immunoblot analysis showed that the 22-, 23-, and 24-kilodalton proteins are immunologically related and that these proteins are present in tubers and as higher molecular mass forms in leaves, but not in stems, roots, and stolons. The ratios of amino acid composition were compared among the three purified proteins, and the aminoterminal amino acid sequences were determined for these three proteins. All three proteins have identical amino-terminal sequences that match the deduced amino acid sequence of an abundant tuber protein cDNA. 1 Supported by a research grant from the Iowa State University Biotechnology Council. Journal Paper No. J-13810 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA. Project No. 2846. This content is only available as a PDF. © 1990 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)

Stoop, Johan M. H.; Peet, Mary M.; Willits, Dan H.; Nelson, Paul V.

doi: 10.1104/pp.94.1.46pmid: 16667717

Abstract The time-course of CO2 assimilation rate and stomatal conductance to step changes in photosynthetic photon flux density (PPFD) was observed in Chrysanthemum × morifolium Ramat. `Fiesta'. When PPFD was increased from 200 to 600 micromoles per square meter per second, the rate of photosynthetic CO2 assimilation showed an initial rapid increase over the first minute followed by a slower increase over the next 12 to 38 minutes, with a faster response in low-light-grown plants. Leaves exposed to small step increases (100 micromoles per square meter per second) reached the new steady-state assimilation rate within a minute. Both stomatal and biochemical limitations played a role during photosynthetic induction, but carboxylation limitations seemed to predominate during the first 5 to 10 minutes. Stomatal control during the slow phase of induction was less important in low-light compared to high-light-grown plants. In response to step decreases in PPFD, photosynthetic rate decreased rapidly and a depression in CO2 assimilation prior to steady-state was observed. This CO2 assimilation `dip' was considerably larger for the large step (400 micromoles per square meter per second) than for the small step. The rapid photosynthetic response seems to be controlled by biochemical processes. High- and low-light-grown plants did not differ in their photosynthetic response to PPFD step decreases. 1 The research reported in this publication was funded (in part) by the North Carolina Agricultural Research Service. This content is only available as a PDF. © 1990 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, Tsai-Yun; Markhart, Albert H.

doi: 10.1104/pp.94.1.54pmid: 16667718

Abstract Electron transport, using succinate as a substrate, was measured polarographically in mitochondria isolated from Phaseolus vulgaris and P. acutifolius plants at 25°C and 32°C. Mitochondria isolated from P. vulgaris plants grown at 32°C had reduced electron transport and were substantially uncoupled. Growth at 32°C had no effect on electron transport or oxidative phosphorylation in P. acutifolius compared to 25°C grown plants. Mitochondria isolated from 25°C grown P. vulgaris plants measured at 42°C were completely uncoupled. Similarly treated P. acutifolius mitochondria remained coupled. The uncoupling of P. vulgaris was due to increased proton permeability of inner mitochondrial membrane. The alternative pathway was more sensitive to heat than the regular cytochrome pathway. At 42°C, no alternative pathway activity was detected. The substantially greater heat tolerance of P. acutifollus compared to P. vulgaris mitochondrial electron transport suggests that mitochondrial sensitivity to elevated temperatures is a major limitation to growth of P. vulgaris at high temperatures and is an important characteristic conveying tolerance in P. acutifolius. 1 Published as paper No. 18,188 of scientific journal series of the Minnesota Experiment Station on research conducted under Minnesota Experiment Station Project 0302-4821-82. This content is only available as a PDF. © 1990 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)

Nouchi, Isamu; Mariko, Shigeru; Aoki, Kazuyuki

doi: 10.1104/pp.94.1.59pmid: 16667719

Abstract To clarify the mechanisms of methane transport from the rhizosphere into the atmosphere through rice plants (Oryza sativa L.), the methane emission rate was measured from a shoot whose roots had been kept in a culture solution with a high methane concentration or exposed to methane gas in the gas phase by using a cylindrical chamber. No clear correlation was observed between change in the transpiration rate and that in the methane emission rate. Methane was mostly released from the culm, which is an aggregation of leaf sheaths, but not from the leaf blade. Micropores which are different from stomata were newly found at the abaxial epidermis of the leaf sheath by scanning electron microscopy. The measured methane emission rate was much higher than the calculated methane emission rate that would result from transpiration and the methane concentration in the culture solution. Rice roots could absorb methane gas in the gas phase without water uptake. These results suggest that methane dissolved in the soil water surrounding the roots diffuses into the cell-wall water of the root cells, gasifies in the root cortex, and then is mostly released through the micropores in the leaf sheaths. 1 This research was supported by funds from the Science and Technology Agency of Japan. This content is only available as a PDF. © 1990 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)