Risk factors and the nomogram model for intraoperatively acquired pressure injuries in children with brain tumours: A retrospective study.

This study aimed to investigate the clinical features and incidence of Intraoperatively Acquired Pressure Injuries (IAPIs) of brain tumours in children, to screen the risk factors and to establish a nomogram model for making prevention strategies against the development of IAPIs. Clinical data of 628 children undergoing brain tumour surgery from August 2019 to August 2021 were extracted from the adverse events and the electronic medical systems. They were randomly divided into a training cohort(n = 471) and a validation cohort(n = 157). The univariate and multivariate analysis was performed to identify the risk factors in training cohort; R software was used to construct a nomogram model; the area under the receiver operator characteristic curve (AUC) and calibration plots were used to judge the predictive performance of the nomogram model; decision curve analysis (DCA) was used to assess the clinical usefulness of the nomogram model. Age, haemorrhage, use of vasopressor, temperature, operation time and operation position were considered as significant risk factors, and enrolled to construct a nomogram model. The results of AUC showed satisfactory discrimination of the nomogram; the calibration plots indicated favourable consistency between the prediction of the nomogram and actual observations in both the training and validation cohorts; DCA showed better net benefit and threshold probability of the nomogram model. The nomogram model illustrates significant predictive ability, which can provide scientific and individual guidance for preventing development of IAPIs.

Activation tagging identifies Arabidopsis transcription factor AtMYB68 for heat and drought tolerance at yield determining reproductive stages.

Heat stress occurring at reproductive stages can result in significant and permanent damage to crop yields. However, previous genetic studies in understanding heat stress response and signaling were performed mostly on seedling and plants at early vegetative stages. Here we identify, using a developmentally defined, gain-of-function genetic screen with approximately 18 000 Arabidopsis thaliana activation-tagged lines, a mutant that maintained productive seed set post-severe heat stress during flowering. Genome walking indicated this phenotype was caused by the insertion of 35S enhancers adjacent to a nuclear localized transcription factor AtMYB68. Subsequent overexpression analysis confirmed that AtMYB68 was responsible for the reproductive heat tolerance of the mutant. Furthermore, these transgenic Arabidopsis plants exhibited enhanced abscisic acid sensitivity at and post-germination, reduced transpirational water loss during a drought treatment, and enhanced seed yield under combined heat and drought stress during flowering. Ectopic expression of AtMYB68 in Brassica napus driven either by 35S or by heat-inducible promoter recapitulated the enhanced reproductive heat stress and drought tolerance phenotypes observed in the transgenic Arabidopsis. The improvement to heat stress is likely due to enhanced pollen viability observed in the transgenic plants. More importantly, the transgenic canola showed significant yield advantages over the non-transgenic controls in multiple locations, multiple season field trials under various drought and heat stress conditions. Together these results suggest that AtMYB68 regulate plant stress tolerance at the most important yield determining stage of plant development, and is an effective target for crop yield protection under current global climate volatility.

MicroRNA-mediated repression of the seed maturation program during vegetative development in Arabidopsis.

The seed maturation program only occurs during late embryogenesis, and repression of the program is pivotal for seedling development. However, the mechanism through which this repression is achieved in vegetative tissues is poorly understood. Here we report a microRNA (miRNA)-mediated repression mechanism operating in leaves. To understand the repression of the embryonic program in seedlings, we have conducted a genetic screen using a seed maturation gene reporter transgenic line in Arabidopsis (Arabidopsis thaliana) for the isolation of mutants that ectopically express seed maturation genes in leaves. One of the mutants identified from the screen is a weak allele of ARGONAUTE1 (AGO1) that encodes an effector protein for small RNAs. We first show that it is the defect in the accumulation of miRNAs rather than other small RNAs that causes the ectopic seed gene expression in ago1. We then demonstrate that overexpression of miR166 suppresses the derepression of the seed gene reporter in ago1 and that, conversely, the specific loss of miR166 causes ectopic expression of seed maturation genes. Further, we show that ectopic expression of miR166 targets, type III homeodomain-leucine zipper (HD-ZIPIII) genes PHABULOSA (PHB) and PHAVOLUTA (PHV), is sufficient to activate seed maturation genes in vegetative tissues. Lastly, we show that PHB binds the promoter of LEAFY COTYLEDON2 (LEC2), which encodes a master regulator of seed maturation. Therefore, this study establishes a core module composed of a miRNA, its target genes (PHB and PHV), and the direct target of PHB (LEC2) as an underlying mechanism that keeps the seed maturation program off during vegetative development.

Synergistic repression of the embryonic programme by SET DOMAIN GROUP 8 and EMBRYONIC FLOWER 2 in Arabidopsis seedlings.

The seed maturation programme occurs only during the late phase of embryo development, and repression of the maturation genes is pivotal for seedling development. However, mechanisms that repress the expression of this programme in vegetative tissues are not well understood. A genetic screen was performed for mutants that express maturation genes in leaves. Here, it is shown that mutations affecting SDG8 (SET DOMAIN GROUP 8), a putative histone methyltransferase, cause ectopic expression of a subset of maturation genes in leaves. Further, to investigate the relationship between SDG8 and the Polycomb Group (PcG) proteins, which are known to repress many developmentally important genes including seed maturation genes, double mutants were made and formation of somatic embryos was observed on mutant seedlings with mutations in both SDG8 and EMF2 (EMBRYONIC FLOWER 2). Analysis of histone methylation status at the chromatin sites of a number of maturation loci revealed a synergistic effect of emf2 and sdg8 on the deposition of the active histone mark which is the trimethylation of Lys4 on histone 3 (H3K4me3). This is consistent with high expression of these genes and formation of somatic embryos in the emf2 sdg8 double mutants. Interestingly, a double mutant of sdg8 and vrn2 (vernalization2), a paralogue of EMF2, grew and developed normally to maturity. These observations demonstrate a functional cooperative interplay between SDG8 and an EMF2-containing PcG complex in maintaining vegetative cell identity by repressing seed genes to promote seedling development. The work also indicates the functional specificities of PcG complexes in Arabidopsis.

Arabidopsis homolog of the yeast TREX-2 mRNA export complex: components and anchoring nucleoporin.

Nuclear pore complexes (NPCs) are vital to nuclear-cytoplasmic communication in eukaryotes. The yeast NPC-associated TREX-2 complex, also known as the Thp1-Sac3-Cdc31-Sus1 complex, is anchored on the NPC via the nucleoporin Nup1, and is essential for mRNA export. Here we report the identification and characterization of the putative Arabidopsis thaliana TREX-2 complex and its anchoring nucleoporin. Physical and functional evidence support the identification of the Arabidopsis orthologs of yeast Thp1 and Nup1. Of three Arabidopsis homologs of yeast Sac3, two are putative TREX-2 components, but, surprisingly, none are required for mRNA export as they are in yeast. Physical association of the two Cdc31 homologs, but not the Sus1 homolog, with the TREX-2 complex was observed. In addition to identification of these TREX-2 components, direct interactions of the Arabidopsis homolog of DSS1, which is an established proteasome component in yeast and animals, with both the TREX-2 complex and the proteasome were observed. This suggests the possibility of a link between the two complexes. Thus this work has identified the putative Arabidopsis TREX-2 complex and provides a foundation for future studies of nuclear export in Arabidopsis.

Forward genetic screening for the improved production of fermentable sugars from plant biomass.

With their unique metabolism and the potential to produce large amounts of biomass, plants are an excellent bio-energy feedstock for a variety of industrial purposes. Here we developed a high-throughput strategy, using the model plant Arabidopsis thaliana, to identify mutants with improved sugar release from plant biomass. Molecular analysis indicates a variety of processes including starch degradation, cell wall composition and polar transport of the plant hormone auxin can contribute to this improved saccharification. To demonstrate translatability, polar auxin transport in maize was either genetically or chemical inhibited and this also resulted in increased sugar release from plant tissues. Our forward genetic approach using Arabidopsis not only uncovers new functions that contribute to cell wall integrity but also demonstrates that information gleaned from this genetic model can be directly translated to monocotyledonous crops such as maize to improve sugar extractability from biomass.

Propofol protects against focal cerebral ischemia via inhibition of microglia-mediated proinflammatory cytokines in a rat model of experimental stroke.

Ischemic stroke induces microglial activation and release of proinflammatory cytokines, contributing to the expansion of brain injury and poor clinical outcome. Propofol has been shown to ameliorate neuronal injury in a number of experimental studies, but the precise mechanisms involved in its neuroprotective effects remain unclear. We tested the hypothesis that propofol confers neuroprotection against focal ischemia by inhibiting microglia-mediated inflammatory response in a rat model of ischemic stroke. Sprague-Dawley rats were subjected to middle cerebral artery occlusion (MCAO) for 2 h followed by 24 h of reperfusion. Propofol (50 mg/kg/h) or vehicle was infused intravenously at the onset of reperfusion for 30 minutes. In vehicle-treated rats, MCAO resulted in significant cerebral infarction, higher neurological deficit scores and decreased time on the rotarod compared with sham-operated rats. Propofol treatment reduced infarct volume and improved the neurological functions. In addition, molecular studies demonstrated that mRNA expression of microglial marker Cd68 and Emr1 was significantly increased, and mRNA and protein expressions of proinflammatory cytokines tumor necrosis factor-α, interleukin-1ß and interleukin-6 were augmented in the peri-infarct cortical regions of vehicle-treated rats 24 h after MCAO. Immunohistochemical study revealed that number of total microglia and proportion of activated microglia in the peri-infarct cortical regions were markedly elevated. All of these findings were ameliorated in propofol-treated rats. Furthermore, vehicle-treated rats had higher plasma levels of interleukin-6 and C-reactive protein 24 h after MCAO, which were decreased after treatment with propofol. These results suggest that propofol protects against focal cerebral ischemia via inhibition of microglia-mediated proinflammatory cytokines. Propofol may be a promising therapeutic agent for the treatment of ischemic stroke and other neurodegenerative diseases associated with microglial activation.

The Arabidopsis BRAHMA chromatin-remodeling ATPase is involved in repression of seed maturation genes in leaves.

Synthesis and accumulation of seed storage proteins (SSPs) is an important aspect of the seed maturation program. Genes encoding SSPs are specifically and highly expressed in the seed during maturation. However, the mechanisms that repress the expression of these genes in leaf tissue are not well understood. To gain insight into the repression mechanisms, we performed a genetic screen for mutants that express SSPs in leaves. Here, we show that mutations affecting BRAHMA (BRM), a SNF2 chromatin-remodeling ATPase, cause ectopic expression of a subset of SSPs and other embryogenesis-related genes in leaf tissue. Consistent with the notion that such SNF2-like ATPases form protein complexes in vivo, we observed similar phenotypes for mutations of AtSWI3C, a BRM-interacting partner, and BSH, a SNF5 homolog and essential SWI/SNF subunit. Chromatin immunoprecipitation experiments show that BRM is recruited to the promoters of a number of embryogenesis genes in wild-type leaves, including the 2S genes, expressed in brm leaves. Consistent with its role in nucleosome remodeling, BRM appears to affect the chromatin structure of the At2S2 promoter. Thus, the BRM-containing chromatin-remodeling ATPase complex involved in many aspects of plant development mediates the repression of SSPs in leaf tissue.

Two naturally occurring deletion mutants of 12S seed storage proteins in Arabidopsis thaliana.

Two naturally occurring Arabidopsis mutants, Cape Verde Islands and Monte (Mr-0), with aberrant 12S seed storage protein (SSP) profiles have been identified by SDS-PAGE. In both mutants, one of the 12S globulin bands is missing while a new band of lower molecular mass is present. Tandem mass spectrometry-mass spectrometry (MS/MS) analyses of the mutant peptides have revealed that both are shorter variants of 12S globulin with deletion sites detected within the alpha-subunits of 12S globulin cruciferin B (CRB) and C (CRC), respectively. Sequence analyses of the genomic DNA flanking the deletion sites have demonstrated that both deletions occurred at the genomic level. These two mutants are referred to as CRBDelta12 and CRCDelta13 with the delta sign indicating a deletion and the number indicating amino acids deleted. Alignment of these two mutant sequences with that of soybean A3B4 subunit, for which the crystal structure was determined recently, have revealed that the CRCDelta13 deletion is located in a hypervariable/disordered region, and will probably not affect the structure of the hexameric globulin. The CRBDelta12 deletion, however, is located in a binding region that is thought to be important for the hexamer formation. However, CRBDelta12 appears to accumulate normally as judged by its band intensity relative to the other SSP subunits on the protein gels. Thus it seems that the seed can, to a certain extent, tolerate some mutations in its storage proteins.