Defective control of growth rate and cell diameter in tip-growing root hairs of the rhd4 mutant of Arabidopsis thaliana

1999 ◽  
Vol 77 (4) ◽  
pp. 494-507 ◽  
Author(s):  
M E Galway ◽  
D C Lane ◽  
J W Schiefelbein
Keyword(s):  
Growth Rate ◽  
Arabidopsis Thaliana ◽  
Cell Wall ◽  
Osmotic Stress ◽  
Tip Growth ◽  
Turgor Pressure ◽  
Root Hairs ◽  
Recessive Mutation ◽  
Cell Diameter ◽  
Hair Diameter

A recessive mutation in the RHD4 gene of Arabidopsis thaliana L. affects the control of tip growth in seedling root hairs. Fully grown rhd4 root hairs are half the length of wild-type (WT) hairs. The hairs are wider, and they vary in diameter during tip growth. Light microscopy and motion analysis revealed that rhd4 hairs grow more slowly and that hair growth rate varies more than in WT hairs. Hair diameter increases at the rhd4 hair tips when tip growth slows. Ultrastructural analysis revealed cell wall thickenings in some mutant hairs. WT hairs were grown in a hyperosmotic medium in an attempt to mimic the rhd4 hairs and investigate the control of root hair morphology. Osmotic stress increased WT hair diameter and induced hair bulging and also increased the diameters of rhd4 hairs. Osmotic stress could disrupt tip growth through reduced turgor pressure and (or) reduced concentrations of cytosolic calcium. Together these results indicate that RHD4 is required to maintain a uniform rate of tip growth in root hairs.Key words: Arabidopsis thaliana, cell wall, cryofixation, mutant, root hairs, tip growth.

scholarly journals Structure and Biomechanics during Xylem Vessel Transdifferentiation in Arabidopsis thaliana

Plants ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 1715
Author(s):  
Eleftheria Roumeli ◽  
Leah Ginsberg ◽  
Robin McDonald ◽  
Giada Spigolon ◽  
Rodinde Hendrickx ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Wall ◽  
Cell Walls ◽  
Turgor Pressure ◽  
Plant Cells ◽  
Building Blocks ◽  
Xylem Vessel ◽  
Primary Cell Wall ◽  
Individual Plant ◽  
Vessel Elements

Individual plant cells are the building blocks for all plantae and artificially constructed plant biomaterials, like biocomposites. Secondary cell walls (SCWs) are a key component for mediating mechanical strength and stiffness in both living vascular plants and biocomposite materials. In this paper, we study the structure and biomechanics of cultured plant cells during the cellular developmental stages associated with SCW formation. We use a model culture system that induces transdifferentiation of Arabidopsis thaliana cells to xylem vessel elements, upon treatment with dexamethasone (DEX). We group the transdifferentiation process into three distinct stages, based on morphological observations of the cell walls. The first stage includes cells with only a primary cell wall (PCW), the second covers cells that have formed a SCW, and the third stage includes cells with a ruptured tonoplast and partially or fully degraded PCW. We adopt a multi-scale approach to study the mechanical properties of cells in these three stages. We perform large-scale indentations with a micro-compression system in three different osmotic conditions. Atomic force microscopy (AFM) nanoscale indentations in water allow us to isolate the cell wall response. We propose a spring-based model to deconvolve the competing stiffness contributions from turgor pressure, PCW, SCW and cytoplasm in the stiffness of differentiating cells. Prior to triggering differentiation, cells in hypotonic pressure conditions are significantly stiffer than cells in isotonic or hypertonic conditions, highlighting the dominant role of turgor pressure. Plasmolyzed cells with a SCW reach similar levels of stiffness as cells with maximum turgor pressure. The stiffness of the PCW in all of these conditions is lower than the stiffness of the fully-formed SCW. Our results provide the first experimental characterization of the mechanics of SCW formation at single cell level.

SRPP, a cell-wall protein is involved in development and protection of seeds and root hairs in Arabidopsis thaliana

2017 ◽  
pp. pcx008 ◽  
Author(s):  
Natsuki Tanaka ◽  
Hiroshi Uno ◽  
Shohei Okuda ◽  
Shizuka Gunji ◽  
Ali Ferjani ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Wall ◽  
Root Hairs ◽  
Cell Wall Protein ◽  
A Cell

scholarly journals Structural Sterols Are Involved in Both the Initiation and Tip Growth of Root Hairs in Arabidopsis thaliana

2010 ◽  
Vol 22 (9) ◽  
pp. 2999-3019 ◽  
Author(s):  
Miroslav Ovečka ◽  
Tobias Berson ◽  
Martina Beck ◽  
Jan Derksen ◽  
Jozef Šamaj ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Tip Growth ◽  
Root Hairs

scholarly journals Systematic mapping of cell wall mechanics in the regulation of cell morphogenesis

2019 ◽  
Vol 116 (28) ◽  
pp. 13833-13838 ◽  
Author(s):  
Valeria Davì ◽  
Louis Chevalier ◽  
Haotian Guo ◽  
Hirokazu Tanimoto ◽  
Katia Barrett ◽  
...  
Keyword(s):  
Cell Wall ◽  
Turgor Pressure ◽  
Lateral Wall ◽  
Cell Diameter ◽  
Cell Morphogenesis ◽  
Size Dependent ◽  
Wall Stiffness ◽  
Large Populations ◽  
Polymeric Layer ◽  
Quantitative Understanding

Walled cells of plants, fungi, and bacteria come with a large range of shapes and sizes, which are ultimately dictated by the mechanics of their cell wall. This stiff and thin polymeric layer encases the plasma membrane and protects the cells mechanically by opposing large turgor pressure derived mechanical stresses. To date, however, we still lack a quantitative understanding for how local and/or global mechanical properties of the wall support cell morphogenesis. Here, we combine subresolution imaging and laser-mediated wall relaxation to quantitate subcellular values of wall thickness (h) and bulk elastic moduli (Y) in large populations of live mutant cells and in conditions affecting cell diameter in the rod-shaped model fission yeast. We find that lateral wall stiffness, defined by the surface modulus, σ = hY, robustly scales with cell diameter. This scaling is valid across tens of mutants spanning various functions—within the population of individual isogenic strains, along single misshaped cells, and even across the fission yeasts clade. Dynamic modulations of cell diameter by chemical and/or mechanical means suggest that the cell wall can rapidly adapt its surface mechanics, rendering stretched wall portions stiffer than unstretched ones. Size-dependent wall stiffening constrains diameter definition and limits size variations; it may also provide an efficient means to keep elastic strains in the wall below failure strains, potentially promoting cell survival. This quantitative set of data impacts our current understanding of the mechanics of cell walls and its contribution to morphogenesis.

Integration and regulation of hyphal tip growth

1995 ◽  
Vol 73 (S1) ◽  
pp. 131-139 ◽  
Author(s):  
I. Brent Heath
Keyword(s):  
Cell Wall ◽  
Tip Growth ◽  
Apical Cell ◽  
Turgor Pressure ◽  
Feedback Regulation ◽  
Regulation Mechanism ◽  
Hyphal Tip Growth ◽  
Species Specific ◽  
Stretch Activated Channels ◽  
Hyphal Tip

Hyphal tip growth is an exquisitely controlled process that forms developmentally regulated, species-specific, even-diameter tubes at rates of up to about 50 μm/min. The traditional view is that this process results from the balance between the expansive force of turgor pressure and the controlled extensibility of the apical cell wall. While these elements are involved, the model places regulation into either the global domain (turgor pressure) or the extracellular environment (the cell wall), neither of which seem well suited to the level of control evinced. Recent evidence suggests that F-actin-rich elements of the cytoskeleton are important in tip morphogenesis. Our current models propose that tip expansion is regulated (restrained under normal turgor pressure and protruded under low turgor) by a peripheral network of F-actin that is attached to the plasmalemma and the cell wall by integrin-containing linkages, thus placing control in the cytoplasm where it is accessible to normal intracellular regulatory systems. The F-actin system also functions in cytoplasmic and organelle motility; control of plasmalemma-located, stretch-activated, Ca2+-transporting, ion channel distribution; vectoral vesicle transport; and exocytosis. Regulation of the system may involve Ca2+, the concentration of which is influenced by the tip-high gradient of the stretch-activated channels, thus suggesting a possible feedback regulation mechanism. Key words: tip growth, fungi, stretch-activated channels, F-actin, Ca2+, hyphae.

scholarly journals LRR-extensins of vegetative tissues are a functionally conserved family of RALF1 receptors interacting with the receptor kinase FERONIA

2019 ◽  
Author(s):  
Aline Herger ◽  
Shibu Gupta ◽  
Gabor Kadler ◽  
Christina Maria Franck ◽  
Aurélien Boisson-Dernier ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Wall ◽  
Plasma Membrane ◽  
Cell Growth ◽  
Mechanical Stability ◽  
Root Hairs ◽  
Cell Wall Integrity ◽  
Receptor Kinase ◽  
Growth Processes ◽  
Evolutionary Diversification

AbstractPlant cell growth requires the coordinated expansion of the protoplast and the cell wall that confers mechanical stability to the cell. An elaborate system of cell wall integrity sensors monitors cell wall structures and conveys information on cell wall composition and growth factors to the cell. LRR-extensins (LRXs) are cell wall-attached extracellular regulators of cell wall formation and high-affinity binding sites for RALF (rapid alkalinization factor) peptide hormones that trigger diverse physiological processes related to cell growth. RALF peptides are also perceived by receptors at the plasma membrane and LRX4 of Arabidopsis thaliana has been shown to also interact with one of these receptors, FERONIA (FER). Here, we demonstrate that several LRXs, including the main LRX protein of root hairs, LRX1, interact with FER and RALF1 to coordinate growth processes. Membrane association of LRXs correlate with binding to FER, indicating that LRXs represent a physical link between intra- and extracellular compartments via interaction with membrane-localized proteins. Finally, despite evolutionary diversification of the LRR domains of various LRX proteins, many of them are functionally still overlapping, indicative of LRX proteins being central players in regulatory processes that are conserved in very different cell types.Author SummaryCell growth in plants requires the coordinated enlargement of the cell and the surrounding cell wall, which is ascertained by an elaborate system of cell wall integrity sensors, proteins involved in the exchange of information between the cell and the cell wall. In Arabidopsis thaliana, LRR-extensins (LRXs) are localized in the cell wall and are binding RALF peptides, hormones that regulate cell growth-related processes. LRX4 also binds the plasma membrane-localized receptor kinase FERONIA (FER), establishing a link between the cell and the cell wall. It is not clear, however, whether the different LRXs of Arabidopsis have similar functions and how they interact with their binding partners. Here, we demonstrate that interaction with FER and RALFs requires the LRR domain of LRXs and several but not all LRXs can bind these proteins. This explains the observation that mutations in several of the LRXs induce phenotypes comparable to a fer mutant, establishing that LRX-FER interaction is important for proper cell growth. Some LRXs, however, appear to influence cell growth processes in different ways, which remain to be identified.

scholarly journals Transcriptional networks underpinning ploidy related increased leaf potassium in neo-tetraploids

2021 ◽  
Author(s):  
Sina Fischer ◽  
Paulina Flis ◽  
Fang-Jie Zhao ◽  
David E. Salt
Keyword(s):  
Arabidopsis Thaliana ◽  
Cell Wall ◽  
Ion Transport ◽  
Differentially Expressed Genes ◽  
Mutational Analysis ◽  
Root Hairs ◽  
Transcriptional Networks ◽  
Physiological Effects ◽  
K Uptake ◽  
Uptake Transporters

AbstractNeo-tetraploid Arabidopsis thaliana have elevated leaf potassium (K) driven by processes within the root. The root transcriptome of neo-tetraploids is distinct from diploids, with evidence of altered K homeostasis. Mutational analysis revealed that the canonical K-uptake transporters AKT1 and HAK5 are not required for this elevated leaf K in neo-tetraploids, while the endodermis, root hairs, and SOS signaling are. Contrasting the root transcriptomes of neo-tetraploids and diploids of mutants that block the neo-tetraploid K phenotype, allowed us to identify 91 differentially expressed genes associated with elevated leaf K in neo-tetraploids. This set of genes connects WGD to elevated leaf K, and is enriched in functions such as cell wall and Casparian strip development, and ion-transport, in the endodermis, root hairs, and procambium. This gene set provides tools to test the intriguing idea of recreating the physiological effects of WGD within a diploid genome.

Microtubules are at the tips of root hairs and form helical patterns corresponding to inner wall fibrils

1985 ◽  
Vol 75 (1) ◽  
pp. 225-238 ◽  
Author(s):  
C.W. Lloyd ◽  
B. Wells
Keyword(s):  
Cell Wall ◽  
Phosphate Buffer ◽  
Tip Growth ◽  
Root Hairs ◽  
Onion Root ◽  
Apical Dome ◽  
Radish Root ◽  
Contradictory Evidence ◽  
Shadow Cast ◽  
Optimized Conditions

Root hairs have sometimes provided contradictory evidence for microtubule/microfibril parallelism. This tissue was re-examined using optimized conditions for the fixation, before immunofluorescence, of root hairs. In phosphate buffer, microtubules did not enter the apical tip of radish root hairs and were clearly fragmented. However, in an osmotically adjusted microtubule-stabilizing buffer, microtubules were observed within the apical dome and appeared unfragmented. Microtubules are not, therefore, absent from the region where new cell wall is presumed to be generated during tip growth. A spiralling of microtubules was seen at the apices of onion root hairs. Using shadow-cast preparations of macerated radish root hairs, it was confirmed that steeply helical microtubules matched the texture of the inner wall. In onion, the 45 degrees microtubular helices are accompanied by similarly wound inner wall fibrils. Results do not support the view that microtubules are not involved in the oriented deposition of fibrils in root hairs. Instead, they are interpreted in terms of a flexible helical cytoskeleton, which is capable of changing its pitch but is sensitive to fixation conditions.

scholarly journals Osmolyte homeostasis controls single-cell growth rate and maximum cell size of Saccharomyces cerevisiae

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Tom Altenburg ◽  
Björn Goldenbogen ◽  
Jannis Uhlendorf ◽  
Edda Klipp
Keyword(s):  
Growth Rate ◽  
Cell Wall ◽  
Cell Growth ◽  
Single Cell ◽  
Cell Size ◽  
Single Cells ◽  
Turgor Pressure ◽  
Thermodynamic Quantities ◽  
Cell Growth Rate ◽  
Final Size

Abstract Cell growth is well described at the population level, but precisely how nutrient and water uptake and cell wall expansion drive the growth of single cells is poorly understood. Supported by measurements of single-cell growth trajectories and cell wall elasticity, we present a single-cell growth model for yeast. The model links the thermodynamic quantities, such as turgor pressure, osmolarity, cell wall elasto-plasticity, and cell size, applying concepts from rheology and thin shell theory. It reproduces cell size dynamics during single-cell growth, budding, and hyper-osmotic or hypo-osmotic stress. We find that single-cell growth rate and final size are primarily governed by osmolyte uptake and consumption, while bud expansion requires additionally different cell wall extensibilities between mother and bud. Based on first principles the model provides a more accurate description of size dynamics than previous attempts and its analytical simplification allows for easy combination with models for other cell processes.

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