bluuebunny/crossref_metadata_2025_split huggingface dataset:
NaCI Reduces Indole-3-Acetic Acid Levels in the Roots of Tomato Plants Independent of Stress-Induced Abscisic Acid
Authors: Dunlap J. R. , Binzel M. L. 
Published: October 2016

Abstract
Indole-3-acetic acid (IAA) was measured in leaves and roots of tomato (Lycopersicon esculentum) genotypes subjected to salt stress. An abscisic acid (ABA)-deficient mutant of tomato (sitiens), the genetic parent (Rheinlands Ruhm, RR), and a commercial variety (Large Cherry Red, LCR) of tomato were treated with 50 to 300 mM NaCl in nutrient culture. Both LCR and RR had significantly higher levels of IAA in the roots compared with that in sitiens prior to treatment. The initial levels of IAA in the roots of LCR and RR declined by nearly 75% after exposure to NaCl, whereas those in roots from the sitiens mutant remained unchanged. IAA levels in the leaves of all genotypes remained unchanged or increased slightly in response to NaCl. ABA was highest in leaves from the normal genotypes after exposure to NaCl. ABA levels in the roots of sitiens were similar to the levels in the normal genotypes, whereas levels in the leaves were only 10% of the levels found in normal genotypes regardless of the salt treatment. Treatment of LCR and sitiens with exogenous ABA increased the ABA levels in leaves and roots, but there were no measurable changes in endogenous IAA. Therefore, the reduction in IAA appears to result from an ABA-independent effect of NaCl on IAA metabolism in the roots of stressed plants.
Expression of the Agrobacterium rhizogenes rolC Gene in a Deciduous Forest Tree Alters Growth and Development and Leads to Stem Fasciation
Authors: Nilsson O. , Moritz T. , Sundberg B. , Sandberg G. , Olsson O. 
Published: October 2016

Abstract
We have altered the growth and development of a deciduous forest tree by transforming hybrid aspen (Populus tremula x Populus tremuloides) with the Agrobacterium rhizogenes rolC gene expressed under the strong cauliflower mosaic virus 35S promoter. We demonstrate that the genetically manipulated perennial plants, after a period of dormancy, maintain the induced phenotypical changes during the second growing period. Furthermore, mass-spectrometrical quantifications of the free and conjugated forms of indole-3-acetic acid and cytokinins and several gibberellins on one transgenic line correlate the induced developmental alterations such as stem fasciation to changes in plant hormone metabolism. We also show that the presence of the RolC protein increases the levels of the free cytokinins, but not by a process involving hydrolysis of the inactive cytokinin conjugates.
Temporal and Spatial Expression of 1-Aminocyclopropane-1-Carboxylate Oxidase mRNA following Pollination of Immature and Mature Petunia Flowers
Authors: Tang X. , Woodson W. R. 
Published: October 2016

Abstract
Pollination of petunia (Petunia hybrida) flowers induces a rapid increase in ethylene production by styles, which subsequently leads to increased ethylene production by the corolla, inducing senescence. We have investigated the temporal and spatial expression of 1-aminocyclopropane-1-carboxylate (ACC) oxidase transcripts in petunia styles in an attempt to elucidate its role in increased ethylene biosynthesis following pollination. Previously, we reported that the development of petunia flowers was associated with increased ACC oxidase mRNA localized specifically in the stigmatic regions of the style (X. Tang, A.M.T. Gomes, A. Bhatia, W.R. Woodson [1994] Plant Cell 6: 1227–1239). The rapid increase in ethylene production by styles within the 1st h following pollination was correlated with the expression of ACC oxidase mRNAs during development. Pollination of petunia flowers prior to anthesis and the expression of ACC oxidase mRNA led to a substantial increase in ethylene production, but this was delayed by several hours in comparison with flowers at anthesis. This delayed increase in ethylene production by pollinated styles from immature flowers was associated with an increased ACC oxidase transcript abundance. Treatment with the ethylene action inhibitor 2,5-norbornadiene did not affect the early increase in ethylene production or the expression of ACC oxidase mRNAs. No differences in the rate of pollen germination or tube growth were detected when applied to stigmas from immature or mature flowers, indicating that the delay in ethylene production was likely the result of limited ACC oxidase activity. Localization of ACC oxidase mRNAs following pollination by in situ hybridization revealed an abundance of transcripts in transmitting tract tissue within 4 h of pollination of both immature and mature styles, in contrast to their localization in stigmatic cells during development.
Effect of CO2 Concentration on Carbonic Anhydrase and Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Expression in Pea
Authors: Majeau N. , Coleman J. R. 
Published: October 2016

Abstract
The effect of external CO2 concentration on the expression of carbonic anhydrase (CA) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) was examined in pea (Pisum sativum cv Little Marvel) leaves. Enzyme activities and their transcript levels were reduced in plants grown at 1000 [mu]L/L CO2 compared with plants grown in ambient air. Growth at 160 [mu]L/L CO2 also appeared to reduce steady-state transcript levels for rbcS, the gene encoding the small subunit of Rubisco, and for ca, the gene encoding CA; however, rbcS transcripts were reduced to a greater extent at this concentration. Rubisco activity was slightly lower in plants grown at 160 [mu]L/L CO2, and CA activity was significantly higher than that observed in air-grown plants. Transfer of plants from 1000 [mu]L/L to air levels of CO2 resulted in a rapid increase in both ca and rbcS transcript abundance in fully expanded leaves, followed by an increase in enzyme activity. Plants transferred from air to high-CO2 concentrations appeared to modulate transcript abundance and enzyme activity less quickly. Foliar carbohydrate levels were also examined in plants grown continuously at high and ambient CO2, and following changes in growth conditions that rapidly altered ca and rbcS transcript abundance and enzyme activities.
Multiple Aluminum-Resistance Mechanisms in Wheat (Roles of Root Apical Phosphate and Malate Exudation)
Authors: Pellet D. M. , Papernik L. A. , Kochian L. V. 
Published: October 2016

Abstract
Although it is well known that aluminum (Al) resistance in wheat (Triticum aestivum) is multigenic, physiological evidence for multiple mechanisms of Al resistance has not yet been documented. The role of root apical phosphate and malate exudation in Al resistance was investigated in two wheat cultivars (Al-resistant Atlas and Al-sensitive Scout) and two near-isogenic lines (Al-resistant ET3 and Al-sensitive ES3). In Atlas Al resistance is multigenic, whereas in ET3 resistance is conditioned by the single Alt1 locus. Based on root- growth experiments, Atlas was found to be 3-fold more resistant in 20 [mu]M Al than ET3. Root-exudation experiments were conducted under sterile conditions; a large malate efflux localized to the root apex was observed only in Atlas and in ET3 and only in the presence of Al (5 and 20 [mu]M). Furthermore, the more Al-resistant Atlas exhibited a constitutive phosphate release localized to the root apex. As predicted from the formation constants for the Al-malate and Al-phosphate complexes, the addition of either ligand to the root bathing solution alleviated Al inhibition of root growth in Al-sensitive Scout. These results provide physiological evidence that Al resistance in Atlas is conditioned by at least two genes. In addition to the alt locus that controls Al-induced malate release from the root apex, other genetic loci appear to control constitutive phosphate release from the apex. We suggest that both exudation processes act in concert to enhance Al exclusion and Al resistance in Atlas.
Expression of the Cucumber Hydroxypyruvate Reductase Gene Is Down-Regulated by Elevated CO2
Authors: Bertoni G. P. , Becker W. M. 
Published: October 2016

Abstract
We examined the effects of CO2 concentration on the white-light-stimulated expression of the cucumber (Cucumis sativus L.) Hpr gene. Hpr encodes hydroxypyruvate reductase, an enzyme important in the photorespiratory glycolate pathway, which plays an integral role in carbon allocation in C3 plants. Because CO2 is an end product of this pathway and because increased CO2 concentrations lessen the need for photorespiration, we tested whether exposure of plants to elevated CO2 would affect white-light-stimulated Hpr gene expression. Exposure of dark-adapted cucumber seedlings to elevated CO2 (2 to 3 times ambient) during a 4-h white-light irradiation significantly inhibited the accumulation of Hpr mRNA. Increasing the CO2 concentration during irradiation to 6 or 9 times ambient did not further inhibit Hpr mRNA accumulation. The depressing effect of high CO2 on Hpr mRNA accumulation was seen in both high and low light, but was more pronounced in higher light. These results suggest that maximum sensitivity to CO2 occurs in conditions near those normally encountered by the plant (high light, CO2 concentration near ambient) and support a model in which white-light-regulated Hpr expression is modulated in part by environmental CO2 concentration.
Effect of Sulfur Nutrition on the Redistribution of Sulfur in Vegetative Soybean Plants
Authors: Sunarpi  , Anderson J. W. 
Published: October 2016

Abstract
Soybean (Glycine max L.) plants were grown with sulfate at 2 (S2) or 20 [mu]M (S20) and treated with [35S]sulfate between d 36 and 38. Growth was continued with or without 20 [mu]M sulfate (i.e. S2 -&gt; S0, S2 -&gt; S20, etc.). When the leaves of S20 -&gt; S20 plants were 70% expanded, they exported S and 35S label from the soluble fraction, largely as sulfate, to new expanding leaves. However, 35S label in the insoluble fraction was not remobilized. Very little of the 35S label in the soluble fraction of the leaves of S20 -&gt; S0 plants was redistributed; most was incorporated into the insoluble fraction. The low levels of S remobilization from the insoluble fraction were attributed to the high level of N in the nutrient solution (15 mM). Most of the 35S label in S2 plants at d 38 occurred in the soluble fraction of the roots. In S2 -&gt; S0 plants the 35S label was incorporated into the insoluble fraction of the roots, but in S2 -&gt; S20 plants 35S label was rapidly exported to leaves 3 to 6. It was concluded that the soluble fraction of roots contains a small metabolically active pool of S and another larger pool that is in slow equilibrium with the small pool.
Subcellular Location of O-Acetylserine Sulfhydrylase Isoenzymes in Cell Cultures and Plant Tissues of Datura innoxia Mill
Authors: Kuske C. R. , Hill K. K. , Guzman E. , Jackson P. J. 
Published: October 2016

Abstract
O-Acetylserine sulfhydrylase (OASS; EC 4.2.99.8) catalyzes the formation of L-cysteine from O-acetylserine and inorganic sulfide. Three OASS isoenzymes that differ in molecular mass and subunit structure are present in shoot and root tissues and in cadmium-resistant and cadmium-susceptible cell cultures of Datura innoxia Mill. Different OASS forms predominate in leaves, roots, and suspension-cell cultures. To determine the subcellular location of the OASS isoenzymes, purified mitochondria, chloroplasts, and cytosolic fractions from protoplasts were obtained. The isoenzymes are compartmentalized in D. innoxia cells, with a different isoenzyme predominant in the chloroplast, cytosol, and mitochondria, suggesting that they serve different functions in the plant cell. The chloroplast form is most abundant in green leaves and leaf protoplasts. The cytosolic form is most abundant in roots and cell cultures. A mitochondrial form is abundant in cell cultures, but is a minor form in leaves or roots. Cadmium-tolerant cell cultures contain 1.8 times as much constitutive OASS activity as the wild-type cell line, and 2.9 times more than the cadmium-hypersensitive cell line. This may facilitate rapid production of glutathione and metal-binding phytochelatins when these cultures are exposed to cadmium.
Localized Wounding by Heat Initiates the Accumulation of Proteinase Inhibitor II in Abscisic Acid-Deficient Plants by Triggering Jasmonic Acid Biosynthesis
Authors: Herde O. , Atzorn R. , Fisahn J. , Wasternack C. , Willmitzer L. , Pena-Cortes H. 
Published: October 2016

Abstract
To test whether the response to electrical current and heat treatment is due to the same signaling pathway that mediates mechanical wounding, we analyzed the effect of electric-current application and localized burning on proteinase inhibitor II (Pin2) gene expression in both wild-type and abscisic acid (ABA)-deficient tomato (Lycopersicon esculentum Mill.) and potato (Solanum phureja) plants. Electric-current application and localized burning led to the accumulation of Pin2 mRNA in potato and tomato wild-type plants. Among the treatments tested, only localized burning of the leaves led to an accumulation of Pin2 mRNA in the ABA-deficient plants. Electric-current application, like mechanical injury, was able to initiate ABA and jasmonic acid (JA) accumulation in wild-type but not in ABA-deficient plants. In contrast, heat treatment led to an accumulation of JA in both wild-type and ABA-deficient plants. Inhibition of JA biosynthesis by aspirin blocked the heat-induced Pin2 gene expression in tomato wild-type leaves. These results suggest that electric current, similar to mechanical wounding, requires the presence of ABA to induce Pin2 gene expression. Conversely, burning of the leaves activates Pin2 gene expression by directly triggering the biosynthesis of JA by an alternative pathway that is independent of endogenous ABA levels.
Changes in Cytokinin Content and Cytokinin Oxidase Activity in Response to Derepression of ipt Gene Transcription in Transgenic Tobacco Calli and Plants
Authors: Motyka V. , Faiss M. , Strand M. , Kaminek M. , Schmulling T. 
Published: October 2016

Abstract
Metabolic control of cytokinin oxidase by its substrate was investigated in planta using wild-type (WT) and conditionally ipt gene-expressing transgenic (IPT) tobacco (Nicotiana tabacum L.) callus cultures and plants. The derepression of the tetracycline (Tc)-dependent ipt gene transcription was followed by a progressive, more than 100-fold increase in total cytokinin content in IPT calli. The activity of cytokinin oxidase extracted from these calli began to increase 16 to 20 h after gene derepression, and after 13 d it was 10-fold higher than from Tc-treated WT calli. An increase in cytokinin oxidase activity, as a consequence of elevated cytokinin levels, was found in detached leaves (8-fold after 4 d) and in roots of intact plants (4-fold after 3 d). The partially purified cytokinin oxidase from WT, repressed IPT, and Tc-derepressed IPT tobacco calli exhibited similar characteristics. It had the same broad pH optimum (pH 6.5–8.5), its activity in vitro was enhanced 4-fold in the presence of copper-imidazole, and the apparent Km(N6-[[delta]2iso-pentenyl]adenine) values were in the range of 3.1 to 4.9 [mu]M. The increase in cytokinin oxidase activity in cytokinin-overproducing tissue was associated with the accumulation of a glycosylated form of the enzyme. The present data indicate the substrate induction of cytokinin oxidase activity in different tobacco tissues, which may contribute to hormone homeostasis.
Analyzing the Light Energy Distribution in the Photosynthetic Apparatus of C4 Plants Using Highly Purified Mesophyll and Bundle-Sheath Thylakoids
Authors: Pfundel E. , Nagel E. , Meister A. 
Published: October 2016

Abstract
The chlorophyll fluorescence characteristics of mesophyll and bundle-sheath thylakoids from plant species with the C4 dicarboxylic acid pathway of photosynthesis were investigated using flow cytometry. Ten species with the NADP-malic enzyme (NADP-ME) biochemical type of C4 photosynthesis were tested: Digitaria sanguinalis (L.) Scop., Euphorbia maculata L., Portulaca grandiflora Hooker, Saccharum officinarum L., Setaria viridis (L.) Beauv., Zea mays L., and four species of the genus Flaveria. This study also included three species with NAD-ME biochemistry (Atriplex rosea L., Atriplex spongiosa F. Muell., and Portulaca oleracea L.). Two C4 species of unknown biochemical type were investigated: Cyperus papyrus L. and Atriplex tatarica L. Pure mesophyll and bundle-sheath thylakoids were prepared by flow cytometry and characterized by low-temperature fluorescence spectroscopy. In pure bundle-sheath thylakoids from many species with C4 photosynthesis of the NADP-ME type, significant amounts of photosystem II (PSII) emission can be detected by fluorescence spectroscopy. Simulation of fluorescence excitation spectra of these thylakoids showed that PSII light absorption contributes significantly to the apparent excitation spectrum of photosystem I. Model calculations indicated that the excitation energy of PSII is efficiently transferred to photosystem I in bundle-sheath thylakoids of many NADP-ME species.
Evidence for Opposing Effects of Calmodulin on Cortical Microtubules
Authors: Fisher D. D. , Gilroy S. , Cyr R. J. 
Published: October 2016

Abstract
Microtubule integrity within the cortical array was visualized in detergent-lysed carrot (Daucus carota L.) protoplasts that were exposed to various exogenous levels of Ca2+ and calmodulin (CaM). CaM appears to help stabilize cortical microtubules against the destabilizing action of Ca2+/CaM complexes at low Ca2+ concentrations, but not at higher Ca2+ concentrations. The hypothesis that CaM interacts with microtubules at two different sites, determined by the concentration of Ca2+, is supported by the effects of the CaM antagonists N-(6-aminohexyl)-1-naphthalene-sulfonamide and N-(6-aminohexyl)-5-chloro-1-naphthalenesulfanamide (20 [mu]M) and by affinity chromatography. Two classes of proteins were identified that interact with tubulin and bind to CaM. One class required Ca2+ for CaM binding, whereas the second class bound only when Ca2+ concentrations were low (&lt;320 nM). Thus, CaM's ability to have two opposing effects upon microtubules may be regulated by the concentration of intracellular Ca2+ and its differential interactions with microtubule-associated proteins. Experimental manipulation of intracellular Ca2+ concentrations, as monitored by Indo-1, revealed that the effect of Ca2+ is specific to the cortical microtubules and does not affect actin microfilaments in these cells.
An Inducible Glutathione S-Transferase in Soybean Hypocotyl Is Localized in the Apoplast
Authors: Flury T. , Wagner E. , Kreuz K. 
Published: October 2016

Abstract
Glutathione S-transferases (GSTs) with additional activities as fatty acid hydroperoxidases were investigated in soybean (Glycine max L.) hypocotyls. Aside from the GSTs present in total soluble tissue extracts, enzyme activities and distinct immunoreactive GST polypeptides were also detected in the intercellular washing fluid. Whereas the intracellular isoenzymes were both constitutive and inducible, apoplastic GST and glutathione peroxidase was detectable only in tissues treated with the known GST inducer 2,3,5-triiodobenzoic acid. Monensin inhibited the induced accumulation of apoplastic GST but did not affect the intracellular isoforms. The discovery of apoplastic inducible GST will be discussed in light of the putative function of these enzymes in plants.
Effect of High Temperature on Photosynthesis in Beans (II. CO2 Assimilation and Metabolite Contents)
Authors: Pastenes C. , Horton P. 
Published: October 2016

Abstract
The effect of high temperatures on CO2 assimilation, metabolite content, and capacity for reducing power production in non-photorespiratory conditions has been assessed in two different bean (Phaseolus vulgarus L.) varieties, Blue Lake (commercially available in the United Kingdom) and Barbucho (a noncommercially bred Chilean variety), which are known to differ in their resistance to extreme high temperatures. Barbucho maintains its photosynthetic functions for a longer period of time under extreme heat compared with Blue Lake. The CO2 assimilation rate was increased by increases in temperature, with a decrease in ratio of rates of temperatures differing by 10[deg]C. It is suggested that limitations to CO2 assimilation are caused by metabolic restrictions that can be differentiated between those occurring in the range of 20 to 30[deg]C and 30 to 35[deg]C. It is likely that changes in the capacity for Calvin cycle regeneration and starch synthesis affect photosynthesis in the range of 20 to 30[deg]C. But following an increase in temperature from 30 to 35[deg]C, the supply of reducing power becomes limiting. From analysis of adenylate concentration, transthylakoid energization, and, indirectly, NADPH/NADP+ ratio, it was concluded that the limitation in the assimilatory power was due to an oxidation of the NADPH/NADP+ pool. In the range of 30 to 35[deg]C, the photosystem I quantum yield increased and photosystem II maintained its value. We conclude that the reorganization of thylakoids observed at 30 to 35[deg]C increased the excitation of photosystem I, inducing an increase in cyclic electron transport and a decrease in the supply of NADPH, limiting carbon assimilation.
The Early Entry of Al into Cells of Intact Soybean Roots (A Comparison of Three Developmental Root Regions Using Secondary Ion Mass Spectrometry Imaging)
Authors: Lazof D. B. , Goldsmith J. G. , Rufty T. W. , Linton R. W. 
Published: October 2016

Abstract
Al localization was compared in three developmental regions of primary root of an Al-sensitive soybean (Glycine max) genotype using secondary ion mass spectrometry. In cryosections obtained after a 4-h exposure to 38 [mu]M [Al3+], Al had penetrated across the root and into the stele in all three regions. Although the greatest localized Al concentration was consistently at the root periphery, the majority of the Al in each region had accumulated in cortical cells. It was apparent that the secondary ion mass spectrometry 27Al+ mass signal was spread throughout the intracellular area and was not particularly intense in the cell wall. Inclusion of some cell wall in determinations of the Al levels across the root radius necessitated that these serve as minimal estimates for intracellular Al. Total accumulation of intracellular Al for each region was 60, 73, and 210 nmol g-1 fresh weight after 4 h, increasing with root development. Early metabolic responses to external Al, including those that have been reported deep inside the root and in mature regions, might result directly from intracellular Al. These responses might include ion transport events at the endodermis of mature roots or events associated with lateral root emergence, as well as events within the root tip.