bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of the phosphatase activities of mosses in relation to their environment
Authors: Turner B. L. , Baxter R. , Ellwood N. T. W. , Whitton B. A. 
Published: March 2003

AbstractPhosphatase activities and environmental features were characterized for 12 terrestrial and aquatic mosses in upland northern England, along with four species sampled from subarctic Sweden. Phosphomonoesterase (PMEase) and phosphodiesterase (PDEase) activities of shoot tips were measured using para‐nitrophenyl phosphate (p‐NPP) and bis‐pNPP. All species showed PMEase activity, but not all showed PDEase activity. The mean pH optimum was 5·0 for PMEase and 5·7 for PDEase. The kinetic parameters Km and Vmax were calculated from three linear transformations of the Michaelis–Menten equation. The mean Km values of the mosses ranged between 77 and 468 µm for PMEase and 26 and 414 µm for PDEase. The corresponding Vmax values were 0·6–205 µmol pNP g−1 DW h−1 for PMEase and 1·4–110 µmol pNP g−1 DW h−1 for PDEase. Mosses from Sweden displayed greater Km and smaller Vmax values than those from England. The aquatics Fontinalis antipyretica and Rhynchostegium riparioides displayed two‐phase kinetics for PMEase and PDEase, with Km and Vmax being dependent on substrate concentration. Staining suggested that PMEase activity was located in the cell wall of most mosses. Phosphatase assays provide a rapid method for screening environmental nutrient status and a standard procedure is recommended.
Hydraulic properties and freezing‐induced cavitation in sympatric evergreen and deciduous oaks with contrasting habitats
Authors: Cavender‐Bares J. , Holbrook N. M. 
Published: March 2003

AbstractWe investigated the hydraulic properties in relation to soil moisture, leaf habit, and phylogenetic lineage of 17 species of oaks (Quercus) that occur sympatrically in northern central Florida (USA). Leaf area per shoot increased and Huber values (ratio of sapwood area to leaf area) decreased with increasing soil moisture of species’ habitats. As a result, maximum hydraulic conductance and maximum transpiration were positively correlated with mean soil moisture when calculated on a sapwood area basis, but not when calculated on a leaf area basis. This reveals the important role that changes in allometry among closely related species can play in co‐ordinating water transport capacity with soil water availability. There were significant differences in specific conductivity between species, but these differences were not explained by leaf habit or by evolutionary lineage. However, white oaks had significantly smaller average vessel diameters than red oaks or live oaks. Due to their lower Huber values, maximum leaf specific conductivity (KL) was higher in evergreen species than in deciduous species and higher in live oaks than in red oaks or white oaks. There were large differences between species and between evolutionary lineages in freeze–thaw‐induced embolism. Deciduous species, on average, showed greater vulnerability to freezing than evergreen species. This result is strongly influenced by evolutionary lineage. Specifically, white oaks, which are all deciduous, had significantly higher vulnerability to freezing than live oaks (all evergreen) and red oaks, which include both evergreen and deciduous species. These results highlight the importance of taking evolutionary lineage into account in comparative physiological studies.
Analysis of carbohydrate metabolism of CPD antisense plants and the brassinosteroid‐deficient cbb1 mutant
Authors: Schlüter U. , Köpke D. , Altmann T. , Müssig C. 
Published: March 2003

AbstractBrassinosteroids (BRs) are essential regulators of growth and development. BR‐deficient mutants such as cpd/cbb3 and dwf4 display extreme dwarfism due to a failure in cell elongation. To avoid the severe pleiotropic effects caused by the extreme growth defect, transgenic Arabidopsis lines carrying a construct for antisense inhibition of CPD gene expression were established and subjected to physiological analysis. The CPD‐antisense (α‐CPD) lines display characteristic phenotypic alterations of BR‐deficient plants such as reduced stem and petiole growth, smaller leaves, and a slightly delayed development. The observed changes are intermediate between the corresponding loss‐of‐function mutant (cbb3) and wild‐type plants. In the present study, the primary carbon metabolism of the transgenic lines as well as the BR‐deficient cbb1 (dwf1‐6/dim) mutant was analysed. Gas exchange measurements indicated a reduced assimilatory capacity of the α‐CPD plants. Soil‐grown α‐CPD as well as cbb1 (dwf1‐6) mutant plants show a clear reduction in starch content. The metabolic alterations are accompanied by altered enzyme activities such as reduced invertase and cytosolic β‐amylase activity, and altered expression patterns of genes such as Atbfruct1, Asus1, and ct‐Bmy (encoding a cell wall invertase, sucrose synthase, and plastidic β‐amylase, respectively). The impaired carbon assimilation, as well as the altered enzyme activities and gene expression patterns in the α‐CPD and cbb1 (dwf1‐6) plants, demonstrate the necessity of normal CPD and DIM expression for proper carbon uptake and metabolism and may point to an essential function of BRs. The impaired growth of BR‐deficient plants may be (at least in part) due to reduced photosynthesis.
DNA damage and photosynthesis in Antarctic and Arctic Sanionia uncinata (Hedw.) Loeske under ambient and enhanced levels of UV‐B radiation
Authors: LUD D. , MOERDIJK T. C. W. , VAN DE POLL W. H. , BUMA A. G. J. , HUISKES A. H. L. 
Published: March 2003

AbstractThe response of the bipolar moss Sanionia uncinata (Hedw.) Loeske to ambient and enhanced UV‐B radiation was investigated at an Antarctic (Léonie Island, 67°35′ S, 68°20′ W) and an Arctic (Ny‐Alesund, 78°55′ N, 11°56′ E) site, which differed in ambient UV‐B radiation (UV‐BR: 280–320 nm) levels. The UV‐BR effects on DNA damage and photosynthesis were investigated in two types of outdoor experiments. First of all, sections of turf of S. uncinata were collected in an Arctic and Antarctic field site and exposed outdoors to ambient and enhanced UV‐BR for 2 d using UV‐B Mini‐lamps. During these experiments, chlorophyll a fluorescence, chlorophyll concentration and cyclobutyl pyrimidine dimer (CPD) formation were measured. Secondly, at the Antarctic site, a long‐term filter experiment was conducted to study the effect of ambient UV‐BR on growth and biomass production. Additionally, sections of moss turf collected at both the Antarctic and the Arctic site were exposed to UV‐BR in a growth chamber to study induction and repair of CPDs under controlled conditions. At the Antarctic site, a summer midday maximum of 2·1 W m−2 of UV‐BR did not significantly affect effective quantum yield (ΔF/Fm′) and the ratio of variable to maximal fluorescence (Fv/Fm). The same was found for samples of S. uncinata exposed at the Arctic site, where summer midday maxima of UV‐BR were about 50% lower than at the Antarctic site. Exposure to natural UV‐BR in summer did not increase CPD values significantly at both sites. Although the photosynthetic activity remained largely unaffected by UV‐B enhancement, DNA damage clearly increased as a result of UV‐B enhancement at both sites. However, DNA damage induced during the day by UV‐B enhancement was repaired overnight at both sites. Results from the long‐term filter experiment at the Antarctic site indicated that branching of S. uncinata was reduced by reduction of ambient summer levels of UV‐BR, whereas biomass production was not affected. Exposure of specimens collected from both sites to UV‐BR in a growth chamber indicated that Antarctic and Arctic S. uncinata did not differ in UV‐BR‐induced DNA damage. It was concluded that S. uncinata from both the Antarctic and the Arctic site is well adapted to ambient levels of UV‐BR.
Molecular characterization of Endothia gyrosa isolates from Eucalyptus in South Africa and Australia
Authors: Venter M. , Wingfield M. J. , Coutinho T. A. , Wingfield B. D. 
Published: March 2003

Endothia gyrosa is a canker pathogen best known as the causal agent of pin oak blight in North America, and causes cankers on other woody hosts such as Castanea spp. and Liquidambar spp. In South Africa, Australia and Tasmania, a fungus identified as E. gyrosa has been recorded on Eucalyptus spp. Some morphological differences exist between the North American fungus and the isolates from Eucalyptus. Phylogenetic relationships between E. gyrosa from North America and E. gyrosa from South Africa and Australia, as well as that of the related fungi Cryphonectria parasitica and C. cubensis, were studied using PCR‐based restriction fragment length polymorphism (RFLP) and sequences of the internal transcribed spacer (ITS) region of the rRNA operon. Endothia gyrosa isolates from South Africa produced the same RFLP banding patterns as those from Australia, which differed markedly from North American isolates of E. gyrosa. In a phylogram based on the DNA sequences, the Australian and South African isolates of E. gyrosa resided in a single, well resolved clade, distinct from North American isolates. Isolates of C. parasitica grouped in the same clade as the South African and Australian isolates of E. gyrosa, but C. cubensis was distantly related to them. The molecular data suggest that the E. gyrosa isolates from South Africa and Australia represent a distinct taxon, and probably belong to the genus Cryphonectria.
Detection of Colletotrichum coccodes from soil and potato tubers by conventional and quantitative real‐time PCR
Authors: Cullen D. W. , Lees A. K. , Toth I. K. , Duncan J. M. 
Published: March 2003

Colletotrichum coccodes is the causal agent of the potato blemish disease black dot. Two PCR primer sets were designed to sequences of the ribosomal internal transcribed spacer (ITS1 and ITS2) regions for use in a nested PCR. The genus‐specific outer primers (Cc1F1/Cc2R1) were designed to regions common to Colletotrichum spp., and the species‐specific nested primers (Cc1NF1/Cc2NR1) were designed to sequences unique to C. coccodes. The primer sets amplified single products of 447 bp (Cc1F1/Cc2R1) and 349 bp (Cc1NF1/Cc2NR1) with DNA extracted from 33 European and North American isolates of C. coccodes. The specificity of primers Cc1NF1/Cc2NR1 was confirmed by the absence of amplified product with DNA of other species representing the six phylogenetic groups of the genus Colletotrichum and 46 other eukaryotic and prokaryotic plant pathogenic species. A rapid procedure for the direct extraction of DNA from soil and potato tubers was used to verify the PCR assay for detecting C. coccodes in environmental samples. The limit of sensitivity of PCR for the specific detection of C. coccodes when inoculum was added to soils was 3·0 spores per g, or the equivalent of 0·06 microsclerotia per g soil, the lowest level of inoculum tested. Colletotrichum coccodes was also detected by PCR in naturally infested soil and from both potato peel and peel extract from infected and apparently healthy tubers. Specific primers and a TaqMan fluorogenic probe were designed to perform quantitative real‐time (TaqMan) PCR to obtain the same levels of sensitivity for detection of C. coccodes in soil and tubers during a first‐round PCR as with conventional nested PCR and gel electrophoresis. This rapid and quantitative PCR diagnostic assay allows an accurate estimation of tuber and soil contamination by C. coccodes.
Phytophthora infestans's 10‐year truce with Holland: a long‐term analysis of potato late‐blight epidemics in the Netherlands
Authors: Zwankhuizen M. J. , Zadoks J. C. 
Published: March 2003

A sequence of 47 potato late‐blight (Phytophthora infestans) epidemics in the Netherlands, from 1950 to 1996, was analysed using agronomic and meteorological variables. The intensity of annual epidemics was characterized by an index of disease intensity (DI, 0 = absence of late blight; 4 = severe epidemic). Three periods were identified, with average DIs of 2·9, 0 and 2, respectively. Period I (1950–68) had relatively regular epidemics; period II (1969–78) was virtually blight free; and period III (1979–96) showed large variations in disease intensity. Disease‐enhancing factors were number of days with precipitation, and number of hours with temperatures between 10 and 27°C and relative humidity >90% during the growing season. Limiting factors were number of hours with temperatures >27°C, and amount of global radiation. Linear discriminant analysis of DI using the blight status of the previous year and meteorological variables correctly classified up to 40 years out of 47 (87·0%), with five out of the six incorrectly classified years falling in period III. Blight status of the previous year and number of days with precipitation were important discriminating variables.
A Role for Complement C5 in Organism Containment and Granulomatous Response during Murine Tuberculosis
Authors: Actor J. K. , Breij E. , Wetsel R. A. , Hoffmann H. , Hunter Jr R. L. , Jagannath C. 
Published: March 2003

The molecular mechanisms underlying protective granuloma formation and control of bacterial growth during infection with Mycobacterium tuberculosis (MTB) are not yet completely understood. MTB‐infected mice with natural deficiency in complement component C5 are unable to develop productive granulomatous responses, and are impaired in limiting organism growth within the lung. To address the molecular basis for this histologic dysfunction, congenic complement C5‐sufficient (B10.D2‐H2d H2‐T18c Hcl/nSnJ) and complement C5‐deficient strains (B10.D2‐H2d H2‐T18c Hco/oSnJ) congenic mice were infected with Mycobacterium tuberculosis, and cytokine and chemokine responses were examined. Twelve and 28 days after infection, lungs showed elevated messages for multiple inflammatory cytokines in both congenic strains. Interleukin (IL)‐12(p40) mRNA was also induced during infection in C5‐deficient mice, although levels were significantly decreased compared to C5‐sufficient congenics. C5‐deficient mice also demonstrated reduced KC, MIP‐2, IP‐10, and MCP‐1 mRNA. The defect may directly involve C5‐mediated effects on macrophage responses; C5‐deficient bone marrow derived macrophages had significantly reduced secretion of KC, MIP‐1α and MIP‐2 compared to C5‐sufficient macrophages following in vitro infection. These findings indicate a role for C5 in mediation of chemotactic and activation events that are the basis for granulomatous responses during murine tuberculosis.
Self‐Peptides with Intermediate Capacity to Bind and Stabilize MHC Class I Molecules may be Immunogenic
Authors: Andersen M. L. M. , Ruhwald M. , Nissen M. H. , Buus S. , Claesson M. H. 
Published: March 2003

AbstractThirty self‐peptides were selected on the basis of their predicted binding to H‐2b molecules. The binding of peptides was ascertained experimentally by biochemical (KD measurements) and cellular [major histocompatibility complex class I (MHC‐I) stabilization] assays. A weak, but significant, correlation between KD measurements and MHC‐I stabilization was observed. Mice (n = 99) were immunized with individual peptides. Twenty‐eight peptides were found to induce peptide‐specific cytotoxic activity, and a total of 84 mice developed significant cytotoxic T lymphocyte (CTL) responses after immunization. Only one of the 21 mice immunized with high‐affinity peptides developed a peptide‐specific CTL response of 29 lytic units per 106 splenocytes, whereas 11 of the 42 mice immunized with intermediate‐affinity peptides developed peptide‐specific CTL responses at this level (P < 0.05). These observations suggest the absence of tolerance towards most MHC‐I‐restricted self‐peptides and that strong antiself immunity can be generated preferentially towards self‐peptides with an intermediate affinity for MHC‐I. These data should be considered in the design of tumour vaccines based on MHC‐I‐binding self‐peptides.
Novel Specificity of Anti‐U1A Autoimmune Patient Sera
Authors: Faig O. Z. , Lutz C. S. 
Published: March 2003

AbstractWe have previously described a novel complex of proteins which contains the U1snRNP‐A protein (U1A) but no other small nuclear ribonucleoprotein particle (snRNP) components (O'Connor et al., RNA 1997;3:1444–55). Antibodies to this novel complex inhibit both splicing and polyadenylation in vitro of a test pre‐mRNA (O'Connor et al., RNA 1997;3:1444–55; Lutz et al., RNA 1998;4:1493–9). This novel complex of proteins was identified using an unusual mouse monoclonal antibody (MoAb), called MAb 12E12. We were interested to know if autoimmune patient sera were similar to this MoAb. We have discovered a novel specificity of systemic lupus erythematosus patient sera reminiscent of MAb 12E12 in that the patient serum, like 12E12, (1) does not recognize U1A when bound to U1 RNA, (2) recognizes primarily the epitopes in the amino‐terminal third of the protein, including RNA recognition motif 1 (RRM1) and (3) inhibits in vitro polyadenylation. These findings may lead to the discovery of previously undescribed autoantigens as components of the novel protein complex, and may provide insight into autoimmune diseases.
Downregulation of Mac‐1 Expression in Monocytes by Surface‐Bound IgG
Authors: Fernández‐Calotti P. X. , Salamone G. , Gamberale R. , Trevani A. , Vermeulen M. , Geffner J. , Giordano M. 
Published: March 2003

AbstractPhysical and functional association between the β2‐integrin Mac‐1 (CD11b/CD18) and receptors of immunoglobulin G (IgG) (FcγRs) has been previously reported. In this study, we examined the modulation of Mac‐1 expression by IgG in different leucocyte populations. Our data show that human monocytes, but not neutrophils, macrophages, dendritic or natural killer cells, downregulate the expression of Mac‐1 after overnight exposure to surface‐bound IgG. This effect, which requires at least 6 h of incubation, is not associated with a general downmodulation of membrane antigens, and is selectively induced by immobilized IgG (iIgG), as the stimulation of monocytes with N‐formyl‐methionyl‐leucyl‐phenylalanine, lipopolysaccharide, tumour necrosis factor‐α (TNF‐α) or soluble IgG did not modify the Mac‐1 expression after 18 h in culture. The loss of Mac‐1 was completely prevented by blocking antibodies (Abs) directed to FcγRII (CD32) or CD18. On the other hand, the serine protease inhibitor, phenyl methyl sulphonyl fluoride, but not inhibitors of cysteine proteases or neutral endopeptidases, partially prevented the downregulation of Mac‐1 by iIgG. Monocytes cultured overnight on iIgG exhibited a dramatic decrease in their capacity to ingest zymosan particles that could be attributed to the reduced expression of Mac‐1. However, there was no inhibition of TNF‐α production induced by zymosan, suggesting that Mac‐1‐dependent responses require different levels of its expression to be fully activated.
Characterization of DNA sequences that mediate nuclear protein binding to the regulatory region of the Pisum sativum (pea) chlorophyl a/b binding protein gene AB80: identification of a repeated heptamer motif
Authors: Argüello Gerardo , García‐Hernández Enrique , Sánchez Mireya , Gariglio Patricio , Herrera‐Estrella Luis , Simpson June 
Published: March 2003

SummaryTwo protein factors binding to the regulatory region of the pea chlorophyl a/b binding protein gene AB80 have been identified. One of these factors is found only in green tissue but not in etiolated or root tissue. The second factor (denominated ABF‐2) binds to a DNA sequence element that contains a direct heptamer repeat TCTCAAA. It was found that presence of both of the repeats is essential for binding. ABF‐2 is present in both green and etiolated tissue and in roots and factors analogous to ABF‐2 are present in several plant species. Computer analysis showed that the TCTCAAA motif is present in the regulatory region of several plant genes.
The in‐vitro synthesized tomato shikimate kinase precursor is enzymatically active and is imported and processed to the mature enzyme by chloroplasts
Authors: Schmid Jürg , Schaller Andreas , Leibinger Urs , Boll Werner , Amrhein Nikolaus 
Published: March 2003

SummaryFull‐length cDNA clones encoding shikimate kinase (EC 2.7.1.71), an enzyme of the central section of the shikimate pathway, have been isolated from tomato (Lycopersicon esculentum L., cv. UC82b). The open reading frame has the capacity to encode a peptide of 300 amino acids. The in‐vitro synthesized peptide catalysed the phosphorylation of shikimate thus confirming the identity of the isolated cDNA clones. The N‐terminal portion of the deduced amino acid sequence resembles known chloroplast‐specific transit peptides. The existence of such a transit peptide was proven by the uptake of the in‐vitro synthesized peptide as well as its processing by isolated chloroplasts. Multiple sites of polyadenylation were observed in shikimate kinase mRNAs. The results of Northern and Southern blot analyses are consistent with the existence of only one shikimate kinase gene per haploid genome in tomato. These results are discussed with respect to the dual pathway hypothesis of the shikimate pathway in higher plants.
Procedure for whole mount fluorescence in situ hybridization of interphase nuclei on Arabidopsis thaliana
Authors: Bauwens Serge , Katsanis Katerina , Van Montagu Marc , Van Oostveldt Patrick , Engler Gilbert 
Published: March 2003

SummaryA procedure for whole mount fluorescence in situ hybridization (FISH) on plant tissue is reported. The technique was demonstrated on seedlings and flowers of Arabidopsis thaliana L. with rDNA as a probe, labelled, both for direct and indirect detection. It was found that fixation in 1% formaldehyde yielded the best results with respect to morphology and hybridization efficiency. The combination of whole mount FISH and confocal scanning laser microscopy allowed the nuclear localization of the rDNA loci in all tissues of both seedlings and flowers. Direct labelling yielded the best signal‐to‐noise ratio, especially in the apical zones of the seedlings. The technique was further illustrated on seedlings of A. thaliana in double labelling experiments with rDNA and a tandemly repeated, 500 bp sequence of A. thaliana. Although nuclei in all tissues in the seedling exhibited both signals, hybridization efficiency for both signals was reduced in the dense, apical zones as compared with single labelling experiments with rDNA.
A laccase‐like phenoloxidase is correlated with lignin biosynthesis in Zinnia elegans stem tissues
Authors: Liu Lan , Dean Jeffrey F.D. , Friedman William E. , Eriksson Karl‐Erik L. 
Published: March 2003

SummaryStem tissues from different internodes of 4–6 week‐old Zinnia elegans cv. Envy plants were sectioned and stained with chromogenic substrates previously used in studies of laccases (p‐diphenol:O2 oxidoreductases) isolated from tree tissues. The pattern of color development found when stem sections were stained in the presence and absence of H2O2 suggested that p‐diphenol:O2 oxidoreductase activity was tightly correlated spatially and temporally with the lignification of secondary cell walls in developing primary xylem. The correlation between this laccase‐like phenoloxidase activity and lignification appeared tighter than that between lignification and peroxidases stained using the same substrates. Zymogram analysis of the phenoloxidase activities catalyzed by enzymes that were not boiled prior to separation by SDS—PAGE suggested that a single enzyme was predominantly responsible for the laccase‐like phenoloxidase activity in Zinnia stems. Some of this enzyme was released from cell wall residue by washing with high ionic strength buffer; however, substantial amounts of the enzyme could only be recovered after treatment of the residue with cell wall‐degrading enzymes. This phenoloxidase appears to share significant characteristics with the coniferyl alcohol oxidase isolated from developing secondary xylem in pines, which suggests that such enzymes may be widespread in vascular plants.