bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photo‐inhibition and seasonal photosynthetic performance of the seaweed Laminaria saccharina during a simulated tidal cycle: chlorophyll fluorescence measurements and pigment analysis
Authors: Gevaert F. , Creach A. , Davoult D. , Holl A.‐C. , Seuront L. , Lemoine Y. 
Published: March 2003

Abstract Laminaria saccharina (Lamouroux) form the largest, most abundant and conspicuous seaweed populations along the French coast of the eastern English Channel. As they are located in the intertidal zone, they are exposed to considerable irradiance variations, mainly related to tidal cycles. The response of these macro‐algae to light variations over a simulated daily tidal cycle was investigated in the laboratory during spring, autumn and winter using chlorophyll fluorescence and pigment analysis. The maximum quantum yield of photosystem II (PSII) photochemistry (Fv/Fm) and the operating PSII efficiency (ΦPSII) showed clear daily cycles according to the irradiance variation throughout the 12 h simulated tidal cycle, whereas the pattern of the relative photosynthetic electron transport rate (rETR) was not so obvious. The algae reacted to the light increase by developing photoprotective mechanisms able to dissipate the excess energy reaching PSII by the de‐epoxidation of violaxanthin into zeaxanthin. Because of their better acclimation to strong irradiance, spring populations were less affected by this light treatment than were winter populations. In particular, L. saccharina showed more pigments of the xanthophyll cycle in spring to cope with strong irradiance exposure. Alternatively, they developed their antenna complexes in winter to harvest a maximum of light.
Genetic parameters and QTL analysis of δ13C and ring width in maritime pine
Authors: Brendel O. , Pot D. , Plomion C. , Rozenberg P. , Guehl J.‐M. 
Published: March 2003

AbstractClassical quantitative genetics and quantitative trait dissection analysis (QTL) approaches were used in order to investigate the genetic determinism of wood cellulose carbon isotope composition (δ13C, a time integrated estimate of water use efficiency) and of diameter growth and their relationship on adult trees (15 years) of a forest tree species (maritime pine). A half diallel experimental set‐up was used to (1) estimate heritabilities for δ13C and ring width and (2) to decompose the phenotypic δ13C/growth correlation into its genetic and environmental components. Considerable variation was found for δ13C (range of over 3‰) and for ring width (range of over 5 mm) and significant heritabilities (narrow sense 0·17/0·19 for δ13C and ring width, respectively, 100% additivity). The significant phenotypic correlation between δ13C and ring width was not determined by the genetic component, but was attributable to environmental components. Using a genetic linkage map of a full‐sib family, four significant and four suggestive QTLs were detected for δ13C, the first for δ13C in a forest tree species, as far as known to the authors. Two significant and four suggestive QTLs were found for ring width. No co‐location of QTLs was found between δ13C and growth.
Homeoviscous and functional adaptations of mitochondrial membranes to growth temperature in soybean seedlings
Authors: Davy De Virville J. , Cantrel C. , Bousquet A.‐L. , Hoffelt M. , Tenreiro A.‐M. , Vaz Pinto V. , Arrabaça J. D. , Caiveau O. , Moreau F. , Zachowski A. 
Published: March 2003

AbstractThe present study investigated whether the cold‐sensitive character of soybean is reflected at the level of mitochondrial membranes. When exposed to an increase of temperature (from 25 to 35 °C), mitochondrial membranes were characterized by a higher phosphatidylcholine : phosphatidylethanolamine ratio and a lower content in 18 : 3 fatty acid. After a reduction of temperature (from 25 to 18 °C) the opposite changes were found. Lipid lateral diffusion and local microviscosity appeared to be comparable in mitochondria from plantlets grown at 25 or 35 °C when assayed at the respective growth temperatures. Some functional aspects (cytochrome c oxidase activity or membrane conductance) tended to this behaviour whereas others (respiration rate or maximum membrane potential) did not. On the other hand, membranes from plants grown at 18 °C were more rigid. Moreover, as illustrated by cytochrome c oxidase activity or respiration rate, functional measurements suggested that these membranes were less active at this temperature. Thus the dynamic characteristics and functional properties measured in mitochondrial membranes were in favour of an adaptive trend at 35 °C, but not at 18 °C despite changes in lipid composition, in accordance with the cold‐sensitive character of the plant.
Modelling stomatal conductanceof field‐grown sunflower under varying soil water content and leafenvironment: comparison of three models of stomatal response toleaf environment and coupling with an abscisic acid‐based modelof stomatal response to soil drying
Authors: Gutschick V. P. , Simonneau T. 
Published: March 2003

AbstractStomatal conductance, gs, responds both tothe immediate or local environment of the leaf, such as CO2 partialpressure and irradiance, and to root‐sourced signals of water stress,particularly abscisic acid (ABA). Two models for the combined controlof gs were formulated and tested in sunflower(Helianthus annuus). First, several empirical models weretested for the local control, demonstrating that the Ball–Berrymodel [Ball, Woodrow & Berry (in Progress in PhotosynthesisResearch Vol. 4, pp. 5.221–5.224: M. Nijhoff,Dordrecht, The Netherlands) 1987] is consistently amongthe most accurate. A problem of statistical non‐independence inthis model is shown to be minor. The model offers regularity ofparameter values among most species and, despite an oversimplicationin representing known humidity‐response mechanisms, it incorporates othersignalling loops from CO2 and assimilation. In the firstcombined model, ABA as its concentration in xylem sap, [ABA]xy,down‐regulates the slope, m, in the Ball–Berry modelby the factor gfac = exp(– β[ABA]xy).The ABA‐induced reduction in gs decreases CO2 assimilation andsurface humidity, thus appearing to induce the local‐control mechanismto amplify the ABA‐induced stomatal closure. In the second combinedmodel, gs is estimated as the minimum of the local(Ball–Berry) response and the product gfac gs,max,with gs,max as a maximal unstressed conductance.Both models can predict gs from the external environmentalvariables with good accuracy (r2 near 0·8 over20‐fold variations in gs). Further analyses showthat gs responds to humidity almost quadraticallyrather than linearly. It also responds to assimilation as a powerlaw with an exponent that is significantly less than 1. These limitations,shared by other models, suggest more research into biochemical signalling.
Water‐deficit‐induced translational control in Nicotiana tabacum
Authors: KAWAGUCHI R. , WILLIAMS A. J. , BRAY E. A. , BAILEY‐SERRES J. 
Published: March 2003

ABSTRACTThe effect of prolonged water deficit on mRNA translation was quantitatively analysed in apical and basal leaves of whole tobacco (Nicotiana tabacum) plants. The level of large polysomes (six or more ribosomes per mRNA) was significantly higher in apical than basal leaves under well‐watered conditions. In both young and old leaves, water deficit caused a progressive reduction in levels of polysomes with concomitant increases in 80S monosomes, indicative of reduced initiation of translation. Despite the global reduction in polysome formation over 144 h of water deficit, the water‐deficit‐induced putative lipid transfer protein (ltp) mRNA was associated with large polysomes and LTP content increased. Osmotin (osm) mRNA, another water‐deficit‐induced transcript, also remained associated with large polysomes during prolonged water deficit. In contrast, mRNAs encoding the non‐stress proteins ribulose bisphosphate carboxylase/oxygenase small subunit (rbcS) and eukaryotic initiation factor 4A (eIF4A) decreased in abundance and shifted to small polysomes and non‐polysomal complexes, indicating that initiation of translation of these mRNAs was impaired by water deficit. These results show that translational regulation is a component of the water‐deficit response and the differential translation of individual mRNAs is distinct in leaves of different age.
Expression of a celery mannose 6‐phosphate reductase in Arabidopsis thaliana enhances salt tolerance and induces biosynthesis of both mannitol and a glucosyl‐mannitol dimer
Authors: ZHIFANG G. , LOESCHER W. H. 
Published: March 2003

ABSTRACTMannitol, a sugar alcohol that may serve as a compatible solute to cope with salt stress, is synthesized via the action of a mannose‐6‐phosphate reductase (M6PR) in celery (Apium graveolens L). In contrast to previous approaches that have used a bacterial gene to engineer mannitol biosynthesis in plants and other organisms, Arabidopsis thaliana, a non‐mannitol producer, was transformed with the celery leaf M6PR gene under control of the CaMV 35S promotor. In all independent Arabidopsis M6PR transformants, mannitol accumulated throughout the plants in amounts ranging from 0·5 to 6 µmol g−1 fresh weight. A novel compound, not found in either celery or Arabidopsis, 1‐O‐β‐d‐glucopyranosyl‐d‐mannitol, also accumulated in vegetative tissues of mature plants in amounts up to 4 µmol g−1 fresh weight, but not in flowers and seeds. In the absence of NaCl, all transformants were phenotypically the same as the wild type; however, in the presence of NaCl, mature transgenic plants showed a high level of salt tolerance, i.e. growing, completing normal development, flowering, and producing seeds in soil irrigated with 300 mm NaCl in the nutrient solution. These results demonstrate a major role in developing salt‐tolerant plants by means of introducing mannitol biosynthesis using M6PR.
Stomatal responses of C3, C3‐C4 and C4Flaveria species to light and intercellular CO2 concentration: implications for the evolution of stomatal behaviour
Authors: HUXMAN T. E. , MONSON R. K. 
Published: March 2003

ABSTRACTStomatal function mediates physiological trade‐offs associated with maintaining a favourable H2O balance in leaf tissues while acquiring CO2 as a photosynthetic substrate. The C3 and C4 species appear to have different patterns of stomatal response to changing light conditions, and variation in this behaviour may have played a role in the functional diversification of the different photosynthetic pathways. In the current study, we used gain analysis theory to characterize the stomatal conductance response to light intensity in nine different C3, C4 and C3‐C4 intermediate species Flaveria species. The response of stomatal conductance (gs) to a change in light intensity represents both a direct (related to a change in incident light intensity, I) and indirect (related to a change in intercellular CO2 concentration, Ci) response. The slope of the line relating the change in gs to Ci was steeper in C4 species, compared with C3 species, with C3‐C4 species having an intermediate response. This response reflects the greater relative contribution of the indirect versus direct component of the gs versus I response in the C4 species. The C3‐C4 species, Flaveria floridana, exhibited a C4‐like response whereas the C3‐C4 species, Flaveria sonorensis and Flaveria chloraefolia, exhibited C3‐like responses, similar to their hypothesized position along the evolutionary trajectory of the development of C4 photosynthesis. There was a positive correlation between the relative contribution of the indirect component of the gs versus I response and water use efficiency when evaluated across all species. Assuming that the C3‐C4 intermediate species reflect an evolutionary progression from fully expressed C3 ancestors, the results of the current study demonstrate an increase in the contribution of the indirect component of the gs versus I response as taxa evolve toward the C4 extreme. The greater relative contribution of the indirect component of the stomatal response occurs through both increases in the indirect stomatal components and through decreases in the direct. Increases in the magnitude of the indirect component may be related to the maintenance of higher water use efficiencies in the intermediate evolutionary stages, before the appearance of fully integrated C4 photosynthesis.
Induction of resistance to downy mildew (Peronospora parasitica) in cauliflower by DL‐β‐amino‐n‐butanoic acid (BABA)
Authors: Silué D. , Pajot E. , Cohen Y. 
Published: March 2003

Of the three isomers of aminobutyric acid, only the β isomer (BABA) was effective in inducing resistance against Peronospora parasitica, the causal agent of downy mildew, in cauliflower (Brassica oleracea var. botrytis). A single foliar spray applied to 7‐day‐old seedlings protected the plants against Peronospora parasitica for at least 15 days. Of the enantiomers (R and S), only the R was effective. Resistance was accompanied by a hypersensitive‐like reaction (necrotic spots) which was evident before inoculation. BABA was systemically effective when applied to the roots, but failed to protect cotyledons adjacent to treated ones. Unlike other chemical inducers, BABA was effective when applied several hours postinoculation. It had no effect on P. parasitica spore germination. In cauliflower seedlings, BABA did not induce the accumulation of the pathogenesis‐related protein PR‐1, PR‐2, PR‐3, PR‐5 and PR‐9. Only treated and challenged seedlings accumulated PR‐2.
Systemic spread of Plum pox virus (PPV) in Mariana plum GF 8‐1 in relation to shoot growth
Authors: Ferri M. Bodin , Costes E. , Quiot J.‐B. , Dosba F. 
Published: March 2003

Infection of Prunus spp. by Plum pox virus (PPV) is characterized by an uneven distribution of the virus within the tree and branches. In order to gain a better understanding of this distribution, a method for modelling tree growth was used. PPV spread was followed within susceptible Mariana plum clone GF 8‐1 shoots for 4 months after inoculation. Shoot growth was unaffected by the presence of the virus. Symptoms appeared on leaves produced in the most actively growing parts of the shoots, i.e. at the beginning of the season. PPV was detected in leaves other than those showing symptoms. The proportion of leaves with detectable virus decreased from the zone showing symptoms, with 100% ELISA‐positive responses, to the shoot tip with no detectable virus in leaves produced between 111 and 127 days after inoculation. Furthermore, a higher proportion of positive ELISA results was obtained below the zone showing symptoms (77%) compared with 50% above. PPV was detected in 95% of the most vigorous shoots 71 days after inoculation compared with 37% of slower‐growing, later‐produced shoots.
In vitro inhibition of soil microorganisms by 2‐phenylethyl isothiocyanate
Authors: Smith B. J. , Kirkegaard J. A. 
Published: March 2003

Isothiocyanates (ITCs) are produced by the enzymatic hydrolysis of glucosinolates in cruciferous plants and can kill fungi, oomycetes and bacteria. The effect of 2‐phenylethyl ITC (2‐PE ITC), the main ITC liberated from the roots of canola, was tested in vitro on a range of fungi, oomycetes and bacteria. Bacteria were generally more tolerant than the eukaryotic pathogens to 2‐PE ITC, although both groups showed considerable variability in response (ED90 ranging from 0·005 to 1·5 mm for eukaryotes, and from 0·33 to greater than 3·34 mm for complete inhibition of bacterial growth). While intraspecies variability was low, interspecies variability was high within some genera. Amongst the eukaryotes, Trichoderma spp. were the most tolerant to 2‐PE ITC, while other genera, including Aphanomyces, Gaeumannomyces, Phytophthora and Thielaviopsis, were very sensitive. A range of responses was exhibited by Pythium spp. and the different anastomosis groups of Rhizoctonia solani. A simple laboratory screening may be an effective way to identify candidate soilborne pathogens for control in rotation cropping systems which include a Brassica crop phase.
Molecular detection of Fusarium solani f. sp. glycines in soybean roots and soil
Authors: Li S. , Hartman G. L. 
Published: March 2003

A polymerase chain reaction (PCR)‐based method was developed to detect DNA of Fusarium solani f. sp. glycines, the cause of soybean sudden death syndrome. Two pairs of primers, Fsg1/Fsg2 designed from the mitochondrial small subunit ribosomal RNA gene, and FsgEF1/FsgEF2 designed from the translation elongation factor 1‐α gene, produced PCR products of 438 and 237 bp, respectively. Primer specificity was tested with DNA from 82 F. solani f. sp. glycines, 55 F. solani non‐SDS isolates, 43 isolates of 17 soybean fungal pathogens and the oomycete Phytophthora sojae, and soybean. The sensitivity of primer Fsg1/Fsg2 was 10 pg while that of FsgEF1/FsgEF2 was 1 ng when using F. solani f. sp. glycines total genomic DNA or down to 103 macroconidia g−1 soil. Nested PCR increased the sensitivity of the PCR assay 1000‐fold to 10 fg using primers Fsg1/Fsg2, and 1 pg using primers FsgEF1/FsgEF2. F. solani f. sp. glycines DNA was detected in field‐grown soybean roots and soil by PCR using either single pairs of primers or the combination of two pairs of primers. The occurrence of F. solani f. sp. glycines was determined using nested PCR for 47 soil samples collected from soybean fields in 20 counties of Illinois in 1999. F. solani f. sp. glycines was detected in soil samples from all five Illinois Agricultural Statistic Districts including 100, 89, 50, 92 and 50% of the samples from East, Central, North‐east and West Districts, respectively.
Mesenchymal Stem Cells Inhibit and Stimulate Mixed Lymphocyte Cultures and Mitogenic Responses Independently of the Major Histocompatibility Complex
Authors: Le Blanc K. , Tammik L. , Sundberg B. , Haynesworth S. E. , Ringdén O. 
Published: March 2003

AbstractWe aimed to study the effects of mesenchymal stem cells (MSCs) on alloreactivity and effects of T‐cell activation on human peripheral blood lymphocytes (PBLs) in vitro. MSCs were expanded from the bone marrow of healthy subjects. MSCs isolated from second to third passage were positive for CD166, CD105, CD44, CD29, SH‐3 and SH‐4, but negative for CD34 and CD45. MSCs cultured in osteogenic, adipogenic or chondrogenic media differentiated, respectively, into osteocytes, adipocytes or chondrocytes. MSC added to PBL cultures had various effects, ranging from slight inhibition to stimulation of DNA synthesis. The stimulation index (SI = (PBL + MSC)/PBL) varied between 0.2 and 7.3. The SI was not affected by the MSC dose or by the addition of allogeneic or autologous MSCs to the lymphocytes.Suppression of proliferative activity was observed in all experiments after the addition of 10,000–40,000 MSCs to mixed lymphocyte cultures (MLCs). Lymphocyte proliferation was 10–90%, compared with a control MLC run in parallel without MSCs. In contrast, the addition of fewer MSCs (10–1000 cells) led to a less consistent suppression or a marked lymphocyte proliferation in several experiments, ranging from 40 to 190% of the maximal lymphocyte proliferation in control MLCs. The ability to inhibit or stimulate T‐cell alloresponses appeared to be independent of the major histocompatibility complex, as results were similar using ‘third party’ MSCs or MSCs that were autologous to the responder or stimulating PBLs. The strongest inhibitory effect was seen if MSCs were added at the beginning of the 6 day culture, and the effect declined if MSCs were added on day 3 or 5. Marked inhibitory effects of allogeneic and autologous MSCs (15,000) were also noted after mitogenic lymphocyte stimulation by phytohaemagglutinin (median lymphocyte proliferation of 30% of controls), Concanavalin A (56%) and protein A (65%). Little, if any, inhibition occurred after stimulation with pokeweed mitogen. Low numbers of MSCs (150 cells) were unable to inhibit mitogen‐induced T‐cell responses.MSCs have significant immune modulatory effects on MLCs and after mitogenic stimulation of PBL. High numbers of MSCs suppress alloreactive T cells, whereas very low numbers clearly stimulated lymphocyte proliferation in some experiments. The effect of a larger number of MSCs on MLCs seems more dependent on cell dose than histocompatibility and could result from an ‘overload’ of a stimulatory mechanism.
The Chemokines CCL5, CCL2 and CXCL12 Play Significant Roles in the Migration of Th1 Cells into Rheumatoid Synovial Tissue
Authors: Shadidi K. R. , Aarvak T. , Henriksen J. E. , Natvig J. B. , Thompson K. M. 
Published: March 2003

AbstractAs the T‐cell population in the synovial tissue (ST) in rheumatoid arthritis (RA) is dominated by T helper (Th) 1 cells, this study was designed to examine whether there is a preferential migration of polarized T cells to ST, and to identify the chemokines responsible for the migration. This was done by developing 10 T‐cell clones specific for an arbitrary antigen (mouse immunoglobulin G (IgG)) from the peripheral blood (PB) of a healthy donor sensitized to mouse IgG. The Th polarizations of the clones were determined by measuring secreted interferon‐γ and interleukin‐4, following anti‐CD3 stimulation. Migration to pools of RA ST cell‐derived supernatants was analysed. Expression of the chemokine receptors CCR1, CCR2, CCR3, CCR4, CCR5, CCR6, CCR7, CCR8, CXCR3 and CXCR4 were analysed by flow cytometry. Th1 clones showed significantly higher migration to RA ST cell‐derived supernatant compared with Th2 clones. Blocking of either of the chemokines, CCL5 or CCL2, strongly inhibited migration of the Th1 cells between 56 and 77%, while blocking of CXCL12 inhibited migration between 44 and 61%. Blocking of CXCL10 had only a minor inhibitory effect. Our results demonstrate a selective migration of Th1 cells to RA ST supernatant and that blocking either CCL5, CCL2 or CXCL12 significantly inhibits T‐cell migration. This indicates that CCL5, CCL2 and CXCL12 play significant roles in attracting Th1 cells towards the RA ST, and may prove potent targets for obstructing T‐cell migration to the synovium.