bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pea Mutants with Reduced Sensitivity to Far-Red Light Define an Important Role for Phytochrome A in Day-Length Detection
Authors: Weller J. L. , Murfet I. C. , Reid J. B. 
Published: October 2016

Abstract
In garden pea (Pisum sativum L.), a long-day plant, long photoperiods promote flowering by reducing the synthesis or transport of a graft-transmissible inhibitor of flowering. Previous physiological studies have indicated that this promotive effect is predominantly achieved through a response that requires long exposures to light and for which far-red (FR) light is the most effective. These characteristics implicate the action of phytochrome A (phyA). To investigate this matter further, we screened ethylmethane sulfonate-mutagenized pea seedlings for FR-unresponsive, potentially phyA-deficient mutants. Two allelic, recessive mutants were isolated and were designated fun1 for FR unresponsive. The fun1–1 mutant is specifically deficient in the PHYA apoprotein and has a seedling phenotype indistinguishable from wild type when grown under white light. However, fun1–1 plants grown to maturity under long photoperiods show a highly pleiotropic phenotype, with short internodes, thickened stems, delayed flowering and senescence, longer peduncles, and higher seed yield. This phenotype results in large part from an inability of fun1–1 to detect day extensions. These results establish a crucial role for phyA in the control of flowering in pea, and show that phyA mediates responses to both red and FR light. Furthermore, grafting and epistasis studies with fun1 and dne, a mutant deficient in the floral inhibitor, show that the roles of phyA in seedling deetiolation and in day-length detection are genetically separable and that the phyA-mediated promotion of flowering results from a reduction in the synthesis or transport of the floral inhibitor.
The Ascorbate Carrier of Higher Plant Plasma Membranes Preferentially Translocates the Fully Oxidized (Dehydroascorbate) Molecule
Authors: Horemans N. , Asard H. , Caubergs R. J. 
Published: October 2016

Abstract
Recently, the uptake of 14C-labeled ascorbate (ASC) into highly purified bean (Phaseolus vulgaris L.) plasma membrane vesicles was demonstrated in our laboratory. However, the question of the redox status of the transported molecule (ASC or dehydroascorbate [DHA]) remained unanswered. In this paper we present evidence that DHA is transported through the plasma membrane. High-performance liquid chromatography analysis of the redox status of ASC demonstrated that freshly purified plasma membranes exhibit a high ASC oxidation activity. Although it is not yet clear whether this activity is enzymatic, it complicates the interpretation of ASC-transport experiments in vitro and in vivo. In an attempt to correlate the ASC redox status to transport of the molecule, the ability of different compounds to reduce DHA was analyzed and their effect on ASC-transport activity tested. Administering of various reductants resulted in different levels of inhibition of ASC uptake (dithiothreitol &gt; dithioerythritol &gt; β-mercaptoethanol &gt; β-mercaptopropanol). Glutathione, cysteine, dithionite, and thiourea did not significantly affect ASC transport. Statistical analysis indicated a strong correlation of the Spearman rank correlation coefficient (Rs) of 0.919 (P = 0.0005, n = 9) between the level of ASC oxidation and the amount of transported molecules into the vesicles. The administering of ASC oxidants such as ferricyanide and ASC oxidase resulted in a stimulated ASC uptake into the plasma membrane vesicles. Together, our results demonstrate that a vitamin C carrier in purified bean plasma membranes translocates DHA from the apoplast to the cytosol.
Restoration of Phototropic Responsiveness in Decapitated Maize Coleoptiles
Authors: Kaldenhoff R. , Iino M. 
Published: October 2016

Abstract
The literature indicates that the tip of maize (Zea mays L.) coleoptiles has the localized functions of producing auxin for growth and perceiving unilateral light stimuli and translocating auxin laterally for phototropism. There is evidence that the auxin-producing function of the tip is restored in decapitated coleoptiles. We examined whether the functions for phototropism are also restored by using blue-light conditions that induced a first pulse-induced positive phototropism (fPIPP) and a time-dependent phototropism (TDP). When the apical 5 mm, in which photosensing predominantly takes place, was removed, no detectable fPIPP occurred even if indole-3-acetic acid (lanolin mixture) was applied to the cut end. However, when the blue-light stimulation was delayed after decapitation, fPIPP became inducible in the coleoptile stumps supplied with indole-3-acetic-acid/lanolin (0.01 mg g-1), indicating that phototropic responsiveness was restored. This restoration progressed 1 to 2 h after decapitation, and the curvature response became comparable to that of intact coleoptiles. The results for TDP were qualitatively similar, but some quantitative differences were observed. It appeared that the overall TDP was based on a major photosensing mechanism specific to the tip and on at least one additional mechanism not specific to the tip, and that the tip-specific TDP was restored in decapitated coleoptiles with kinetics similar to that for fPIPP. It is suggested that the photoreceptor system, which accounts for fPIPP and a substantial part of TDP, is regenerated in decapitated coleoptiles, perhaps together with the mechanism for lateral auxin translocation.
Involvement of Cytochrome P450 in Glucosinolate Biosynthesis in White Mustard (A Biochemical Anomaly)
Authors: Bennett R. N. , Kiddle G. , Wallsgrove R. M. 
Published: October 2016

Abstract
One of the first steps in glucosinolate biosynthesis is the conversion of amino acids to their aldoximes. The biochemistry of this process is controversial, and several very different enzyme systems have been described. The major glucosinolate in white mustard (Sinapis alba) is sinalbin, which is derived from tyrosine via its aldoxime, and this conversion is catalyzed by a cytochrome P450 (Cyt P450) monooxygenase. Phenylethyl- and alkenylglucosinolates are also present in white mustard leaves, as are the enzymes catalyzing the relevant aldoxime formation from homophenylalanine and methionine homologs, respectively. These enzymes are similar to those found in Brassica sp. and are distinct from the tyrosine-dependent enzyme in that they contain no heme and are unaffected by Cyt P450 inhibitors. They are instead inhibited by the flavoprotein inhibitor diphenylene iodonium and by Cu2+. In both white mustard and oilseed rape (Brassica napus) methyl jasmonate specifically stimulates indolylglucosinolate biosynthesis and yet has no effect on sinalbin accumulation in either cotyledons or leaves of white mustard. White mustard appears to be unique among crucifers in having a Cyt P450 aldoxime-forming enzyme for biosynthesis of one glucosinolate, although it also contains all of the non-Cyt P450 enzyme systems found in other members of the family. Sinalbin biosynthesis in white mustard is therefore an inappropriate model system for the synthesis of other glucosinolates in crucifers, including canola and oilseed rape.
Enrichment in Specific Soluble Sugars of Two Eucalyptus Cell-Suspension Cultures by Various Treatments Enhances Their Frost Tolerance via a Noncolligative Mechanism
Authors: Travert S. , Valerio L. , Fouraste I. , Boudet A. M. , Teulieres C. 
Published: October 2016

Abstract
A cell-suspension culture obtained from the hybrid Eucalyptus gunnii/Eucalyptus globulus was hardened by exposure to lower temperatures, whereas in the same conditions cells from a hybrid with a more frost-sensitive genotype, Eucalyptus cypellocarpa/Eucalyptus globulus, were not able to acclimate. During the cold exposure the resistant cells accumulated soluble sugars, in particular fructose and sucrose, with a limited increase in cell osmolality. In contrast, the cell suspension that was unable to acclimate did not accumulate soluble sugars in response to the same cold treatment. To an extent similar to that induced after a cold acclimation, frost-hardiness of the cells increased after a 14-h incubation with specific soluble sugars such as sucrose, raffinose, fructose, and mannitol. Such hardening was also observed for long-term cultures in mannitol-enriched medium. This cryoprotective effect of sugars without exposure to lower temperatures was observed in both the resistant and the sensitive genotypes. Mannitol was one of the most efficient carbohydrates for the cryoprotection of eucalyptus. The best hardiness (a 2.7-fold increase in relative freezing tolerance) was obtained for the resistant cells by the cumulative effect of cold-induced acclimation and mannitol treatment. This positive effect of certain sugars on eucalyptus freezing tolerance was not colligative, since it was independent of osmolality and total sugar content.
Accelerated Early Growth of Rice at Elevated CO2 (Is It Related to Developmental Changes in the Shoot Apex?)
Authors: Jitla D. S. , Rogers G. S. , Seneweera S. P. , Basra A. S. , Oldfield R. J. , Conroy J. P. 
Published: October 2016

Abstract
The influence of elevated CO2 on the development of the shoot apex and on subsequent vegetative growth and grain yield was investigated using rice (Oryza sativa L. cv Jarrah) grown in flooded soil at either 350 or 700 [mu]L CO2 L-1. At 8 d after planting (DAP), elevated CO2 increased the height and diameter of the apical dome and lengths of leaf primordia and tiller buds but had no effect on their numbers. By 16 DAP, there were five tiller buds in the apex at 700 [mu]L CO2 L-1 compared with only three tiller buds at 350 [mu]L CO2 L-1. These changes in development of the shoot apex at high CO2 were forerunners to faster development of the vegetative shoot at elevated CO2 between 11 and 26 DAP as evidenced by increases in the relative growth rates of the shoot and tillers. Accelerated development at high CO2 was responsible for the 42% increase in tiller number at the maximum tillering stage and the 57% enhancement of grain yield at the final harvest. The link between high CO2 effects on development during the first 15 DAP and final tiller number and grain yield was demonstrated by delaying exposure of plants to high CO2 for 15 d. The delay totally inhibited the tillering response to high CO2, and the increase in grain yield of 20% arose from a greater number of grains per panicle. Consequently, it can be concluded that accelerated development in the shoot apex early in development is crucial for obtaining maximum increases in grain yield at elevated atmospheric CO2 concentrations.
Antenna Size Dependency of Photoinactivation of Photosystem II in Light-Acclimated Pea Leaves
Authors: Park II Y. , Chow W. S. , Anderson J. M. 
Published: October 2016

Abstract
Utilization of absorbed light energy by photosystem (PS) II for O2 evolution depends on the light-harvesting antenna size, but the role of antenna size in the photoinactivation of PSII seems controversial. To address this controversy, pea (Pisum sativum L.) plants were grown in low (50 [mu]mol m-2 s-1) or high (650 [mu]mol m-2 s-1) light. The doubled functional antenna size of PSII in low light allows each PSII to utilize twice as many photons at given flash light energies for O2 evolution. The application of a target theory to depict the photon dose dependency of PSII photoinactivation measured by repetitive-flash O2 yield and the ratio of variable to maximal chlorophyll fluorescence indicates that photoinactivation of PSII is probably a single-hit process in which repair or photoprotective mechanisms are only slightly involved. Furthermore, the exacerbation of photoinactivation of PSII with greater antenna size under anaerobic conditions strongly indicates that photoinactivation of PSII depends on antenna size.
Effects of Osmoprotectants upon NaCl Stress in Rice
Authors: Garcia A. B. , Engler JdA. , Iyer S. , Gerats T. , Van Montagu M. , Caplan A. B. 
Published: October 2016

Abstract
Plants accumulate a number of osmoprotective substances in response to NaCl stress, one of them being proline (Pro). While characterizing some of the changes in solute accumulation in NaCl-stressed rice (Oryza sativa L.), we identified several other potential osmoprotectants. One such substance, trehalose, begins to accumulate in small amounts in roots after 3 d. We performed a series of experiments to compare the effects of Pro and trehalose on ion accumulation to determine whether the two chemicals protect the same physiological processes. We found that Pro either has no effect or, in some cases, exasperates the effect of NaCl on growth inhibition, chlorophyll loss, and induction of a highly sensitive marker for plant stress, the osmotically regulated salT gene. By contrast, low to moderate concentrations of trehalose reduce Na+ accumulation, salT expression, and growth inhibition. Somewhat higher concentrations (10 mM) prevent NaCl-induced loss of chlorophyll in blades, preserve root integrity, and enhance growth. The results of this study indicate that during osmotic stress trehalose or carbohydrates might be more important for rice than Pro.
The Effect of Elevated Partial Pressures of CO2 on the Relationship between Photosynthetic Capacity and N Content in Rice Leaves
Authors: Nakano H. , Makino A. , Mae T. 
Published: October 2016

Abstract
The effects of growth CO2 levels on the photosynthetic rates; the amounts of ribulose-1,5-bisphosphate carboxylase (Rubisco), chlorophyll (Chl), and cytochrome f; sucrose phosphate synthase activity; and total N content were examined in young, fully expanded leaves of rice (Oryza sativa L.). The plants were grown hydroponically under two CO2 partial pressures of 36 and 100 Pa at three N concentrations. The light-saturated photosynthesis at 36 Pa CO2 was lower in the plants grown in 100 Pa CO2 than those grown in 36 Pa CO2. Similarly, the amounts of Rubisco, Chl, and total N were decreased in the leaves of the plants grown in 100 Pa CO2. However, regression analysis showed no differences between the two CO2 treatments in the relationship between photosynthesis and total N or in the relationship between Rubisco and Chl and total N. Although a relative decrease in Rubisco to cytochrome f or sucrose phosphate synthase was found in the plants grown in 100 Pa CO2, this was the result of a decrease in total N content by CO2 enrichment. The activation state of Rubisco was also unaffected by growth CO2 levels. Thus, decreases in the photosynthetic capacity of the plants grown in 100 Pa CO2 could be simply accounted for by a decrease in the absolute amount of leaf N.
Recovery from Heat Shock in Heat-Tolerant and Nontolerant Variants of Creeping Bentgrass
Authors: Park S. Y. , Chang K. C. , Shivaji R. , Luthe D. S. 
Published: October 2016

Abstract
Recovery from the heat-shock response was tested in heat-tolerant (selected bentgrass [SB]) and nontolerant (nonselected bentgrass [NSB]) variants of creeping bentgrass (Agrostis palustris Huds.) SB increased incorporation of radioactive amino acids into protein 2 h earlier than NSB when leaf blades were incubated at the recovery temperature following heat shock. Electrophoresis indicated that heat-shock protein (HSP) synthesis decreased and normal protein synthesis increased at 4 h in SB and at 6 to 8 h in NSB. Increased synthesis of normal proteins was not due to increased abundance of normal mRNAs, which were equivalent in SB and NSB at 4 h. But at 4 h, more of the normal mRNA population was associated with polysomes in SB than in NSB. Synthesis of HSP70 and HSP18 decreased earlier in SB than in NSB. The decreased synthesis of these HSPs appeared to be correlated with decreased mRNA abundance. But at 4 h, some of the HSP18 mRNA may have been associated with heat-shock granules in SB. Synthesis of HSP25 continued through the 8-h recovery in both variants. Although the abundance of HSP25 was equivalent in SB and NSB during heat shock and recovery, more HSP25 mRNA was associated with polysomes in SB than in NSB.
Influence of Plant Growth at High CO2 Concentrations on Leaf Content of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase and Intracellular Distribution of Soluble Carbohydrates in Tobacco, Snapdragon, and Parsley
Authors: Moore Bd. , Palmquist D. E. , Seemann J. R. 
Published: October 2016

Abstract
We have examined the possible role of leaf cytosolic hexoses and the expression of mannitol metabolism as mechanisms that may affect the repression of photosynthetic capacity when plants are grown at 1000 versus 380 [mu]L L-1 CO2. In plants grown at high CO2, leaf ribulose-1,5-bisphosphate carboxylase/oxygenase content declined by [greater than or equal to]20% in tobacco (Nicotiana sylvestris) but was not affected in the mannitol-producing species snapdragon (Antirrhinum majus) and parsley (Petroselinum hortense). In the three species mesophyll glucose and fructose at midday occurred almost entirely in the vacuole (&gt;99%), irrespective of growth CO2 levels. The estimated cytosolic concentrations of glucose and fructose were [less than or equal to]100 [mu]M. In the three species grown at high CO2, total leaf carbohydrates increased 60 to 100%, but mannitol metabolism did not function as an overflow mechanism for the increased accumulation of carbohydrate. In both snapdragon and parsley grown at ambient or high CO2, mannitol occurred in the chloroplast and cytosol at estimated midday concentrations of 0.1 M or more each. The compartmentation of leaf hexoses and the metabolism of alternate carbohydrates are further considered in relation to photosynthetic acclimation to high levels of CO2.
Salicylic Acid Is Needed in Hypersensitive Cell Death in Soybean but Does Not Act as a Catalase Inhibitor
Authors: Tenhaken R. , Rubel C. 
Published: October 2016

Abstract
The function of salicylic acid (SA) in hypersensitive cell death was studied in a soybean (Glycine max)-Pseudomonas syringae pv glycinea system. The infection of cell cultures with bacteria leads to a hypersensitive reaction (HR), which is dependent on an appropriate avirulence gene and on low concentrations of SA. The requirement for SA is essential for a process shortly before the onset of the HR-caused cell death 5 to 6 h after infection with bacteria. SA given 10 to 12 h after infection or preincubation cannot rescue the completion of the cell death program. SA does not inhibit catalase or ascorbate peroxidase in soybean. In addition, the in vivo capacity of the cell culture for the rapid metabolism of H2O2 is not altered by SA. This clearly shows that SA is needed for the HR-caused cell death for a reaction downstream of the oxidative burst. Lipid peroxides accumulate during the HR, but the loss of membrane control precedes the generation of lipid peroxides. The accumulation of lipid peroxides in the HR can be prevented by lipid antioxidants. Nevertheless, cell death kinetics remain unaltered in the presence of antioxidants. It is concluded that lipid peroxides are a consequence of cell death, but not the primary cause of it.
Gene-Expression Patterns and Levels of Jasmonic Acid in Rice Treated with the Resistance Inducer 2,6-Dichloroisonicotinic Acid
Authors: Schweizer P. , Buchala A. , Metraux J. P. 
Published: October 2016

Abstract
Acquired disease resistance can be induced in rice (Oryza sativa) by a number of synthetic or natural compounds, but the molecular mechanisms behind the phenomenon are poorly understood. One of the synthetic inducers of resistance, 2,6-dichloroisonicotinic acid (INA), efficiently protected rice leaves from infection by the rice blast fungus Magnaporthe grisea (Hebert) Barr. A comparison of gene-expression patterns in plants treated with INA versus plants inoculated with the compatible pathogen M. grisea or the incompatible pathogen Pseudomonas syringae pv syringae revealed only a marginal overlap: 6 gene products, including pathogenesis-related proteins (PR1-PR9), accumulated in both INA-treated and pathogen-attacked leaves, whereas 26 other gene products accumulated only in INA-treated or only in pathogen-attacked leaves. Lipoxygenase enzyme activity and levels of nonconjugated jasmonic acid (JA) were enhanced in leaves of plants treated with a high dose of INA (100 ppm). Exogenously applied JA enhanced the gene induction and plant protection caused by lower doses of INA (0.1 to 10 ppm) that by themselves did not give rise to enhanced levels of endogenous (-)-JA. These data suggest that INA, aside from activating a pathogen-induced signaling pathway, also induces events that are not related to pathogenesis. JA acts as an enhancer of both types of INA-induced reactions in rice.
Activation of Host Defense Mechanisms by Elevated Production of H2O2 in Transgenic Plants
Authors: Wu G. , Shortt B. J. , Lawrence E. B. , Leon J. , Fitzsimmons K. C. , Levine E. B. , Raskin I. , Shah D. M. 
Published: October 2016

Abstract
Active oxygen species have been postulated to perform multiple functions in plant defense, but their exact role in plant resistance to diseases is not fully understood. We have recently demonstrated H2O2-mediated disease resistance in transgenic potato (Solanum tuberosum) plants expressing a foreign gene encoding glucose oxidase. In this study we provide further evidence that the H2O2-mediated disease resistance in potato is effective against a broad range of plant pathogens. We have investigated mechanisms underlying the H2O2-mediated disease resistance in transgenic potato plants. The constitutively elevated levels of H2O2 induced the accumulation of total salicylic acid severalfold in the leaf tissue of transgenic plants, although no significant change was detected in the level of free salicylic acid. The mRNAs of two defense-related genes encoding the anionic peroxidase and acidic chitinase were also induced. In addition, an increased accumulation of several isoforms of extracellular peroxidase, including a newly induced one, was observed. This was accompanied by a significant increase in the lignin content of stem and root tissues of the transgenic plants. The results suggest that constitutively elevated sublethal levels of H2O2 are sufficient to activate an array of host defense mechanisms, and these defense mechanisms may be a major contributing factor to the H2O2-mediated disease resistance in transgenic plants.
Separation of Photolabile-Phytochrome and Photostable-Phytochrome Actions on Growth and Microtubule Orientation in Maize Coleoptiles (A Physiological Approach)
Authors: Fischer K. , Schopfer P. 
Published: October 2016

Abstract
For separating the physiological actions of photolabile (phy-l) and photostable phytochromes, we compared the effects of red (R) and far-red (FR) light on elongation growth and microtubule reorientation in segments of maize (Zea mays L.) coleoptiles raised either in darkness (phy-l present) or preirradiated with R (phy-l eliminated). In 4.5-d-old dark-grown seedlings R first promoted growth and induced a transverse microtubule orientation. In continuous R the phytochrome action responsible for these responses was replaced by an opposite phytochrome action that produced a stable growth inhibition and longitudinal microtubule orientation. In R-preirradiated segments only the second type of phytochrome action could be observed. Reversion experiments with FR light pulses demonstrated that both types of phytochrome action were dependent on the FR-absorbing form of phytochrome and mirrored the actual phytochrome state after 1 h. We conclude from these and related results that growth promotion and transverse microtubule orientation are mediated by phy-l, whereas growth inhibition and longitudinal microtubule orientation are mediated by photostable phytochrome. The opposite actions of the two phytochromes can be separated by preirradiating the seedlings with R. Photoresponsiveness ascribed to phy-l disappeared after 5 d. phy-l appears to play a distinct but transitory role in coleoptile development.