1,720,962 research outputs found
Functional analysis of AtZIP4, AtZIP6 and AtZIP9 metal transporters of Arabidopsis thaliana and Expression of Saccharomyces cerevisiae ZRC1 in different plant species.
Full text linkPlants have developed a variety of adaptive strategies to take up sufficient quantities of essential macro- and micro-nutrients and avoid their excessive accumulation, which could be toxic. Metal transporters play an essential role in this homeostatic network by controlling the metal efflux across cellular membranes and compartments. The ZIP (ZRT IRT1-like Proteins: Zinc-regulated transporter Iron-regulated transporter 1-like protein) family of metal transporter is involved in this complex network. We have focused on three ZIP-family members: AtZIP4, AtZIP6 and AtZIP9, for which very little information is available. These genes have not been yet characterized although a possible role in micronutrients vascular system uploading and root uptake was hypothesized. ZIP6 is not part of the four main groups in the ZIP family and Milner et al., (2013) have highlighted its higher expression in roots than in shoots, whereas no expression modulation at varying Zn and Fe concentrations (Wintz et al., 2003). The transcript level of ZIP6 seems to be constitutively higher in the Zn hyperaccumulator Arabidopsis halleri ssp. halleri than in A. thaliana, independently of the Zn concentration (Becher et al., 2003). ZIP9 is clustered together with ZIP4, sharing c.a. 60% identity and 77% similarity at the amino acid sequence. Wintz et al. (2003) have shown that in A. thaliana both ZIP4 and ZIP9 are up-regulated in roots and shoots in Zn-deficient conditions. In A. halleri roots, ZIP9 is up-regulated upon Zn-deficiency and down-regulated in presence of high Zn concentrations. In A. thaliana shoots, ZIP9 level is detectable only upon excess Zn (Weber et al., 2004). The aim of this project is the functional analysis of AtZIP6 and AtZIP9, to understand their expression pattern and their subcellular localization. AtZIP6 and AtZIP9 knock-out mutant lines were investigated and will be used for testing metal tolerance and accumulation in order to identify which metal(s) are transported by these proteins. The high similarity between ZIP9 and ZIP4 prompted us to add AtZIP4 mutant our analysis to avoid a possible functional complementation. Furthermore, over-expressing A. thaliana lines have also been obtained fusing the 35S constitutive promoter to the AtZIP6 and AtZIP9 coding sequence in order to perform a phenotypic characterization and a metal accumulation analysis in comparison to single zip4, zip6, zip9, double zip6/zip9, zip4/zip9, zip4/zip6 and a triple zip4/zip6/zip9 knock-out mutants and wild-type lines Another part of the project concerns the effect of heterologous yeast genes in A. thaliana, tobacco and poplar plants, analyzing their ability in heavy metal accumulation. ZRC1 gene was selected since it induces Zn/Cd resistance in Saccharomyces cerevisiae. ScZRC1 is a vacuolar transporter that mediates the detoxification of Zn excess storing it into the vacuole (MacDiarmid et al., 2003). ScZRC1 belongs to the CDF transporter family and might have also a putative role in Cd detoxification
Involvement of the Putative N-Acetylornithine Deacetylase from Arabidopsis thaliana in Flowering and Fruit Development
No full textIn eukaryotic cells, the non-proteinogenic amino acid ornithine is the precursor of arginine and polyamines (PAs). The final step of ornithine biosynthesis occurs in plants via a cyclic pathway catalyzed by N(2)-acetylornithine:N-acetylglutamate acetyltransferase (NAOGAcT). An alternative route for ornithine formation, the linear pathway, has been reported for enteric bacteria and a few other organisms; the acetyl group of N(2)-acetylornithine is released as acetate by N(2)-acetylornithine deacetylase (NAOD). NAOD activity has never been demonstrated in plants, although many putative NAOD-like genes have been identified. In this investigation, we examined the effect of down-regulation of the putative Arabidopsis thaliana NAOD gene by using AtNAOD-silenced (sil#17) and T-DNA insertional mutant (atnaod) plants. The ornithine content was consistently reduced in sil#17 and atnaod plants compared with wild-type plants, suggesting that in addition to NAOGAcT action, AtNAOD contributes to the regulation of ornithine levels in plant cells. Ornithine depletion was associated with altered levels of putrescine and spermine. Reduced AtNAOD expression resulted in alterations at the reproductive level, causing early flowering and impaired fruit setting. In this regard, the highest level of AtNAOD expression was observed in unfertilized ovules. Our findings suggest that AtNAOD acts as a positive regulator of fruit setting and agree with those obtained in tomato auxin-synthesizing parthenocarpic plants, where induction of SlNAOD was associated with the onset of ovary growth. Thus, here we have uncovered the first hints of the functions of AtNAOD by connecting its role in flower and fruit development with the regulation of ornithine and PA levels
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
Genetic engineering of Nannochloropsis oceanica to produce canthaxanthin and ketocarotenoids
Full text linkBackground
Canthaxanthin is a ketocarotenoid with high antioxidant activity, and it is primarily produced by microalgae, among which Nannochloropsis oceanica, a marine alga widely used for aquaculture. In the last decade, N. oceanica has become a model organism for oleaginous microalgae to develop sustainable processes to produce biomolecules of interest by exploiting its photosynthetic activity and carbon assimilation properties. N. oceanica can accumulate lipids up to 70% of total dry weight and contains the omega-3 fatty acid eicosapentaenoic acid (EPA) required for both food and feed applications. The genome sequence, other omics data, and synthetic biology tools are available for this species, including an engineered strain called LP-tdTomato, which allows homologous recombination to insert the heterologous genes in a highly transcribed locus in the nucleolus region. Here, N. oceanica was engineered to induce high ketocarotenoid and canthaxanthin production.
Results
We used N. oceanica LP-tdTomato strain as a background to express the key enzyme for ketocarotenoid production, a β-carotene ketolase (CrBKT) from Chlamydomonas reinhardtii. Through the LP-tdTomato strain, the transgene insertion by homologous recombination in a highly transcribed genomic locus can be screened by negative fluorescence. The overexpression of CrBKT in bkt transformants increased the content of carotenoids and ketocarotenoids per cell, respectively, 1.5 and 10-fold, inducing an orange/red color in the bkt cell cultures. Background (LP) and bkt lines productivity were compared at different light intensities from 150 to 1200 μmol m-2 s-1: at lower irradiances, the growth kinetics of bkt lines were slower compared to LP, while higher productivity was measured for bkt lines at 1200 μmol m-2 s-1. Despite these results, the highest canthaxanthin and ketocarotenoids productivity were obtained upon cultivation at 150 μmol m-2 s-1.
Conclusions
Through targeted gene redesign and heterologous transformation, ketocarotenoids and canthaxanthin content were significantly increased, achieving 0.3% and 0.2% dry weight. Canthaxanthin could be produced using CO2 as the only carbon source at 1.5 mg/L titer. These bkt-engineered lines hold potential for industrial applications in fish or poultry feed sectors, where canthaxanthin and ketocarotenoids are required as pigmentation agents
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
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