GCN5 modulates salicylic acid homeostasis by regulating H3K14ac levels at the 5ʹ and 3ʹ ends of its target genes

The modification of histones by acetyl groups has a key role in the regulation of chromatin structure and transcription. The Arabidopsis thaliana histone acetyltransferase GCN5 regulates histone modifications as part of the Spt-Ada-Gcn5 Acetyltransferase (SAGA) transcriptional coactivator complex. GCN5 was previously shown to acetylate lysine 14 of histone 3 (H3K14ac) in the promoter regions of its target genes even though GCN5 binding did not systematically correlate with gene activation. Here, we explored the mechanism through which GCN5 controls transcription. First, we fine-mapped its GCN5 binding sites genome-wide and then used several global methodologies (ATAC-seq, ChIP-seq and RNA-seq) to assess the effect of GCN5 loss-of-function on the expression and epigenetic regulation of its target genes. These analyses provided evidence that GCN5 has a dual role in the regulation of H3K14ac levels in their 5′ and 3′ ends of its target genes. While the gcn5 mutation led to a genome-wide decrease of H3K14ac in the 5′ end of the GCN5 down-regulated targets, it also led to an increase of H3K14ac in the 3′ ends of GCN5 up-regulated targets. Furthermore, genome-wide changes in H3K14ac levels in the gcn5 mutant correlated with changes in H3K9ac at both 5′ and 3′ ends, providing evidence for a molecular link between the depositions of these two histone modifications. To understand the biological relevance of these regulations, we showed that GCN5 participates in the responses to biotic stress by repressing salicylic acid (SA) accumulation and SA-mediated immunity, highlighting the role of this protein in the regulation of the crosstalk between diverse developmental and stress-responsive physiological programs. Hence, our results demonstrate that GCN5, through the modulation of H3K14ac levels on its targets, controls the balance between biotic and abiotic stress responses and is a master regulator of plant-environmental interactions

Identifying the palliative care needs of frail, older, housebound patients in the community: A cross-sectional study

Background: The early introduction of palliative care can have a positive impact on the quality of life of patients suffering from life-limiting diseases. However, the palliative care needs of older, frail, housebound patients are still mostly unknown, as is the impact of frailty on the importance of these needs. Objectives: To identify the palliative care needs of frail, older, housebound patients in the community. Methods: We conducted a cross-sectional observational study. This study took place in a single primary care center and included patients who were ≥65 years old, housebound, followed by the Geriatric Community Unit of the Geneva University Hospitals. Results: Seventy-one patients completed the study. Most patients were female (56.9%), and mean age (SD) was 81.1 (±7.9). The Edmonton Symptom Assessment Scale mean (SD) score was higher in frail patients as opposed to vulnerable patients for tiredness ( p = 0.016), drowsiness ( p = 0.0196), loss of appetite ( p = 0.0124), and impaired feeling of well-being ( p = 0.0132). There was no difference in spiritual well-being, measured by the spiritual scale subgroup of the Functional Assessment of the Chronic Illness Therapy–Spiritual Well-Being scale (FACIT-sp) between frail and vulnerable participants, although scores in both groups were low. Caregivers were mainly spouses (45%) and daughters (27.5%) with a mean (SD) age of 70.7 (±13.6). The overall carer–burden measured by the Mini-Zarit was low. Significance of results: Older, frail, housebound patients have specific needs that differ from non-frail patients and should guide future palliative care provision. How and when palliative care should be provided to this population remains to be determined.</p

Defining Two Chemosensory Arrays in Shewanella oneidensis

International audienceShewanella oneidensis has 2 functional chemosensory systems named Che1 and Che3, and 27 chemoreceptors. Che3 is dedicated to chemotaxis while Che1 could be involved in RpoS posttranslational regulation. In this study, we have shown that two chemoreceptors Aer2so and McpAso, genetically related to the Che1 system, form distinct core-signaling units and signal to Che1 and Che3, respectively. Moreover, we observed that Aer2so is a cytoplasmic dynamic chemoreceptor that, when in complex with CheA1 and CheW1, localizes at the two poles and the centre of the cells. Altogether, the results obtained indicate that Che1 and Che3 systems are interconnected by these two chemoreceptors allowing a global response for bacterial survival

Influence of the secondary X-Rays on the organic matter at Mars’ near-surface

International audienceIn 2015 the SAM experiment on board the curiosity rover discovered the first organic molecule endogenous to Mars. This molecule is certainly the result of the reaction of a still unknown molecule with the perchlorates/chlorates present in the Martian soil [1]. Since then, other organics have been discovered: sulfur and nitrogen bearing molecules [2-3] and chlorohydrocarbons [4]. Those chlorohydrocarbons compounds could be generated by a reaction which may occur at Mars’ near-surface induced by the harsh radiative environment, e.g. direct radiation (UV, high energy X- and γ-rays) and secondary photons produced by the interaction of direct radiations with the martian regolith (low energy secondary X-rays). Additionally, organic molecules are detected in lower concentration than expected from modelling [5], suggesting organic matter degradation over geological time. Our team thus investigates the influence of radiations on organic molecules under simulated Mars’ surface conditions. In the present study, we mainly focused on the action of X-rays (hard and soft X-ray) on various organic molecules, the chiral amino acids L-alanine and L-phenylalanine and two potential precursors of chlorobenzene, benzoic and trimesic acids. These molecules were irradiated pure but also in contact with calcium perchlorate in order to better understand the roles in perchlorates present in the Martian soil. We also studied the molecules within mineral matrices in the form of pellets, in absence and in presence of perchlorates (max 3 % weight)

Influence of the secondary X-Rays on the organic matter at Mars’ near-surface

International audienceIn 2015 the SAM experiment on board the curiosity rover discovered the first organic molecule endogenous to Mars. This molecule is certainly the result of the reaction of a still unknown molecule with the perchlorates/chlorates present in the Martian soil [1]. Since then, other organics have been discovered: sulfur and nitrogen bearing molecules [2-3] and chlorohydrocarbons [4]. Those chlorohydrocarbons compounds could be generated by a reaction which may occur at Mars’ near-surface induced by the harsh radiative environment, e.g. direct radiation (UV, high energy X- and γ-rays) and secondary photons produced by the interaction of direct radiations with the martian regolith (low energy secondary X-rays). Additionally, organic molecules are detected in lower concentration than expected from modelling [5], suggesting organic matter degradation over geological time. Our team thus investigates the influence of radiations on organic molecules under simulated Mars’ surface conditions. In the present study, we mainly focused on the action of X-rays (hard and soft X-ray) on various organic molecules, the chiral amino acids L-alanine and L-phenylalanine and two potential precursors of chlorobenzene, benzoic and trimesic acids. These molecules were irradiated pure but also in contact with calcium perchlorate in order to better understand the roles in perchlorates present in the Martian soil. We also studied the molecules within mineral matrices in the form of pellets, in absence and in presence of perchlorates (max 3 % weight)

Influence of the secondary X-Rays on the organic matter at Mars’ near-surface

International audienceIn 2015 the SAM experiment on board the curiosity rover discovered the first organic molecule endogenous to Mars. This molecule is certainly the result of the reaction of a still unknown molecule with the perchlorates/chlorates present in the Martian soil [1]. Since then, other organics have been discovered: sulfur and nitrogen bearing molecules [2-3] and chlorohydrocarbons [4]. Those chlorohydrocarbons compounds could be generated by a reaction which may occur at Mars’ near-surface induced by the harsh radiative environment, e.g. direct radiation (UV, high energy X- and γ-rays) and secondary photons produced by the interaction of direct radiations with the martian regolith (low energy secondary X-rays). Additionally, organic molecules are detected in lower concentration than expected from modelling [5], suggesting organic matter degradation over geological time. Our team thus investigates the influence of radiations on organic molecules under simulated Mars’ surface conditions. In the present study, we mainly focused on the action of X-rays (hard and soft X-ray) on various organic molecules, the chiral amino acids L-alanine and L-phenylalanine and two potential precursors of chlorobenzene, benzoic and trimesic acids. These molecules were irradiated pure but also in contact with calcium perchlorate in order to better understand the roles in perchlorates present in the Martian soil. We also studied the molecules within mineral matrices in the form of pellets, in absence and in presence of perchlorates (max 3 % weight)

Understanding the Influence of the Secondary X-Rays on the Organic Matter at Mars' Near-Surface with the Soleil Synchrotron Beam Line LUCIA

International audienceThe SAM instrument onboard NASA Curiosity rover revealed organic matter indigenous to Mars samples through the detection of chlorohydrocarbons, and sulfur and nitrogen bearing molecules. Chlorohydrocarbons are thought to mainly originate from a reaction of unidentified higher molecular mass organic compounds with perchlorates and chlorates present in the soil. The reaction may occur at Mars' near-surface induced by the harsh radiative environment, e.g. direct radiation (UV, high energy X- and γ-rays) and secondary photons produced by the interaction of direct radiations with the martian regolith (low energy secondary X-rays). Additionally, organic molecules are detected in lower concentration than expected from modelling, suggesting organic matter degradation over geological time. Our team thus investigates the influence of radiations on organic molecules under simulated Mars' surface conditions. In the present study, we mainly focused on the action of X-rays on four organic molecules, the chiral amino acids L-alanine and L-phenylalanine and two potential precursors of chlorobenzene (one of the chlorohydrocarbons detected by SAM), benzoic and trimesic acids. Those pure molecules deposits are produced by sublimation on an optical window or mixed with perchlorate. We also studied the molecules within mineral matrices in the form of pellets, in absence and in presence of perchlorates

Understanding the Influence of the Secondary X-Rays on the Organic Matter at Mars' Near-Surface with the Soleil Synchrotron Beam Line LUCIA

International audienceThe SAM instrument onboard NASA Curiosity rover revealed organic matter indigenous to Mars samples through the detection of chlorohydrocarbons, and sulfur and nitrogen bearing molecules. Chlorohydrocarbons are thought to mainly originate from a reaction of unidentified higher molecular mass organic compounds with perchlorates and chlorates present in the soil. The reaction may occur at Mars' near-surface induced by the harsh radiative environment, e.g. direct radiation (UV, high energy X- and γ-rays) and secondary photons produced by the interaction of direct radiations with the martian regolith (low energy secondary X-rays). Additionally, organic molecules are detected in lower concentration than expected from modelling, suggesting organic matter degradation over geological time. Our team thus investigates the influence of radiations on organic molecules under simulated Mars' surface conditions. In the present study, we mainly focused on the action of X-rays on four organic molecules, the chiral amino acids L-alanine and L-phenylalanine and two potential precursors of chlorobenzene (one of the chlorohydrocarbons detected by SAM), benzoic and trimesic acids. Those pure molecules deposits are produced by sublimation on an optical window or mixed with perchlorate. We also studied the molecules within mineral matrices in the form of pellets, in absence and in presence of perchlorates

Impact of secondary X-Rays on the possible precursors of chlorinated organic compounds detected at the Mars surface (MarsOrganiX)

International audienceThe Sample Analysis at Mars (SAM) instrument onboard NASA Curiosity rover revealed for the first time, organic matter indigenous to a Martian sample with the detection of chlorohydrocarbons [1]. These molecules are thought to originate from a reaction of unidentified higher molecular mass organic matter with Martian perchlorates in the pyrolytic oven of the instrument. However, other reactions may occur at Mars' near-surface induced by the harsh radiative environment, e.g. direct radiation (UV light, high energy X- and γ-rays) and secondary photons produced by the interaction of direct radiations with the Martian regolith (low energy secondary X-rays). Additionally, organic molecules are detected in a lower concentration than expected from modelling [2], suggesting organic matter degradation over geological time. This degradation could be induced by the radiation at the Mars surface. For these reasons, we investigate the influence of radiations on organic molecules (L-Alanine, Benzoic, phthalic acid with or without presence of perchlorates) under simulated Mars' surface conditions at the laboratory. To address the influence of high energy X-rays directly reaching Mars surface on the degradation of organic molecules, a synchrotron session was undertaken on the PSICHE beam line in October 2017 (Gif sur Yvette, France). The reactivity and chemical characterization of L-alanine and benzoic acid exposed to hard X-rays (25-50 keV) did not show any degradation, up to 8 hours of irradiation, of organics nor formation of chlorohydrocarbons. The X-rays of the PSICHE beam line may have been too energetic for degrading efficiently organic molecules [3, 4]. For that reason, a new set of experiments have been done on the LUCIA beamline which combines both low energy X-rays and high photon flux, allowing to simulate processes at the geological-timescale of Mars. The use of this line also permits to follow the evolution of the samples in real time using XANES/EXAFS techniques. To follow the evolution of our samples, we used infrared spectroscopy and gas chromatography coupled to mass spectrometry analytical techniques. The energetic range provided by the monochromatic beam of LUCIA has been used to simulate the secondary fluorescence from the major elements present in the Martian near-surface, for up to a simulated 80 million years of irradiation time on Mar