Reduced RG-II pectin dimerization disrupts differential growth by attenuating hormonal regulation.

Defects in cell wall integrity (CWI) profoundly affect plant growth, although, underlying mechanisms are not well understood. We show that in mutant, CWI defects from compromising dimerization of RG-II pectin, a key component of cell wall, attenuate the expression of auxin response factors . As a result, polar auxin transport components are misexpressed, disrupting auxin response asymmetry, leading to defective apical hook development.

Segmentation and characterization of macerated fibers and vessels using deep learning.

Purpose: Wood comprises different cell types, such as fibers, tracheids and vessels, defining its properties. Studying cells' shape, size, and arrangement in microscopy images is crucial for understanding wood characteristics. Typically, this involves macerating (soaking) samples in a solution to separate cells, then spreading them on slides for imaging with a microscope that covers a wide area, capturing thousands of cells.

Cell wall integrity modulates HOOKLESS1 and PHYTOCHROME INTERACTING FACTOR4 expression controlling apical hook formation.

Formation of the apical hook in etiolated dicot seedlings results from differential growth in the hypocotyl apex and is tightly controlled by environmental cues and hormones, among which auxin and gibberellins (GAs) play an important role. Cell expansion is tightly regulated by the cell wall, but whether and how feedback from this structure contributes to hook development are still unclear. Here, we show that etiolated seedlings of the Arabidopsis (Arabidopsis thaliana) quasimodo2-1 (qua2) mutant, defective in pectin biosynthesis, display severe defects in apical hook formation and maintenance, accompanied by loss of asymmetric auxin maxima and differential cell expansion.

High-throughput characterization of cortical microtubule arrays response to anisotropic tensile stress.

Background: Plants can perceive and respond to mechanical signals. For instance, cortical microtubule (CMT) arrays usually reorganize following the predicted maximal tensile stress orientation at the cell and tissue level. While research in the last few years has started to uncover some of the mechanisms mediating these responses, much remains to be discovered, including in most cases the actual nature of the mechanosensors.

Characterising the mechanics of cell-cell adhesion in plants.

Cell-cell adhesion is a fundamental feature of multicellular organisms. To ensure multicellular integrity, adhesion needs to be tightly controlled and maintained. In plants, cell-cell adhesion remains poorly understood.

FERONIA and microtubules independently contribute to mechanical integrity in the Arabidopsis shoot.

To survive, cells must constantly resist mechanical stress. In plants, this involves the reinforcement of cell walls, notably through microtubule-dependent cellulose deposition. How wall sensing might contribute to this response is unknown.

Effects of Arabidopsis wall associated kinase mutations on ESMERALDA1 and elicitor induced ROS.

Angiosperm cell adhesion is dependent on interactions between pectin polysaccharides which make up a significant portion of the plant cell wall. Cell adhesion in Arabidopsis may also be regulated through a pectin-related signaling cascade mediated by a putative O-fucosyltransferase ESMERALDA1 (ESMD1), and the Epidermal Growth Factor (EGF) domains of the pectin binding Wall associated Kinases (WAKs) are a primary candidate substrate for ESMD1 activity. Genetic interactions between WAKs and ESMD1 were examined using a dominant hyperactive allele of WAK2, WAK2cTAP, and a mutant of the putative O-fucosyltransferase ESMD1.

External Mechanical Cues Reveal a Katanin-Independent Mechanism behind Auxin-Mediated Tissue Bending in Plants.

Tissue folding is a central building block of plant and animal morphogenesis. In dicotyledonous plants, hypocotyl folds to form hooks after seedling germination that protects their aerial stem cell niche during emergence from soil. Auxin response factors and auxin transport are reported to play a key role in this process.

Microtubule Response to Tensile Stress Is Curbed by NEK6 to Buffer Growth Variation in the Arabidopsis Hypocotyl.

Growth variability generates mechanical conflicts in tissues. In plants, cortical microtubules usually align with maximal tensile stress direction, thereby mechanically reinforcing cell walls, and channeling growth rate and direction. How this is achieved remains largely unknown and likely involves microtubule regulators.

Polar expedition: mechanisms for protein polar localization.

Most cells show asymmetry in their shape or in the organization of their components that results in poles with different properties. This is a fundamental feature that participates in modulating the development of an organism and its responses to external stimuli. In plants, a number of proteins that are important for developmental and physiological processes have been shown to display polar localization.

Feeling Stressed or Strained? A Biophysical Model for Cell Wall Mechanosensing in Plants.

Mechanical signals have recently emerged as a major cue in plant morphogenesis, notably influencing cytoskeleton organization, gene expression, protein polarity, or cell division. Although many putative mechanosensing proteins have been identified, it is unclear what mechanical cue they might sense and how this would occur. Here we briefly explain the notions of mechanical stress and strain.

ImageJ SurfCut: a user-friendly pipeline for high-throughput extraction of cell contours from 3D image stacks.

Background: Many methods have been developed to quantify cell shape in 2D in tissues. For instance, the analysis of epithelial cells in Drosophila embryogenesis or jigsaw puzzle-shaped pavement cells in plant epidermis has led to the development of numerous quantification methods that are applied to 2D images. However, proper extraction of 2D cell contours from 3D confocal stacks for such analysis can be problematic.

Mechanical Conflicts in Twisting Growth Revealed by Cell-Cell Adhesion Defects.

Many plants grow organs and tissues with twisted shapes. Arabidopsis mutants with impaired microtubule dynamics exhibit such a phenotype constitutively. Although the activity of the corresponding microtubule regulators is better understood at the molecular level, how large-scale twisting can emerge in the mutants remains largely unknown.

An Image Analysis Pipeline to Quantify Emerging Cracks in Materials or Adhesion Defects in Living Tissues.

Microcracks in materials reflect their mechanical properties. The quantification of the number or orientation of such cracks is thus essential in many fields, including engineering and geology. In biology, cracks in soft tissues can reflect adhesion defects, and the analysis of their pattern can help to deduce the magnitude and orientation of tensions in organs and tissues.

A tension-adhesion feedback loop in plant epidermis.

Mechanical forces have emerged as coordinating signals for most cell functions. Yet, because forces are invisible, mapping tensile stress patterns in tissues remains a major challenge in all kingdoms. Here we take advantage of the adhesion defects in the mutant to deduce stress patterns in tissues.

Plant Physiology: FERONIA Defends the Cell Walls against Corrosion.

A new study uncovers the role of wall sensing and remodeling in the plant response to salt stress, identifying the FERONIA receptor kinase as a key player in that process, likely through direct sensing of cell wall pectins.

Why plants make puzzle cells, and how their shape emerges.

The shape and function of plant cells are often highly interdependent. The puzzle-shaped cells that appear in the epidermis of many plants are a striking example of a complex cell shape, however their functional benefit has remained elusive. We propose that these intricate forms provide an effective strategy to reduce mechanical stress in the cell wall of the epidermis.

Developing a 'thick skin': a paradoxical role for mechanical tension in maintaining epidermal integrity?

Plant aerial epidermal tissues, like animal epithelia, act as load-bearing layers and hence play pivotal roles in development. The presence of tension in the epidermis has morphogenetic implications for organ shapes but it also constantly threatens the integrity of this tissue. Here, we explore the multi-scale relationship between tension and cell adhesion in the plant epidermis, and we examine how tensile stress perception may act as a regulatory input to preserve epidermal tissue integrity and thus normal morphogenesis.

Cell adhesion in plants is under the control of putative O-fucosyltransferases.

Cell-to-cell adhesion in plants is mediated by the cell wall and the presence of a pectin-rich middle lamella. However, we know very little about how the plant actually controls and maintains cell adhesion during growth and development and how it deals with the dynamic cell wall remodeling that takes place. Here we investigate the molecular mechanisms that control cell adhesion in plants.

A galactosyltransferase acting on arabinogalactan protein glycans is essential for embryo development in Arabidopsis.

Arabinogalactan proteins (AGPs) are a complex family of cell-wall proteoglycans that are thought to play major roles in plant growth and development. Genetic approaches to studying AGP function have met limited success so far, presumably due to redundancy within the large gene families encoding AGP backbones. Here we used an alternative approach for genetic dissection of the role of AGPs in development by modifying their glycan side chains.

[The necklace from the 660 grave in Megara Iblea].

The article analyzes the 660 grave in Megara Iblea, a Greek colony in Sicily, in which a woman has been buried. On her breast a magnificent neckless was found, made of amulets recalling the travel of the sun during the summer solstice. Some objects allude to solar cults (a cock; round pendants), others seem to came from Gallia and Macedonia (summer far West and East), others recall archeological contexts such as tombs in Marvinci, in the Vardar Valley, and allude to relations with female practices of medicine and magic and to female roles characterized by extraordinary powers, due to being descendants of the Sun god.