Lipid composition and habitat selection in higher plants

Lipid analyses of the leaves of Empetrum nigrum subspp. hermaphroditum with an upland distribution in the U.K. and the lowland E. nigrum subspp. nigrum revealed a) that the lowland subspecies had higher total and neutral lipid levels throughout 1979 b) that total lipid levels remained constant within the leaves of both subspecies throughout the year. c) that storage lipid (triacylglycerols) contributed 1.4% and 4.5% to the total lipid of subspecies hermaphroditum and nigrum respectively. This data is inconsistent with the suggestion that the high leaf total lipid levels associated with alpine species represent high levels of storage lipid. Instead it is suggested that the high lipid content of Empetrum leaves may be a reflection of a well-developed waxy cuticle. It'is pseudacorus occupies habitats characterized by poor O2 availability and is able to tolerate up to two months total anoxia without any loss in viability. By contrast the cultivated Iris qerrnanica var Quechei typically a plant of well drained soils suffers 100% mortality during 8 weeks anoxia. Further the cut primary shoot of I. germanica was observed to be more susceptible to anoxic injury than the I. remainder of the rhizome. As the biosynthesis of polyunsaturated fatty acids requires the participation of molecular oxygen it was thought profitable to compare what changes occurred in the anoxia tolerant I. pseudacorus and intolerant I. germanica when subject to anoxic stress. In I. pseudocorus there were a number of lipid modification during anoxia. Glycolipids declined dramatically and although all fatty acids declined it was surprising that saturated acids decreased the most. It was suggested that the decline in glycolipids might reflect mobilization of carbohydrate reserves and/or a replenishment of the fatty acid pool through glycolipid breakdown. The significance of the alterations in membrane fluidity which might be expected to result from alterations in the saturated /unsaturated ratio remain unexplained. By complete contrast, the anoxia intolerant I. germanica although possessing a highly similar lipid profile exhibited no changes in lipid composition in response to anoxia. Therefore membrane dysfunction through lipid component omission is not a major factor in anoxic mortality. Through production of cytotoxic species such as H2O2, O2, OH and 1O2, O2 may bring about peroxidative damage. On rexposure to air it was found that the highly anoxia sensitive primary shoot tissue of I. germanica produced 38 times more malondialdehyde (M.D.A. - a lipid peroxidation product) than material which was maintained aerobically. 1. pseudacorus did not exhibit such differences. Although the overall levels of M.D.A. are higher in I. pseudacorus it may be that the primary shoot tissue contains efficient endogenous secondary protection mechanisms to make good peroxidative damage. However, in the natural environment it is unlikely that the species would ever be exposed to such rapid alterations in O2 concentrations

Partial inhibition of ABA-induced stomatal closure by calcium-channel blockers.

ABA-induced increases in [Ca2+]cyt (cytosolic free Ca2+) may result from Ca2+ influx from the apoplast and/or release from intracellular stores. In this paper, Ca2+-channel blockers have been used to investigate this question in the detached epidermis of Commelina communis. Examples from the benzothiazepine, dihydropyridine and phenylalkylamine series all inhibited ABA-induced stomatal closure: (+/-) verapamil > nifedipine > diltiazem. Inhibition was partial, the magnitude of the effect being dependent on both the concentration of ABA and that of the channel blocker. The maximum inhibition observed in the presence of 100 nM ABA was approximately 66% at high (100 nM) concentrations of (+/-) verapamil or nifedipine. In the near absence of extracellular Ca2+ (2 mM EGTA) ABA-induced stomatal closure was reduced by approximately 22% and the inhibition by Ca2+-channel blockers abolished. Inhibition by (+/-) verapamil was totally reversible and exhibited signs of stereospecificity, the s(-) enantiomer being a more potent inhibitor of ABA-induced stomatal closure than the R(+) enantiomer. Bay K 8644 (a fluorinated analogue of nifedipine) exhibited biphasic action on 500 uM Ca2+-induced stomatal closure, i.e. agonistic at low concentrations (10 nM), antagonistic at high concentrations (> 10 nM to 100 uM), but did not affect ABA-induced stomatal closure. These results suggest that Ca2+ release from intracellular stores may be important in the ABA-induced increase in [Ca2+]cyt associated with stomatal closure. They do not, however, exclude a contribution of Ca2+ influx from the apoplast

COVID-19 and Hospital Palliative Care – a service evaluation exploring the symptoms and outcomes of 186 patients and the impact of the pandemic on specialist Hospital Palliative Care

Background: Patients hospitalised with COVID-19 have increased morbidity and mortality, which requires extensive involvement of specialist Hospital Palliative Care Teams. Evaluating the response to the surge in demand for effective symptom management can enhance provision of Palliative Care in this patient population. Aim: To characterise the symptom profile, symptom management requirements and outcomes of hospitalised COVID-19 positive patients referred for Palliative Care, and to contextualise Palliative Care demands from COVID-19 against a ‘typical’ caseload from 2019. Design: Service evaluation based on a retrospective cohort review of patient records. Setting/participants: One large health board in Scotland. Demographic data, patient symptoms, drugs/doses for symptom control, and patient outcomes were captured for all COVID-19 positive patients referred to Hospital Palliative Care Teams between 30th March and 26th April 2020. Results: Our COVID-19 cohort included 186 patients (46% of all referrals). Dyspnoea and agitation were the most prevalent symptoms (median 2 symptoms per patient). 75% of patients were prescribed continuous subcutaneous infusion for symptom control, which was effective in 78.6% of patients. Compared to a ‘typical’ caseload, the COVID-19 cohort were on caseload for less time (median 2 vs 5 days; p < 0.001) and had a higher death rate (80.6% vs 30.3%; p < 0.001). The COVID-19 cohort replaced ‘typical’ caseload; overall numbers of referrals were not increased. Conclusions: Hospitalised COVID-19 positive patients referred for Palliative Care may have a short prognosis, differ from ‘typical’ caseload, and predominantly suffer from dyspnoea and agitation. Such symptoms can be effectively controlled with standard doses of opioids and benzodiazepines

Plant virus infections control stomatal development

Stomata are important regulators of carbon dioxide uptake and transpirational water loss. They also represent points of vulnerability as bacterial and fungal pathogens utilise this natural opening as an entry portal, and thus have an increasingly complex relationship. Unlike the situation with bacterial and fungal pathogens, we know very little about the role of stomata in viral infection. Here we report findings showing that viral infection influences stomatal development in two susceptible host systems (Nicotiana tabacum with TMV (Tobacco mosaic virus), and Arabidopsis thaliana with TVCV (Turnip vein-clearing virus)), but not in resistant host systems (Nicotiana glutinosa and Chenopodium quinoa with TMV). Virus infected plants had significantly lower stomatal indices in systemic leaves of susceptible systems; N. tabacum 9.8% reduction and A. thaliana 12.3% reduction, but not in the resistant hosts. Stomatal density in systemic leaves was also significantly reduced in virus infected A. thaliana by 19.6% but not in N. tabacum or the resistant systems. In addition, transpiration rate was significantly reduced in TMV infected N. tabacum

Evolution of the calcium-based intracellular signalling system

To progress our understanding of molecular evolution from a collection of well-studied genes toward the level of the cell, we must consider whole systems. Here, we reveal the evolution of an important intracellular signaling system. The calcium-signaling toolkit is made up of different multidomain proteins that have undergone duplication, recombination, sequence divergence, and selection. The picture of evolution, considering the repertoire of proteins in the toolkit of both extant organisms and ancestors, is radically different from that of other systems. In eukaryotes, the repertoire increased in both abundance and diversity at a far greater rate than general genomic expansion. We describe how calcium-based intracellular signaling evolution differs not only in rate but in nature, and how this correlates with the disparity of plants and animals

Measuring stress signalling responses of stomata in isolated epidermis of graminaceous species.

Our current understanding of guard cell signalling pathways is derived from studies in a small number of model species. The ability to study stomatal responses in isolated epidermis has been an important factor in elucidating the mechanisms by which the stomata of these species respond to environmental stresses. However, such approaches have rarely been applied to study guard cell signalling in the stomata of graminaceous species (including many of the world’s major crops), in which the guard cells have a markedly different morphology to those in other plants. Our understanding of guard cell signalling in these important species is therefore much more limited. Here, we describe a procedure for the isolation of abaxial epidermal peels from barley, wheat and Brachypodium distachyon. We show that isolated epidermis from these species contains viable guard cells that exhibit typical responses to abscisic acid (ABA) and CO2, as determined by measurements of stomatal apertures. We use the epidermal peel assay technique to investigate in more detail interactions between different environmental factors in barley guard cells, and demonstrate that stomatal closure in response to external CO2 is inhibited at higher temperatures, whilst sensitivity to ABA is enhanced at 30°C compared to 20°C and 40°C