bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fine scale distribution of ectomycorrhizal fungi and roots across substrate layers including coarse woody debris in a mixed forest
Authors: Tedersoo Leho , Kõljalg Urmas , Hallenberg Nils , Larsson Karl‐Henrik 
Published: June 2003

Summary• Ectomycorrhizal (ECM) fungi are widespread plant root symbionts in boreal forests, but information is lacking on the fine scale distribution of roots and fungi in substrate patches of different quality, including coarse woody debris (CWD).• Wood and soil cores were taken systematically both horizontally and vertically through decayed logs and underlying soil layers in a mixed forest. Root tips were counted and ECM fungi identified by morphotyping and sequencing.• The abundance of root tips and ECM fungi was highly variable on a 5‐cm scale. Most species were replaced on a 50‐cm scale. Detrended correspondence analysis demonstrated strong preference of resupinate thelephoroid and athelioid fungi and Sebacinaceae for CWD, whereas ascomycetes and euagarics appeared more frequently in mineral soil. Clavulicium delectabile was determined to be an ECM fungus for the first time.• ECM fungi occupy different niches and show variable distribution patterns. CWD plays an important role as a habitat both for roots and ECM fungi. We suggest sampling larger soil cores and selecting random root tips in future studies. Sequencing is a powerful tool in ECM community studies.
Wanted: pathogenesis‐related marker molecules for Fusarium oxysporum
Authors: Recorbet Ghislaine , Steinberg Christian , Olivain Chantal , Edel Véronique , Trouvelot Sophie , Dumas‐Gaudot Eliane , Gianinazzi Silvio , Alabouvette Claude 
Published: June 2003

SummaryAlthough Fusarium oxysporum pathogens cause severe wilts in about 80 botanical species, the mechanisms of pathogenicity and symptom induction are poorly understood. Knowledge about the genetic and biochemical pathways involved in the pathogenesis of F. oxysporum would be invaluable in getting targets for both fungicide development and search for biocontrol agents. In this respect, we described the main approaches that have been developed to identify some mechanisms underlying the pathogenesis of F. oxysporum. During the last decades, the potential functions triggering of F. oysporum pathogenicity have mainly been investigated by comparing soilborne pathogenic strains with nonpathogenic ones with regards to the analysis of the pre‐ and infection stages and of the resulting plant–fungus interactions. The relatively recent progress in the molecular biology of this fungus has allowed complementary approaches to be developed in order to identify key factors involved in F. oxysporum pathogenicity. Screening mutants of F. oxysporum for loss of virulence led to the successful identification of some pathogenesis‐related factors, such as hydrophobicity or attachment of germlings. Taken together, the strategies described above support the idea that changes in fungal metabolism is also of importance in triggering of F. oxysporum pathogenesis.
Intraspecific comparative genomics to identify avirulence genes from Phytophthora
Authors: Bos Jorunn I. B. , Armstrong Miles , Whisson Stephen C. , Torto Trudy A. , Ochwo Mildred , Birch Paul R. J. , Kamoun Sophien 
Published: June 2003

SummaryMembers of the oomycete genus Phytophthora cause some of the most devastating plant diseases in the world and are arguably the most destructive pathogens of dicot plants. Phytophthora research has entered the genomics era. Current genomic resources include expressed sequence tags from a variety of developmental and infection stages, as well as sequences of selected regions of Phytophthora genomes. Genomics promise to impact upon our understanding of the molecular basis of infection by Phytophthora, for example, by facilitating the isolation of genes encoding effector molecules with a role in virulence and avirulence. Based on prevalent models of plant–pathogen coevolution, some of these effectors, notably those with avirulence functions, are predicted to exhibit significant sequence variation within populations of the pathogen. This and other features were used to identify candidate avirulence genes from sequence databases. Here, we describe a strategy that combines data mining with intraspecific comparative genomics and functional analyses for the identification of novel avirulence genes from Phytophthora. This approach provides a rapid and efficient alternative to classical positional cloning strategies for identifying avirulence genes that match known resistance genes. In addition, this approach has the potential to uncover ‘orphan’ avirulence genes for which corresponding resistance genes have not previously been characterized.
Models of shoot apical meristem function
Authors: Tooke Fiona , Battey Nick 
Published: June 2003

SummaryIn this review we describe how concepts of shoot apical meristem function have developed over time. The role of the scientist is emphasized, as proposer, receiver and evaluator of ideas about the shoot apical meristem. Models have become increasingly popular over the last 250 years, and we consider their role. They provide valuable grounding for the development of hypotheses, but in addition they have a strong human element and their uptake relies on various degrees of persuasion. The most influential models are probably those that most data support, consolidating them as an insight into reality; but they also work by altering how we see meristems, re‐directing us to influence the data we collect and the questions we consider meaningful.

Contents

Summary
37

I.
Introduction
37

II.
How things began
38

III.
Cytology
39

IV.
Morphology
41

V.
Developmental genetics
44

VI.
Conclusions
49

Acknowledgements
50

References
50
Transcranial Doppler Ultrasonographic Features During Drug Withdrawal From Drug‐Induced Headache. A Transcranial Doppler Follow‐up Study
Authors: Haase Claus G. , Diener Hans‐Christoph 
Published: June 2003

Background.—A vascular component in ergotamine‐induced headache has been proposed. No study has been carried out to evaluate cerebral hemodynamic changes by means of transcranial Doppler during withdrawal from migraine medication; in particular, ergotamine‐containing drugs.Method.—We examined 21 patients suffering from drug‐induced headache during their in‐hospital withdrawal from ergotamine (n=8) and compared them with patients during withdrawal from analgesics (n=13) and with healthy controls (n=14). Cerebral blood flow velocities were measured with transcranial Doppler, and pulsatility indices were calculated. Blood pressure, heart rate, and end‐tidal carbon dioxide were documented. A subjective analog headache rating scaling was used for day‐to‐day evaluation of headache severity.Results.—Mean cerebral blood flow velocities dropped significantly after discontinuation of ergotamine‐containing drugs but not after stopping common analgesics. Pulsatility indices remained unchanged. Cerebral blood flow velocities were higher in drug‐ingesting patients compared to the control group and showed significant changes in patients with headache using ergotamine and in those using analgesics. Carbon dioxide, heart rate, and blood pressure remained unchanged. The headache rating scale did not show a constant trend.Comments.—Our results indicate that ergotamine and, to a lesser extent, common analgesics including caffeine might influence cerebral blood flow velocities and pulsatility indices causing transient and reversible disturbance of cerebral autoregulation.
The Epidemiology of Migraine: A Retrospective Study in Italian Emergency Departments
Authors: De Carli G.F. , Fabbri L. , Cavazzuti L. , Roncolato M. , Agnello V. , Recchia G. 
Published: June 2003

This study was conducted to measure the frequency of contact with emergency departments in Italy because of migraine, and to compare the initial diagnosi s of headache with the diagnosis after application of the International Headache Society (IHS) criteria.A retrospective observational method was used, consisting of an analysis of the records of patients admitted to nine Italian emergency departments during different 4‐month periods in 1994. Comparison of the initial diagnosis with the diagnosis after application of the IHS diagnostic criteria was performed.More than 31 million emergency department contacts were reported in Italy during 1994. In the same year, 543 630 patients visited the nine emergency departments enrolled in the study, with 169 569 of these contacts occurring in the 4‐month period analyzed in the study. We excluded from the analysis all cases of secondary headache fully recognized at the emergency department admission (ie, traumas, intracranial pathology, systemic diseases). The total number of patients included in our analysis was 1043 (0.6%). The 934 patients who could be fully evaluated were initially classified as having migraine; cluster headache; headache not otherwise specified; or diagnosed in the emergency department as suffering from headache, but reclassified by other departments as suffering from a different disease. After retrospective application of the IHS classification, the diagnostic distribution was modified, revealing that 18% of patients with migraine and 5% with cluster headaches had previously been classified as having headache not otherwise specified; a further 6% of cases with migraine and 0.4% of patients with cluster headache had previously been classified as having secondary headaches. The diagnosis of headache not otherwise specified was made with notable frequency, indicating the limits of emergency department logs and the difficulty in carrying out a retrospective analysis and reassessment of diagnosis.The majority (88%) of patients assessed had not taken drugs for headache in the 48 hours before the emergency department contact, suggesting that in Italy emergency departments are used instead of a visit to the general practitioner. Nonsteroidal anti‐inflammatory drugs were the most frequently prescribed drugs in the emergency departments for this group of diagnoses.The research revealed, on the one hand, that headache is a numerically significant phenomenon in the emergency department setting and, on the other, the need to apply prospective designs to this kind of survey.
Cytogenetic comparison between clear cell sarcoma and a case of acral clear cell melanoma
Authors: Zelger Bettina G. , Debiec‐Rychter Maria , Sciot Raf , Zelger Bernhard 
Published: June 2003

Summary Background: Clear cell melanoma is a recently described variant of melanoma characterized by prominent clear cell features similar to clear cell sarcoma. Patients and methods: The present report describes a deeply invasive case of clear cell melanoma clinically, histologically, immunohistochemically, ultrastructurally and with the FISH technique and compares these findings with those in clear cell sarcoma. Results: A 68‐year‐old male presented with an ulcerated, deeply invasive melanoma on the heel, corresponding to Clark level V, with a maximum tumour thickness of more than 14 mm; follow‐up revealed inguinal lymph‐node and lung metastases. Apart from characteristic histological features of melanoma with intraepidermal involvement, the lesion was immunohistochemically positive for S100 protein, with HMB45 and A103 (anti‐human Melan‐A/MART‐1), and ultrastructurally showed melanosomes. In deeply invasive parts, the lesion was indistinguishable from clear cell sarcoma, exhibiting nests, fascicles and sheets of pale‐staining epithelioid to spindle‐shaped cells (‘clear cells’) with scattered Touton‐like multinucleated giant cells. Cytogenetic analysis using the FISH technique revealed a 12q13 chromosomal break in the vicinity of the ATF1 gene but without ATF1 disruption. Conclusion: These findings may indicate the possible involvement of the ATF1 gene in clear cell melanoma tumorigenesis, similar to clear cell sarcoma with classical t(12;22) translocation.
Na+/H+ Exchange Activity in the Plasma Membrane of Arabidopsis
Authors: Qiu Quan-Sheng , Barkla Bronwyn J. , Vera-Estrella Rosario , Zhu Jian-Kang , Schumaker Karen S. 
Published: June 2003

AbstractIn plants, Na+/H+ exchangers in the plasma membrane are critical for growth in high levels of salt, removing toxic Na+ from the cytoplasm by transport out of the cell. The molecular identity of a plasma membrane Na+/H+ exchanger in Arabidopsis (SOS1) has recently been determined. In this study, immunological analysis provided evidence that SOS1 localizes to the plasma membrane of leaves and roots. To characterize the transport activity of this protein, purified plasma membrane vesicles were isolated from leaves of Arabidopsis. Na+/H+ exchange activity, monitored as the ability of Na to dissipate an established pH gradient, was absent in plants grown without salt. However, exchange activity was induced when plants were grown in 250 mm NaCl and increased with prolonged salt exposure up to 8 d. H+-coupled exchange was specific for Na, because chloride salts of other monovalent cations did not dissipate the pH gradient. Na+/H+ exchange activity was dependent on Na (substrate) concentration, and kinetic analysis indicated that the affinity (apparent K m) of the transporter for Na+ is 22.8 mm. Data from two experimental approaches supports electroneutral exchange (one Na+ exchanged for one proton): (a) no change in membrane potential was measured during the exchange reaction, and (b) Na+/H+ exchange was unaffected by the presence or absence of a membrane potential. Results from this research provide a framework for future studies into the regulation of the plant plasma membrane Na+/H+ exchanger and its relative contribution to the maintenance of cellular Na+ homeostasis during plant growth in salt.
Dual Regulation of the Arabidopsis High-Affinity Root Iron Uptake System by Local and Long-Distance Signals
Authors: Vert Grégory A. , Briat Jean-François , Curie Catherine 
Published: June 2003

Abstract
Regulation of the root high-affinity iron uptake system by whole-plant signals was investigated at the molecular level in Arabidopsis, through monitoring FRO2 and IRT1 gene expression. These two genes encode the root ferric-chelate reductase and the high-affinity iron transporter, respectively, involved in the iron deficiency-induced uptake system. Recovery from iron-deficient conditions and modulation of apoplastic iron pools indicate that iron itself plays a major role in the regulation of root iron deficiency responses at the mRNA and protein levels. Split-root experiments show that the expression of IRT1 and FRO2 is controlled both by a local induction from the root iron pool and through a systemic pathway involving a shoot-borne signal, both signals being integrated to tightly control production of the root iron uptake proteins. We also show that IRT1 and FRO2 are expressed during the day and down-regulated at night and that this additional control is overruled by iron starvation, indicating that the nutritional status prevails on the diurnal regulation. Our work suggests, for the first time to our knowledge, that like in grasses, the root iron acquisition in strategy I plants may also be under diurnal regulation. On the basis of the new molecular insights provided in this study and given the strict coregulation of IRT1 and FRO2 observed, we present a model of local and long-distance regulation of the root iron uptake system in Arabidopsis.
Analysis of Xyloglucan Fucosylation in Arabidopsis
Authors: Perrin Robyn M. , Jia Zhonghua , Wagner Tanya A. , O'Neill Malcolm A. , Sarria Rodrigo , York William S. , Raikhel Natasha V. , Keegstra Kenneth 
Published: June 2003

AbstractXyloglucan (XyG) is a load-bearing primary wall component in dicotyledonous and non-graminaceous monocotyledonous plants. XyG fucosyltransferase (FUTase), encoded by the Arabidopsis gene AtFUT1, directs addition of fucose (Fuc) residues to terminal galactose residues on XyG side chains. Reverse transcription-polymerase chain reaction and analysis of promoter-β-glucuronidase transgenic plants indicated highest expression of AtFUT1 in the upper portion of elongating inflorescence stems of Arabidopsis. XyG FUTase activity was highest in Golgi vesicles prepared from growing Arabidopsis tissues and low in those isolated from mature tissues. There was no discernible correlation between the Fuc contents of XyG oligosaccharides derived from different Arabidopsis organs and the level of AtFUT1 expression in the organs. Thus, organ-specific variations in AtFUT1 expression and enzyme activity probably reflect differential rates of cell wall biosynthesis, rather than differences in levels of XyG fucosylation. The effects of manipulating AtFUT1 expression were examined using an Arabidopsis mutant (atfut1) containing a T-DNA insertion in the AtFUT1 locus and transgenic plants with strong constitutive expression of AtFUT1. No Fuc was detected in XyG derived from leaves or roots of atfut1. Plants overexpressing AtFUT1 had higher XyG FUTase activity than wild-type plants, but the XyG oligosaccharides derived from the transgenic and wild-type plants contained comparable amounts of Fuc, indicating that suitable acceptor substrates are limiting. Galactosyl residues had slightly higher levels of O-acetylation in XyG from plants that overexpressed AtFUT1 than in XyG from wild-type plants. O-Acetylation of galactose residues was considerably reduced in Fuc-deficient mutants (atfut1, mur1, and mur2) that synthesize XyG containing little or no Fuc. These results suggest that fucosylated XyG is a suitable substrate for at least one O-acetyltransferase in Arabidopsis.
Seed-Specific Overexpression of an Endogenous Arabidopsis Phytoene Synthase Gene Results in Delayed Germination and Increased Levels of Carotenoids, Chlorophyll, and Abscisic Acid
Authors: Lindgren L. Ove , Stålberg Kjell G. , Höglund Anna-Stina 
Published: June 2003

Abstract
Phytoene synthase catalyzes the dimerization of two molecules of geranylgeranyl pyrophosphate to phytoene and has been shown to be rate limiting for the synthesis of carotenoids. To elucidate if the capacity to produce phytoene is limiting also in the seed of Arabidopsis (Wassilewskija), a gene coding for an endogenous phytoene synthase was cloned and coupled to a seed-specific promoter, and the effects of the overexpression were examined. The resulting transgenic plants produced darker seeds, and extracts from the seed of five overexpressing plants had a 43-fold average increase of β-carotene and a total average amount of β-carotene of approximately 260 μg g– 1 fresh weight. Lutein, violaxanthin, and chlorophyll were significantly increased, whereas the levels of zeaxanthin only increased by a factor 1.1. In addition, substantial levels of lycopene and α-carotene were produced in the seeds, whereas only trace amounts were found in the control plants. Seeds from the transgenic plants exhibited delayed germination, and the degree of delay was positively correlated with the increased levels of carotenoids. The abscisic acid levels followed the increase of the carotenoids, and plants having the highest carotenoid levels also had the highest abscisic acid content. Addition of gibberellic acid to the growth medium only partly restored germination of the transgenic seeds.
The Identification of Candidate Genes for a Reverse Genetic Analysis of Development and Function in the Arabidopsis Gynoecium
Authors: Scutt Charles P. , Vinauger-Douard Marion , Fourquin Chloé , Ailhas Jérôme , Kuno Norihito , Uchida Kenko , Gaude Thierry , Furuya Masaki , Dumas Christian 
Published: June 2003

AbstractThe screening for mutants and their subsequent molecular analysis has permitted the identification of a number of genes of Arabidopsis involved in the development and functions of the gynoecium. However, these processes remain far from completely understood. It is clear that in many cases, genetic redundancy and other factors can limit the efficiency of classical mutant screening. We have taken the alternative approach of a reverse genetic analysis of gene function in the Arabidopsis gynoecium. A high-throughput fluorescent differential display screen performed between two Arabidopsis floral homeotic mutants has permitted the identification of a number of genes that are specifically or preferentially expressed in the gynoecium. Here, we present the results of this screen and a detailed characterization of the expression profiles of the genes identified. Our expression analysis makes novel use of several Arabidopsis floral homeotic mutants to provide floral organ-specific gene expression profiles. The results of these studies permit the efficient targeting of effort into a functional analysis of gynoecium-expressed genes.
A Role for the GCC-Box in Jasmonate-Mediated Activation of the PDF1.2 Gene of Arabidopsis
Authors: Brown Rebecca L. , Kazan Kemal , McGrath Ken C. , Maclean Don J. , Manners John M. 
Published: June 2003

Abstract
The PDF1.2 gene of Arabidopsis encoding a plant defensin is commonly used as a marker for characterization of the jasmonate-dependent defense responses. Here, using PDF1.2 promoter-deletion lines linked to the β-glucoronidase-reporter gene, we examined putative promoter elements associated with jasmonate-responsive expression of this gene. Using stably transformed plants, we first characterized the extended promoter region that positively regulates basal expression from the PDF1.2 promoter. Second, using promoter deletion constructs including one from which the GCC-box region was deleted, we observed a substantially lower response to jasmonate than lines carrying this motif. In addition, point mutations introduced into the core GCC-box sequence substantially reduced jasmonate responsiveness, whereas addition of a 20-nucleotide-long promoter element carrying the core GCC-box and flanking nucleotides provided jasmonate responsiveness to a 35S minimal promoter. Taken together, these results indicated that the GCC-box plays a key role in conferring jasmonate responsiveness to the PDF1.2 promoter. However, deletion or specific mutations introduced into the core GCC-box did not completely abolish the jasmonate responsiveness of the promoter, suggesting that the other promoter elements lying downstream from the GCC-box region may also contribute to jasmonate responsiveness. In other experiments, we identified a jasmonate- and pathogen-responsive ethylene response factor transcription factor, AtERF2, which when overexpressed in transgenic Arabidopsis plants activated transcription from the PDF1.2, Thi2.1, and PR4 (basic chitinase) genes, all of which contain a GCC-box sequence in their promoters. Our results suggest that in addition to their roles in regulating ethylene-mediated gene expression, ethylene response factors also appear to play important roles in regulating jasmonate-responsive gene expression, possibly via interaction with the GCC-box.