bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification and characterization of a salt‐stress‐induced plasma membrane H+‐ATPase in tomato
Authors: Kalampanayil B. D. , Wimmers L. E. 
Published: March 2003

AbstractPlant plasma membrane H+‐ATPases (PM H+‐ATPases) energize the secondary transport of Na+ from the cytosol across the plasma membrane and so may play a role in the plant response to salt stress. A PM H+‐ATPase gene in rice is closely linked to a locus responsible for increased salt resistance. PM H+‐ATPases are encoded by large gene families, including 10–12 in tomato (Lycopersicon esculentum). Salt stress stimulates the accumulation of PM H+‐ATPase transcripts in a variety of plants but the effect of salt stress on the expression of specific isoforms has not been investigated. We isolated a partial‐length cDNA clone of a novel tomato PM H+‐ATPase gene from salt‐stressed expanded leaf tissue and characterized its expression in response to salt and osmotic stress. The gene, LHA8, is a member of the subfamily including AHA1, AHA2, AHA3, AHA4, AHA9, LHA4, PHA2 and PMA4, and is most closely related to the Nicotiana plumbaginifolia gene PMA6. LHA8 transcript accumulation is induced by NaCl exposure. LHA8 is not expressed at detectable levels in roots or expanded leaves and is present at very low levels in unexpanded leaves. LHA8 expression is induced in expanded leaves, unexpanded leaves and roots. Induction appears to be specific to the ionic, rather than the osmotic, effects of NaCl because iso‐osmotic levels of polyethylene glycol do not induce message accumulation.
Multivariate analysis of intraspecific responses to UV‐B radiation in white clover (Trifolium repensL.)
Authors: Hofmann R. W. , Campbell B. D. , Fountain D. W. , Jordan B. R. , Greer D. H. , Hunt D. Y. , Hunt C. L. 
Published: March 2003

ABSTRACTWhite clover (Trifolium repensL.) is experiencing increased levels of ultraviolet‐B (UV‐B) radiation in temperate pastures due to the depletion of the stratospheric ozone layer. Based on 17 morphological, morphogenetic and physiological attributes, this study analysed the consequences of enhanced UV‐B on 26 white clover populations using principal components analysis (PCA). After 18 d of exposure to 13·3 kJ m−2d−1UV‐B in controlled environments, UV‐B significantly decreased above‐ground and below‐ground plant growth attributes, epidermal cell surface area and maximum quantum efficiency of photosystem II photochemistry (Fv/Fm). Aspects of cell division and cell expansion both were negatively affected by UV‐B. Stomatal density, specific leaf mass, root‐to‐shoot ratio and levels of UV‐B‐absorbing compounds increased in response to UV‐B. In the multivariate analysis, the main dimension of UV‐B sensitivity was characterized by changes in plant growth attributes. Alterations in partitioning within and between plant organs constituted a secondary tier of UV‐B responsiveness. Plant characteristics related to UV‐B tolerance included lower growth rate, smaller epidermal cell surface area and higher UV‐B‐induced levels of UV‐B‐absorbing compounds. The results suggest overall UV‐B tolerance for slower‐growing populations from less productive habitats with higher natural UV‐B irradiance.
Drought‐induced senescence is characterized by a loss of antioxidant defences in chloroplasts
Authors: Munné‐Bosch S. , Jubany‐Marí T. , Alegre L. 
Published: March 2003

AbstractThe relationship between drought, oxidative stress and leaf senescence was evaluated in field‐grown sage (Salvia officinalis L.), a drought‐susceptible species that shows symptoms of senescence when exposed to stress. Despite the photoprotection conferred by the xanthophyll cycle, drought‐stressed senescing leaves showed enhanced lipid peroxidation, chlorophyll loss, reduced photosynthetic activity and strong reductions of membrane‐bound chloroplastic antioxidant defences (i.e. β‐carotene and α‐tocopherol), which is indicative of oxidative stress in chloroplasts. H2O2 accumulated in drought‐stressed senescing leaves. Subcellular localization studies showed that H2O2 accumulated first in xylem vessels and the cell wall and later in the plasma membrane of mesophyll cells, but not in chloroplasts, indicating reactive oxygen species other than H2O2 as direct responsible for the oxidative stress observed in the chloroplasts of drought‐stressed senescing leaves. The strong degradation of β‐carotene and α‐tocopherol suggests an enhanced formation of singlet oxygen as the putative reactive oxygen species responsible for oxidative stress to senescing chloroplasts. This study demonstrates that oxidative stress in chloroplasts mediates drought‐induced leaf senescence in sage growing in Mediterranean field conditions.
Osmolyte accumulation: can it really help increase crop yield under drought conditions?
Authors: Serraj R. , Sinclair T. R. 
Published: March 2003

AbstractOsmolyte accumulation (OA) is frequently cited as a key putative mechanism for increasing yields of crops subjected to drought conditions. The hypothesis is that OA results in a number of benefits that sustain cell and tissue activity under water‐deficit conditions. It has been proposed as an effective tolerance mechanism for water deficits, which could be enhanced in crops by traditional plant breeding, marker‐assisted selection or genetic engineering, to generate drought‐tolerant crops. However, field studies examining the association between OA and crop yield have tended to show no consistent benefit. The few, often‐cited, investigations with positive associations were obtained under severe water deficits with extremely low yields or conditions with special water‐supply scenarios when much of the benefit is plant survival. Under conditions where water deficits threaten crop survival, yields are so low that even large fractional yield gains offer little practical benefit to growers. Indeed, the often‐cited benefit of turgor maintenance in cells is likely to result in crop behaviour that is exactly opposite to what is beneficial to crops. The one clear mechanism identified in this review for beneficial yield responses to OA is in the maintenance of root development in order to reach water that may be available deeper in the soil profile.
Water uptake profile response of corn to soil moisture depletion
Authors: Li Y. , Fuchs M. , Cohen S. , Cohen Y. , Wallach R. 
Published: March 2003

AbstractThe effects of soil moisture distribution on water uptake of drip‐irrigated corn were investigated by simultaneously monitoring the diurnal evolution of sap flow rate in stems, of leaf water potential, and of soil moisture, during intervals between successive irrigations. The results invalidate the steady‐state resistive flow model for the continuum. High hydraulic capacitance of wet soil and low hydraulic conductivity of dry soil surrounding the roots damped significantly diurnal fluctuations of water flow from bulk soil to root surface. By contrast, sap flow responded directly to the large diurnal variation of leaf water potential. In wet soil, the relation between the diurnal courses of uptake rates and leaf water potential was linear. Water potential at the root surface remained nearly constant and uniformly distributed. The slope of the lines allowed calculating the resistance of the hydraulic path in the plant. Resistances increased in inverse relation with root length density. Soil desiccation induced a diurnal variation of water potential at the root surface, the minimum occurring in the late afternoon. The increase of root surface water potential with depth was directly linked to the soil desiccation profile. The development of a water potential gradient at the root surface implies the presence of a significant axial resistance in the root hydraulic path that explains why the desiccation of the soil upper layer induces an absolute increase of water uptake rates from the deeper wet layers.
Role of leaf apoplast in silicon‐mediated manganese tolerance of Cucumis sativus L.
Authors: Rogalla H. , Römheld V. 
Published: March 2003

AbstractSilicon (Si) supplied as sodium silicate (1·8 mm) clearly decreased symptoms of manganese (Mn) toxicity in Cucumis sativus L. (cv. Chinesische Schlange) grown in nutrient solution with low to elevated Mn concentrations (0·5–1000 µm). Despite approximately the same total Mn content in the leaves, plants not treated with Si had higher Mn concentrations in the intercellular washing fluid (IWF) compared with plants treated with Si, especially in the BaCl2‐ and DTPA‐exchangeable fraction of the leaf apoplast. The Mn concentration of the IWF correlated positively with the severity of Mn‐toxicity symptoms and negatively with the Si supply. Furthermore, in Si‐treated plants less Mn was located in the symplast (< 10%) and more Mn was bound to the cell wall (> 90%) compared with non‐Si‐treated plants (about 50% in each compartment). Manganese present in Si‐treated plants is therefore less available and for this reason less toxic than in plants not treated with Si. It is concluded that Si‐mediated tolerance of Mn in C. sativus is a consequence of stronger binding of Mn to cell walls and a lowering of Mn concentration within the symplast. These results support the role of Si as an important beneficial element in plant nutrition.
Use of decreasing foliar carbon isotope discrimination during water limitation as a carbon tracer to study whole plant carbon allocation
Authors: Arndt S. K. , Wanek W. 
Published: March 2003

AbstractFoliar carbon isotope discrimination (Δ) of C3 plants decreases in water‐deficit situations as discrimination by the photosynthetic primary carboxylation reaction decreases. This diminished Δ in leaves under water deficit can be used as a tracer to study whole plant carbon allocation patterns. Carbon isotope composition (δ13C value) of leaf hot water extracts or leaf tissue sap represents a short‐term integral of leaf carbon isotope discrimination and thus represents the δ13C value of source carbon that may be distributed within a plant in water‐deficit situations. By plotting the δ13C values of source carbon against the δ13C values of sink tissues, such as roots or stems, it is possible to assess carbon allocation to and incorporation into sink organs in relation to already present biomass. This natural abundance labelling method has been tested in three independent experiments, a one‐year field study with the fruit tree species Ziziphus mauritiana and peach (Prunus persica), a medium‐term drought stress experiment with Ziziphus rotundifolia trees in the glasshouse, and a short‐term drought stress experiment with soybean (Glycine max). The data show that the natural abundance labelling method can be applied to qualitatively assess carbon allocation in drought‐stressed plants. Although it is not possible to estimate exact fluxes of assimilated carbon during water deficit the method represents an easy to use tool to study integrated plant adaptations to drought stress. In addition, it is a less laborious method that can be applied in field studies as well as in controlled experiments, with plants from any developmental stage.
Development of conventional and quantitative real‐time PCR assays for the detection and identification of Rhizoctonia solani AG‐3 in potato and soil
Authors: Lees A. K. , Cullen D. W. , Sullivan L. , Nicolson M. J. 
Published: March 2003

A specific and sensitive PCR assay was developed for the detection and identification of Rhizoctonia solani AG‐3, the main causal pathogen of stem canker and black scurf of potato. A conventional primer set (Rs1F2 and Rs2R1) was designed from the nuclear ribosomal internal transcribed spacer (ITS1 and ITS2) regions of R. solani. Following PCR amplification, a 0·5‐kb product was amplified from DNA of all isolates of AG‐3 using primers Rs1F2 and Rs2R1. No product was amplified when DNA from isolates belonging to a range of other R. solani anastomosis groups or from a selection of other potato pathogens was tested, confirming the specificity of the primers for AG‐3 only. Rhizoctonia solani AG‐3 was also detected in potato tissue with varying black scurf severity, and in soil inoculated with sclerotia of R. solani to a minimum detection level of 5 × 10−4 g sclerotia/g soil. In addition, specific primers RsTqF1 (based on the Rs1F2 sequence) and RsTqR1, and a TaqMan™ fluorogenic probe RQP1, were designed to perform real‐time quantitative (TaqMan) PCR. The conventional PCR and real‐time PCR assays were compared and combined with direct DNA extraction from soil and a seed‐baiting method to determine the most reliable method for the detection and quantification of AG‐3 in both artificially inoculated field soil and naturally infested soils. It was shown that direct DNA extractions from soil could be problematic, although AG‐3 was detectable using this method combined with the real‐time PCR assay. The amplification of Rhizoctonia solani by seed baiting increased the sensitivity of the assay compared with direct extraction of DNA from the soil, and AG‐3 was detectable in artificially inoculated and naturally infested soils when seed baiting was combined with either the conventional PCR or the real‐time PCR assay. The potential for using these rapid and quantitative AG‐3‐specific assays to address epidemiological questions and as tools for decision‐making in disease management is discussed.
Detection of Strawberry crinkle virus in plants and aphids by RT‐PCR using conserved L gene sequences
Authors: Posthuma K. I. , Adams A. N. , Hong Y. , Kirby M. J. 
Published: March 2003

About 10% of the large (L) protein gene of Strawberry crinkle virus (SCV) was sequenced after amplification with degenerate primers designed to conserved regions of the rhabdovirus L protein. The virus sequence was extended to 1362 nucleotides through rapid amplification of cDNA ends. One pair of degenerate L gene primers amplified a 683‐bp fragment from four different isolates of SCV cultured in the experimental host Physalis pubescens; the nucleotide sequences of these fragments differed by < 1% to 10% indicating the suitability of this region as a diagnostic target. This information enabled the development of a reverse transcription polymerase chain reaction (RT‐PCR) detection method for SCV using primers designed to the L gene sequence. SCV was amplified from infected P. pubescens (573 bp fragment) and from infected Chaetosiphon fragaefolii aphids (770 bp fragment). SCV was also detected by RT‐PCR in total RNA extracts from three strawberry plants showing symptoms typical of SCV infection but failed when the intensity of the disease symptoms decreased. However, both SCV positive‐sense RNA, and negative‐sense genomic RNA, were detected by nested PCR in chronically infected strawberry plants sampled in September.
Potato latent virus: a proposed new species in the genus Carlavirus
Authors: Brattey C. , Badge J. L. , Burns R. , Foster G. D. , George E. , Goodfellow H. A. , Mulholland V. , McDonald J. G. , Jeffries C. J. 
Published: March 2003

A previously undescribed carlavirus, potato latent virus (PotLV), was found infecting the potato cultivar Red La Soda imported from the USA. The particles were filamentous and slightly curved, with modal lengths of 530 and 670 nm. The 11 kDa protein encoded downstream from the coat protein contained a ‘zinc‐finger’ motif characteristic of carlaviruses, and RT–PCR using a carlavirus‐specific primer gave a PCR product of 857 bp. Antibodies produced to PotLV did not detect other carlaviruses when used in ELISA and the coat‐protein nucleic acid sequence of PotLV showed < 67% similarity with the other carlaviruses tested. The closest similarity was with the Andean strain of potato virus S. Unusually for a carlavirus, PotLV systemically infected Nicotiana bigelovii, N. glutinosa, N. rustica, N. tabacum and Physalis floridana.
Movement of Xanthomonas campestris pv. vitians in the stems of lettuce and seed contamination
Authors: Barak J. D. , Koike S. T. , Gilbertson R. L. 
Published: March 2003

Xanthomonas campestris pv. vitians, the causal agent of bacterial leaf spot of lettuce (BLS), can be seedborne, but the mechanism by which the bacteria contaminates and/or infects lettuce seed is not known. In this study, the capacity of X. campestris pv. vitians to enter and translocate within the vascular system of lettuce plants was examined. The stems of 8‐ to 11‐week‐old lettuce plants were stab‐inoculated, and movement of X. campestris pv. vitians was monitored at various intervals. At 4, 8, 12 and 16 h post‐inoculation (hpi), X. campestris pv. vitians was recovered from 2 to 10 cm above (depending on stem length) and 2 cm below the inoculation site. Xanthomonas campestris pv. vitians was also recovered from surface‐disinfested stem sections of spray‐inoculated plants. Together, these results are consistent with X. campestris pv. vitians invading and moving systemically within the vascular system of lettuce plants. To investigate the mechanism of seed contamination, lettuce plants at the vegetative stage of growth were spray‐inoculated with X. campestris pv. vitians and allowed to develop BLS. Seed collected from these plants had a 2% incidence of X. campestris pv. vitians external colonization, but no bacteria were recovered from within the seed.
Autoantibody to the Leucine Zipper Region of 52 kDa Ro/SSA Binds Native 60 kDa Ro/SSA: Identification of a Tertiary Epitope with Components from 60 kDa Ro/SSA and 52 kDa Ro/SSA
Authors: Kurien B. T. , Chambers T. L. , Thomas P. Y. , Frank M. B. , Scofield R. H. 
Published: March 2003

Anti‐Ro (or SSA) is found in the sera of patients with autoimmune rheumatic illnesses. All patients with anti‐Ro defined by precipitation bind a 60 000 Da antigen (60 kDa Ro), whereas some patients also bind a 52 000 Da molecule (52 kDa Ro). In general, antibody binding is directed against native 60 kDa Ro and denatured 52 kDa Ro. The mechanism by which anti‐52 kDa Ro arises in the setting of anti‐60 kDa Ro is unknown. Conflicting data exist as to the existence of a physical interaction between the two proteins in cells and as to cross‐reacting antibodies. Antibodies were affinity purified from a peptide within the leucine zipper region of 52 kDa Ro. These purified antibodies binding the 197–207 peptide from 52 kDa Ro (anti‐52LZ) bound native 60 kDa Ro as well as denatured 52 kDa Ro. In addition, anti‐52LZ also bound up to four regions from the sequence of 60 kDa Ro and a single conformational epitope of 60 kDa Ro. Thus, these primary sites represent components of the tertiary epitope. We hypothesized that if this was the case, these peptides making up a tertiary epitope would show molecular interaction. In fact, peptides from 60 kDa Ro have a molecular interaction with the 52 kDa Ro peptide as well as full‐length 52 kDa Ro when assessed by surface plasmon resonance. The leucine‐zipper region peptide from 52 kDa Ro bound three of the four peptides from 60 kDa Ro. These data suggest that these two molecular species, 60 and 52 kDa Ro, form a conformational epitope. This relationship may explain why anti‐52 kDa Ro is found in association with anti‐60 kDa Ro.
Connectivity Patterns in Tuberculosis and Leprosy Patients are Indistinguishable from that of Healthy Donors
Authors: Tovar‐Rivera T. , Sánchez‐Colón S. , Padierna‐Olivos L. , Massó‐Rojas F. , Estrada‐Parra S. , Mondragón‐González R. , Jiménez‐Martínez M. C. , Sánchez‐García F. J. 
Published: March 2003

Connectivity, the self‐defined interactions between antigen‐recognising molecules in a network system can in part be assessed by measuring the reactivity of a given serum against an ordered set of immunoglobulin (Ig)G F(ab′)2 fractions, separated by means of isoelectric focusing so that, the serum reactivity against the whole set of fractions defines a characteristic pattern of connectivity. Deviations from the normal condition (healthy donors) have so far been documented for two autoimmune diseases: systemic lupus erythematosus (SLE) and pemphigus vulgaris, as well as for human immundeficiency virus (HIV)‐1 infection. We tested here if bacterial infections lead to alterations in connectivity. In addition, we wanted to test if two antigenically related bacteria would produce similar or otherwise distinctive connectivity patterns. Connectivity analysis was applied on the sera from tuberculosis and leprosy patients and the sera from healthy donors were used as control.No statistically significant differences between the three groups studied were found. These results have implications for theories that set the origin of autoimmune diseases in microbial infections. To the best of our knowledge, this is the first attempt to analyze the connectivity status in bacterial infections.
Clonal Analysis of a Human Antimouse Antibody (HAMA) Response
Authors: Thorpe S. J. , Turner C. , Heath A. , Feavers I. , Vatn I. , Natvig J. B. , Thompson K. M. 
Published: March 2003

AbstractCirculating human antimouse antibodies (HAMAs) directed to mouse immunoglobulin G (IgG) are clinically significant, compromising mouse antibody therapy and imaging, and interfering in immunological assays. To investigate the HAMA response, 20 stable cell lines secreting human monoclonal antibodies reactive with mouse IgG were established from a donor with a history of exposure to mice. Their subclass and domain specificities were established by solid‐phase binding, indirect haemagglutination assays and immunoblotting, using Igs of known subclass and Ig fragments. The heavy‐chain variable region gene usage was determined for 12 HAMAs.Eight HAMAs were IgM, 11 HAMAs were IgG4 and one HAMA was IgG1, indicating an IgG4‐dominated response. All of the IgG HAMAs reacted with epitopes present on the Fc portion; one was subclass‐specific, nine were subclass‐restricted and two were pan‐IgG‐reactive. Measurement of their affinities gave dissociation constants typically in the nanomolar range. Seven and five HAMAs were derived from variable heavy‐chain 3 (VH3) and VH1 gene segments, respectively. The IgG HAMAs used different VH segments to the IgM HAMAs. JH regions were coded by JH4 in eight HAMAs. DH segment usage appeared to be restricted in the IgM HAMAs. Two IgG HAMAs were clonally related. These monoclonal HAMAs are potentially useful as reagents for detecting mouse IgG and as reference reagents for the investigation of the HAMA response in patients undergoing mouse monoclonal antibody therapy and for the investigation of the influence of HAMAs on immunodiagnostic tests.