Biology subjects

Ostergaard, L.

Publications and source records attributed to Ostergaard, L..

24 records · Page 2Linked to original sources

bioRxiv2020

CRISPR-Cas9-mediated editing of myb28 impairs glucoraphanin accumulation of Brassica oleracea in the field

We sought to quantify the role of MYB28 in the regulation of aliphatic glucosinolate biosynthesis and associated sulphur metabolism in field-grown B. oleracea with the use of CRISPR-Cas9-mediated gene editing technology. We describe the first characterised myb28 knockout mutant in B. oleracea, and the first UK field trial of CRISPR-Cas9-mediated gene edited plants under the European Court of Justice interpretation of the 2001/18 EU GMO directive. We report that knocking-out myb28 results in downregulation of aliphatic glucosinolate biosynthesis genes and reduction in accumulation of the methionine-derived glucosinolate, glucoraphanin, in leaves and florets of field-grown myb28 mutant broccoli plants. There were no significant changes to the accumulation of sulphate, S-methyl cysteine sulfoxide and indole glucosinolate in leaf and floret tissues.

plant biology↗

bioRxiv2019

Direct ETTIN-auxin interaction controls chromatin state in gynoecium development

Hormonal signalling in animals often involves direct transcription factor-hormone interactions that modulate gene expression1, 2. In contrast, plant hormone signalling is most commonly based on de-repression via the degradation of transcriptional repressors3. Recently, we uncovered a non-canonical signalling mechanism for the plant hormone auxin in organ development with strong similarity to animal hormonal pathways. In this mechanism, auxin directly affects the activity of the auxin response factor ETTIN (ETT) towards regulation of target genes without the requirement for protein degradation4, 5. Here we show that auxin binds ETT to modulate gene expression and that this ETT-auxin interaction leads to the dissociation of ETT from co-repressor proteins of the TOPLESS/TOPLESS-RELATED family followed by histone acetylation and the induction of target gene expression. Whilst canonical ARFs are classified as activators or repressors6, ETT is able to switch chromatin locally between repressive and de-repressive states in an instantly-reversible auxin-dependent manner.

plant biology↗

bioRxiv2019

Longitudinal, Multiparametric MRI Assessment of repetitive mild TBI in rats

Repetitive mild traumatic brain injury (mTBI) has long term health effects and may result in the development of neurodegenerative or neuropsychiatric disorders. Histology shows axonal and dendritic beading, synaptic atrophy, vasodilation and gliosis occuring within hours/days post-mTBI. However, current neuroimaging techniques are unable to detect the early effects of repetitive mTBI. Consequently, mTBI brain scans are normal appearing and inconclusive. Hence, neuroimaging markers capable of detecting subtle microstructural and functional alterations are needed. We present results from longitudinal, multiparametric magnetic resonance imaging (MRI) assessment of repetitive mTBI in rats. We employ advanced in-vivo diffusion MRI (dMRI) to probe brain microstructural alterations, perfusion MRI to assess cerebral blood flow (CBF), close to the injury site, and proton MR spectroscopy to assess metabolic alterations in the ipsilateral cerebral cortex. High resolution anatomical scans were also acquired. In agreement with clinical observations, anatomical scans of rats were normal appearing even after repeated mTBI. Throughout, significance is regarded as p<0.05 post false discovery rate correction. dMRI revealed significant microstructural remodelling in ipsilateral hippocampus (reduced radial kurtosis), may be due to axonal/dendritic beading, demyelination, synaptic atrophy and edema. Consistent with prior reports of reduced cell/fiber density in mTBI, we find significantly increased mean diffusivity in ipsilateral corpus callosum. We also find significantly decreased glutathione (GSH) and increased total Choline (tCho) following second and third mTBI (vs baseline), also reported in clinical mTBI cohorts. Reduced GSH suggests oxidative stress and increase in tCho indicate cell damage/repair. CBF did not change significantly, however, high variability in CBF following the second and third mTBI suggest increased variability in CBF likely due to tissue hypoxia and oxidative stress. Oxidative stress may affect capillary blood flow by disturbing pericyte capillary contraction. Around 40% of pericytes retract after mTBI causing pericyte depletion and white matter dysfunction as suggested by dMRI findings. Multiparametric MRI detects meaningful mTBI-induced alterations otherwise undetectable with conventional MRI. Similar strategies may provide useful information to aid diagnosis of human mTBI.

neuroscience↗

bioRxiv2019

The power of model-to-crop translation illustrated by reducing seed loss from pod shatter in oilseed rape

In the 1980s, plant scientists descended on a small weed Arabidopsis thaliana (thale cress) and developed it into a powerful model system to study plant biology. The massive advances in genetics and genomics since then has allowed us to obtain incredibly detailed knowledge on specific biological processes of Arabidopsis growth and development, its genome sequence and the function of many of the individual genes. This wealth of information provides immense potential for translation into crops to improve their performance and address issues of global importance such as food security. Here we describe how fundamental insight into the genetic mechanism by which seed dispersal occurs in members of the Brassicaceae family can be exploited to reduce seed loss in oilseed rape (Brassica napus). We demonstrate that by exploiting data on gene function in model species, it is possible to adjust the pod-opening process in oilseed rape thereby significantly increasing yield. Specifically, we identified mutations in multiple paralogues of the INDEHISCENT and GA4 genes in B. napus and have overcome genetic redundancy by combining mutant alleles. Finally, we present novel software for the analysis of pod shatter data that is applicable to any crop for which seed dispersal is a serious problem. These findings highlight the tremendous potential of fundamental research in guiding strategies for crop improvement.\n\nKeymessageElucidation of key regulators in Arabidopsis fruit patterning has facilitated knowledge-translation into crop species to address yield loss caused by premature seed dispersal (pod shatter).

plant biology↗

bioRxiv2019

Comparison of classification methods for tissue outcome after ischemic stroke

In acute ischemic stroke, identifying brain tissue at high risk of infarction is important for clinical decision-making. This tissue may be identified with suitable classification methods from magnetic resonance imaging (MRI) data. The aim of the present study was to assess comparatively the performance of five popular classification methods (Adaptive Boosting (ADA), Logistic Regression (LR), Artificial Neural Networks (ANN), Random Forest (RF), and Support Vector Machine (SVM)) in identifying tissue at high risk of infarction on human voxel-based brain imaging data. The classification methods were used with eight MRI parameters including diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) obtained in 55 patients. Sensitivity, specificity, the area under the receiver operating curve (ROC) as well as the area under the precision-recall curve criteria were used to compare the method performances. The methods performed equally in terms of sensitivity and specificity while the results of the area under the ROC were significantly better for ADA, LR, ANN and RF. However, there was no statistically significant difference between the performances of these five classification methods regarding the area under the precision-recall curve, which was the main comparison metric.

neuroscience↗

bioRxiv2018

Homogenization of capillary flow and oxygenation in deeper cortical layers correlates with increased oxygen extraction

Our understanding of how capillary blood flow and oxygen distribute across cortical layers to meet the local metabolic demand is incomplete. We addressed this question by using two-photon imaging of microvascular oxygen partial pressure (PO2) and flow in the whisker barrel cortex in awake mice at rest. Our measurements in layers I-V show that the capillary red-blood-cell flux and oxygenation heterogeneity, and the intracapillary resistance to oxygen delivery, all decrease with depth, reaching a minimum around layer IV, while the depth-dependent oxygen extraction fraction is increased in layer IV, where oxygen demand is presumably the highest. Our findings suggest that homogenization of physiological observables relevant to oxygen transport to tissue is an important part of the microvascular network adaptation to a local brain metabolism increase. These results will inform the biophysical models of layer-specific cerebral oxygen delivery and consumption and improve our understanding of diseases that affect the cerebral microcirculation.\n\nIMPACT STATEMENTHomogenization of cortical capillary blood flow and oxygenation underpins an important mechanism, by which the microvascular network adapts to an increase in the local brain oxidative metabolism.

neuroscience↗