2,048 research outputs found
Abscisic acid induces CBF gene transcription and subsequent induction of cold-regulated genes via the CRT promoter element
No full textMany cold-regulated genes of Arabidopsis are inducible by abscisic acid (ABA) as well as by cold. This has been thought to occur via two separate signaling pathways, with ABA acting via ABA-responsive promoter elements and low temperature activating the C-repeat element (CRT; dehydration-responsive) promoter element via CBF (DREB1) transcription factors. We show here that ABA is also capable of activating the CRT promoter element. Although the more recently discovered ABA-inducible CBF4 transcription factor might have accounted for this, we show here that CBF1-3 transcript levels also increase in response to elevated ABA levels. This increase in CBF1-3 transcript levels appears to be at least in part due to increased activity of the CBF promoters in response to ABA. A total of 125 bp of the CBF2 promoter, which has previously been shown to be sufficient for cold-, mechanical-, and cycloheximide-induced expression, was also sufficient for ABA-induced expression. However, the ABA-responsive promoter element-like motif within this region is not needed for ABA-induced expression. An observed increase in CBF protein levels after ABA treatment, together with previous data showing that increased CBF levels are sufficient for cold-regulated gene induction, suggests that ABA-induced increases in CBF1-3 transcript levels do have the potential to activate the CRT. Our data indicate therefore that activation of the CRT may also occur via a novel ABA-inducible signaling pathway using the normally cold-inducible CBFs
MARC 21 para recursos contínuos
No full textTranslation and adaptation of the MARC 21 Format for Bibliographic Data, and MARC 21 Format for Holdings Data, Network Development and MARC Standards Office, Library of Congress, USA, by Angela Salles. Rio de Janeiro, 2010. 2 v. V.1 MARC 21 format for bibliographic data (updated until October 2010). V.2 MARC 21 format for data collection (Holdings) (updated until October 2008)
MARC 21 para recursos contínuos.
No full textTradução e adaptação de MARC 21 Format for Bibliographic Data e MARC 21 Format for Holdings Data, da Network Development and MARC Standards Office, da Library of Congress, USA, por Angela Salles
The ?-subunit of the heterotrimeric G-protein affects jasmonate responses in Arabidopsis thaliana
No full textHeterotrimeric G-proteins have been implicated in having a role in many plant signalling pathways. To understand further the role of G-proteins, a preliminary experiment was performed to assess the impact of the G? subunit loss-of-function mutation gpa1-1 on the Arabidopsis transcriptome. The analysis indicated that the G? subunit may play a role in response to jasmonic acid (JA). Consistent with this, G? mutants showed a reduced response to JA in inhibition of chlorophyll accumulation and root growth, whilst G? gain-of-function plants overexpressing G? showed the opposite phenotype. The levels of JA and related compounds were unaffected in the gpa1-1 mutant, as was autoregulation of the Allene Oxide Synthase (AOS) gene that encodes a key enzyme for JA biosynthesis. In contrast, further analyses using G? loss- and gain-of-function Arabidopsis lines indicated that G? positively modulates the expression of the Vegetative Storage Protein (VSP) gene. This indicates that the G? subunit regulates a subset of JA-regulated genes defining a branch point in this signalling pathway in Arabidopsis. Further analysis of the impact of G? loss of function upon the JA-regulated transcriptome using Arabidopsis full genome arrays indicated that up to 29% of genes that are >2-fold regulated by JA in the wild type are misregulated in the G? mutant. This supports the observation that a significant proportion of, but not all, JA-regulated gene expression is mediated by G
Marc Jacobs Unseen
No full textMarc Jacobs Unseen is ‘the first publication dedicated to Marc Jacobs’s highly influential creations’*, described by The Observer as ‘a rare insight’ and Vogue as ‘a real revelation’. The particular focus of this critical appraisal is the personal archive (a recurring feature in Webb’s practice), notably those of the subject (Marc Jacobs), the photographer (Robert Fairer), and the author (Webb). The genesis of the text for this sole-authored book that accompanies new primary material in the form of Fairer’s previously unseen backstage images, is research from Webb’s own archive, amassed over four decades during his career at the forefront of the fashion industry, and represents a culmination of the author’s commitment to the promotion of the importance of the archive as material culture, as methodology and as providing an individual insight into creative thinking. The text takes the form of painstakingly assembled commentaries, each presenting a study of specific collections, highlighting particular garments and ensembles along with an analysis of environment and staging. ‘Working with Iain R. Webb…was illuminating,’ says Fairer. Jacobs Unseen is a valuable and illuminating analysis for both colleagues and students, especially those working in areas of fashion design, journalism and visual communication
The regulation and role of oxidative signal-inducible 1 protein kinase in Arabidopsis thaliana
No full textWord processed copy.Includes bibliographical references (leaves 209-232).This study attempted to further characterise OXI1 protein kinase. Confocal microscopy and subcellular fractionation studies revealed a cytosolic localisation pattern for OXI1. Employment of a bioinformatics approach confirmed the induction of OXI1 gene expression in response to a range of AOS generating stimuli. However, the transcriptional increase of OXI1 in response to salinity and heat appears to be of no biological significance since the oxi1 mutant did not display altered tolerance to these two stresses in comparison to wild type
Professor Alan R. Bromberg\u27s Rule 10b-5
No full textProfessor Alan Bromberg was the foremost authority in the law of Rule 10b-5. In this article, the author Professor Marc Steinberg, Professor Bromberg\u27s colleague for 25 years, highlights Professor Bromberg\u27s scholarship in this area. Focusing on key U.S. Supreme Court decisions and congressional legislation, Professor Steinberg reflects on the dialogue that he had with Professor Bromberg through the years on these developments. As this article illustrates, Professor Bromberg enjoyed a truly impressive academic career
The discovery of SycO reveals a new function for type three secretion effector chaperones
No full textThe Type Three Secretion (T3S) system is a device used by many Gram-negative pathogens that allows bacteria to deliver effector proteins straight into the eukaryotic cell cytosol. These effectors interfere with various signaling pathways to subvert the host cell functions. The secretion machinery of the T3S system consist of a basal body spanning the bacterial inner and outer membrane followed by a stiff hollow needle outside the bacterium. The fully assembled secretion apparatus constitute a continuous hollow conduit that connects the bacteria to the eukaryotic target cell. After cell contact, virulence proteins -called effectors- are injected directly into the cytosol of the host cell via the T3S apparatus. Several effectors of the T3S system require the assistance of specific cytosolic chaperones to be efficiently exported. There are three classes of T3S chaperones. Effector proteins are assisted by Class I chaperones. Although Class I chaperones are well characterized, their main function is still a matter of controversy. In this thesis, we demonstrate that orf155 encodes a specific chaperone for the effector YopO that we called SycO. We showed that SycO enhances YopO secretion in vitro and is required for translocation of YopO into infected cells. By pulldown assay we demonstrated that residues 20 to 77 of YopO are required and sufficient for SycO binding. Using crosslinking experiments and size exclusion chromatography analysis, we determined the stoichiometry of purified SycO and YopO-SycO complexes. SycO alone forms dimers in solution and the YopO-SycO complex has a 1:2 stoichiometry. These results suggested that SycO is a typical chaperone of the Class I. YopO is a serine/theronine kinase that interacts with Rho and Rac and disrupts the cytoskeleton of the target cells. YopO has been shown to localize at the cell plasma-membrane. By transfection of YopO-EGFP hybrid proteins into HEK293T cells, we demonstrated that the chaperone-binding domain (CBD) coincides with the membrane localization domain of YopO. Nevertheless, the CBD was not needed for the kinase activity of YopO. By ultracentrifugation, we also showed that the CBD causes YopO aggregation in the bacteria, when SycO does not cover it. Further, we show that the CBD of YopE and YopT also caused aggregation in the bacteria in the absence of SycE and SycT respectively. YopE, YopT and T3S effectors in other systems also act at the membrane of the eukaryotic host cell. We propose a new hypothesis concerning the role of T3S chaperones. The sub-cellular localization domain of effectors is aggregation-prone and creates the need for a chaperone inside bacteria. We propose that masking such aggregation-prone localization domains may be a general function for type III effector chaperones
Equilibrium transition study for a hybrid MAV
No full textWind tunnel testing was performed on a VTOL aircraft in order to characterize longitudinal flight behavior during an equilibrium transition between vertical and horizontal flight modes. Trim values for airspeed, pitch, motor speed and elevator position were determined. Data was collected by independently varying the trim parameters, and stability and control derivatives were identified as functions of the trim pitch angle. A linear fractional representation model was then proposed, along with several methods to improve longitudinal control of the aircraft
An investigation into Grade R teachers' experiences of implementing numeracy in Grade R
No full textThis research study investigates how selected Grade R teachers implement numeracy in their classrooms, based on their experiences, personal beliefs and perceptions. This study adopts the view that a teacher's practice is not only informed on what she believes about her learners, but also on how she organises her classroom environment and her own teaching practice. However, the teacher cannot be divorced from the political and historical
background of Early Childhood Development (ECD), as these factors have an impact on her numeracy implementation. Integrated in this research study is thus not only a comprehensive historical analysis of the historical and political background of ECD, but also an in-depth look at the complex curriculum road the Grade R teacher had to travel over the past twelve years. The aim of this case study is to understand and describe what is happening in Grade R classrooms when numeracy is implemented, as well as identifying possible barriers which Grade R teachers may experience in implementing numeracy. The author utilized an adapted Interactive Qualitative Analysis Framework to explore Grade R teachers' views and experiences. Open-ended focus group interviews were used to develop a framework for individual interviews. This interview framework guided the data collection of nine audio-video tapes of classroom activities and nine semi-structured individual interviews. Analysis of the individual interviews revealed each teacher's understanding as well as her perceptions and needs regarding the implementation of numeracy in her classroom. The transcriptions of the individual interviews were compared to the audio-video tapes of what happened in each classroom. This was done in order to determine whether the teachers' practices were consistent with what they said in the interviews. Paradoxes and inconsistencies were documented. The historical and political analysis of ECD illustrates the complex development of ECD in
South Africa over the last few decades. It therefore also highlights and brings to the fore the complex journey that Grade R teachers had to navigate in adapting their practice to ever changing curriculum requirements. The empirical results show that there are inconsistencies between what selected teachers know and believe, and what they are implementing. However, "silent themes" which did not come to the fore in the focus group or individual interviews, were identified in the audiovideo tapes of classroom activities. Also, many "silent themes" indicate that there are numerous concerns, such as lack of proficiency in bridging the gap between theory and practice, regarding the implementation of numeracy in Grade R. It was found that many of the selected Grade R teachers struggle to implement numeracy in their classrooms, as they lack the skills and support to teach numeracy in a Grade R context
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