bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correlation between leaf growth variables suggest intrinsic and early controls of leaf size in Arabidopsis thaliana
Authors: COOKSON SARAH J. , VAN LIJSEBETTENS MIEKE , GRANIER CHRISTINE 
Published: September 2005

ABSTRACTLeaf development is affected by both internal (genetic) and external (environmental) regulatory factors. The aim of this work was to investigate how leaf growth variables are related to one another in a range of environments. The leaf growth variables of wild‐type Arabidopsis thaliana and leaf development mutants (ang4, ron2‐1, elo1, elo2 and elo4) were studied under different incident light treatments (light and shade). The leaves studied were altered in various leaf development variables, such as the duration of expansion, relative and absolute expansion rates, epidermal cell size, epidermal cell number and initiation rate. Final leaf area was correlated to maximal absolute leaf expansion rate and cell number, but not to duration of leaf expansion or cell size. These relationships were common to all studied genotypes and light conditions, suggesting that leaf size is determined early in development. In addition, the early variables involved in leaf development were correlated to one another, and initial relative expansion rate was negatively correlated to the duration of expansion. These relationships between the leaf development variables were used to construct a conceptual model of leaf size control.
The combined action of 9 lipoxygenase and galactolipase is sufficient to bring about programmed cell death during tobacco hypersensitive response
Authors: CACAS JEAN‐LUC , VAILLEAU FABIENNE , DAVOINE CELINE , ENNAR NAJLA , AGNEL JEAN‐PIERRE , TRONCHET MAURICE , PONCHET MICHEL , BLEIN JEAN‐PIERRE , ROBY DOMINIQUE , TRIANTAPHYLIDES CHRISTIAN , MONTILLET JEAN‐LUC 
Published: September 2005

ABSTRACTOxylipins, derived from fatty acid hydroperoxides (FAHs), are thought to play different roles during plant pathogen interactions. During hypersensitive response (HR) some of them serve as signals necessary for defence gene activation whereas others could contribute to pathogen killing or could participate in the execution of plant programmed cell death (PCD) associated with this resistance. In order to address the role of these compounds in the latter process, we have closely observed lipid peroxidation, the first step of this metabolic pathway, under different situations which led either to accelerated or inhibited HR cell death. The oxidative process has been studied in cryptogein‐elicited tobacco leaves and during Ralstonia solanacearum‐induced HR. It was shown that FAH accumulation was preceded by the co‐ordinated rise in 9 lipoxygenase (9 LOX) and galactolipase activities in addition to the transcription of a set of four genes encoding 9 LOX and patatin‐like proteins, NtPAT1‐3. The latter gene expression was at the origin of a metabolic pathway allowing the release of poly‐unsaturated fatty acids from plastid galactolipids and their oxidation into free 9 FAHs. This 9 LOX‐dependent lipid peroxidation was found to be sufficient to lead to HR cell death. Finally, during the bacterial‐induced HR, lipid peroxidation appeared as a composite of metabolites of enzymatic and non‐enzymatic origins and suggested the role of H2O2 as an important source of oxidant that might, in synergy with 9 FAHs, contribute to cell death execution.
Microelectrode and 133Cs nuclear magnetic resonance evidence for variable cytosolic and cytoplasmic nitrate pools in maize root tips
Authors: RADCLIFFE S. A. , MILLER A. J. , RATCLIFFE R. G. 
Published: September 2005

ABSTRACTThe effect of nitrate uptake on the subcellular distribution of tissue nitrate in 2–5 mm maize root tips was investigated by two complementary methods. First a novel in vivo analysis using 133Cs nuclear magnetic resonance (NMR) was used to demonstrate changes in the cytoplasmic and vacuolar pools during caesium nitrate uptake. This method depended on interpreting the nitrate‐induced changes in the positions of the cytoplasmic and vacuolar caesium signals. The assignment of the signals was confirmed by using in vivo39K NMR to observe the displacement of cytoplasmic potassium into the vacuole during caesium uptake, and in vivo133Cs NMR to observe the displacement of cytoplasmic caesium into the vacuole during potassium uptake. Secondly nitrate‐selective microelectrodes were used to quantify the change in the cytosolic nitrate activity that occurred in the outermost cells of root tips under the same conditions. Both methods showed that the detected nitrate pool increased over a period of 8–10 h in the presence of 10 m m nitrate and it is concluded that the data provide support for the view that homeostasis in the cytosolic and cytoplasmic nitrate pools is not necessarily an invariant characteristic of root tips.
Nitrogen acquisition, PEP carboxylase, and cellular pH homeostasis: new views on old paradigms
Authors: BRITTO DEV T. , KRONZUCKER HERBERT J. 
Published: September 2005

ABSTRACTThe classic biochemical pH‐stat model of cytosolic pH regulation in plant cells presupposes a pH‐dependent biosynthesis and degradation of organic acids, specifically malic acid, in the cytosol. This model has been used to explain the higher tissue accumulation of organic acids in nitrate (NO3–)‐grown, relative to ammonium (NH4+)‐grown, plants, the result of proposed cytosolic alkalinization by NO3–metabolism, and acidification by NH4+metabolism. Here, a critical examination of the model shows that its key assumptions are fundamentally problematic, particularly in the context of the effects on cellular pH of nitrogen source differences. Specifically, the model fails to account for proton transport accompanying inorganic nitrogen transport, which, if considered, renders the H+production of combined transport and assimilation (although not the accumulation) to be equal for NO3–and NH4+as externally provided N sources. We show that the model's evidentiary basis in total‐tissue mineral ion and organic acid analysis is not directly relevant to subcellular (cytosolic) pH homeostasis, while the analysis of the ionic components of the cytosol is relevant to this process. A literature analysis further shows that the assumed greater activity of the enzyme phosphoenolpyruvate (PEP) carboxylase under nitrate nutrition, which is a key characteristic of the biochemical pH‐stat model as it applies to nitrogen source, is not borne out in numerous instances. We conclude that this model is not tenable in its current state, and propose an alternative model that reaffirms the anaplerotic role of PEP carboxylase within the context of N nutrition, in the production of carbon skeletons for amino acid synthesis.
A unique mode of parasitism in the conifer coral treeParasitaxus ustus(Podocarpaceae)
Authors: FEILD TAYLOR S. , BRODRIBB TIM J. 
Published: September 2005

ABSTRACTAlmost all parasitic plants, including more than 3000 species, are angiosperms. The only suggested gymnosperm exception is the New Caledonian conifer,Parasitaxus ustus, which forms a bizarre graft‐like attachment to the roots of another coniferFalcatifolium taxoides. Yet, the degree of resource dependence ofParasitaxusonFalcatifoliumhas remained speculative. Here we show thatParasitaxusis definitively parasitic, but it displays a physiological habit unlike any known angiosperm parasite. Despite possessing chloroplasts, it was found that the burgundy red shoots ofParasitaxuslack significant photosynthetic electron transport. However unlike non‐photosynthetic angiosperm parasites (holoparasites), tissues ofParasitaxusare considerably enriched in13carbon relative to its host. In line with anatomical observations of fungal hyphae embedded in the parasite/host union, stable carbon isotopic measurements indicate that carbon transport from the host toParasitaxusmost likely involves a fungal partner. Therefore,Parasitaxusparallels fungus‐feeding angiosperms (mycoheterotrophs) that steal carbon from soil mycorrhizal fungi. Yet with its tree‐like habit, association with fungi residing within the host union, high stomatal conductance, and low water potential, it is demonstrated thatParasitaxusfunctions unlike any known angiosperm mycoheterotroph or holoparasite.Parasitaxusappears to present a unique physiological chimera of mistletoe‐like water relations and fungal‐mediated carbon trafficking from the host.
Light‐dependent conversion of carotenoids in the parasitic angiosperm Cuscuta reflexa L.
Authors: SNYDER ALISON M. , CLARK BRUCE M. , BUNGARD RALPH A. 
Published: September 2005

ABSTRACTThe parasitic angiosperm Cuscuta reflexa contains unusually high amounts of the carotenoids lutein‐5,6‐epoxide and 9‐cis‐violaxanthin. In this study the light‐dependent conversions of these carotenoids in entire plant tissue and purified LHCIIb was compared with that of the xanthophyll cycle carotenoid violaxanthin when plants are exposed to high irradiance followed by low irradiance. In entire tissue under high irradiance, similar conversion kinetics and stoichiometry with de‐epoxidation products suggest that both lutein‐5,6‐epoxide and all‐trans‐violaxanthin are equally suitable substrates for de‐epoxidase. This is not the case under low irradiance as, although epoxidation of zeaxanthin and antheraxanthin rapidly restores the violaxanthin pool, the recovery of the lutein‐5,6‐epoxide pool is comparatively slow and has no stoichiometric relationship with its de‐epoxidation product, lutein. Light‐dependent changes in the concentration of 9‐cis‐violaxanthin mimic violaxanthin. However, the inability to detect de‐epoxidation products or to de‐epoxidize 9‐cis‐violaxanthin in vitro suggests that it is not subject to de‐epoxidation and, instead, its concentration changes may reflect the equilibrium between isomers of violaxanthin. Light exposure did not affect the composition of carotenoids bound to purified LHCIIb, indicating that these bound carotenoids are not subject to de‐epoxidation and do not contribute to the isomer pool equilibrium. The biosynthetic origins of lutein‐5,6‐epoxide and the potential role of these carotenoid cycles in photoprotection are discussed.
Citrus abscission and Arabidopsis plant decline in response to 5‐chloro‐3‐methyl‐4‐nitro‐1H‐pyrazole are mediated by lipid signalling
Authors: ALFEREZ FERNANDO , SINGH SHILA , UMBACH ANN L. , HOCKEMA BRANDON , BURNS JACQUELINE K. 
Published: September 2005

ABSTRACTThe compound 5‐chloro‐3‐methyl‐4‐nitro‐1H‐pyrazole (CMNP) is a pyrazole‐derivative that induces abscission selectively in mature citrus (Citrus sinensis) fruit when applied to the canopy and has herbicidal activity on plants when applied to roots. Despite the favourable efficacy of this compound, the mode of action remains unknown. To gain information about the mode of action of CMNP, the effect of application to mature citrus fruit and Arabidopsis thaliana roots was explored. Peel contact was essential for mature fruit abscission in citrus, whereas root drenching was essential for symptom development and plant decline in Arabidopsis. CMNP was identified as an uncoupler in isolated soybean (Glycine max) mitochondria and pea (Pisum sativum) chloroplasts and an inhibitor of alcohol dehydrogenase in citrus peel, but not an inhibitor of protoporphyrinogen IX oxidase. CMNP treatment reduced ATP content in citrus peel and Arabidopsis leaves. Phospholipase A2 (PLA2) and lipoxygenase (LOX) activities, and lipid hydroperoxide (LPO) levels increased in flavedo of citrus fruit peel and leaves of Arabidopsis plants treated with CMNP. An inhibitor of PLA2 activity, aristolochic acid (AT), reduced CMNP‐induced increases in PLA2 and LOX activities and LPO levels in citrus flavedo and Arabidopsis leaves and greatly reduced abscission in citrus and delayed symptoms of plant decline in Arabidopsis. However, AT treatment failed to halt the reduction in ATP content. Reduction in ATP content preceded the increase in PLA2 and LOX activities, LPO content and the biological response. The results indicate a link between lipid signalling, abscission in citrus and herbicidal damage in Arabidopsis.
Ozone induced emissions of biogenic VOC from tobacco: relationships between ozone uptake and emission of LOX products
Authors: BEAUCHAMP JONATHAN , WISTHALER ARMIN , HANSEL ARMIN , KLEIST EINHARD , MIEBACH MARCO , NIINEMETS ÜLO , SCHURR ULI , WILDT JÜRGEN 
Published: September 2005

ABSTRACTVolatile organic compound (VOC) emissions from tobacco (Nicotiana tabacum L. var. Bel W3) plants exposed to ozone (O3) were investigated using proton‐transfer‐reaction mass‐spectrometry (PTR‐MS) and gas chromatography mass‐spectrometry (GC‐MS) to find a quantitative reference for plants’ responses to O3 stress. O3 exposures to illuminated plants induced post‐exposure VOC emission bursts. The lag time for the onset of volatile C6 emissions produced within the octadecanoid pathway was found to be inversely proportional to O3 uptake, or more precisely, to the O3 flux density into the plants. In cases of short O3 pulses of identical duration the total amount of these emitted C6 VOC was related to the O3 flux density into the plants, and not to ozone concentrations or dose–response relationships such as AOT 40 values. Approximately one C6 product was emitted per five O3 molecules taken up by the plant. A threshold flux density of O3 inducing emissions of C6 products was found to be (1.6 ± 0.7) × 10−8 mol m−2 s−1.
The determination of membrane transport parameters with the cell pressure probe: theory suggests that unstirred layers have significant impact
Authors: TYREE MELVIN T. , KOH SHARON , SANDS PETER 
Published: September 2005

ABSTRACTA simulation model was written to compute the time‐kinetics of turgor pressure, P, change in Chara corallina during cell pressure probe experiments. The model allowed for the contribution of a membrane plus zero, one, or two unstirred layers of any desired thickness. The hypothesis that a cell with an unstirred layer is a composite membrane that will follow the same kind of kinetics with or without unstirred layers was tested. Typical ‘osmotic pulse’ experiments yield biphasic curves with minimum or maximum pressures, Pmin(max), at time tmin(max) and a solute exponential decay with halftime . These observed data were then used to compute composite membrane properties, namely the parameters Lp = the hydraulic conductance, σ = reflection coefficient and Ps = solute permeability using theoretical equations. Using the simulation model, it was possible to fit an experimental data set to the same values of Pmin(max), tmin(max) and incorporating different, likely values of unstirred layer thickness, where each thickness requires a unique set of plasmalemma membrane values of Lp, σ and Ps. We conclude that it is not possible to compute plasmalemma membrane properties from cell pressure probe experiments without independent knowledge of the unstirred layer thickness.
CO2 enrichment predisposes foliage of a eucalypt to freezing injury and reduces spring growth
Authors: BARKER DAVID H. , LOVEYS BETH R. , EGERTON JOHN J. G. , GORTON HOLLY , WILLIAMS WILLIAM E. , BALL MARILYN C. 
Published: September 2005

ABSTRACTSeedlings of Eucalyptus pauciflora, were grown in open‐top chambers fumigated with ambient and elevated [CO2], and were divided into two populations using 10% light transmittance screens. The aim was to separate the effects of timing of light interception, temperature and [CO2] on plant growth. The orientation of the screens exposed plants to a similar total irradiance, but incident during either cold mornings (east‐facing) or warm afternoons (west‐facing). Following the first autumn freezing event elevated CO2‐grown plants had 10 times more necrotic leaf area than ambient CO2 plants. West‐facing plants had significantly greater (25% more) leaf damage and lower photochemical efficiency (Fv/Fm) in comparison with east‐facing plants. Following a late spring freezing event east‐facing elevated CO2 plants suffered a greater sustained loss in Fv/Fm than west‐facing elevated CO2‐ and ambient CO2‐grown plants. Stomatal conductance was lower under elevated CO2 than ambient CO2 except during late spring, with the highest leaf temperatures occurring in west‐facing plants under elevated CO2. These higher leaf temperatures apparently interfered with cold acclimation thereby enhancing frost damage and reducing the ability to take advantage of optimal growing conditions under elevated CO2.
Defoliation alters the relative contributions of recent and non‐recent assimilate to root exudation from Festuca rubra
Authors: PATERSON ERIC , THORNTON BARRY , MIDWOOD ANDREW J. , SIM ALLAN 
Published: September 2005

ABSTRACTThe deposition of organic compounds from plant roots is a key determinant of rhizosphere microbial activity and community structure. Consequently, C‐flow from roots to soil is an important process in coupling plant and microbial productivity, via impacts on microbial nutrient cycling in soil. Experimentally, isotopic tracers (13C or 14C) are used to track C inputs to soil and microbial communities. However, in many such studies the relationship between labelled C‐flows and total C‐flows are not established, limiting the interpretative value of the results. In this study, we applied steady‐state near natural abundance 13CO2 labelling to determine the impact of partial defoliation of Festuca rubra on root exudation. This approach in axenic culture facilitated determination of the contribution of pre‐ and post‐defoliation assimilates both to root C‐flow and plant tissues. The results demonstrated that total root exudation was increased in the two days following defoliation. This was concurrent with reduced net CO2 assimilation and reduced allocation of post‐defoliation assimilates below‐ground and to active root meristems. Through determination of the δ13C of root exudates, it was established that the source of the increased root exudation was pre‐defoliation assimilate. However, this response was transient, with reduced deposition of pre‐ and post‐defoliation assimilates from roots during the period 2–4 d following defoliation. The results highlight the limitations of pulse‐labelling approaches as a means of quantifying impacts of treatments on root exudation, particularly where the treatment is likely to affect plant C‐partitioning or the balance between deposition to, and re‐mobilization from, C‐storage pools.
The Arabidopsis csb3 mutant reveals a regulatory link between salicylic acid‐mediated disease resistance and the methyl‐erythritol 4‐phosphate pathway
Authors: Gil Ma José , Coego Alberto , Mauch‐Mani Brigitte , Jordá Lucia , Vera Pablo 
Published: September 2005

SummaryWe report on constitutive subtilisin3 (csb3), an Arabidopsis mutant showing strikingly enhanced resistance to biotrophic pathogens. Epistasis analyses with pad4, sid2, eds5, NahG, npr1, dth9 and cpr1 mutants revealed that the enhanced resistance of csb3 plants requires intact salicylic acid (SA) synthesis and perception. CSB3 encodes a 1‐hydroxy‐2‐methyl‐2‐butenyl 4‐diphosphate synthase, the enzyme controlling the penultimate step of the biosynthesis of isopentenyl diphosphate via the 2‐C‐methyl‐d‐erythritol‐4‐phosphate (MEP) pathway in the chloroplast. CSB3 is expressed constitutively in healthy plants, and shows repression in response to bacterial infection. We also show the pharmacological complementation of the enhanced‐resistance phenotype of csb3 plants with fosmidomycin, an inhibitor of the MEP pathway, and propose that CSB3 represents a point of metabolic convergence modulating the magnitude of SA‐mediated disease resistance to biotrophic pathogens.
hca: an Arabidopsis mutant exhibiting unusual cambial activity and altered vascular patterning
Authors: Pineau Christophe , Freydier Amandine , Ranocha Philippe , Jauneau Alain , Turner Simon , Lemonnier Gaëtan , Renou Jean‐Pierre , Tarkowski Petr , Sandberg Göran , Jouanin Lise , Sundberg Björn , Boudet Alain‐Michel , Goffner Deborah , Pichon Magalie 
Published: September 2005

SummaryBy screening a T‐DNA population of Arabidopsis mutants for alterations in inflorescence stem vasculature, we have isolated a mutant with a dramatic increase in vascular tissue development, characterized by a continuous ring of xylem/phloem. This phenotype is the consequence of premature and numerous cambial cell divisions in both the fascicular and interfascicular regions that result in the loss of the alternate vascular bundle/fiber organization typically observed in Arabidopsis stems. The mutant was therefore designated high cambial activity (hca). The hca mutation also resulted in pleiotropic effects including stunting and a delay in developmental events such as flowering and senescence. The physiological characterization of hca seedlings in vitro revealed an altered auxin and cytokinin response and, most strikingly, an enhanced sensitivity to cytokinin. These results were substantiated by comparative microarray analysis between hca and wild‐type plants. The genetic analysis of hca indicated that the mutant phenotype was not tagged by the T‐DNA and that the hca mutation segregated as a single recessive locus, mapping to the long arm of chromosome 4. We propose that hca is involved in mechanisms controlling the arrangement of vascular bundles throughout the plant by regulating the auxin–cytokinin sensitivity of vascular cambial cells. Thus, the hca mutant is a useful model for examining the genetic and hormonal control of cambial growth and differentiation.
LORE1, an active low‐copy‐number TY3‐gypsy retrotransposon family in the model legume Lotus japonicus
Authors: Madsen Lene Heegaard , Fukai Eigo , Radutoiu Simona , Yost Christopher Karl , Sandal Niels , Schauser Leif , Stougaard Jens 
Published: September 2005

SummaryWe have identified a low‐copy‐number retrotransposon family present in nine to 10 copies in the Lotus japonicus model legume genome, and characterized its activity. LORE1 (Lotus retrotransposon 1) belongs to the Ty3‐gypsy group of elements, and is a long terminal repeat (LTR) retrotransposon. Genetic mapping located LORE1 elements in gene‐rich regions of Lotus chromosomes, and analysis of native as well as new insertion sites revealed integration outside the highly repetitive sequences of centromeres and telomeres. Sequencing of individual LORE1 family members identified several intact elements, and analysis of new insertions showed that at least one member is active and reinserts into functional genes, creating gene‐disruption mutations. Southern blot analysis and SSAP on a selection of symbiotic mutants revealed up to 12 new insertion sites in individual mutant lines and a Mendelian segregation of new inserts. Expression analysis showed that LORE1 elements are transcribed in all organs analysed and, in contrast to other active retrotransposons, LORE1 appears not to be transcriptionally upregulated during in vitro tissue culture. Activity of LORE1 in callus and whole plants suggests that a simple insertion mutagenesis based on endogenous LORE1 elements can be established for Lotus.
Cerebral cortical laminar necrosis on diffusion‐weighted MRI in hypoglycaemic encephalopathy
Authors: Yoneda Y. , Yamamoto S. 
Published: September 2005

AbstractBackground  Laminar necrosis of the cerebral cortex characterized neuropathologically by delayed selective neuronal necrosis occurs in hypoglycaemic encephalopathy and other brain diseases.Case report  A 37‐year‐old male with insulin‐treated Type 1 diabetes mellitus developed hypoglycaemic encephalopathy associated with respiratory failure. Brain diffusion‐weighted MRI during the subacute period demonstrated high signals along the cerebral cortex. Brain single‐photon emission computed tomography showed diffuse, severe cerebral hypoperfusion. The patient remained comatose and died 1 month later.Conclusions  High signals along the cortical bands on diffusion‐weighted MRI suggest cortical laminar necrosis, although a postmortem examination was unavailable. Sustained hypoglycaemic brain injury, possibly associated with respiratory hypoxia, may be the underlying mechanism.