1,720,954 research outputs found
Sulfate-induced stomata closure requires the canonical ABA signal transduction machinery
Get PDFPhytohormone abscisic acid (ABA) is the canonical trigger for stomatal closure upon abiotic stresses like drought. Soil-drying is known to facilitate root-to-shoot transport of sulfate. Remarkably, sulfate and sulfide—a downstream product of sulfate assimilation—have been independently shown to promote stomatal closure. For induction of stomatal closure, sulfate must be incorporated into cysteine, which triggers ABA biosynthesis by transcriptional activation of NCED3. Here, we apply reverse genetics to unravel if the canonical ABA signal transduction machinery is required for sulfate-induced stomata closure, and if cysteine biosynthesis is also mandatory for the induction of stomatal closure by the gasotransmitter sulfide. We provide genetic evidence for the importance of reactive oxygen species (ROS) production by the plasma membrane-localized NADPH oxidases, RBOHD, and RBOHF, during the sulfate-induced stomatal closure. In agreement with the established role of ROS as the second messenger of ABA-signaling, the SnRK2-type kinase OST1 and the protein phosphatase ABI1 are essential for sulfate-induced stomata closure. Finally, we show that sulfide fails to close stomata in a cysteine-biosynthesis depleted mutant. Our data support the hypothesis that the two mobile signals, sulfate and sulfide, induce stomatal closure by stimulating cysteine synthesis to trigger ABA production
The role of sulfite reductase in assimilatory sulfate reduction in Arabidopsis thaliana
No full textReductive assimilation of inorganic sulfate to sulfide is an essential metabolic process in higher plants for the synthesis of cysteine and all downstream compounds containing reduced sulfur in the cell. Sulfite reductase (SiR) palys a central role in the assimilatory sulfate reduction pathway by catalyzing the reduction of sulfite to sulfide. An Arabidopsis T-DNA insertion line (sir1-1) with an insertion in the promoter region of SiR was isolated in order to address the exact role of SiR in vivo. Detailed characterization of sir1-1 revealed that homozygous sir1-1 plants are viable, but severely affected in growth. Homozygous sir1-1 plants flower and set viable seeds, albeit later than wild-type plants grown under the same conditions. Evaluation of SiR transcript levels in the leaves of sir1-1 plants revealed that the mRNA was down-regulated to about 50% of wild-type level. Consequently, the amount of SiR protein and the SiR activity were reduced in the same manner. The significant differences between the leaves of sir1-1 and Col-0 plants for most of the sulfur-containing and other related compounds such as cysteine, O-acetylserine (OAS), sulfate, nitrate, total glucosinolates, total carbon (C), nitrogen (N), and sulfur (S) suggests strong perturbations in the entire metabolism of sir1-1 plants. A reduction of approximately 25.6-fold and 32.7-fold in the incorporation of 35S label into cysteine and GSH fractions, respectively, of sir1-1 leaves compared to wild-type plants was observed, suggesting the fact that the activity of SiR generates a severe bottleneck in the sulfur assimilation pathway. Investigations of the transcript levels through microarray analysis revealed that the expression of many genes related to sulfur metabolism was altered in response to reduced sulfide synthesis. Out of 920 selected genes related to sulfur metabolism, the expression of 67 genes in the leaves and 180 genes in the roots of sir1-1, were significantly up- or down-regulated compared to wild-type. The high affinity sulfate transporters, sulfate transporter 1;1 (SULTR 1;1) and sulfate transporter 1;2 (SULTR 1;2) showed a significant up-regulation in the roots of sir1-1 compared to Col-0. The up-regulation of the high affinity sulfate transporters in the roots of sir1-1 suggests that instead of steady-state sulfate levels, the amount of reduced sulfur present in the cell, likely forms the signal for their their induction. The preliminary results for a second T-DNA insertion line (sir1-2) strongly indicate that an insertion more closer to the gene, in the promoter region of SiR causes early seedling lethality. All results point towards the exclusiveness of SiR for sufite reduction and that its optimal activity is essential for the normal growth of Arabidopsis plants. Treatment of different Arabidopsis lines with selenate, which is quite similar to sulfate, caused an increase in the total sulfur and selenium contents of the plants. This might happen due to the up-regulation of sulfate transporters which might eventually lead to an increase in total sulfur and selenium due to elevated sulfate/selenate contents
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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