bluuebunny/crossref_metadata_2025 huggingface dataset:
Renal transcription of high‐affinity type‐2 cationic amino acid transporter is up‐regulated in LPS‐stimulated rodents
Authors: Yang S. , Huang C.‐J. , Tsai P.‐S. , Cheng C.‐R. , Stevens B. R. , Skimming J. W.
Published: February 2004

Objective:  Sepsis stimulates renal nitric oxide (NO) biosynthesis through up‐regulation of inducible NO synthase (iNOS) expression. Type‐2 cationic amino acid transporter (CAT‐2) mediation of trans‐membrane L‐arginine (L‐Arg) transportation has been identified as one of the crucial regulatory mechanisms involved in the formation of NO by iNOS. We had previously shown that CAT‐2B, a high‐affinity alternative‐spliced transcript of the CAT‐2, is involved in induced NO biosynthesis by iNOS (Nitric Oxide, 2002). In this present study, we sought to assess the effects of sepsis on the expression of CAT‐2B in lipopolysaccharide (LPS)‐stimulated rat kidney.

Methods:  Forty rats were randomized to either a normal saline (N/S)‐treated group or a LPS‐treated group. Renal NO production was determined using chemiluminescence. Semi‐quantitative RT‐PCR was used to determine the mRNA concentrations of iNOS and L‐Arg transporters (CAT‐1, CAT‐2 and CAT‐2B) in kidney.

Results:  Lipopolysaccharide‐coinduced iNOS, CAT‐2 and CAT‐2B mRNA expression in kidney and caused renal NO overproduction. A significant linear regression relationship was defined between renal NO concentrations and iNOS, CAT‐2 and CAT‐2B, respectively. On the contrary, CAT‐1 expression was not affected by LPS‐stimulation.

Conclusions:  We provide the first evidence to illustrate that sepsis/septic shock induces the transcription of high‐affinity CAT‐2B in renal tissues. Transcription of iNOS, CAT‐2 and CAT‐2B correlates well with renal NO biosynthesis. Regulation of L‐Arg uptake by modulating the expression regulation of induced CAT‐2 and CAT‐2B might be a potential target for therapies against renal pathologic conditions related to NO overproduction.
In‐situ investigation of grain boundary and triple junction kinetics in aluminium – 10 p.p.m. magnesium
Authors: Mattissen D. , Wærø A. , Molodov D. A. , Shvindlerman L. S. , Gottstein G.
Published: February 2004

A special technique for in‐situ observation and recording of triple junction motion is introduced. The described method makes it possible to study the motion of connected grain boundaries, i.e. triple junctions and their geometry. The results of an investigation of the steady‐state motion of grain boundary systems with triple junctions in aluminium–magnesium are presented. The analysed triple junctions show a distinctive deviation of contact angle from the equilibrium value 120° as assumed for the deviation of the Von Neumann–Mullins relation. The type of triple junction can have an essential influence on grain boundary motion and thus on grain growth.
Quantifying recrystallization by electron backscatter diffraction
Authors: Jazaeri H. , Humphreys F. J.
Published: February 2004

The use of high‐resolution electron backscatter diffraction in the scanning electron microscope to quantify the volume fraction of recrystallization and the recrystallization kinetics is discussed. Monitoring the changes of high‐angle grain boundary (HAGB) content during annealing is shown to be a reliable method of determining the volume fraction of recrystallization during discontinuous recrystallization, where a large increase in the percentage of high‐angle boundaries occurs during annealing. The results are shown to be consistent with the standard methods of studying recrystallization, such as quantitative metallography and hardness testing. Application of the method to a highly deformed material has shown that it can be used to identify the transition from discontinuous to continuous recrystallization during which there is no significant change in the percentage of HAGB during annealing.
Reconstruction of grains and subgrains from electron backscatter diffraction maps
Authors: Humphreys F. J.
Published: February 2004

Electron backscatter diffraction maps are capable of yielding a substantial amount of quantitative information about grains, subgrains and boundaries, and the amount and quality of the data may be substantially increased if the pixels of the map are re‐analysed so as to ‘reconstruct’ complete grains or subgrains. The paper discusses the various methods of grain reconstruction and the use of such methods to obtain microstructural information correlating the parameters of dimension, position, orientation and misorientation, which cannot usually be obtained by other means. Grain reconstruction also reveals the nature, location and contacts of all the triple junctions in the microstructure, and the paper discusses two important examples of how these data may be further analysed using automated routines. Boundary connectivity and the length and direction of likely paths along which grain boundary events such as creep fracture or stress corrosion may occur can readily be determined. The overall alignment of boundaries in deformed metals, with respect to the crystallography and the deformation geometry, may be determined as a function of the length and misorientation of the boundary segments.
Phase differentiation via combined EBSD and XEDS
Authors: Nowell M. M. , Wright S. I.
Published: February 2004

Electron backscatter diffraction (EBSD) and orientation imaging microscopy have become established techniques for analysing the crystallographic microstructure of single and multiphase materials. In certain instances, however, it can be difficult and/or time intensive to differentiate phases within a material by crystallography alone. Traditionally a list of candidate phases is specified prior to data collection. The crystallographic information extracted from the diffraction patterns is then compared with the crystallographic information from these candidate phases, and a best‐fit match is determined. Problems may arise when two phases have similar crystal structures. The phase differentiation process can be improved by collecting chemical information through X‐ray energy‐dispersive spectroscopy (XEDS) simultaneously with the crystallographic information through EBSD and then using the chemical information to pre‐filter the crystallographic phase candidates. This technique improves both the overall speed of the data collection and the accuracy of the final characterization. Examples of this process and the limitations involved will be presented and discussed.
A study of recrystallization in single‐phase aluminium using in‐situ annealing in the scanning electron microscope
Authors: Hurley P. J. , Humphreys F. J.
Published: February 2004

In‐situ annealing experiments were performed in the scanning electron microscope on a single‐phase Al−0.13Mg alloy cold rolled to different strain levels. Once the validity of the technique had been verified by comparison of the recrystallization kinetics and final grain size with bulk annealed samples, the method was used in combination with electron back‐scattered diffraction (EBSD) to study the potential mechanisms for recrystallization in this alloy. During annealing of material rolled to moderate strains (ɛt < 0.7), the primary mechanism was strain‐induced boundary migration (SIBM). In material rolled to higher true strains (ɛt > 1.4), recrystallization occurred extensively along pre‐existing cube bands and EBSD measurements showed that the mean size of cells within the cube bands was larger than for all other orientations measured, suggesting a size advantage was responsible for the strengthening of cube texture during recrystallization. SIBM was shown to occur concurrently with the nucleation along cube bands but this contributed a lower proportion of nucleation sites during recrystallization.
The role of misorientation and phosphorus content on grain growth and intergranular fracture in iron–carbon–phosphorus alloys
Authors: Williams G. O. , Randle V. , Cowan J. R. , Spellward P.
Published: February 2004

The relationship between the crystallography of intergranular fracture and phosphorus segregation has been investigated in a Fe−0.06wt%P−0.002wt%C alloy aged for 1 h at temperatures between 600 °C and 1000 °C. Two novel techniques were devised for the investigation: first, electron back‐scatter diffraction (EBSD) across the reconstructed fracture surface and, second, a combination of Auger electron spectroscopy, stereophotogrammetry and microscopy to measure phosphorus and carbon on fracture facets combined with EBSD measurements direct from the fracture surface. In total, 700 misorientations were measured from across the reconstructed fracture surface and in ‘control’ areas away from the fracture. It was found that Σ 3s were in general more resistant to brittle fracture than were random boundaries, and it was suggested that alloys of this type could be grain boundary engineered to improve fracture resistance by a short anneal in the austenite region to increase the final proportion of Σ 3s. Sixteen fracture facets yielded combined Auger/EBSD data. The combined Auger/EBSD methodology to acquire joint crystallographic and segregation information from facets was shown to be feasible, although laborious. There were significantly more {110} planes than any other type in the sample population of facets from which combined segregation/crystallography data had been collected. The data suggested that there was on average lower phosphorus segregation on fracture facets that were near {110} than on other intergranular fracture facets.
The integration of experimental in‐situ EBSD observations and numerical simulations: a novel technique of microstructural process analysis
Authors: Piazolo S. , Jessell M. W. , Prior D. J. , Bons P. D.
Published: February 2004

The combination of subgrain‐ and grain‐scale microstructural data collected during in‐situ heating experiments and numerical simulations of equivalent microstructural development offers an innovative and powerful tool in the advancement of the understanding of microstructural processes. We present a system that fully integrates subgrain‐ to grain‐scale crystallographic data obtained during in‐situ observations during heating experiments in a scanning electron microscope and the two‐dimensional hybrid numerical modelling system Elle. Such a system offers the unique opportunity to test and verify theories for microstructural development, as predictions made by numerical simulations can be directly coupled to appropriate physical experiments and, conversely, theoretical explanations of experimental observations should be testable with numerical simulations. Discrepancies between data obtained with both techniques suggest the need for an in‐depth investigation and thus open up new avenues of theory development, modification and verification. In addition, because in numerical models it is possible to select the processes modelled, the effect of individual processes on the microstructural development of a specific material can be quantified. To illustrate the potential and methodology of the so‐called EBSD2Elle system, two in‐situ experiments and their equivalent numerical experiments are presented. These are static heating experiments of (a) an annealed Ni‐foil coupled with a front tracking model for grain growth and (b) a cold deformed rock salt with kinetic Monte Carlo simulations for subgrain growth.
EBSD and TEM investigation of the hot deformation substructure characteristics of a type 316L austenitic stainless steel
Authors: Cizek P. , Whiteman J. A. , Rainforth W. M. , Beynon J. H.
Published: February 2004

The evolution of crystallographic texture and deformation substructure was studied in a type 316L austenitic stainless steel, deformed in rolling at 900 °C to true strain levels of about 0.3 and 0.7. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) were used in the investigation and a comparison of the substructural characteristics obtained by these techniques was made. At the lower strain level, the deformation substructure observed by EBSD appeared to be rather poorly developed. There was considerable evidence of a rotation of the pre‐existing twin boundaries from their original orientation relationship, as well as the formation of highly distorted grain boundary regions. In TEM, at this strain level, the substructure was more clearly revealed, although it appeared rather inhomogeneously developed from grain to grain. The subgrains were frequently elongated and their boundaries often approximated to traces of {111} slip planes. The corresponding misorientations were small and largely displayed a non‐cumulative character. At the larger strain, the substructure within most grains became well developed and the corresponding misorientations increased. This resulted in better detection of sub‐boundaries by EBSD, although the percentage of indexing slightly decreased. TEM revealed splitting of some sub‐boundaries to form fine microbands, as well as the localized formation of microshear bands. The substructural characteristics observed by EBSD, in particular at the larger strain, generally appeared to compare well with those obtained using TEM. With increased strain level, the mean subgrain size became finer, the corresponding mean misorientation angle increased and both these characteristics became less dependent on a particular grain orientation. The statistically representative data obtained will assist in the development of physically based models of microstructural evolution during thermomechanical processing of austenitic stainless steels.
Application of the EBSD technique to describe the initiation and growth behaviour of microstructurally short fatigue cracks in a duplex steel
Authors: Krupp U. , Düber O. , Christ H.‐J. , Künkler B. , Schick A. , Fritzen C.‐P.
Published: February 2004

Up to 90% of the fatigue life of engineering alloys results from the initiation and propagation of microstructurally short cracks. Owing to their strong interactions with microstructural features, e.g. grain and phase boundaries, they exhibit substantially non‐uniform propagation kinetics as compared with the growth rate of long cracks, which can be well described using a power‐law function of the range of the stress‐intensity factor ΔK. In the present paper interactions between the crystallographic misorientation of grain and phase boundaries and microcracks in an austenitic/ferritic stainless steel are discussed and quantified by means of fatigue experiments in combination with the electron backscattered diffraction technique. In the second part a numerical model for the simulation of microcracks is introduced, which is capable of taking real microstructural arrangements into consideration.
Investigation of the microstructure and mesotexture formed during thermomechanical controlled rolling in microalloyed steels
Authors: Wu S. J. , Davis C. L.
Published: February 2004

Thermomechanical controlled rolling (TMCR) has been widely used as an effective method to improve the properties of steels. In the present paper, two commercial TMCR microalloyed steels were investigated. The grain size distributions and grain boundary misorientation angles were measured using electron backscattered diffraction patterns obtained using orientation imaging microscopy (OIM). The equivalent grain diameters were also measured using optical microscopy. Mixed coarse‐ and fine‐grained regions were observed and the microhardness values were measured for both areas. Grain boundary misorientation angle distributions showed that the magnitude of mesotexture developed in the steel is dependent upon the rolling passes, the reduction ratio and the rolling temperatures including the finish rolling temperature. The surface layer, up to 2 mm depth, in Com‐A steel had about 55% of grain boundaries with a misorientation angle below 12°, much higher than in the central area (∼30%), whereas Com‐B steel showed similar distributions from the rolling surface to the centre. Misorientation results obtained from laboratory rolled steel plates with various TMCR procedures are also discussed as are OIM results from Charpy impact brittle fracture surfaces examining the effect of misorientation on crack propagation.
EBSD characterization of carbide–carbide boundaries in WC–Co composites
Authors: Farooq M. U. , Klement U.
Published: February 2004

A sample of WC‐6wt%Co was investigated for grain boundary character distribution and occurrence of coincidence site lattice (CSL) boundaries on a statistical basis. For this purpose orientation measurements of the grains were carried out using electron back‐scattered diffraction (EBSD). The dominant misorientation relationships were determined by complementary EBSD data representation tools such as orientation maps, misorientation angle distribution histograms and the sectioned three‐dimensional misorientation space. It was found that the grain boundary character distribution of the material is nearly random and the CSL boundaries are not present in statistically significant amounts. It was also found that the amount of binder phase does not play a role in the formation of special boundaries. The paper focuses on the methodology of characterizing grain boundaries in a hexagonal material using EBSD.
Microstructural and microtextural characterization of oxide scale on steel using electron backscatter diffraction
Authors: Birosca S. , Dingley D. , Higginson R. L.
Published: February 2004

High‐temperature oxidation of steel has been extensively studied. The microstructure of iron oxides is, however, not well understood because of the difficulty in imaging it using conventional methods, such as optical or electron microscopy. A knowledge of the oxide microstructure and texture is critical in understanding how the oxide film behaves during high‐temperature deformation of steels and more importantly how it can be removed following processing. Recently, electron back‐scatter diffraction (EBSD) has proved to be a powerful technique for distinguishing the different phases in scales. This technique gives valuable information both on the microstructure and on the orientation relationships between the steel and the scale layers. In the current study EBSD has been used to investigate the microstructure and microtexture of iron oxide layers grown on interstitial free steel at different times and temperatures. Heat treatments have been carried out under normal oxidation conditions in order to relate the results to real steel manufacturing in industry. The composition, morphologies, microstructure and microtexture of selected conditions have been studied using EBSD.
Progressive steps in the development of electron backscatter diffraction and orientation imaging microscopy
Authors: Dingley D.
Published: February 2004

Ten years ago electron backscatter diffraction (EBSD) became available to a wider group active in materials research. This paper highlights some of the more significant developments in camera technology and software developments that have arisen since then. The use of slow‐scan charge couple device cameras for phase identification and rapid determination of orientation image micrographs is reviewed. The current limiting spatial resolution of the technique is shown to be less than 10 nm. A procedure for improving lattice spacing measurement by utilizing the full resolution of the camera is described with experimental measurements on silicon and nickel showing relative errors of plus/minus 3%. An investigation of partially recrystallized aluminium shows how the recrystallized fraction can be extracted with confidence but that the mapping of substructure in the highly deformed regions is questionable. Phase identification is described for complex cases in which the phase data tabulated in standard databases do not correspond to what is observed in the EBSD patterns. Phase mapping in a complex mineral in which chemical data and EBSD data are collected simultaneously is shown to be improved by recording both the chemical and the EBSD data into computer memory and proceeding with the phase discrimination and orientation measurement in off‐line analysis.
Modelling NADH turnover in plant mitochondria
Authors: Hagedorn Peter H. , Flyvbjerg Henrik , Møller Ian M.
Published: February 2004

NADH is central to the functioning of mitochondrial respiration. It is produced by enzymes in, or associated with, the tricarboxylic acid cycle in the matrix, and it is oxidized by two respiratory chain enzymes in the inner membrane, the rotenone‐sensitive complex I and the rotenone‐insensitive internal NADH dehydrogenase (NDin). A simplified kinetic model for NADH turnover in the matrix of plant mitochondria is presented. Only the two main NADH‐producing enzymes, NAD‐malate dehydrogenase [EC 1.1.1.37] (MDH) and NAD‐malic enzyme [EC 1.1.1.39] (ME), are considered. This model reproduces the complex behaviour of malate oxidation by isolated mitochondria in response to additions of ADP (state 3/state 4), NAD+ and/or rotenone, as well as to changes in pH. It is found that MDH always operates at or close to equilibrium. Changes in the activity of complex I, NDin, or ME are predicted to cause clear changes in the pattern of malate oxidation. In general, the model predicts high sensitivity to changes in the ME activity. In contrast, MDH activity can be reduced 100‐fold without detectable changes in malate oxidation. It is demonstrated that it is not the high activity, but the equilibrium properties of MDH that are important for the redox‐buffering function of MDH in the mitochondrial matrix. Binding of NAD+ and NADH in the matrix reduces the concentrations of free NAD+ and NADH, depending on the concentration of binding sites and the binding strength. On the basis of the modelling results it is estimated that a significant proportion of the mitochondrial NAD is bound.
Ion uptake in Pinus banksiana treated with sodium chloride and sodium sulphate
Authors: Franklin Jennifer A. , Zwiazek Janusz J.
Published: February 2004

Within its wide range across Canada, jack pine is exposed to salinity from both natural and anthropogenic sources. To compare the effects of Cl and SO4 on salt injury, sand and solution‐culture grown jack pine (Pinus banksiana Lamb.) seedlings were treated with nutrient solutions containing 60 or 120 mM NaCl, 60 mM Na2SO4, or a mixture of 60 mM NaCl and 30 mM Na2SO4. After 5 weeks of salt treatments, concentrations of Cl, K, Na, and SO4 were determined in roots, stem and needles of the current and previous years growth, and in necrotic needles. To determine the role of water uptake in the absorption and translocation of salts in plants, total transpiration was measured as the loss of water from a sealed system and related to total plant uptake of Cl, Na, and SO4. Sodium uptake and root‐to‐shoot transport rates were greater in treatments containing Cl. A delay in root‐to‐shoot transport of both Na and Cl indicates retention of these ions in the roots. Electrolyte leakage of needles was more closely related to treatment Cl concentrations than treatment Na concentrations. The transport of Na ions to the shoot was related to the presence of Cl, but was not related to transpiration rate.
Cloning and salt‐induced, ABA‐independent expression of choline mono‐oxygenase in Atriplex prostrata
Authors: Wang Li‐Wen , Showalter Allan M.
Published: February 2004

Certain plants accumulate glycinebetaine, a type of osmoprotectant, in response to salinity. Glycinebetaine is synthesized in these plants via the two‐step oxidation of choline, and the first step is catalysed by choline mono‐oxygenase (CMO; EC 1.14.15.7). Cloned by RT‐PCR and 3′‐RACE, the cDNA of Atriplex prostrata CMO (ApCMO) is 1669 bp in length and encodes a full‐length protein of 438 amino acids. The deduced amino acid sequence of ApCMO revealed a Rieske‐type [2Fe‐2S] cluster motif and a mononuclear non‐heme Fe binding motif, and shares 82.9% identity and 87.2% similarity with the deduced amino acid sequence of spinach CMO. Accumulation of CMO transcript and glycinebetaine both increased in response to NaCl treatment. Without salt treatment, CMO mRNA was detected in stems and 5‐day‐old seedlings, but not in leaves, roots and older seedlings. With salt treatment, CMO mRNA accumulated dramatically in stems, leaves and roots, with the most abundant accumulation occurring in young stems. Although abscisic acid may initiate global physiological reactions in response to osmotic stress, it did not induce the expression of CMO in A. prostrata. In summary, salt‐induction of CMO mRNA in A. prostrata is more substantial than that reported in spinach and sugar beet, and the plant may serve as a useful model to study regulation of glycinebetaine synthesis by environmental stress.
Exposure of roots of cucumber (Cucumis sativus) to low temperature severely reduces root pressure, hydraulic conductivity and active transport of nutrients
Authors: Lee Seong Hee , Singh Adya Prasad , Chung Gap Chae , Ahn Sung Ju , Noh Eun Kyeung , Steudle Ernst
Published: February 2004

When root temperature dropped below 25°C, there was a sharp drop in the root pressure (Pr) and hydraulic conductivity of excised roots (Lpr) of young cucumber (Cucumis sativus L.) seedlings as measured with the root pressure probe. A detailed analysis of root hydraulics provided evidence for a larger reduction in the osmotic component of Lpr (77%) in comparison with the hydrostatic component (34%) in response to the exposure of the root system to 13°C. The activity of the plasma membrane H+‐ATPase (EC 3.6.1.35) was reduced from 30 to 16 µmol Pi mg−1 protein h−1 upon exposure to 8°C for 1 day. Ultrastructural observations showed no evidence of loosening of the microstructure of endodermal cell walls in low temperature (LT)‐treated roots. It is concluded that the rapid drop in the Pr in response to LT is largely caused by a reduction in the activity of the plasma membrane H+‐ATPase rather than by loosening of the endodermal wall which would cause substantial solute losses. On the other hand, water permeability of root cell membrane at LT was related to changes in the activity (open/closed state) of water channels.
Abiotic stress alters transcript profiles and activity of glutathione S‐transferase, glutathione peroxidase, and glutathione reductase in Euphorbia esula
Authors: Anderson James V. , Davis David G.
Published: February 2004

Glutathione S‐transferase (GST), glutathione peroxidase (GPX), and glutathione reductase (GR) are enzymes that utilize glutathione to play an important role in plant defense mechanisms. In leafy spurge (Euphorbia esula L.), transcript and activity profiles for these enzymes are differentially influenced in tissue exposed to xenobiotic (diclofop‐methyl) and environmental stress (cold and drought). Five different EeGST cDNA (including phi, tau, theta, and zeta class GSTs), one EeGPX cDNA, and one EeGR cDNA showed differential expression patterns in leafy spurge plants exposed to diclofop‐methyl‐, cold‐ and drought‐stress. Tissue treated with diclofop‐methyl also had increased GST, GPX and GR activities that were preceded or paralleled by increased gene expression. Transcript profiles resulting from drought‐stressed plants were similar to transcript profiles from diclofop‐methyl‐treated plants but not cold‐stressed plants. GPX activity in leafy spurge protein extracts was not bound to either S‐hexylglutathione‐ or glutathione‐agarose columns but instead co‐migrated with fractions of GST activity that also were not bound by affinity chromatography. Fractions of GST proteins that were bound to S‐hexylglutathione revealed that increased GST activity in diclofop‐methyl‐treated tissue could be identified as phi‐ and tau‐type GSTs.
Contribution of current carbon assimilation in supplying root exudates of Lolium perenne measured using steady‐state 13C labelling
Authors: Thornton Barry , Paterson Eric , Midwood Andrew J. , Sim Allan , Pratt Shona M.
Published: February 2004

Coupling growth of Lolium perenne L. in sterile solution culture with steady‐state 13CO2 labelling allowed quantification of the contribution of C, assimilated either before or after a specific time point, both to plant compartments and root exudates. Plants were grown for 27 days in atmospheres containing CO2 with δ13C signatures of either −13.5 or −36.1‰. Air supplies to plants were then reciprocally switched to the opposing signature (day 0), plants were destructively harvested and root exudates collected over the next 8 days. Following the switch, C assimilated after day 0 and transported to the roots initially only appeared in root tips, later appearing in both tip and non‐tip material. The δ13C signature of the root exudate changed exponentially with time. Assimilation pre‐ and post‐day 0 contributed equally to exudate C at 4.5 days. Beyond day 8, assimilation pre‐day 0 still contributed 41.7% of exudate C. Over all 8 days, a linear relationship existed between the δ13C signatures of root tips and exudate, suggesting that all newly assimilated C in the exudate was from root tips. Results imply pulse‐labelling approaches to study root exudates are discriminative in the sources of exudates labelled and in the sites from which exudation occurs.
Transcriptional regulation of proline biosynthesis in Medicago truncatula reveals developmental and environmental specific features
Authors: Armengaud Patrick , Thiery Laurent , Buhot Nathalie , Grenier‐de March Ghislaine , Savouré Arnould
Published: February 2004

The model legume plant Medicago truncatula accumulates free proline in response to hyperosmotic stress as do many other organisms. In order to analyse the transcriptional regulation of proline biosynthesis in M. truncatula, three cDNAs encoding Δ1‐pyrroline‐5‐carboxylate synthetase (P5CS1, P5CS2; EC not assigned) and ornithine δ‐aminotransferase (OAT; EC 2.6.1.13) were isolated. The cDNAs shared high homologies with the other plant sequences and genomic organization analysis indicated the presence of two P5CS and two putative OAT genes. The two P5CS genes showed differing transcript level regulation according to organs and in response to osmotic stress. MtP5CS1 steady‐state transcript levels in the different plant organs were correlated with proline levels but transcript abundance was unaffected by osmotic stresses. MtP5CS2 transcripts were poorly detected in all organs but were strongly accumulated in shoots of salt‐stressed plants. We suggest a specific of MtP5CS1 and MtP5CS2 as a housekeeping product and as a stress specific isoform, respectively. MtOAT transcripts were predominantly detected in roots and shoots of unstressed plants. Salt‐stress treatment induced the accumulation of MtOAT transcripts in the whole plant whatever the developmental stage. In salt‐stressed roots, a positive correlation was found between proline and MtOAT transcript accumulation. These results suggest that both ornithine and glutamate biosynthesis pathways contribute to the osmotic stress‐induced proline accumulation in M. truncatula.
A new SBP‐box gene BpSPL1 in silver birch (Betula pendula)
Authors: Lännenpää Mika , Jänönen Isto , Hölttä‐Vuori Maarit , Gardemeister Marika , Porali Ilkka , Sopanen Tuomas
Published: February 2004

The SBP‐box gene family represents a group of plant‐specific genes encoding putative transcription factors. Thus far, SBP‐domain protein binding sites have been found in the promoters of Arabidopsis APETALA1 and Antirrhinum SQUAMOSA. A putative SBP‐domain binding element has been observed in the promoter of BpMADS5, a close homologue of Arabidopsis FRUITFULL in silver birch (Betula pendula). A novel SBP‐box gene from birch named BpSPL1 has been cloned and characterized. The nucleotide sequence of BpSPL1 is similar to Antirrhinum SBP2 and Arabidopsis SPL3, apart from the unique finding that BpSPL1 does not contain an intron typical to all other known SBP‐box genes studied thus far. According to Northern blot analysis, BpSPL1 is expressed in birch inflorescences as well as in shoots and leaves. Studies using electrophoretic mobility shift assay demonstrate that there are nuclear proteins in birch inflorescences which specifically bind to the SBP binding element of the promoter of BpMADS5. BpSPL1 expressed in Escherichia coli also specifically binds to this element. According to Southern blot analysis, there are at least two SBP‐box genes in birch. The results suggest that SBP‐box genes are involved in the regulation of flower development in birch.
Probing corticular photosynthesis through in vivo chlorophyll fluorescence measurements: evidence that high internal CO2 levels suppress electron flow and increase the risk of photoinhibition
Authors: Manetas Yiannis
Published: February 2004

Twigs of many woody plants possess chlorenchyma under a well‐developed periderm which lacks stomata and impedes both gas diffusion and light penetration. The so‐called corticular photosynthesis, occurring in the shade and under extremely high CO2 concentrations, was probed in this study through in vivo chlorophyll fluorescence measurements. Field comparisons between twigs and corresponding leaves in five species indicated that both the dark‐ and light‐adapted PSII photochemical efficiencies are considerably lower in twigs at all incident photon fluence rates, in spite of the significant attenuation of solar radiation by the periderm. Light saturation curves for linear electron transport rates (corrected according to the actual light intensities reaching twig chlorenchyma) were compatible with a shade‐acclimated photosynthetic machinery, showing very low maximum electron transport rates (at approximately 5% of the corresponding leaf values) and threshold irradiances for light saturation. However, removing periderms from twig segments (i.e. relieving the twig interior form the high CO2 partial pressures) considerably improved the light‐adapted (but not the dark‐adapted) PSII photochemical efficiency, allowing the assumption that the high internal CO2 levels may interfere with the smooth functioning of photosynthesis. Indeed, laboratory experiments with twig segments equilibrated under various CO2 levels (0.036–20%), resulted in a progressive decrease of light‐adapted PSII photochemical yield, with the values obtained at 20% CO2 being similar to those obtained with intact twigs in the field. Further experiments indicated that high CO2 combined with high light suppressed the development of a photoprotective non‐photochemical quenching through a reduction of its fast relaxing component, accompanied by a higher risk of photoinhibition. It is suggested that high internal CO2 concentrations in twigs impede photosynthesis possibly through acidification of protoplasm and impairment of the pH‐dependent high energy state quenching followed by reduction in the efficiency of heat dissipation.
Resistance of Phaseolus species to ice crystallization at subzero temperature
Authors: Balasubramanian Parthiba , Vandenberg Albert , Hucl Pierre , Gusta Lawrence
Published: February 2004

Dry bean (Phaseolus vulgaris L.) cultivars possess little or no freezing tolerance and are killed at the temperature of ice formation in their tissues. An increase in frost tolerance by 2–3°C would expand dry bean production in the short growing seasons of the Canadian prairies and possibly to higher altitudes in the tropics where episodic frosts occur during the growing season. The objective of this study was to determine the differences in frost resistance of Phaseolus species in both controlled and field environments. Leaflets of dry bean cv. CDC Nighthawk, and wild relatives from the primary gene pool (P. vulgaris var. mexicanus Freytag and P. vulgaris var. aborigineus (Burkart) Baudet) and the tertiary gene pool (P. acutifolius var. tenuifolius A. Gray, P. filiformis Bentham, P. angustissimus A. Gray and P. ritensis M.E. Jones) were subjected to subzero temperatures with and without ice nucleation to determine the levels of tolerance and avoidance, respectively. The lethal temperature at which 50% of the leaflets were killed (LT50) was 0.5–1°C lower for species of the tertiary gene pool compared to those from the primary gene pool. Leaflets of species from the tertiary gene pool were also characterized by extensive supercooling compared to leaflets of species from the primary gene pool. Resistance of Phaseolus species to spring and autumn frosts were determined on seedlings transplanted to the field. Phaseolus angustissimus, a species of the tertiary gene pool had the highest seedling survival in response to both autumn and spring frosts, when the minimum air temperatures were −5 and −7°C, respectively. Frost resistance of Phaseolus angustissimus, if successfully introgressed into bean germplasm, may enable the development of frost resistant dry bean cultivars.
Ecophysiological analysis of two arctic sedges under reduced root temperatures
Authors: Starr Gregory , Neuman Dawn S. , Oberbauer Steven F.
Published: February 2004

Shoot physiological activity in arctic vascular plants may be controlled by low soil temperatures. While leaves may be exposed to moderate temperatures during the growing season, root temperatures often remain near freezing. In this study, two tundra sedges, Eriophorum vaginatum and Carex bigellowii, were subjected to reduced soil temperatures, and photosynthetic parameters (light saturated photosynthesis Amax, variable to maximal fluorescence and Fv/Fm stomatal conductance) and abscisic acid concentrations were determined. Stomatal conductance and Amax for both E. vaginatum and C. bigellowii strongly decreased with declining soil temperatures. Decreasing soil temperature, however, impacted Fv/Fm to a much lesser degree. Root and leaf ABA concentrations increased with decreasing root temperature. These observations support the contention that soil temperature is a significant photosynthetic driving factor in arctic sedges exposed to variable root and shoot temperatures. Because these two species comprise approximately 30% of the vascular ground cover of wet tussock tundra, the soil temperature responses of these sedges potentially scale up to significant effects on ecosystem carbon exchange.
Fusicoccin affects cytochrome c leakage and cytosolic 14‐3‐3 accumulation independent of H+‐ATPase activation
Authors: Malerba Massimo , Crosti Paolo , Cerana Raffaella , Bianchetti Renato
Published: February 2004

Fusicoccin (FC) is a well known toxin acting as a 14‐3‐3 protein‐mediated activator of the plasma membrane H+‐ATPase and the biochemical and physiological changes induced in the cell by this toxin have, up to now, been ascribed to the increased rate of proton extrusion by this pump leading to external acidification and cell hyperpolarization. In a recent work (Malerba M et al. 2003, Physiologia Plantarum, 119: 480–488) it was shown that, besides the previously well studied changes, FC induces a large stimulation of H2O2 production, an activation of alternative respiration and a leakage of cytochrome c from mitochondria. In this article further studies on the relation between the H2O2 overproduction and medium acidification are reported. The increase in the rate of H2O2 accumulation is particularly evident when high concentrations of the toxin ensure a rapid acidification of the medium, but it is not obtained when the time‐course of acidification is reproduced by external acid additions. The FC‐dependent H2O2 overproduction is strongly inhibited by inhibitors of the H+‐ATPase activity, such as vanadate and erythrosin B, and it does not occur when the activation of the H+‐ATPase is prevented by phenylarsine oxide (PAO), an inhibitor of the activating interaction between the enzyme and its regulative 14‐3‐3 protein. Interestingly, all these inhibitors only partially prevent the leakage of cytochrome c from the mitochondria. A kinetic analysis of FC‐dependent changes of 14‐3‐3s shows that the initial increase in the plasma membrane level of these proteins, presumably due to translocation of free cytosolic forms, is followed by a remarkable increase in the level of the 14‐3‐3 proteins located in the cytosol. This latter change is not prevented by inhibitors of the activity or activation of the H+‐ATPase. These results suggest that, besides the H+‐ATPase activation, FC can induce other cell changes possibly mediated by changes of the regulative 14‐3‐3 proteins.
Properties of a polygalacturonase‐inhibiting protein isolated from ‘Oroblanco’ grapefruit
Authors: D'hallewin Guy , Schirra Mario , Powell Ann L. T. , Greve L. Carl , Labavitch John M.
Published: February 2004

Polygalacturonase inhibiting protein (PGIP) was extracted from ‘Oroblanco’ grapefruit type (triploid pummelo‐grapefruit) albedo tissue, purified and partially characterized. Extraction was carried out at 4°C with a high ionic strength extraction buffer. After dialysis and concentration by ultrafiltration the extract was chromatographed on concanavalin A‐Sepharose. The PGIP activity was bound by the lectin and then eluted using 250 mM α‐methyl mannopyranoside, resulting in a 17‐fold purification of the PGIP and demonstrating its glycoprotein nature. The anion‐exchange and size‐exclusion chromatography steps that followed gave a PGIP that was 857‐fold purified relative to the initial tissue extract, and having a 44 kDa molecular weight, as estimated by SDS‐PAGE electrophoresis. PGIP inhibition activity was tested with endo‐polygalacturonase (EC 3.2.1.15) produced by Penicillium italicum and Botrytis cinerea. The radial diffusion and reducing sugar assays showed that P. italicum and B. cinerea endo‐PGs were affected by PGIP, whereas no endo‐PG activity was detected in the culture filtrate of P. digitatum. In vitro tests revealed that PGIP inhibited P. italicum and B. cinerea growth. By contrast, the influence of PGIP on P. digitatum, growth was negligible, perhaps because this fungus does not produce endo‐PG. Following heating for 10 min at 65°C the inhibitory activity of PGIP was reduced by 43%. PGIP activity decreased further as heating temperature increased, and was completely suppressed after heating at 100°C for 10 min.
Effects of Rhizoctonia infection and drought on peroxidase and chitinase activity in Norway spruce (Picea abies)
Authors: Nagy Nina Elisabeth , Fossdal Carl Gunnar , Dalen Lars Sandved , Lönneborg Anders , Heldal Inger , Johnsen Øystein
Published: February 2004

Seedlings of Norway spruce were exposed to fungal infection and drought in order to investigate differences in their stress responses on the enzymatic level. Six‐week‐old seedlings were infected with the root rot fungus Rhizoctonia, or subjected to drought, respectively. Changes at the enzymatic level were more rapid and significantly higher in infected plants in comparison with drought‐stressed spruce plants. Rhizoctonia infection resulted in early local and systemic increase in peroxidase and chitinase activity. The most prominent isoforms responding were highly basic peroxidases and chitinases (pI 9–9.5) and several acidic chitinases (pI3–4). An increased intensity of similar peroxidase isoforms was found in drought‐affected plants. Two peroxidase isoforms (with pI < 9) accumulated exclusively in response to drought. These results suggest that at an early stage of infection and drought stress, the two stresses can be distinguished by the temporal appearance and isoform profile of peroxidases and chitinases. Changes in enzyme activity appeared before changes in physiological parameters, thus these isoform profiles could be used as early markers of stress conditions in spruce.
Photophysiology and primary production of phytoplankton in freshwater
Authors: Wilhelm Christian , Becker Anette , Toepel Jörg , Vieler Astrid , Rautenberger Ralf
Published: February 2004

In the last 10 years enormous progress has been made in developing new instruments to collect physiological data from natural phytoplankton. In this review we summarize the motivation which has powered this engagement and focus on new technologies used to measure fluorescence, absorption and biochemical compositions of natural phytoplankton cells from nature. Combining the knowledge of phytoplankton structure along with taxon‐specific measurements of photosynthetic activity and biochemical cell composition, can lead to new models which increase the reliability of water quality prediction. Furthermore, recent progress in the analysis of photophysiological fitness of phytoplankton cells has revealed new knowledge about the phylogenetic diversity of metabolic strategies to cope with light and nutrient stress. Future progress in single cell analysing systems will be discussed.
The indole alkaloids brucine, yohimbine, and hypaphorine are indole‐3‐acetic acid‐specific competitors which do not alter auxin transport
Authors: Jambois Anne , Ditengou Franck Anicet , Kawano Tomonori , Delbarre Alain , Lapeyrie Frédéric
Published: February 2004

The indole alkaloids brucine and yohimbine, just like hypaphorine, counteract indole‐3‐acetic acid (IAA) activity in seedling roots, root hairs and shoots, but do not appear to alter auxin transport in roots or in cultured cells. In roots, the interactions between IAA and these three alkaloids appear competitive and specific since these molecules interact with IAA but with neither 1‐naphthaleneacetic acid (NAA) or 2,4‐dichlorophenoxyacetic acid (2,4‐D), two synthetic auxins. The data reported further support the hypothesis that hypaphorine brucine and yohimbine compete with IAA on some auxin‐binding proteins likely to be auxin receptors and that 2,4‐D and NAA are not always perceived by the same receptor as IAA or the same component of that receptor. At certain steps of plant development and in certain cells, endogenous indole alkaloids could be involved in IAA activity regulation together with other well‐described mechanisms such as conjugation or degradation. Hypaphorine with other active indole alkaloids remaining to be identified, might be regarded as a new class of IAA antagonists.
Methyl jasmonate and cis‐jasmone do not dispose of the herbivore‐induced jasmonate burst in Nicotiana attenuata
Authors: Von Dahl Caroline C. , Baldwin Ian T.
Published: February 2004

The oxylipin pathway mediates wound‐ and herbivore‐induced defense reactions in Nicotiana attenuata as evidenced by a transient jasmonic acid (JA)‐burst that precedes these defense responses. The fate of this induced JA‐burst remains unknown. Two derivatives of JA, its methylester, methyl jasmonate (MeJA) and cis‐jasmone (cisJ), are thought to be a means of disposing of JA through volatilization at the plant surface. In N. attenuata, the headspace quantities of these compounds did not change over 3 days, although levels of MeJA and cisJ increased 100‐ and 70‐fold, respectively, in surface extracts of attacked leaves after feeding of Manduca sexta larvae or application of larval regurgitant to mechanical wounds. Inhibition of the wound‐induced increase in JA with indole‐3‐acetic acid (IAA) revealed an association between the JA accumulation and subsequent increases in MeJA and cisJ. Induced systemic increases of MeJA were not of local origin and therefore do not contribute to the inactivation of the JA‐burst in the wounded leaf. The total amount of MeJA and cisJ produced could only account for 9% of the JA‐burst elicited by herbivore attack and therefore their production do not represent major disposal pathways of JA in N. attenuata.