The coordination of spindle‐positioning forces during the asymmetric division of the Caenorhabditis elegans zygote

In Caenorhabditis elegans zygote, astral microtubules generate forces essential to position the mitotic spindle, by pushing against and pulling from the cortex. Measuring microtubule dynamics there, we revealed the presence of two populations, corresponding to pulling and pushing events. It offers a unique opportunity to study, under physiological conditions, the variations of both spindle‐positioning forces along space and time. We propose a threefold control of pulling force, by polarity, spindle position and mitotic progression. We showed that the sole anteroposterior asymmetry in dynein on‐rate, encoding pulling force imbalance, is sufficient to cause posterior spindle displacement. The positional regulation, reflecting the number of microtubule contacts in the posterior‐most region, reinforces this imbalance only in late anaphase. Furthermore, we exhibited the first direct proof that dynein processivity increases along mitosis. It reflects the temporal control of pulling forces, which strengthens at anaphase onset following mitotic progression and independently from chromatid separation. In contrast, the pushing force remains constant and symmetric and contributes to maintaining the spindle at the cell centre during metaphase.     

Allocation of scarce resources in Africa during COVID‐19: Utility and justice for the bottom of the pyramid?

The COVID‐19 pandemic has raised important universal public health challenges. Conceiving ethical responses to these challenges is a public health imperative but must take context into account. This is particularly important in sub‐Saharan Africa (SSA). In this paper, we examine how some of the ethical recommendations offered so far in high‐income countries might appear from a SSA perspective. We also reflect on some of the key ethical challenges raised by the COVID‐19 pandemic in low‐income countries suffering from chronic shortages in health care resources, and chronic high morbidity and mortality from non‐COVID‐19 causes. A parallel is drawn between the distribution of severity of COVID‐19 disease and the classic “Fortune at the bottom of the pyramid” model that is relevant in SSA. Focusing allocation of resources during COVID‐19 on the ‘thick’ part of the pyramid in Low‐to‐Middle Income Countries (LMICs) could be ethically justified on utilitarian and social justice grounds, since it prioritizes a large number of persons who have been economically and socially marginalized. During the pandemic, importing allocation frameworks focused on the apex of the pyramid from the global north may therefore not always be appropriate. In a post‐COVID‐19 world, we need to think strategically about how health care systems can be financed and structured to ensure broad access to adequate health care for all who need it. The root problems underlying health inequity, exposed by COVID‐19, must be addressed, not just to prepare for the next pandemic, but to care for people in resource poor settings in non‐pandemic times.     

Correction to: Relative Importance of Climate,Soil and Plant Functional Traits During the Early Decomposition Stage of Standardized Litter

Ecosystems - A correction to this paper has been published: https://doi.org/10.1007/s10021-021-00614-y     

A New Computational Efficient Approach for Trabecular Bone Analysis using Beam Models Generated with Skeletonized Graph Technique

Micro-finite element (FE) analysis is a well established technique for the evaluation of the elastic properties of trabecular bone, but is limited in its application due to the large number of elements that it requires to represent the complex internal structure of the bone. In this paper, we present an alternative FE approach that makes use of a recently developed 3D-Line Skeleton Graph Analysis (LSGA) technique to represent the complex internal structure of trabecular bone as a network of simple straight beam elements in which the beams are assigned geometrical properties of the trabeculae that they represent. Since an enormous reduction of cputime can be obtained with this beam modeling approach, ranging from approximately 1,200 to 3,600 for the problems investigated here, we think that the FE modeling technique that we introduced could potentially constitute an interesting alternative for the evaluation of the elastic mechanical properties of trabecular bone.     

Differential effects of cysteine and methionine residues in the antioxidant activity of human serum albumin

Antioxidant properties of human serum albumin (HSA) may explain part of its beneficial role in various diseases related to free radical attack. In the present study, the antioxidant role of Cys and Met was studied by copper-mediated oxidation of human low density lipoproteins and by free radical-induced blood hemolysis which essentially assessed metal-chelating and free radical scavenging activities, respectively. Mild conditions were set up to specifically modify Cys and Met residues by N-ethylmaleimide (NEM) and chloramine T treatments, respectively. We found that Met and Cys accounted for 40–80% of total antioxidant activity of HSA. Copper binding to HSA was decreased by about 50% with chloramine T treatment of Met whereas no change was observed after NEM treatment of Cys. Although other amino acid residues are likely to be involved in anti-/prooxidant properties of HSA, from our data, we propose that Cys chiefly works as a free radical scavenger whereas Met mainly acts as a metal chelator.     

Microwave-assisted Synthesis of Novel Thiazolocarbazoles and Evaluation as Potential Anticancer Agents. Part III

Novel 6-substituted thiazolocarbazole derivatives have been synthesized under microwave irradiation via the corresponding imino-1,2,3-dithiazoles. In vitro antitumor potential of these polyheterocyclic compounds was evaluated. Among all the tested thiazolocarbazoles, compound 10 is the most effective in inhibiting cell growth.     

Association mapping and meta-analysis: two complementary approaches for the detection of reliable Septoria tritici blotch quantitative resistance in bread wheat (Triticum aestivum L.)

Septoria tritici blotch (STB), caused by the ascomycete Mycosphaerella graminicola, is one of the most ubiquitous and important diseases of bread wheat worldwide. The aim of this study was to identify markers linked to loci conferring resistance to STB from seven biparental populations. Linkage analysis, meta-analysis and association mapping were combined to identify robust quantitative trait loci (QTLs) for resistance. Linkage analysis led to the detection of 115 QTLs for resistance to STB and 66 QTLs linked to plant height and/or earliness. Meta-analysis clustered these 115 QTLs into 27 Meta-QTLs (MQTLs) of pathogen resistance, of which 14 were found to be linked to plant height and/or earliness. Both the relationship between dwarfing and susceptibility to STB and the significant negative correlation between earliness and STB symptoms were confirmed. Eleven loci were linked to STB resistance by association mapping using a general linear model and/or a mixed linear model, of which eight co-located with STB MQTLs and two co-located with individual QTLs. Associated markers located in MQTL regions enhanced the relevance of the results and validated the potential of an association mapping approach. With several biparental populations, meta-analysis is the most relevant form of genetic analysis study, but association mapping can be used as a validation method. Regions linked to resistance in both methods should be relevant for use in breeding programs for improving resistance to STB in wheat varieties. The main interest in comparing both approaches is to detect robust loci that will be functional in many genetic backgrounds rather than just in one or a few specific backgrounds.     

Priming of the Arabidopsis pattern‐triggered immunity response upon infection by necrotrophic Pectobacterium carotovorum bacteria

Boosted responsiveness of plant cells to stress at the onset of pathogen‐ or chemically induced resistance is called priming. The chemical β‐aminobutyric acid (BABA) enhances Arabidopsis thaliana resistance to hemibiotrophic bacteria through the priming of the salicylic acid (SA) defence response. Whether BABA increases Arabidopsis resistance to the necrotrophic bacterium Pectobacterium carotovorum ssp. carotovorum (Pcc) is not clear. In this work, we show that treatment with BABA protects Arabidopsis against the soft‐rot pathogen Pcc. BABA did not prime the expression of the jasmonate/ethylene‐responsive gene PLANT DEFENSIN 1.2 (PDF1.2), the up‐regulation of which is usually associated with resistance to necrotrophic pathogens. Expression of the SA marker gene PATHOGENESIS RELATED 1 (PR1) on Pcc infection was primed by BABA treatment, but SA‐defective mutants demonstrated a wild‐type level of BABA‐induced resistance against Pcc. BABA primed the expression of the pattern‐triggered immunity (PTI)‐responsive genes FLG22‐INDUCED RECEPTOR‐LIKE KINASE 1 (FRK1), ARABIDOPSIS NON‐RACE SPECIFIC DISEASE RESISTANCE GENE (NDR1)/HAIRPIN‐INDUCED GENE (HIN1)‐LIKE 10 (NHL10) and CYTOCHROME P450, FAMILY 81 (CYP81F2) after inoculation with Pcc or after treatment with purified bacterial microbe‐associated molecular patterns, such as flg22 or elf26. PTI‐mediated callose deposition was also potentiated in BABA‐treated Arabidopsis, and BABA boosted Arabidopsis stomatal immunity to Pcc. BABA treatment primed the PTI response in the SA‐defective mutants SA induction deficient 2‐1 (sid2‐1) and phytoalexin deficient 4‐1 (pad4‐1). In addition, BABA priming was associated with open chromatin configurations in the promoter region of PTI marker genes. Our data indicate that BABA primes the PTI response upon necrotrophic bacterial infection and suggest a role for the PTI response in BABA‐induced resistance.