Characterization of singlet oxygen-accumulating mutants isolated in a screen for altered oxidative stress response in Chlamydomonas reinhardtii

<p>Abstract</p> <p>Background</p> <p>When photosynthetic organisms are exposed to harsh environmental conditions such as high light intensities or cold stress, the production of reactive oxygen species like singlet oxygen is stimulated in the chloroplast. In <it>Chlamydomonas reinhardtii </it>singlet oxygen was shown to act as a specific signal inducing the expression of the nuclear glutathione peroxidase gene <it>GPXH/GPX5 </it>during high light stress, but little is known about the cellular mechanisms involved in this response. To investigate components affecting singlet oxygen signaling in <it>C. reinhardtii</it>, a mutant screen was performed.</p> <p>Results</p> <p>Mutants with altered <it>GPXH </it>response were isolated from UV-mutagenized cells containing a <it>GPXH</it>-arylsulfatase reporter gene construct. Out of 5500 clones tested, no mutant deficient in <it>GPXH </it>induction was isolated, whereas several clones showed constitutive high <it>GPXH </it>expression under normal light conditions. Many of these <it>GPXH </it>overexpressor (<it>gox</it>) mutants exhibited higher resistance to oxidative stress conditions whereas others were sensitive to high light intensities. Interestingly, most <it>gox </it>mutants produced increased singlet oxygen levels correlating with high <it>GPXH </it>expression. Furthermore, different patterns of altered photoprotective parameters like non-photochemical quenching, carotenoid contents and α-tocopherol levels were detected in the various <it>gox </it>mutants.</p> <p>Conclusions</p> <p>Screening for mutants with altered <it>GPXH </it>expression resulted in the isolation of many <it>gox </it>mutants with increased singlet oxygen production, showing the relevance of controlling the production of this ROS in photosynthetic organisms. Phenotypic characterization of these <it>gox </it>mutants indicated that the mutations might lead to either stimulated triplet chlorophyll and singlet oxygen formation or reduced detoxification of singlet oxygen in the chloroplast. Furthermore, changes in multiple protection mechanisms might be responsible for high singlet oxygen formation and <it>GPXH </it>expression, which could either result from mutations in multiple loci or in a single gene encoding for a global regulator of cellular photoprotection mechanisms.</p

Социально-философский анализ процессов модернизации в Китайской Народной Республике

Проанализированы основные изменения, произошедшие в обществе, в политической системе Китая в связи с началом реформ и модернизации после прихода к власти Дэн Сяопина. Дан анализ основных положений программы модернизации, предложенной руководством КНР. Освещены теоретико-методологические предпосылки модернизации КНР. Выделены основные мировоззренческие и методологические элементы теории социализма с китайской специфики

Understanding environmental and fisheries factors causing fluctuations in mud crab and blue swimmer crab fisheries in Northern Australia to inform harvest strategies

The current project investigated relationships between environmental factors and harvests of crabs in the Gulf of Carpentaria (GoC), northern Australia. This was in response to industry and managerial concerns about consistent declines in harvests of GoC Giant Mud Crab (Scylla serrata). In the orthern Territory (NT), declines occurred between 2009 and 2016, whilst in Queensland (Qld), declines occurred between 2013 and 2016. The declines occurred despite different management arrangements (e.g. NT harvests females, whereas Qld does not), suggesting common environmental factors were involved

Effects of controlled inspiratory muscle training in patients with COPD: a meta-analysis

The purpose of this meta-analysis is to review studies investigating the efficacy of inspiratory muscle training (IMT) in chronic obstructive pulmonary disease (COPD) patients and to find out whether patient characteristics influence the efficacy of IMT. A systematic literature search was performed using the Medline and Embase databases. On the basis of a methodological framework, a critical review was performed and summary effect-sizes were calculated by applying fixed and random effects models. Both IMT alone and IMT as adjunct to general exercise reconditioning significantly increased inspiratory muscle strength and endurance. A significant effect was found for dyspnoea at rest and during exercise. Improved functional exercise capacity tended to be an additional effect of IMT alone and as an adjunct to general exercise reconditioning, but this trend did not reach statistical significance. No significant correlations were found for training effects with patient characteristics. However, subgroup analysis in IMT plus exercise training revealed that patients with inspiratory muscle weakness improved significantly more compared to patients without inspiratory muscle weakness. From this review it is concluded that inspiratory muscle training is an important addition to a pulmonary rehabilitation programme directed at chronic obstructive pulmonary disease patients with inspiratory muscle weakness. The effect on exercise performance is still to be determined

Understanding IFNλ in rheumatoid arthritis

Unraveling the mechanisms underlying the inflammatory response in rheumatoid arthritis is crucial in order to better understand the disease and to develop novel therapeutic approaches. Although the effect of type I interferons on fibroblasts and in the context of rheumatoid arthritis has been described for some time, little is known on the effects of the type III interferons, also known as IFNλ. In a previous issue, Xu and colleagues demonstrate that one of the members of the IFNλ family, IFNλ1, enhances Toll-like receptor expression and consequently promotes the production of proinflammatory cytokines known to be involved in initiating and maintaining the inflammatory responses in rheumatoid arthritis