1,721,123 research outputs found
Compatible and incompatible interactions between callus tissue and mycorrhizal or pathogenic fungi.
No full textTissue cultures of Nicotiana tabacum were utilized to investigate the mechanisms associated with host specificity and non-host incompatibility in mycorrhizal and pathogenic fungi. They were tested for expression of resistance to different species of mycorrhizal fungi and to a fungal pathogen of tobacco, Thielaviopsis basicola, by monitoring the production of callose, phenolic compounds and peroxidases in dual cultures. Tobacco cells reacted to the presence of all the mycorrhizal fungi with callose deposits, whereas callose was nearly always absent in tobacco cells inoculated with their pathogen T. basicola. The broad-host range ectomycorrhizal fungi Hebeloma crustuliniforme, Laccaria laccata and Suillus granulatus elicited less intense responses than did Hymenoscyphus ericae. The results obtained for phenolic production and peroxidase activity were consistently similar to those obtained for callose deposition. They showed that H. ericae, an endomycorrhizal symbiont of Ericaceae, was highly incompatible with tobacco cells and that the tobacco pathogen T. basicola did not elicit strong reactions in the cells of its host. In this paper, the possibility of utilizing callus cultures as a simple model system to study both the different degrees of compatibility and the early events of recognition between mycorrhizal fungi and their host or non-host plants is discussed
Comparative determination of some phytohormones in wild-type and genetically modified plants by gas chromatography–mass spectrometry and high-performance liquid chromatography–tandem mass spectrometry
No full textThe analytical performances of two optimized analytical methodologies used for the determination of
auxins, cytokinins, and abscisic acid in plant samples were critically compared. Phytohormones were
extracted from Nicotiana glauca samples using a modified Bieleski solvent and determined both by gas
chromatography–mass spectrometry (GC–MS), after derivatization with N,O-bis(trimethylsilyl)trifluoroacetamide
(BSTFA), and by high-performance liquid chromatography–tandem mass spectrometry (HPLC–
MS/MS) on the Bieleski extract without any further treatment. HPLC–MS/MS gave better results in terms
of higher coefficients of determination of the calibration curves, higher and more reproducible recoveries,
lower limits of detection, faster sample preparation, and higher sample throughput. Thus, two sets of N.
glauca and N. langsdorffii samples, both wild-type and genetically modified by inserting the glucocorticoid
receptor (GR) gene encoding for the rat glucocorticoid receptor, were first characterized by reverse transcriptase-
polymerase chain reaction (RT-PCR) analysis and then analyzed by HPLC–MS/MS. Significant differences
in the phytohormone content between the two sample sets were found and are very important
in terms of understanding the mechanisms and effects on growth processes and the development of
transgenic plants
Detection of fragmented genomic DNA by PCR-free piezoelectric sensing using a denaturation approach
No full textDevelopment of well-automated and miniaturized gene analysis methods is the objective at which research is currently aiming. Recent works report examples of miniaturized PCR devices1 pointing at high-speed PCR. However, a great improvement in DNA sequence analysis would come by direct detection in nonamplified genomic DNA. Biosensors represent an interesting candidate for DNA detection. In particular, several DNA-based sensors have been reported. Most of the work was applied to PCR-amplified samples, and only few works, operating directly with genomic DNA, appeared in the literature with different detection principles.
In this paper, a piezoelectric sensor for direct detection of sequences in nonamplified genomic DNA is reported.
The system relies on realtime and label-free detection of the hybridization reaction between an immobilized probe (25-mer) and the complementary sequence in solution. The DNA probe is immobilized on the gold electrodes of 10 MHz quartz crystals. Genomic DNA was extracted from the plant, Nicotiana glauca, used as a model system. The target sequence was a portion of the
promoter region (35S, present in various genetically modified organisms (GMOs), used as a marker for GMO screening
Combination of amplification and post-amplification strategies to improve optical DNA sensing
No full textApproaches to optimise detection of polymerase chain reaction (PCR) amplified DNA samples by an optical sensor based on surface plasmon resonance (SPR) (BiacoreX(TM
Comparative evaluation of the metabolic profile in genetically modified (GMPs) and non-genetically modified plants (non GMPs).
No full textThe rat glucocorticoid receptor integration in Nicotiana langsdorffii genome affects plant responses to abiotic stresses and to arbuscular mycorrhizal symbiosis
Full text linkThe present study reports evidence of the pleiotropic effects caused by the insertion of the rat glucocorticoid receptor (GR) into the genome of Nicotiana langsdorffii. Transgenic N. langsdorffii-GR plants and the wild-type genotypes were analysed for their phenotypic and physiological characteristics. The integration of the GR gene affected flowering, growth habit, leaf morphology and stomatal pattern. Furthermore, GR plants showed an increased tolerance to heavy metal, drought and heat stress as evidenced by electrolyte leakage and by cell dedifferentiation and differentiation capability after recovery from stress treatments. We also monitored the establishment of the beneficial symbiosis between transgenic plants and the mycorrhizal fungus Funneliformis mosseae whose presymbiotic growth was significantly reduced by root exudates of N. langsdorffii-GR plants. The observed pleiotropic responses of transgenic plants may be a consequence of the hormonal imbalance, putatively due to the interaction of the GR receptor with the host genetic background. Our findings suggest that N. langsdorffii-GR plants can be used as a functional model system for the study of plant responses to a series of environmental stimuli
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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