Production of reactive oxygen species in excised, desiccated and cryopreserved explants of Trichilia dregeana Sond

AbstractThe tropical tree Trichilia dregeana Sond. has recalcitrant seeds that cannot be stored by conventional seed banking methods that include drying and storage at low temperatures, or by using cryopreservation protocols that have been successfully applied to recalcitrant-seeded species such as Castanea sativa. We recently showed that in C. sativa both excision of the embryonic axes and subsequent dehydration cause transitory (5min) bursts of extracellular superoxide (O2−) production. Here we show that both excision and partial dehydration of the embryonic axes from seeds of T. dregeana cause large, prolonged extracellular bursts of O2−. Furthermore, during rehydration after cryopreservation, another burst of O2− occurs with slightly different kinetics. Compared with C. sativa, rates of O2− production in T. dregeana are approximately twice as great and decline much more slowly, suggesting that excessive radical formation may be responsible for poor survival of the axes following cryopreservation. Fractionating the cell wall proteins of embryonic axes and cotyledons in conjunction with electrophoretic analyses of the fractions showed that most O2− was produced by two peroxidases with molecular masses of c. 50 and 80kD that were loosely bound to the cell walls of the embryonic axes. Future successful cryopreservation of T. dregeana would appear to depend on manipulations of O2− production, and the discovery of peroxidases as the enzymes responsible described here may help in the development of more effective protocols

In vitro hardening — the role of supra-optimal sucrose on acclimation stress in Kniphofia leucocephala

Supra-optimal sucrose concentrations (6% and 9%) in vitro resulted in morphological and ultrastructural differences between control and stressed plantlets of Kniphofia leucocephala. Shoot length, in particular, was significantly reduced by increasing sucrose concentrations. Supra-optimal sucrose concentrations did not confer significant benefits on the stressed plantlets after transplanting, indicated by the similar maximum photochemical efficiency of photosystem A. However, environmental stresses ex vitro may not have been sufficiently great to elicit different responses from the control and stressed plantlets

Geographical and temporal distribution of SARS-CoV-2 clades in the WHO European Region, January to June 2020

We show the distribution of SARS-CoV-2 genetic clades over time and between countries and outline potential genomic surveillance objectives. We applied three available genomic nomenclature systems for SARS-CoV-2 to all sequence data from the WHO European Region available during the COVID-19 pandemic until 10 July 2020. We highlight the importance of real-time sequencing and data dissemination in a pandemic situation. We provide a comparison of the nomenclatures and lay a foundation for future European genomic surveillance of SARS-CoV-2.Peer reviewe

Tocilizumab in patients admitted to hospital with COVID-19 (RECOVERY): a randomised, controlled, open-label, platform trial

Background: In this study, we aimed to evaluate the effects of tocilizumab in adult patients admitted to hospital with COVID-19 with both hypoxia and systemic inflammation. Methods: This randomised, controlled, open-label, platform trial (Randomised Evaluation of COVID-19 Therapy [RECOVERY]), is assessing several possible treatments in patients hospitalised with COVID-19 in the UK. Those trial participants with hypoxia (oxygen saturation <92% on air or requiring oxygen therapy) and evidence of systemic inflammation (C-reactive protein ≥75 mg/L) were eligible for random assignment in a 1:1 ratio to usual standard of care alone versus usual standard of care plus tocilizumab at a dose of 400 mg–800 mg (depending on weight) given intravenously. A second dose could be given 12–24 h later if the patient's condition had not improved. The primary outcome was 28-day mortality, assessed in the intention-to-treat population. The trial is registered with ISRCTN (50189673) and ClinicalTrials.gov (NCT04381936). Findings: Between April 23, 2020, and Jan 24, 2021, 4116 adults of 21 550 patients enrolled into the RECOVERY trial were included in the assessment of tocilizumab, including 3385 (82%) patients receiving systemic corticosteroids. Overall, 621 (31%) of the 2022 patients allocated tocilizumab and 729 (35%) of the 2094 patients allocated to usual care died within 28 days (rate ratio 0·85; 95% CI 0·76–0·94; p=0·0028). Consistent results were seen in all prespecified subgroups of patients, including those receiving systemic corticosteroids. Patients allocated to tocilizumab were more likely to be discharged from hospital within 28 days (57% vs 50%; rate ratio 1·22; 1·12–1·33; p<0·0001). Among those not receiving invasive mechanical ventilation at baseline, patients allocated tocilizumab were less likely to reach the composite endpoint of invasive mechanical ventilation or death (35% vs 42%; risk ratio 0·84; 95% CI 0·77–0·92; p<0·0001). Interpretation: In hospitalised COVID-19 patients with hypoxia and systemic inflammation, tocilizumab improved survival and other clinical outcomes. These benefits were seen regardless of the amount of respiratory support and were additional to the benefits of systemic corticosteroids. Funding: UK Research and Innovation (Medical Research Council) and National Institute of Health Research

Convalescent plasma in patients admitted to hospital with COVID-19 (RECOVERY): a randomised controlled, open-label, platform trial

Background: Many patients with COVID-19 have been treated with plasma containing anti-SARS-CoV-2 antibodies. We aimed to evaluate the safety and efficacy of convalescent plasma therapy in patients admitted to hospital with COVID-19. Methods: This randomised, controlled, open-label, platform trial (Randomised Evaluation of COVID-19 Therapy [RECOVERY]) is assessing several possible treatments in patients hospitalised with COVID-19 in the UK. The trial is underway at 177 NHS hospitals from across the UK. Eligible and consenting patients were randomly assigned (1:1) to receive either usual care alone (usual care group) or usual care plus high-titre convalescent plasma (convalescent plasma group). The primary outcome was 28-day mortality, analysed on an intention-to-treat basis. The trial is registered with ISRCTN, 50189673, and ClinicalTrials.gov, NCT04381936. Findings: Between May 28, 2020, and Jan 15, 2021, 11558 (71%) of 16287 patients enrolled in RECOVERY were eligible to receive convalescent plasma and were assigned to either the convalescent plasma group or the usual care group. There was no significant difference in 28-day mortality between the two groups: 1399 (24%) of 5795 patients in the convalescent plasma group and 1408 (24%) of 5763 patients in the usual care group died within 28 days (rate ratio 1·00, 95% CI 0·93–1·07; p=0·95). The 28-day mortality rate ratio was similar in all prespecified subgroups of patients, including in those patients without detectable SARS-CoV-2 antibodies at randomisation. Allocation to convalescent plasma had no significant effect on the proportion of patients discharged from hospital within 28 days (3832 [66%] patients in the convalescent plasma group vs 3822 [66%] patients in the usual care group; rate ratio 0·99, 95% CI 0·94–1·03; p=0·57). Among those not on invasive mechanical ventilation at randomisation, there was no significant difference in the proportion of patients meeting the composite endpoint of progression to invasive mechanical ventilation or death (1568 [29%] of 5493 patients in the convalescent plasma group vs 1568 [29%] of 5448 patients in the usual care group; rate ratio 0·99, 95% CI 0·93–1·05; p=0·79). Interpretation: In patients hospitalised with COVID-19, high-titre convalescent plasma did not improve survival or other prespecified clinical outcomes. Funding: UK Research and Innovation (Medical Research Council) and National Institute of Health Research

Partial dehydration and ABA induce tolerance to desiccation-induced ion leakage in the moss Atrichum androgynum

A simple ion leakage assay was used to test if specific hardening treatments can increase desiccation tolerance in the moss Atrichum androgynum. Reducing the relative water content (RWC) of apical stem segments to c. 0.6 for 3 d, followed by storing the material fully hydrated for 1 d typically reduced the proportion of intracellular K’ lost following desiccation by between 15 and 20% compared with controls kept moist. Reducing the RWC of the plants further during hardening by using air of lower humidities during hardening did not further increase tolerance. An optimal increase in tolerance occurred after 3 d of hardening; no further increase in tolerance occurred by extending the hardening period to 5 d. While heat shock had no effect, treating the moss with abscisic acid (ABA) for 1h followed by storage for 3 d in the light increased resistance to ion leakage to the same extent as partial dehydration. The ABA-induced increase in tolerance was much less if plants were pre-treated in the dark, and could be abolished by simultaneously treating the moss with the protein synthesis inhibitor cyclohexamide. Results indicated that A androgynum possesses inducible tolerance mechanisms that reduce desiccation-induced damage

Some aspects of the water relations of the lichen Xanthomaculina hottentotta (Ach.) Hale from the Namib desert

The water relations of the desert lichen Xanthomaculina hottentotta were investigated using thermocouple psychrometry. Although the water relations of X. hottentotta were similar to those of other lichens from xeric habitats, X. hottentotta lost less K+ following sudden re-wetting, contained less intercellular water and had a higher ψπs than these lichens. The implications of these findings for the water relations of X. hottentotta are discussed

Induction of desiccation tolerance mechanisms occurs in both the fast-drying filmy fern Crepidomanes inopinatum and the slow-drying fern Loxogramme abyssinica

© 2020 SAAB The desiccation tolerant (DT) fern species Crepidomanes inopinatum and Loxogramme abyssinica often grow together in the understory of KwaZulu-Natal Afromontane forests. Crepidomanes inopinatum is a “filmy” fern that dries rapidly because it lacks a cuticle; by contrast L. abyssinica possesses a cuticle, and therefore dries slowly. It was predicted that because C. inopinatum dries quickly, this species would have little time available to induce DT mechanisms, and therefore mainly relies on constitutive mechanisms. By comparison, the slow-drying L. abyssinica has time to put DT mechanism in place, and therefore may depend more on inducible mechanisms. Here we tested whether a drying-rehydration cycle induces two mechanisms often suggested to contribute DT, specifically increases in the activity of two reactive oxygen species (ROS) scavenging enzymes and the concentration of soluble sugars. Measurement of chlorophyll fluorescence parameters showed that both species recover rapidly during rehydration after desiccation, confirming that both are genuinely poikilohydric. In both species slow desiccation increased the activity of the ROS scavenging enzyme superoxide dismutase (SOD), and the concentrations of soluble sugars. Desiccation had little effect on the activity of the (ROS) scavenging enzyme peroxidases (POX) in either species, suggesting that maintenance of POX activity is a constitutive DT mechanism. However, the main difference between the two species was that de-acclimation occurred in the filmy fern; moist storage under cool dim light for a week reduced DT. By contrast, in the fern with a cuticle no de-acclimation occurred. However, overall, results suggest that counter to our original hypothesis, inducible DT mechanisms occur even in filmy ferns that desiccate rapidly