Heat Shock Signaling in Land Plants: From Plasma Membrane Sensing to the Transcription of Small Heat Shock Proteins.

Heat stress events are major factors limiting crop productivity. During summer days, land plants must anticipate in a timely manner upcoming mild and severe temperature. They respond by accumulating protective heat-shock proteins (HSPs), conferring acquired thermotolerance. All organisms synthetize HSPs; many of which are members of the conserved chaperones families. This review describes recent advances in plant temperature sensing, signaling, and response. We highlight the pathway from heat perception by the plasma membrane through calcium channels, such as cyclic nucleotide-gated channels, to the activation of the heat-shock transcription factors (HSFs). An unclear cellular signal activates HSFs, which act as essential regulators. In particular, the HSFA subfamily can bind heat shock elements in HSP promoters and could mediate the dissociation of bound histones, leading to HSPs transcription. Although plants can modulate their transcriptome, proteome, and metabolome to protect the cellular machinery, HSP chaperones prevent, use, and revert the formation of misfolded proteins, thereby avoiding heat-induced cell death. Remarkably, the HSP20 family is mostly tightly repressed at low temperature, suggesting that a costly mechanism can become detrimental under unnecessary conditions. Here, the role of HSP20s in response to HS and their possible deleterious expression at non-HS temperatures is discussed

How do humans and plants feel the heat?

The 2021 Nobel prize was awarded for the discovery of the animal thermosensory channel TRPV1. We highlight notable shared features with the higher plant thermosensory channel CNGC2/4. Both channels respond to temperature-induced changes in plasma membrane fluidity, leading to hyperphosphorylation of the HSF1 transcription factor via a specific heat-signaling cascade

Moderate Fever Cycles as a Potential Mechanism to Protect the Respiratory System in COVID-19 Patients.

Mortality in COVID-19 patients predominantly results from an acute respiratory distress syndrome (ARDS), in which lungs alveolar cells undergo programmed cell death. Mortality in a sepsis-induced ARDS rat model is reduced by adenovirus over-expression of the HSP70 chaperone. A natural rise of body temperature during mild fever can naturally accumulate high cellular levels of HSP70 that can arrest apoptosis and protect alveolar lung cells from inflammatory damages. However, beyond 1-2 h of fever, no HSP70 is being further produced and a decreased in body temperature required to the restore cell's ability to produce more HSP70 in a subsequent fever cycle. We suggest that antipyretics may be beneficial in COVID-19 patients subsequent to several hours of mild (<38.8°C) advantageous fever, allowing lung cells to accumulate protective HSP70 against damages from the inflammatory response to the virus SARS-CoV-2. With age, the ability to develop fever and accumulate HSP70 decreases. This could be ameliorated, when advisable to do so, by thermotherapies and/or physical training

Resveratrol and related stilbene derivatives induce stress granules with distinct clearance kinetics.

Stress granules (SGs) are ribonucleoprotein functional condensates that form under stress conditions in all eukaryotic cells. Although their stress-survival function is far from clear, SGs have been implicated in the regulation of many vital cellular pathways. Consequently, SG dysfunction is thought to be a mechanistic point of origin for many neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS). Additionally, SGs are thought to play a role in pathogenic pathways as diverse as viral infection and chemotherapy resistance. There is a growing consensus on the hypothesis that understanding the mechanistic regulation of SG physical properties is essential to understanding their function. Although the internal dynamics and condensation mechanisms of SGs have been broadly investigated, there have been fewer investigations into the timing of SG formation and clearance in live cells. Because the lifetime of SG persistence can be a key factor in their function and tendency toward pathological dysregulation, SG clearance mechanisms deserve particular attention. Here we show that resveratrol and its analogues piceatannol, pterostilbene, and 3,4,5,4'-tetramethoxystilbene induce G3BP-dependent SG formation with atypically rapid clearance kinetics. Resveratrol binds to G3BP, thereby reducing its protein-protein association valency. We suggest that altering G3BP valency is a pathway for the formation of uniquely transient SGs

Diabetes, hypertension, body mass index, smoking and COVID-19-related mortality: a systematic review and meta-analysis of observational studies.

We conducted a systematic literature review and meta-analysis of observational studies to investigate the association between diabetes, hypertension, body mass index (BMI) or smoking with the risk of death in patients with COVID-19 and to estimate the proportion of deaths attributable to these conditions. Relevant observational studies were identified by searches in the PubMed, Cochrane library and Embase databases through 14 November 2020. Random-effects models were used to estimate summary relative risks (SRRs) and 95% CIs. Certainty of evidence was assessed using the Cochrane methods and the Grading of Recommendations, Assessment, Development and Evaluations framework. A total of 186 studies representing 210 447 deaths among 1 304 587 patients with COVID-19 were included in this analysis. The SRR for death in patients with COVID-19 was 1.54 (95% CI 1.44 to 1.64, I <sup>2</sup> =92%, n=145, low certainty) for diabetes and 1.42 (95% CI 1.30 to 1.54, I <sup>2</sup> =90%, n=127, low certainty) for hypertension compared with patients without each of these comorbidities. Regarding obesity, the SSR was 1.45 (95% CI 1.31 to 1.61, I <sup>2</sup> =91%, n=54, high certainty) for patients with BMI ≥30 kg/m <sup>2</sup> compared with those with BMI <30 kg/m <sup>2</sup> and 1.12 (95% CI 1.07 to 1.17, I <sup>2</sup> =68%, n=25) per 5 kg/m <sup>2</sup> increase in BMI. There was evidence of a J-shaped non-linear dose-response relationship between BMI and mortality from COVID-19, with the nadir of the curve at a BMI of around 22-24, and a 1.5-2-fold increase in COVID-19 mortality with extreme obesity (BMI of 40-45). The SRR was 1.28 (95% CI 1.17 to 1.40, I <sup>2</sup> =74%, n=28, low certainty) for ever, 1.29 (95% CI 1.03 to 1.62, I <sup>2</sup> =84%, n=19) for current and 1.25 (95% CI 1.11 to 1.42, I <sup>2</sup> =75%, n=14) for former smokers compared with never smokers. The absolute risk of COVID-19 death was increased by 14%, 11%, 12% and 7% for diabetes, hypertension, obesity and smoking, respectively. The proportion of deaths attributable to diabetes, hypertension, obesity and smoking was 8%, 7%, 11% and 2%, respectively. Our findings suggest that diabetes, hypertension, obesity and smoking were associated with higher COVID-19 mortality, contributing to nearly 30% of COVID-19 deaths. CRD42020218115

Effect of hydroxychloroquine with or without azithromycin on the mortality of coronavirus disease 2019 (COVID-19) patients: a systematic review and meta-analysis.

Hydroxychloroquine or chloroquine with or without azithromycin have been widely promoted to treat coronavirus disease 2019 (COVID-19) following early in vitro antiviral effects against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The aim of this systematic review and meta-analysis was to assess whether chloroquine or hydroxychloroquine with or without azithromycin decreased COVID-19 mortality compared with the standard of care. PubMed, Web of Science, Embase Cochrane Library, Google Scholar and MedRxiv were searched up to 25 July 2020. We included published and unpublished studies comparing the mortality rate between patients treated with chloroquine or hydroxychloroquine with or without azithromycin and patients managed with standard of care. Patients ≥18 years old with confirmed COVID-19. Chloroquine or hydroxychloroquine with or without azithromycin. Effect sizes were pooled using a random-effects model. Multiple subgroup analyses were conducted to assess drug safety. The initial search yielded 839 articles, of which 29 met our inclusion criteria. All studies except one were conducted on hospitalized patients and evaluated the effects of hydroxychloroquine with or without azithromycin. Among the 29 articles, three were randomized controlled trials, one was a non-randomized trial and 25 were observational studies, including 11 with a critical risk of bias and 14 with a serious or moderate risk of bias. After excluding studies with critical risk of bias, the meta-analysis included 11 932 participants for the hydroxychloroquine group, 8081 for the hydroxychloroquine with azithromycin group and 12 930 for the control group. Hydroxychloroquine was not significantly associated with mortality: pooled relative risk (RR) 0.83 (95% CI 0.65-1.06, n = 17 studies) for all studies and RR = 1.09 (95% CI 0.97-1.24, n = 3 studies) for randomized controlled trials. Hydroxychloroquine with azithromycin was associated with an increased mortality (RR = 1.27; 95% CI 1.04-1.54, n = 7 studies). We found similar results with a Bayesian meta-analysis. Hydroxychloroquine alone was not associated with reduced mortality in hospitalized COVID-19 patients but the combination of hydroxychloroquine and azithromycin significantly increased mortality

A pair of tabersonine 16-hydroxylases initiates the synthesis of vindoline in an organ dependent manner in Catharanthus roseus

Hydroxylation of tabersonine at the C-16 position, catalyzed by tabersonine 16-hydroxylase (T16H), initiates the synthesis of vindoline that constitutes the main alkaloid accumulated in leaves of Catharanthus roseus. Over the last decade, this reaction has been associated with CYP71D12 cloned from undifferentiated C. roseus cells. In this study, we isolated a second cytochrome P450 (CYP71D351) displaying T16H activity. Biochemical characterization demonstrated that CYP71D12 and CYP71D351 both exhibit high affinity for tabersonine and narrow substrate specificity, making of T16H, to our knowledge, the first alkaloid biosynthetic enzyme displaying two isoforms encoded by distinct genes characterized to date in C. roseus. However, both genes dramatically diverge in transcript distribution in planta. While CYP71D12 (T16H1) expression is restricted to flowers and undifferentiated cells, the CYP71D351 (T16H2) expression profile is similar to the other vindoline biosynthetic genes reaching a maximum in young leaves. Moreover, transcript localization by carborundum abrasion and RNA in situ hybridization demonstrated that CYP71D351 messenger RNAs are specifically located to leaf epidermis, which also hosts the next step of vindoline biosynthesis. Comparison of high- and low-vindoline-accumulating C. roseus cultivars also highlights the direct correlation between CYP71D351 transcript and vindoline levels. In addition, CYP71D351 down-regulation mediated by virus-induced gene silencing reduces vindoline accumulation in leaves and redirects the biosynthetic flux toward the production of unmodified alkaloids at the C-16 position. All these data demonstrate that tabersonine 16-hydroxylation is orchestrated in an organ-dependent manner by two genes including CYP71D351, which encodes the specific T16H isoform acting in the foliar vindoline biosynthesis