Expression of the ggpPS gene for glucosylglycerol biosynthesis from Azotobacter vinelandii improves the salt tolerance of Arabidopsis thaliana

Many organisms accumulate compatible solutes in response to salt or desiccation stress. Moderate halotolerant cyanobacteria and some heterotrophic bacteria synthesize the compatible solute glucosylglycerol (GG) as their main protective compound. In order to analyse the potential of GG to improve salt tolerance of higher plants, the model plant Arabidopsis thaliana was transformed with the ggpPS gene from the γ-proteobacterium Azotobacter vinelandii coding for a combined GG-phosphate synthase/phosphatase. The heterologous expression of the ggpPS gene led to the accumulation of high amounts of GG. Three independent Arabidopsis lines showing different GG contents were characterized in growth experiments. Plants containing a low (1–2 μmol g−1 FM) GG content in leaves showed no altered growth performance under control conditions but an increased salt tolerance, whereas plants accumulating a moderate (2–8 μmol g−1 FM) or a high GG content (around 17 μmol g−1 FM) showed growth retardation and no improvement of salt resistance. These results indicate that the synthesis of the compatible solute GG has a beneficial effect on plant stress tolerance as long as it is accumulated to an extent that does not negatively interfere with plant metabolism

Metabolic control of DNA methylation in naive pluripotent cells.

Naive epiblast and embryonic stem cells (ESCs) give rise to all cells of adults. Such developmental plasticity is associated with genome hypomethylation. Here, we show that LIF-Stat3 signaling induces genomic hypomethylation via metabolic reconfiguration. Stat3-/- ESCs show decreased α-ketoglutarate production from glutamine, leading to increased Dnmt3a and Dnmt3b expression and DNA methylation. Notably, genome methylation is dynamically controlled through modulation of α-ketoglutarate availability or Stat3 activation in mitochondria. Alpha-ketoglutarate links metabolism to the epigenome by reducing the expression of Otx2 and its targets Dnmt3a and Dnmt3b. Genetic inactivation of Otx2 or Dnmt3a and Dnmt3b results in genomic hypomethylation even in the absence of active LIF-Stat3. Stat3-/- ESCs show increased methylation at imprinting control regions and altered expression of cognate transcripts. Single-cell analyses of Stat3-/- embryos confirmed the dysregulated expression of Otx2, Dnmt3a and Dnmt3b as well as imprinted genes. Several cancers display Stat3 overactivation and abnormal DNA methylation; therefore, the molecular module that we describe might be exploited under pathological conditions

Maternal mutations of FOXF1 cause Alveolar capillary dysplasia despite not being imprinted

Alveolar capillary dysplasia with misalignment of pulmonary veins (ACDMPV) is a rare cause of pulmonary hypertension in newborns. Maternally inherited point mutations in Forkhead Box F1 gene (FOXF1), deletions of the gene or its long-range enhancers on the maternal allele are responsible for this neonatal lethal disorder. Here we describe monozygotic twins and one full-term newborn with ACD and gastrointestinal malformations caused by de novo mutations of FOXF1 on the maternal inherited alleles. Since this parental transmission is consistent with genomic imprinting, the parent-of-origin specific monoallelic expression of genes, we have undertaken a detailed analysis of both allelic expression and DNA methylation. FOXF1 and its neighboring gene FENDRR were both biallelically expressed in a wide range of fetal tissues, including lung and intestine. Furthermore detailed methylation screening within the 16q24.1 regions failed to identify regions of allelic methylation, suggesting that disrupted imprinting is not responsible for ACDMPV

Metabolic control of DNA methylation in naive pluripotent cells.

Naive epiblast and embryonic stem cells (ESCs) give rise to all cells of adults. Such developmental plasticity is associated with genome hypomethylation. Here, we show that LIF-Stat3 signaling induces genomic hypomethylation via metabolic reconfiguration. Stat3-/- ESCs show decreased α-ketoglutarate production from glutamine, leading to increased Dnmt3a and Dnmt3b expression and DNA methylation. Notably, genome methylation is dynamically controlled through modulation of α-ketoglutarate availability or Stat3 activation in mitochondria. Alpha-ketoglutarate links metabolism to the epigenome by reducing the expression of Otx2 and its targets Dnmt3a and Dnmt3b. Genetic inactivation of Otx2 or Dnmt3a and Dnmt3b results in genomic hypomethylation even in the absence of active LIF-Stat3. Stat3-/- ESCs show increased methylation at imprinting control regions and altered expression of cognate transcripts. Single-cell analyses of Stat3-/- embryos confirmed the dysregulated expression of Otx2, Dnmt3a and Dnmt3b as well as imprinted genes. Several cancers display Stat3 overactivation and abnormal DNA methylation; therefore, the molecular module that we describe might be exploited under pathological conditions

Novel sulI binary vectors enable an inexpensive foliar selection method in Arabidopsis

<p>Abstract</p> <p>Background</p> <p>Sulfonamide resistance is conferred by the <it>sul</it>I gene found on many <it>Enterobacteriaceae </it>R plasmids and Tn21 type transposons. The <it>sul</it>I gene encodes a sulfonamide insensitive dihydropteroate synthase enzyme required for folate biosynthesis. Transformation of tobacco, potato or <it>Arabidopsis </it>using <it>sul</it>I as a selectable marker generates sulfadiazine-resistant plants. Typically <it>sul</it>I-based selection of transgenic plants is performed on tissue culture media under sterile conditions.</p> <p>Findings</p> <p>A set of novel binary vectors containing a <it>sul</it>I selectable marker expression cassette were constructed and used to generate transgenic <it>Arabidopsis</it>. We demonstrate that the <it>sul</it>I selectable marker can be utilized for direct selection of plants grown in soil with a simple foliar spray application procedure. A highly effective and inexpensive high throughput screening strategy to identify transgenic <it>Arabidopsis </it>without use of tissue culture was developed.</p> <p>Conclusion</p> <p>Novel <it>sul</it>I-containing <it>Agrobacterium </it>binary vectors designed to over-express a gene of interest or to characterize a test promoter in transgenic plants have been constructed. These new vector tools combined with the various beneficial attributes of sulfonamide selection and the simple foliar screening strategy provide an advantageous alternative for plant biotechnology researchers. The set of binary vectors is freely available upon request.</p

Photosynthesis-dependent H₂O₂ transfer from chloroplasts to nuclei provides a high-light signalling mechanism

Chloroplasts communicate information by signalling to nuclei during acclimation to fluctuating light. Several potential operating signals originating from chloroplasts have been proposed, but none have been shown to move to nuclei to modulate gene expression. One proposed signal is hydrogen peroxide (H2O2) produced by chloroplasts in a light-dependent manner. Using HyPer2, a genetically encoded fluorescent H2O2 sensor, we show that in photosynthetic Nicotiana benthamiana epidermal cells, exposure to high light increases H2O2 production in chloroplast stroma, cytosol and nuclei. Critically, over-expression of stromal ascorbate peroxidase (H2O2 scavenger) or treatment with DCMU (photosynthesis inhibitor) attenuates nuclear H2O2 accumulation and high light-responsive gene expression. Cytosolic ascorbate peroxidase over-expression has little effect on nuclear H2O2 accumulation and high light-responsive gene expression. This is because the H2O2 derives from a sub-population of chloroplasts closely associated with nuclei. Therefore, direct H2O2 transfer from chloroplasts to nuclei, avoiding the cytosol, enables photosynthetic control over gene expression

Achlya mitochondrial DNA: gene localization and analysis of inverted repeats

Mitochondrial DNA from four strains of the oomycete Achlya has been compared and nine gene loci mapped, including that of the ribosomal protein gene, var1 . Examination of the restriction enzyme site maps showed the presence of four insertions relative to a map common to all four strains. All the insertions were found in close proximity to genic regions. The four strains also cotained the inverted repeat first observed in A. ambisexualis (Hudspeth et al. 1983), allowing an examination by analysis of retained restriction sites of the evolutionary stability of repeated DNA sequences relative to single copy sequences. Although the inverted repeat is significantly more stable than single copy sequences, more detailed analysis indicated that this stability is limited to the portion encoding the ribosomal RNA genes. Thus, the apparent evolutionary stability of the repeat does not appear to derive from the inverted repeat structure per se.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47563/1/438_2004_Article_BF00330510.pd

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570