Effect of EDTA on two RNases from wheat leaves

Two RNases, designated WL-RNase I and II, were separated fromextracts of senescing wheat leaves. WL-RNase II, but not WL-RNaseI, was inhibited by EDTA. A period of time was necessary forthe full effect of EDTA to be observed. Zinc ions abolishedthe EDTA effect. ¹Most of the data are taken from a Ph. D. Thesis submitted tothe University of London by L. SODEK. A portion of the workwas cooperative between the University of Illinois and the U.S.Dept. of Agriculture. Mention of a trademark or proprietaryproduct does not constitute a guarantee or warranty of the productby the U.S. Dept. of Agriculture, and does not imply its approvalto the exclusion of other products that may also be suitable ²Research Chemist, Crops Research Division, Agricultural ResearchService, United States Department of Agriculture (Received October 3, 1969; )     

Respiration rate of fruit flesh from red and green sides of 'Cortland' apples

Respiration rate of apple flesh from red and green side of ‘Cortland’apples was measured using Gilson respirometer. Respiration fromred side was greater for both pre and post climacteric fruit.Flesh from the red side was also higher in soluble solids, freshweight and dry weight. ¹Contribution No. 1283 of the Rhode Island Agricultural ExperimentStation. ²Present address: Department of Agronomy, U. P. College of Agriculture,College Laguna, Philippines. (Received July 23, 1968; )     

ORNITHINE CYCLE ENZYMES IN THE BLUE-GREEN ALGA NOSTOC MUSCORUM

Cell-free extracts of a bacteria-free culture of Nostoc muscorumwere used to demonstrate the occurrence of part of the KREBS-HENSELEITornithine cycle in blue-green algae. Evidence is presented forthe conversion of ammonia and bicarbonate to carbamyl phosphateand the coupling of carbamyl phosphate to ornithtne to yieldcitrulline. Attempts to demonstrate the conversion of citrullineto arginine were not successful. ¹Present address: Scripts Institute of Oceanography, Universityof California, La Jolla, California, U.S.A. ²Present address: Department of Biochemistry and Nutrition,The University of Texas Medical Branch, Galveston, Texas, U.S.A.     

Effect of Methionine Sulfoximine on Photosynthetic Carbon Metabolism in Wheat Leaves

Methionine sulfoximine (MSO) greatly reduced the carbon dioxideexchange rate (CER) of detached wheat (Triticum aestivvm L.cv Roland) leaves in 21% O₂, but only slightly reduced it in2% O₂. A supply of 50 mM NH₄Cl had little effect on the CERirrespective of the O₂ concentration. A simultaneous additionof glutamine and MSO protected against the inhibition of photosynthesisto a considerable extent and caused the accumulation of moreNH₃ than did the addition of MSO alone. Fixation of ¹⁴CO₂ in wheat leaves was inhibited by MSO treatmentin 22% O₂, and there was decreased incorporation of ¹⁴G intoamino acids and sugars and increased label into acid fractions.The addition of MSO and glutamine together eliminated the effectof MSO on the photosynthetic ¹⁴CO₂ fixation pattern. NH₄Cl stimulatedthe synthesis of amino acids from ¹⁴CO₂, especially the synthesisof serine in 22% O₂. Our observations show that factors other than the uncouplingof photophosphorylation by accumulated NH₃ may be responsiblefor the early stage of photosynthesis inhibition by MSO underphotorespiratory conditions. ¹Present address: Department of Agricultural Chemistry, KyushuUniversity, Fukuoka 812 Japan. ²Also at U.S. Department of Agriculture, Agricultural ResearchService, Urbana, Illionois 61801, U.S.A. (Received September 13, 1983; Accepted February 2, 1984)     

Properties of S-adenosyl-L-methionine-magnesium-protoporphyrin IX methyltransferase from barley

S-Adenosyl-L-methionine-magnesium-protoporphyrin IX methyltransferase(EC 2.1.1.11 [EC] ) is present in greening barley seedlings associatedwith the particulate fraction. This enzyme was purified 20 foldusing protamine and ammonium sulfate precipitation. The enzymewas active over a wide pH range with highest activity at pH7.5. The Km values for Mg-protoporphyrin IX and S-adenosylmethioninewere 48 and 39 µM, respectively; S-adenosylethionine andS-adenosyihomocysteine were competitive inhibitors with respectto S-adenosylmethionine; hemin inhibition was non-competitivewith respect to Mg-protoporphyrin IX; thiol compounds exhibiteda stimulatory effect on enzyme activity. The properties of theenzyme are discussed and compared with the enzyme from otherorganisms. ¹ This research was supported in part by the Utah State AgriculturalExperiment Station. ² Present address: Department of Chemistry, Boston University,Boston, Massachusetts, U. S. A. ³ Present address: Department of Biochemistry and Microbiology,Faculty of Pharmacy, Comenius University, Bratislava, Czechoslovakia. (Received February 20, 1978; )     

Protein Synthesis Linked to Respiration and Phosphorylation in Intact Euglena Mitochondria

Highly purified condensed mitochondria obtained from bleachedmutant. W₁₀BSmL of Euglena gracilis Klebs var bacillaris Coriincorporate [³⁵S]methionine into protein when fortified withmalate, ADP, Mg²⁺, phosphate and a sucrose osmoticum. Twentyto twenty-five polypeptide bands were found to be labeled inorganello when the labeled protein was subjected to sodium dodecylsulfatepolyacrylamide gel electrophoresis. Methionine incorporation,but not respiration or oxidative phosphorylation, was blockedby chloramphenicol and other 70S ribosomal translation inhibitorsbut cycloheximide and ribonuclease were without effect. Inhibitorsof electron transport and uncouplers of oxidative phosphorylationwere excellent inhibitors of protein synthesis. Thus, thesemitochondrial preparations carry out protein synthesis in organellothat is linked to respiration and oxidative phosphorylation. ¹Present address: VA Hospital Outpatient Clinic, 17 Court St.,Boston, MA 02115, U.S.A. ²Present address: Laboratories de Microbiologia e Inmunologia,Universidad Catolica de Chile, Casilla 114-D, Santiago, Chile. ³Present address: Botany Department, University of Massachusetts,Amherst, MA 01003, U.S.A. (Received June 17, 1985; Accepted October 28, 1985)     

Induction of Cytosolic Acetyl-Coenzyme A Carboxylase in Pea Leaves by Ultraviolet-B Irradiation

Levels of subunits of two acetyl-coenzyme A carboxylases werehigh in small leaves of Pisum sativum, decreased with growth,and remained constant in fully expanded leaves. Irradiationof fully expanded leaves induced the cytosolic isozyme only.This result suggests a key role for the cytosolic enzyme inprotection against UV-B. ¹Present address: Laboratory of Molecular Genetics, BiotechnologyInstitute, Akita Prefectural College of Agriculture, 2-2 Minami,Ohgata, Akita, 010-04 Japan ²Present address: Laboratory of Plant Molecular Biology, Schoolof Agricultural Sciences Nagoya University, Nagoya, 464-01 Japan     

Dark Reduction of P700+ in Photosystem I Particles by Illuminated Chlorophyllide

Illumination of chlorophyllide dissolved in a wet organic solventgenerates an unknown species of chlorophyllide which is capableof reducing P700⁺ in darkness ata considerably high rate inthe absence of ascorbate and redox mediators. The formationof this derivative species is accompanied by bleaching of boththe red and blue absorption bands of chlorophyllide concomitantwith the appearance of a new peak at around 500 nm. The generationof reducing capability is stimulated by the presence of basesbut does not require reducing agents. Some of the propertiesof this reaction are discussed in comparison with the Krasnovskiireaction. ¹Present address: Department of Environmental Biology, ResearchSchool of Biological Science, The Australian National University,Canberra City, ACT 2601, Australia. ³Present address: Department of Biology, Indiana University,Bloomington, IN 47405, U.S.A. (Received June 6, 1985; Accepted November 20, 1985)     

Polyamines and Somatic Embryogenesis in Carrot. III. Effects of Methylglyoxal bis(guanylhydrazone)

The effects of methylglyoxal bis(guanylhydrazone) (MGBG) onsomatic embryogenesis, titres of cellular polyamines and 1-aminocyclopropane-l-carboxylicacid, and the activity of arginine decarboxylase (ADC) werestudied using suspension cultures of carrot (Daucus carota L.).Whereas MGBG (0.1–0.5 mM) significantly inhibited thecellular levels of spermidine and spermine, putrescine levelswere higher in the treated tissue. MGBG also promoted ACC levelsin the cells. The activity of ADC was inhibited in the presenceof MGBG. Somatic embryogenesis in the auxin-free medium wascompletely inhibited by MGBG. The effects of MGBG on somaticembryogenesis were reversed by 0.1–0.2 mM spermidine butnot by spermine. These results are consistent with the suggestionthat an interaction between ethylene and polyamine bio-syntheticpathways through competition for the common precursor, S-adenosylmethionine,plays an important role in the development of somatic embryosin carrot cell cultures. ¹Scientific Contribution Number 1649 from the New HampshireAgricultural Experiment Station. This research was supportedby NSF Grant No. DCB-8615945, Central University Research Funds,UNH, and NHAES Project H-233 ²Present address: Nancy S. Papa, In Vitron Corporation, 4649LeBourget Drive, St. Louis, MO 63134, U.S.A. ³Present address: Dr. A. Jamal Khan, Department of Plant Science,College of Agriculture, Sultan Qaboos University, P.O. Box-32484,Al-Khod, Muscat, Sultanate of Oman (Received September 17, 1990; Accepted January 21, 1991)     

Characterization of Senescence in Lemna gibba G3: A Determinate Growth System

Frond senescence in Lemna gibba G3 was characterized, and itscontrol by light, ABA and kinetin investigated. The plant exhibitsa determinate growth pattern with a frond producing a set numberof daughter fronds before undergoing senescence and death regardlessof whether or not it flowers. When a frond was cut in half,the distal half (half frond) which lacks any meristem underwentrapid senescence as compared with intact fronds. In both intactand half fronds, the onset of senescence was accelerated byABA and retarded by kinetin. Continuous white light acceleratedsenescence in both intact and half fronds over the dark controls.Under different photoperiodic light regime, the pace of daughterfrond production is accelerated in proportion to the lengthof light period. In half fronds, however, very short photoperiodiclight treatments (e.g. 1L: 23D or 3L: 21D) rather delayed senescenceover the dark controls. Two separate light control systems operatingin opposite directions in Lemana senescence appear to exist. ¹Present address: Department of Biology, Yonsei University,Seoul 120-749, Korea ²Present address: U.S. Department of Agriculture, Aero SpaceBuilding, Rm. 323, 901 D Street, S.W., Washington, D.C. 20251-2200, U.S.A. (Received July 13, 1989; Accepted May 8, 1990)     

Purification and characterization of uroporphyrinogen decarboxylase from tobacco leaves

1. Uroporphyrinogen decarboxylase which catalyzes the formationof coproporphyrinogen from uroporphyrinogen is located in thesoluble fraction of tobacco leaves and was purified 72 foldthrough ammonium sulphate precipitation and calcium phosphosphategel absorption. 2. Kinetic studies indicated that the apparentMichaelis constant was 1 ? 10^-6 M for uroporphyrinogen III (pH6.5; 37?C). Uroporphyrinogen III served as a much better substratethan uroporphyrinogen I under the standard conditions of thisstudy. 3. Enzyme activity was inhibited by thiol reagents andheavy divalent cations and was stimulated by some chelatingagents. 4. Both chloride and fluoride salts inhibited the formationof coproporphyrinogen from uroporphyrinogen. ¹Present address: Department of Chemistry, Simon Fraser University,Burnaby 2, British Columbia, Canada. ²Present address: Biology Department, Utah State University,Logan, Utah 84322, U. S. A. (Received June 8, 1974; )     

PURIFICATION AND PROPERTIES OF SERINE HYDROXYMETHYLTRANSFERASE FROM NICOTIANA RUSTICA L.

Serine hydroxymethyltransferase was partially purified fromNicotiana rustica roots. The pH optimum for the enzyme is 4.0.A requirement for pyridoxal phosphate and a divalent cationwas shown, and the enzyme was inhibited by sulfhydryl reagentsand the reaction is folic acid-dependent. ¹Contribution from the Department of Biochemistry and publishedwith the approval of the Director of Research as Paper No. 2175in the Journal Series ²Present address; Spruance Research Laboratories, E. I. du Pontde Nemours and Company, Inc., Post Office Box 1477, Richmond,Virginia 23212, U.S.A.     

A Mutant of Arabidopsis thaliana That Defines a New Locus for Glycine Decarboxylation

A novel photorespiratory mutant of Arabidopsis thaliana, designatedgld2, was isolated based on a growth requirement for abnormallyhigh levels of atmospheric CO₂. Photosynthetic CO₂ fixationwas inhibited in the mutant following illumination in air butnot in atmosphere containing 2% O₂. Photosynthetic assimilationof ¹⁴CO₂ in an atmosphere containing 50% O₂ resulted in accumulationof 48% of the soluble label in glycine in the mutant comparedto 9% in the wild type. The rate of glycine decarboxylationby isolated mitochondria from the mutant was reduced to 6% ofthe wild type rate. In genetic crosses, the mutant complementedtwo previously described photorespiratory mutants of A. thalianathat accumulate glycine during photosynthesis in air due todefects in glycine decarboxylase (glyD, now designated gld1)and serine transhydroxymethylase (stm). Because glycine decarboxylaseis a complex of four enzymes, these results are consistent witha mutation in a glycine decarboxylase subunit other than thataffected in the gld1 mutant. The two gld loci were mapped tochromosomes 2 and 5, respectively. ³Present address: Department of Crop and Soil Sciences, MichiganState University, East Lansing, MI 48824, U.S.A. ⁴Present address: Department of Applied Bioscience, Facultyof Agriculture, Hokkaido University, Kita-Ku, Sapporo, 060 Japan ⁵Present address: Department of Biology, Carnegie Institutionof Washington, 290 Panama Street, Standford, CA 94305, U.S.A.     

Effects of Exogenous Auxin on the Regulation of Elongation Growth of Excised Segments of Vigna Hypocotyls under Osmotic Stress

IAA applied simultaneously with osmotica greatly enhanced theadaptive recovery of the elongation growth of segments of Vignahypocotyls during osmotic stress irrespective of whether ornot absorbable solutes were present. IAA stimulated both thesurface pump and the xylem pump, which have been shown to bestimulated by osmotic stress and to control the yielding ofthe cell wall and the absorption of solutes. Thus, wall extensibilityand the effective turgor were further enhanced under osmoticstress in the presence of IAA. These results indicate that thesimultaneous presence of IAA can reduce the inhibition of growthby osmotic stress, and they support numerical predictions basedon the apoplast canal model. The mechanism involved in the rapidrecovery of growth is discussed. ¹ Present address: Research Centre, Guangxi Agricultural University,Xiu Ling Rd., Nanning, Guangxi 530005 China. ² Present address: Biology Institute, Department of GeneralEducation, Nagoya University, 1 Furo-cho, Chikusa-ku, Nagoya,464 Japan. ³ Present address: Graduate School of Integrated Science, YokohamaCity University, 22-2, Seto, Kanazawa-ku, Yokohama, 236 Japan.     

Biological Significance of Divalent Metal Ion Binding to 14-3-3 Proteins In Relationship to Nitrate Reductase Inactivation

In this report we address two questions regarding the regulationof phosphorylated nitrate reductase (pNR; EC 1.6.6.1 [EC] ) by 14-3-3proteins. The first concerns the requirement for millimolarconcentrations of a divalent cation in order to form the inactivepNR: 14-3-3 complex at pH 7.5. The second concerns the reducedrequirement for divalent cations at pH 6.5. In answering thesequestions we highlight a possible general mechanism involvedin the regulation of 14-3-3 binding to target proteins. We showthat divalent cations (e.g. Ca²⁺, Mg²⁺ and Mn²⁺) bind directlyto 14-3-3s, and as a result cause a conformational change, manifestedas an increase in surface hydrophobicity. A similar change isalso obtained by decreasing the pH from pH 7.5 to pH 6.5, inthe absence of divalent cations, and we propose that protonationof amino acid residues brings about a similar effect to metalion binding. A possible regulatory mechanism, where the 14-3-3protein has to be "primed" prior to binding a target protein,is discussed. ¹Co-operative investigations of the U.S. Department of Agriculture,Agricultural Research Service, and the North Carolina AgriculturalResearch Service, Raleigh, NC. This work was supported by agrant from the U.S. Department of Agriculture-National ResearchInitiative (Grant 93-37305-9231 to JLH and SCH). Mention ofa trademark or proprietary product does not constitute a guaranteeor warranty of the product by the USDA or the North CarolinaAgricultural Service. Nor does it imply its approval to theexclusion of other products that might also be suitable.     

The effect of barban on shoot formation in tobacco callus cultures

Shoot formation in tobacco callus was completely inhibited bythe presence of barban in the media during the first 2 daysof culture. Callus transferred to media containing barban from4th to the 12th day showed progressively less inhibition. Similarresults were obtained with GA₃. ¹Present address: Biology Department, Chung Chi College, TheChinese Univ. of Hong Kong, Shatin, N.T., Hong Kong ²Present address: Plant Hormone & Regulator Pioneering ResearchLab., U.S. Dept. Agric, Crops Res. Div., Beltsville, Md., U.S.A. (Received April 21, 1970; )     

Localization and Binding Characteristics of a High-Affinity Binding Site for N--Acetylchitooligosaccharide Elicitor in the Plasma Membrane from Suspension-Cultured Rice Cells Suggest a Role as a Receptor for the Elicitor Signal at the Cell Surface

A high-affinity binding site for N-acetylchitooligosac-chlarideelicitor was found to localize in the plasma membrane from suspension-culturedrice cells. Binding kinetics as well as the specificity of thisbinding site corresponded well with the behavior of the ricecells to the editor. These characteristics suggest that thebinding site represents a functional receptor for N-acetylchitooligosaccharideelicitor in rice. ²Present address: Okinawa Prefectural Livestock ExperimentalStation, 2009-5 Shoshi, Nakijin-son, Okinawa, 905-04 Japan. ³Present address: School of Hygiene and Public Health, The JohnsHopkins University, 615 North Wolfe Street, Baltimore, Maryland,21205 U.S.A. ⁴Present address: University of Tenessee, Microbiology, knoxville,Tennessee, 37996 U.S.A.     

Molecular Cloning and Characterization of S-Adenosyl-L-Methionine:Scoulerine-9-O-Methyltransferase from Cultured Cells of Coptis japonica

S-Adenosyl-L-methionine : scoulerine-9-O-methyltransferase (SMT)catalyzes the transfer of the S-methyl group of S-adenosyl-L-methionineto the 9-hydroxyl group of scoulerine during the biosynthesisof berberine. We have isolated functionally active cDNA clones(pCJSMTs) from a cDNA library prepared from cultured cells ofCoptis japonica. The longest cDNA insert (pCJSMT1) had an openreading frame that encoded 351 amino acids, but the calculatedmolecular mass (38,364 Da) of the deduced product was slightlylower than the experimentally determined molecular mass of purifiedSMT. Rapid amplification of the 5' end of the cDNA indicatedthat the full-length cDNA of SMT consisted of 1,458 nucleotidesthat encoded 381 amino acids. When the full-length cDNA wasexpressed in E. coli, the molecular mass of the expressed SMTwas greater than that of native SMT in Coptis cells. This resultsuggests that SMT might be produced in a pre-mature form andprocessed post-translationally. SMT was also found to exhibitsequence homology to other O-methyltransferases from plantsand N-terminal region of the SMT polypeptide appeared to benecessary for enzymatic activity. ¹Present address: High Quality Life Research Laboratories, SumitomoMetal Industries, Ltd., 3-5 Hikaridai, Seika, Sourakugun, Kyoto,619-02 Japan ²Present address: Suntory Research Center, 1-1-1 Wakayamadai,Shimamoto, Mishima-gun, Osaka, 618 Japan ³Present address: Department of Cell Biology, The Scripps ResearchInstitute, La Jolla, CA 92037 U.S.A.     

Immunocytochemical Localization of Uricase in Peroxisomes of Soybean Cotyledons

Antibodies specific for nodule uricase were used for immunocytochemistryto demonstrate the presence of uricase in cotyledons of soybean(Glycine max) during germination and early seedling growth.The enzyme was localized exclusively in peroxisomes. ¹Permanent address: Department of Plant Cytology and Cytochemistry,University of Lodz, Lodz, Poland ²Current address: Department of Plant Science, University ofArizona, Tucson, AZ 85721, U.S.A.