Singlet oxygen initiates a plastid signal controlling photosynthetic gene expression.

Retrograde signals from the plastid regulate photosynthesis-associated nuclear genes and are essential to successful chloroplast biogenesis. One model is that a positive haem-related signal promotes photosynthetic gene expression in a pathway that is abolished by the herbicide norflurazon. Far-red light (FR) pretreatment and transfer to white light also results in plastid damage and loss of photosynthetic gene expression. Here, we investigated whether norflurazon and FR pretreatment affect the same retrograde signal. We used transcriptome analysis and real-time reverse transcription-polymerase chain reaction (RT-PCR) to analyse the effects of these treatments on nuclear gene expression in various Arabidopsis (Arabidopsis thaliana) retrograde signalling mutants. Results showed that the two treatments inhibited largely different nuclear gene sets, suggesting that they affected different retrograde signals. Moreover, FR pretreatment resulted in singlet oxygen (1 O2 ) production and a rapid inhibition of photosynthetic gene expression. This inhibition was partially blocked in the executer1executer2 mutant, which is impaired in 1 O2 signalling. Our data support a new model in which a 1 O2 retrograde signal, generated by chlorophyll precursors, inhibits expression of key photosynthetic and chlorophyll synthesis genes to prevent photo-oxidative damage during de-etiolation. Such a signal would provide a counterbalance to the positive haem-related signal to fine tune regulation of chloroplast biogenesis.This work was funded by BBSRC grants 51/P17214 and BB/ J018139/1 to M.J.T. and BB/J018694/1 to A.G.S

Overexpression of chloroplast-targeted ferrochelatase 1 results in a genomes uncoupled chloroplast-to-nucleus retrograde signalling phenotype.

Chloroplast development requires communication between the progenitor plastids and the nucleus, where most of the genes encoding chloroplast proteins reside. Retrograde signals from the chloroplast to the nucleus control the expression of many of these genes, but the signalling pathway is poorly understood. Tetrapyrroles have been strongly implicated as mediators of this signal with the current hypothesis being that haem produced by the activity of ferrochelatase 1 (FC1) is required to promote nuclear gene expression. We have tested this hypothesis by overexpressing FC1 and specifically targeting it to either chloroplasts or mitochondria, two possible locations for this enzyme. Our results show that targeting of FC1 to chloroplasts results in increased expression of the nuclear-encoded chloroplast genes GUN4, CA1, HEMA1, LHCB2.1, CHLH after treatment with Norflurazon (NF) and that this increase correlates to FC1 gene expression and haem production measured by feedback inhibition of protochlorophyllide synthesis. Targeting FC1 to mitochondria did not enhance the expression of nuclear-encoded chloroplast genes after NF treatment. The overexpression of FC1 also increased nuclear gene expression in the absence of NF treatment, demonstrating that this pathway is operational in the absence of a stress treatment. Our results therefore support the hypothesis that haem synthesis is a promotive chloroplast-to-nucleus retrograde signal. However, not all FC1 overexpression lines enhanced nuclear gene expression, suggesting there is still a lot we do not understand about the role of FC1 in this signalling pathway. This article is part of the theme issue 'Retrograde signalling from endosymbiotic organelles'.BBRS

Performance, Politics and Media: How the 2010 British General Election leadership debates generated ‘talk’ amongst the electorate.

During the British General Election 2010 a major innovation was introduced in part to improve engagement: a series of three live televised leadership debates took place where the leader of each of the three main parties, Labour, Liberal Democrat and Conservative, answered questions posed by members of the public and subsequently debated issues pertinent to the questions. In this study we consider these potentially ground breaking debates as the kind of event that was likely to generate discussion. We investigate various aspects of the ‘talk’ that emerged as a result of watching the debates. As an exploratory study concerned with situated accounts of the participants experiences we take an interpretive perspective. In this paper we outline the meta-narratives (of talk) associated with the viewing of the leadership debates that were identified, concluding our analysis by suggesting that putting a live debate on television and promoting and positioning it as a major innovation is likely to mean that is how the audience will make sense of it – as a media event

Increased susceptibility to proactive interference in adults with dyslexia?

Recent findings show that people with dyslexia have an impairment in serial-order memory. Based on these findings, the present study aimed to test the hypothesis that people with dyslexia have difficulties dealing with proactive interference (PI) in recognition memory. A group of 25 adults with dyslexia and a group of matched controls were subjected to a 2-back recognition task, which required participants to indicate whether an item (mis)matched the item that had been presented 2 trials before. PI was elicited using lure trials in which the item matched the item in the 3-back position instead of the targeted 2-back position. Our results demonstrate that the introduction of lure trials affected 2-back recognition performance more severely in the dyslexic group than in the control group, suggesting greater difficulty in resisting PI in dyslexia.Peer reviewedFinal Accepted Versio

Seedlings Lacking the PTM Protein Do Not Show a genomes uncoupled (gun) Mutant Phenotype.

The ptm mutant of Arabidopsis does not show a genomes uncoupled mutant phenotype and PTM is therefore unlikely to function in chloroplast-to-nucleus signaling as previously reported

Seasonal diet changes in elephant and impala in mopane woodland

Abstract Elephant and impala as intermediate feeders, having a mixed diet of grass and browse, respond to seasonal fluctuations of forage quality by changing their diet composition. We tested the hypotheses that (1) the decrease in forage quality is accompanied by a change in diet from more monocots in the wet season to more dicots in the dry season and that that change is more pronounced and faster in impala than in elephant; (2) mopane (Colophospermum mopane), the most abundant dicot species, is the most important species in the elephant diet in mopane woodland, whereas impala feed relatively less on mopane due to the high condensed tannin concentration; and (3) impala on nutrient-rich soils have a diet consisting of more grass and change later to diet of more browse than impala on nutrient-poor soils. The phosphorus content and in vitro digestibility of monocots decreased and the NDF content increased significantly towards the end of the wet season, whereas in dicots no significant trend could be detected. We argue that this decreasing monocot quality caused elephant and impala to consume more dicots in the dry season. Elephant changed their diet gradually over a 16-week period from 70% to 25% monocots, whereas impala changed diets rapidly (2-4 weeks) from 95% to 70% monocots. For both elephants and impala, there was a positive correlation between percentage of monocots and dicots in the diet and the in vitro digestibility of these forage items. Mopane was the most important dicot species in the elephant diet and its contribution to the diet increased significantly in the dry season, whereas impala selected other dicot species. On nutrient-rich gabbroic soils, impala ate significantly more monocots than impala from nutrient-poor granitic soils, which was related to the higher in vitro digestibility of the monocots on gabbroic soil. Digestibility of food items appears to be an important determinant of diet change from the wet to the dry season in impala and elephants

The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe

The preponderance of matter over antimatter in the early Universe, the dynamics of the supernova bursts that produced the heavy elements necessary for life and whether protons eventually decay --- these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our Universe, its current state and its eventual fate. The Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed plan for a world-class experiment dedicated to addressing these questions. LBNE is conceived around three central components: (1) a new, high-intensity neutrino source generated from a megawatt-class proton accelerator at Fermi National Accelerator Laboratory, (2) a near neutrino detector just downstream of the source, and (3) a massive liquid argon time-projection chamber deployed as a far detector deep underground at the Sanford Underground Research Facility. This facility, located at the site of the former Homestake Mine in Lead, South Dakota, is approximately 1,300 km from the neutrino source at Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino charge-parity symmetry violation and mass ordering effects. This ambitious yet cost-effective design incorporates scalability and flexibility and can accommodate a variety of upgrades and contributions. With its exceptional combination of experimental configuration, technical capabilities, and potential for transformative discoveries, LBNE promises to be a vital facility for the field of particle physics worldwide, providing physicists from around the globe with opportunities to collaborate in a twenty to thirty year program of exciting science. In this document we provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess.Comment: Major update of previous version. This is the reference document for LBNE science program and current status. Chapters 1, 3, and 9 provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess. 288 pages, 116 figure

Genetic risk and a primary role for cell-mediated immune mechanisms in multiple sclerosis.

Multiple sclerosis is a common disease of the central nervous system in which the interplay between inflammatory and neurodegenerative processes typically results in intermittent neurological disturbance followed by progressive accumulation of disability. Epidemiological studies have shown that genetic factors are primarily responsible for the substantially increased frequency of the disease seen in the relatives of affected individuals, and systematic attempts to identify linkage in multiplex families have confirmed that variation within the major histocompatibility complex (MHC) exerts the greatest individual effect on risk. Modestly powered genome-wide association studies (GWAS) have enabled more than 20 additional risk loci to be identified and have shown that multiple variants exerting modest individual effects have a key role in disease susceptibility. Most of the genetic architecture underlying susceptibility to the disease remains to be defined and is anticipated to require the analysis of sample sizes that are beyond the numbers currently available to individual research groups. In a collaborative GWAS involving 9,772 cases of European descent collected by 23 research groups working in 15 different countries, we have replicated almost all of the previously suggested associations and identified at least a further 29 novel susceptibility loci. Within the MHC we have refined the identity of the HLA-DRB1 risk alleles and confirmed that variation in the HLA-A gene underlies the independent protective effect attributable to the class I region. Immunologically relevant genes are significantly overrepresented among those mapping close to the identified loci and particularly implicate T-helper-cell differentiation in the pathogenesis of multiple sclerosis

Optimization of the doxycycline-dependent simian immunodeficiency virus through in vitro evolution

<p>Abstract</p> <p>Background</p> <p>Vaccination of macaques with live attenuated simian immunodeficiency virus (SIV) provides significant protection against the wild-type virus. The use of a live attenuated human immunodeficiency virus (HIV) as AIDS vaccine in humans is however considered unsafe because of the risk that the attenuated virus may accumulate genetic changes during persistence and evolve to a pathogenic variant. We earlier presented a conditionally live HIV-1 variant that replicates exclusively in the presence of doxycycline (dox). Replication of this vaccine strain can be limited to the time that is needed to provide full protection through transient dox administration. Since the effectiveness and safety of such a conditionally live virus vaccine should be tested in macaques, we constructed a similar dox-dependent SIV variant. The Tat-TAR transcription control mechanism in this virus was inactivated through mutation and functionally replaced by the dox-inducible Tet-On regulatory system. This SIV-rtTA variant replicated in a dox-dependent manner in T cell lines, but not as efficiently as the parental SIVmac239 strain. Since macaque studies will likely require an efficiently replicating variant, we set out to optimize SIV-rtTA through in vitro viral evolution.</p> <p>Results</p> <p>Upon long-term culturing of SIV-rtTA, additional nucleotide substitutions were observed in TAR that affect the structure of this RNA element but that do not restore Tat binding. We demonstrate that the bulge and loop mutations that we had introduced in the TAR element of SIV-rtTA to inactivate the Tat-TAR mechanism, shifted the equilibrium between two alternative conformations of TAR. The additional TAR mutations observed in the evolved variants partially or completely restored this equilibrium, which suggests that the balance between the two TAR conformations is important for efficient viral replication. Moreover, SIV-rtTA acquired mutations in the U3 promoter region. We demonstrate that these TAR and U3 changes improve viral replication in T-cell lines and macaque peripheral blood mononuclear cells (PBMC) but do not affect dox-control.</p> <p>Conclusion</p> <p>The dox-dependent SIV-rtTA variant was optimized by viral evolution, yielding variants that can be used to test the conditionally live virus vaccine approach and as a tool in SIV biology studies and vaccine research.</p