The extracellular EXO protein mediates cell expansion in Arabidopsis leaves

<p>Abstract</p> <p>Background</p> <p>The <it>EXO </it>(<it>EXORDIUM</it>) gene was identified as a potential mediator of brassinosteroid (BR)-promoted growth. It is part of a gene family with eight members in Arabidopsis. <it>EXO </it>gene expression is under control of BR, and <it>EXO </it>overexpression promotes shoot and root growth. In this study, the consequences of loss of <it>EXO </it>function are described.</p> <p>Results</p> <p>The <it>exo </it>loss of function mutant showed diminished leaf and root growth and reduced biomass production. Light and scanning electron microscopy analyses revealed that impaired leaf growth is due to reduced cell expansion. Epidermis, palisade, and spongy parenchyma cells were smaller in comparison to the wild-type. The <it>exo </it>mutant showed reduced brassinolide-induced cotyledon and hypocotyl growth. In contrast, <it>exo </it>roots were significantly more sensitive to the inhibitory effect of synthetic brassinolide. Apart from reduced growth, <it>exo </it>did not show severe morphological abnormalities. Gene expression analyses of leaf material identified genes that showed robust EXO-dependent expression. Growth-related genes such as <it>WAK1</it>, <it>EXP5</it>, and <it>KCS1</it>, and genes involved in primary and secondary metabolism showed weaker expression in <it>exo </it>than in wild-type plants. However, the vast majority of BR-regulated genes were normally expressed in <it>exo</it>. HA- and GFP-tagged EXO proteins were targeted to the apoplast.</p> <p>Conclusion</p> <p>The <it>EXO </it>gene is essential for cell expansion in leaves. Gene expression patterns and growth assays suggest that EXO mediates BR-induced leaf growth. However, EXO does not control BR-levels or BR-sensitivity in the shoot. EXO presumably is involved in a signalling process which coordinates BR-responses with environmental or developmental signals. The hypersensitivity of <it>exo </it>roots to BR suggests that EXO plays a diverse role in the control of BR responses in the root.</p

The extracellular EXO protein mediates cell expansion in Arabidopsis leaves

<p>Abstract</p> <p>Background</p> <p>The <it>EXO </it>(<it>EXORDIUM</it>) gene was identified as a potential mediator of brassinosteroid (BR)-promoted growth. It is part of a gene family with eight members in Arabidopsis. <it>EXO </it>gene expression is under control of BR, and <it>EXO </it>overexpression promotes shoot and root growth. In this study, the consequences of loss of <it>EXO </it>function are described.</p> <p>Results</p> <p>The <it>exo </it>loss of function mutant showed diminished leaf and root growth and reduced biomass production. Light and scanning electron microscopy analyses revealed that impaired leaf growth is due to reduced cell expansion. Epidermis, palisade, and spongy parenchyma cells were smaller in comparison to the wild-type. The <it>exo </it>mutant showed reduced brassinolide-induced cotyledon and hypocotyl growth. In contrast, <it>exo </it>roots were significantly more sensitive to the inhibitory effect of synthetic brassinolide. Apart from reduced growth, <it>exo </it>did not show severe morphological abnormalities. Gene expression analyses of leaf material identified genes that showed robust EXO-dependent expression. Growth-related genes such as <it>WAK1</it>, <it>EXP5</it>, and <it>KCS1</it>, and genes involved in primary and secondary metabolism showed weaker expression in <it>exo </it>than in wild-type plants. However, the vast majority of BR-regulated genes were normally expressed in <it>exo</it>. HA- and GFP-tagged EXO proteins were targeted to the apoplast.</p> <p>Conclusion</p> <p>The <it>EXO </it>gene is essential for cell expansion in leaves. Gene expression patterns and growth assays suggest that EXO mediates BR-induced leaf growth. However, EXO does not control BR-levels or BR-sensitivity in the shoot. EXO presumably is involved in a signalling process which coordinates BR-responses with environmental or developmental signals. The hypersensitivity of <it>exo </it>roots to BR suggests that EXO plays a diverse role in the control of BR responses in the root.</p

Parameter-Free Binarization and Skeletonization of Fiber Networks from Confocal Image Stacks

We present a method to reconstruct a disordered network of thin biopolymers, such as collagen gels, from three-dimensional (3D) image stacks recorded with a confocal microscope. The method is based on a template matching algorithm that simultaneously performs a binarization and skeletonization of the network. The size and intensity pattern of the template is automatically adapted to the input data so that the method is scale invariant and generic. Furthermore, the template matching threshold is iteratively optimized to ensure that the final skeletonized network obeys a universal property of voxelized random line networks, namely, solid-phase voxels have most likely three solid-phase neighbors in a neighborhood. This optimization criterion makes our method free of user-defined parameters and the output exceptionally robust against imaging noise

Microconstriction Arrays for High-Throughput Quantitative Measurements of Cell Mechanical Properties

AbstractWe describe a method for quantifying the mechanical properties of cells in suspension with a microfluidic device consisting of a parallel array of micron-sized constrictions. Using a high-speed charge-coupled device camera, we measure the flow speed, cell deformation, and entry time into the constrictions of several hundred cells per minute during their passage through the device. From the flow speed and the occupation state of the microconstriction array with cells, the driving pressure across each constriction is continuously computed. Cell entry times into microconstrictions decrease with increased driving pressure and decreased cell size according to a power law. From this power-law relationship, the cell elasticity and fluidity can be estimated. When cells are treated with drugs that depolymerize or stabilize the cytoskeleton or the nucleus, elasticity and fluidity data from all treatments collapse onto a master curve. Power-law rheology and collapse onto a master curve are predicted by the theory of soft glassy materials and have been previously shown to describe the mechanical behavior of cells adhering to a substrate. Our finding that this theory also applies to cells in suspension provides the foundation for a quantitative high-throughput measurement of cell mechanical properties with microfluidic devices

Sequential and switchable patterning for studying cellular processes under spatiotemporal control

Attachment of adhesive molecules on cell culture surfaces to restrict cell adhesion to defined areas and shapes has been vital for the progress of in vitro research. In currently existing patterning methods, a combination of pattern properties such as stability, precision, specificity, high-throughput outcome, and spatiotemporal control is highly desirable but challenging to achieve. Here, we introduce a versatile and high-throughput covalent photoimmobilization technique, comprising a light-dose-dependent patterning step and a subsequent functionalization of the pattern via click chemistry. This two-step process is feasible on arbitrary surfaces and allows for generation of sustainable patterns and gradients. The method is validated in different biological systems by patterning adhesive ligands on cell-repellent surfaces, thereby constraining the growth and migration of cells to the designated areas. We then implement a sequential photopatterning approach by adding a second switchable patterning step, allowing for spatiotemporal control over two distinct surface patterns. As a proof of concept, we reconstruct the dynamics of the tip/stalk cell switch during angiogenesis. Our results show that the spatiotemporal control provided by our “sequential photopatterning” system is essential for mimicking dynamic biological processes and that our innovative approach has great potential for further applications in cell science

Photophysiological responses of bottom sea-ice algae to fjord dynamics and rapid freshening

publishedVersio

Effectiveness of Cash-plus Programmes on Early Childhood Outcomes Compared to Cash Transfers Alone: A Systematic Review and Meta-analysis in Low- and Middle-income Countries

Background: To strengthen the impact of cash transfers, these interventions have begun to be packaged as cash-plus programmes, combining cash with additional transfers, interventions, or services. The intervention’s complementary (“plus”) components aim to improve cash transfer effectiveness by targeting mediating outcomes or the availability of supplies or services. This study examined whether cash-plus interventions for infants and children <5 are more effective than cash alone in improving health and well-being

Strain in InP/ZnSe, S core/shell quantum dots from lattice mismatch and shell thickness : material stiffness influence

We investigate the buildup of strain in InP quantum dots with the addition of shells of the lower-lattice constant materials ZnSe and ZnS by Raman spectroscopy. Both materials induce compressive strain in the core, which increases with increasing shell volume. We observe a difference in the shell behavior between the two materials: the thickness-dependence points toward an influence of the material stiffness. ZnS has a larger Young's modulus and requires less material to develop stress on the InP lattice at the interface, while ZnSe requires several layers to form a stress-inducing lattice at the interface. This hints at the material stiffness being an additional parameter of relevance for designing strained core/shell quantum dots

Advancing Our Functional Understanding of Host–Microbiota Interactions: A Need for New Types of Studies

Multicellular life evolved in the presence of microorganisms and formed complex associations with their microbiota, the sum of all associated archaea, bacteria, fungi, and viruses. These associations greatly affect the health and life history of the host, which led to a new understanding of “self” and establishment of the “metaorganism” concept.1 The Collaborative Research Centre (CRC) 1182 aims at elucidating the evolution and function of metaorganisms. Its annual conference, the Young Investigator Research Day (YIRD), serves as a platform for scientists of various disciplines to share novel findings on host–microbiota interactions, thereby providing a comprehensive overview of recent developments and new directions in metaorganism research. Even though we have gained tremendous insights into the composition and dynamics of host‐associated microbial communities and their correlations with host health and disease, it also became evident that moving from correlative toward functional studies is needed to examine the underlying mechanisms of interactions within the metaorganism. Non‐classical model organisms in particular possess significant potential to functionally address many open questions in metaorganism research. Here, we suggest and introduce a roadmap moving from correlation toward a functional understanding of host–microbiota interactions and highlight its potential in emerging ecological, agricultural, and translational medical applications