Plant Physiology

Solomonson, L. P.; Vennesland, Birgit

doi: 10.1104/pp.50.4.421pmid: 16658189

Abstract A study of the growth-inhibiting effect of chlorate on the Berlin strain of Chlorella vulgaris Beijerinck provided complete confirmation of the theory of chlorate toxicity first proposed by Åberg in 1947. Chlorate was toxic to the cells growing on nitrate, and relatively nontoxic to the cells growing on ammonium. The latter cells contained only 0.01 as much NADH-nitrate reductase as the nitrate-grown cells. Chlorate could substitute for nitrate as a substrate of the purified nitrate reductase with Km = 1.2 mm, and Vmax = 0.9Vmax for nitrate. Bromate, and to a much smaller extent, iodate, also served as alternate substrates. Nitrate is a reversible competitive inhibitor of chlorate reduction, which accounts for the partial reversal, by high nitrate concentrations, of the observed inhibition of cell growth by chlorate. During the reduction of chlorate by NADH in the presence of purified nitrate reductase, there was a progressive, irreversible inhibition of the enzyme activity, presumably brought about by the reduction product, chlorite. Both the NADH-nitrate reductase activity and the associated NADH-cytochrome c reductase activity were inactivated to the same extent by added chlorite. The spectral properties of the cytochrome b 557 associated with the purified enzyme were not affected by chlorite. The inactivation of the nitrate reductase by chlorite could account for the toxicity of chlorate to cells grown on nitrate, though the destruction of other cell components by chlorite or its decomposition products cannot be excluded. This content is only available as a PDF. © 1972 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)

Mandels, G. R.; Maguire, Anne

doi: 10.1104/pp.50.4.425pmid: 16658190

Abstract Endogenous respiration of spores of the fungus Myrothecium verrucaria can be stimulated up to over-10 fold by diverse chemicals or by physical treatments. Greatest effects were caused by azide (12-fold at 250 μm) and by 2,4-dinitrophenol (7-fold at 300 μm). Marked stimulation was also caused by 10 μm silver (5-fold), 30 μm pentachlorophenol (6-fold), 10 μm carbonyl cyanide m-chlorophenyl hydrazone (4.5-fold) and 10 μm merthiolate (4-fold). Physical treatments such as heat (50 C), freezing, and sonication at sublethal levels were also stimulatory. Stimulation by azide or dinitrophenol was much greater in young than in old spores, whereas response to other chemicals and to freezing was relatively unaffected by spore age. In older spores the effect of azide was no greater than some other inhibitors. During incubation with azide, the endogenous trehalose reserves decreased and changes in free amino acids occurred, both increases and decreases. Thus anabolic as well as catabolic changes occur as evidenced also by the germination of a few (up to 5%) spores. The mechanisms of stimulation must be varied and complex. Permeability changes in the membrane confining endogenous reserves are proposed as a common initial cause. Additional changes in characteristics of membranes of other subcellular particles, as well as enzymic phenomena such as uncoupling of oxidative phosphorylation, are presumably involved in instances where greater stimulation occurs. The data are consistent with the hypothesis that dormancy in these spores results from separation of substrates from metabolic enzymes and more specifically that metabolites are sequestered rather than enzymes. This content is only available as a PDF. © 1972 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)

Martin, Colin; Thimann, Kenneth V.

doi: 10.1104/pp.50.4.432pmid: 16658191

Abstract When the first leaf of the oat (Avena sativa) seedling is detached and placed in the dark, yellowing and proteolysis take place rapidly. The earlier finding that d-serine promotes this process has led to a further study of the controlling roles of several amino acids. Since the action of serine was found to be more powerful in presence of kinetin than alone, the effects of other amino acids have been restudied in presence of kinetin. Cysteine emerges as a moderately strong promotor of senescence, with glycine and alanine having definite but weaker effects. The serine effect is antagonized by arginine, especially in presence of kinetin, and so is the cysteine effect. This is considered to indicate that these two amino acids act in the same way. The antagonism exerted by arginine is in turn antagonized by canavanine. The protease activities at two pH regions which increase in the oat leaf during senescence react to both p-chlorimercuri-phenylsulfonate and to phenylmethyl-sulfonyl fluoride, and thus may contain both SH and OH groups. The amounts of both these enzyme activities formed in the leaf during 3 days in the dark are increased over 50% by pretreatment with serine, and this increase is very largely prevented by arginine. The amounts of soluble proteins left in the leaf vary as expected in the opposite sense. It is deduced that control of the new formation of proteases plays an important part in senescence. A suggestion is made as to the mechanism of control of senescence in leaves. 2 Present address: University of Witwatersrand, Johannesburg, South Africa. 1 This research was supported in part by Grant GB-11867 from the National Science Foundation. This content is only available as a PDF. © 1972 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)

Horine, Randall K.; Ruesink, Albert W.

doi: 10.1104/pp.50.4.438pmid: 16658192

Abstract Protoplasts of Convolvulus arvensis L. tissue culture regenerated a wall-like structure within 3 days in culture. Although unusually electron dense and atypically amorphous in the electron microscope, this structure could be digested with Myrothecium cellulase but was resistant to protease, a Rohm and Haas pectinase, and a β-1, 3-exoglucanase just like the original wall. A cytochemical test for callose was negative. Wall regeneration required a readily metabolized external carbon source and was not inhibited by a high concentration of cycloheximide, puromycin, or actinomycin D. Protoplast budding was correlated with the wall regeneration, and the latter was related quantitatively to the sucrose concentration in the medium. Although a concentration of 1 μm 2,4-dichlorophenoxy acetic acid is used normally for both general culture of the tissue and for wall regeneration, concentrations of 0 and 0.1 mm, which are highly deleterious to growth, have no appreciable effect on the incidence of the wall-like structure regenerated around protoplasts. The ability of protoplasts to undergo cell wall regeneration was decreased when they were cultured in the presence of proteolytic enzymes. 2 National Defense Education Act predoctoral fellow. 1 The National Science Foundation provided support through Grant GB 8006. This material was included in a doctoral thesis submitted by R. K. Horine to the Graduate School of Indiana University. This content is only available as a PDF. © 1972 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)

Bush, Karen J.; Sweeney, Beatrice M.

doi: 10.1104/pp.50.4.446pmid: 16658193

Abstract The ribulose 1,5-diphosphate carboxylase from Gonyaulax polyedra Stein. has a half-life of about four hours in buffer, but can be stabilized by the addition of 50% glycerol. The optimum pH is 7.8 to 8.0 and the optimum Mg2+ concentration is 3 mm. Heavy metal ions (Cu2+, Hg2+, Ni2+, Zn2+), EDTA, pyrophosphate, and adenosine triphosphate were strongly inhibitory. Ribulose 1,5-diphosphate carboxylase from Gonyaulax was not cold-sensitive or activated by light activation factor from tomato or Gonyaulax. No difference in the activity of this enzyme was detected when extracts prepared at the maximum and the minimum of the circadian rhythm of photosynthesis were compared. The Km of HCO3− was also the same (16 to 19 mm). 2 Present address: Department of Biochemistry, School of Medicine, The University of North Carolina, Chapel Hill, N. C. 27514. 1 This research was supported in part by Grant GB 8418 from the National Science Foundation. This content is only available as a PDF. © 1972 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)

Lai, Y. F.; Thompson, J. E.

doi: 10.1104/pp.50.4.452pmid: 16658194

Abstract A purified membrane fraction featuring ATPase activity was isolated from cotyledon tissue of Phaseolus vulgaris at different stages of germination. The fraction is enriched in both basal and Na+-K+-stimulated ATPase and is relatively free of contamination by fragments of mitochondrial membrane and microsomes. The isolated membranes have been tentatively identified as partially purified plasma membrane. The specific activities of the basal- and cation-sensitive ATPases were high in membrane preparations from young cotyledon tissue but decreased with advancing senescence. Electron microscopy of the preparation showed that the isolated membranes were of primarily vesicular conformation. These vesicles proved to be capable of extruding Na+ and K+ in the presence of ATP. Moreover, the degree of ATP-dependent extrusion varied during germination in a pattern that resembled variations during the same period in the Na+-K+-stimulated ATPase of the isolated fraction. This indicates that as the level of cation-sensitive ATPase on the membrane rises or falls, there is a corresponding change in the ability of the membrane to actively translocate Na+ and K+. This content is only available as a PDF. © 1972 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)

Tezuka, Takafumi; Yamamoto, Yukio

doi: 10.1104/pp.50.4.458pmid: 16658195

Abstract This article gives evidence that NAD kinase activity is controlled by the action of phytochrome. The NADP level rapidly increased in the cotyledons of seedlings of Pharbitis nil strain Violet (a short day plant), when the inductive dark for flowering was interrupted with a 5-minute illumination of red light. Illumination with far red light immediately after illumination with red light counteracted partly the effect of the latter. A partially purified phytochrome preparation from the uppermost internodes including the hook of Pisum sativum var. Alaska contained NAD kinase activity, and this increased greatly on illumination with red light. The effects of red and far red light on NAD kinase activity were reversible. The Km value of NAD kinase in the phytochrome preparation for NAD was 1.84 mm in the dark and 0.90 mm under red light. A broad optimum of the NAD kinase reaction and its photopotentiation appeared in the region of pH 6.6 to 8.6. The NAD kinase activity in a phytochrome preparation from the coleoptiles of Avena sativa was also activated by red light. It was suggested that the Pfr type of phytochrome may contribute to the decrease of the Km value of NAD kinase reaction by causing a conformational alteration of NAD kinase. 2 To whom requests for reprints should be sent. Present address: Department of Agricultural Chemistry, Faculty of Agriculture, Nagoya University, Nagoya 464, Japan. 1 Preliminary accounts of this work have been published elsewhere (10, 16). This content is only available as a PDF. © 1972 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)

Longo, Giovanna P.; Dragonetti, Carola; Longo, Claudio P.

doi: 10.1104/pp.50.4.463pmid: 16658196

Abstract The localization of catalase in isolated maize scutellum glyoxysomes was investigated by means of the diaminobenzidine histochemical reaction. Only the membranes of the glyoxysomes become heavily stained after incubation with diaminobenzidine and H2O2. If the glyoxysomes are lysed with Tricine buffer at pH 9, 70% of the catalase is solubilized, while the remaining 30% is tightly bound to an insoluble fraction formed mostly by glyoxysomal membranes. This suggests that catalase may be present also in the matrix of the glyoxysomes. The lack of staining of the matrix with diaminobenzidine is probably due to the high concentration of catalase in the membranes of the organelles. This content is only available as a PDF. © 1972 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)

Delmer, Deborah Pierson

doi: 10.1104/pp.50.4.469pmid: 16658197

Abstract Phaseolus aureus sucrose synthetase, purified to homogeneity, was assayed in the presence of a variety of biological compounds to test for possible regulatory effectors. The oxidized form of nicotinamide adenine dinucleotide phosphate, as well as indoleacetic acid, gibberellic acid, and pyrophosphate were found to activate the forward reaction (sucrose degradation) and inhibit the reverse reaction (sucrose synthesis). The reduced form of nicotinamide adenine dinucleotide phosphate antagonizes the effect of the oxidized form. Fructose 1-phosphate and divalent cations inhibit the forward and activate the reverse reaction. Pyrophosphate and fructose 1-phosphate are effective only in the presence of magnesium chloride. Uridine triphosphate inhibits both the forward and reverse reactions. All effectors except gibberellic acid are active only in the millimolar range of concentrations; maximal stimulation for any effector is approximately 2-fold. The effects of combinations of effectors are roughly additive. Using pyrophosphate in the presence of magnesium chloride as an effector, results of kinetic studies offer a model by which an effector can activate an enzymatic reaction in one direction and inhibit in the reverse direction. 1 This study was supported by National Science Foundation Grant GB-27386-X. This content is only available as a PDF. © 1972 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)

Storm, David L.; Hassid, W. Z.

doi: 10.1104/pp.50.4.473pmid: 16658198

Abstract Particulate preparations from Phaseolus aureus produce a d-mannosyl-lipid when treated with GDP-d-mannose. This lipid complex appears to be an active d-mannose donor, and some investigators have proposed that its role might be an obligatory intermediate in mannan synthesis of higher plants. When the partially purified d-mannosyl-lipids, isotopically labeled in the d-mannose moiety, were treated with particulate enzymes under a variety of conditions, a negligible amount of material was produced that behaved as a polysaccharide. Endogenous, particle-bound d-mannosyl-14C-lipid prepared from P. aureus particles readily transferred d-mannose to GDP to yield GDP-d-mannose and was hydrolyzed to free d-mannose when treated briefly with 0.01 n HCl at 100 C. The d-mannosyl-lipid, therefore, exhibits active d-mannose transfer potential in its endogenous state. When endogenous glycosyl-lipid was incubated in the absence of GDP-d-mannose-14C, little or no polysaccharide was produced. It was, instead, slowly degraded to d-mannose. Addition of several different unlabeled sugar nucleotides had no effect on the results. Our studies to date, therefore, offer no evidence that the mannosyl-lipid is an obligatory precursor of polysaccharide. 1 This investigation was supported in part by Research Grant A-1418 from the National Institutes of Health, United States Public Health Service, and by Research Grant GB11819 from the National Science Foundation. Support of this work by the Agricultural Experiment Station is also acknowledged. This content is only available as a PDF. © 1972 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)