Cell Elongation Research Articles

SlCHP16 promotes root growth and enhances saline-alkali tolerance of tomato

With the increasing salinization in the world, crop growth and yield had a serious threat. Roots as the organ of the plant direct contact the saline-alkali environment has received more and more attention. The Divergent C1 (DC1) domain protein plays an important role in plant growth, development, and stress response. In this study, overexpression of SlCHP16 promoted tomato root growth, while knocking out SlCHP16 inhibited tomato root growth. In the roots of SlCHP16 overexpressing plants, the auxin synthesis key gene SlTAA2 was significantly up-regulated, which increased auxin synthesis and accumulation and promoted root cell elongation. Meanwhile, the expression levels of cell expanding-related genes SlLRP, SlXTH9 and SlEXPB1 were up-regulated. The opposite was observed in SlCHP16 knockout plants. Under saline-alkali stress, the root growth rate of SlCHP16 overexpressed lines was significantly higher than that of AC, and SlCHP16 knockout lines had poor root development during seed germination and seedling growth. At the same time, after saline-alkali stress treatment, SlCHP16-overexpressing lines showed higher tolerance, while SlCHP16 knockout plants were more sensitive to saline-alkali stress. In conclusion, SlCHP16 promoted root growth and enhanced saline-alkali tolerance in tomato. This work provides new insights into the mechanism of tomato root development and provides resources for developing new salt-alkali tolerant tomato varieties.

Is it really descemetocele? Morphology of extremely thin membrane that remained after severe corneal melting: a case report.

The aim of this study was to report transmission electron microscopic findings of a case with whole corneal descemetocele following infective corneal ulcer for the first time in literature. A 72-year-old male patient presented with infective corneal ulcer. After resolution of the infection, corneoscleral transplantation was performed. The excised very thin corneal membrane was processed for transmission electron microscopic examination. Transmission electron microscopic examination of the specimen revealed many layered structures that consisted of two different types of cells. The first type consisted of lighter staining polygonal cells, while the second consisted of elongated cells with relatively dense staining. All cells were connected with a large number of gap or adherens junctions with intercalation of the cell membranes of adjacent cells. A haphazard distribution of cytoplasmic microfilaments were also observed in all of the cell types. There was no evidence of the presence of endothelial cells throughout the specimen. There was also no evidence of Descemet membrane presence except for a small part adjacent to iris tissue that contained some melanosomes. Although we clinically diagnosed descemetocele, Descemet membrane was not present at the electron microscopic level, and thus, the expression "descemetocele" is inappropriate.

Establishment and characterization of novel spontaneously immortalized larval cell lines from sablefish Anoplopoma fimbria.

Sablefish Anoplopoma fimbria is a groundfish of the North PacificOceantypically found in sea floor habitat at depths to 2700m. Prized as a food fish with exceptionally high market value, sablefish aquaculture has been sought to provide a sustainable source of this fish to meet market demands. While commercial culture has successfully produced market-sized fish in Pacific coastal environments, production has been hampered by disease and the overall lack of information on sablefish health and immunology. To begin to address these knowledge gaps, herein we describe the isolation and characterization of spontaneously immortalized sablefish larval cell lines (AFL). Six sublines were established from pools of early yolk-sac larvae, while attempts to develop tissue-specific-derived cell lines were unsuccessful. The six yolk-sac larval cell lines each display two morphologies in culture, an elongated fibroblast-like cell type, and a rounded squamous or epithelial-like cell type. Cytogenetic characterization suggests that both cell types are diploid (2n = 48) with 24 pairs of chromosomes, 23 pairs of autosomes, and 1 pair of sex chromosomes. A small proportion (11%) of AFL cells display tetraploidy. Incubation temperature and medium composition experiments revealed HEPES buffered L-15 media containing 10-20% FBS at temperatures between 15 and 18° C yielded optimal cell growth. These growth characteristics suggest that sablefish larval cells display a robustness for varying growth conditions. The establishment of AFL cell lines provides a foundational tool to study the physiology, health, immunology, and cell and molecular biology of sablefish.

MmpL3, Wag31, and PlrA are involved in coordinating polar growth with peptidoglycan metabolism and nutrient availability.

This study is performed in Mycobacterium smegmatis, which is used as a model to understand the basic physiology of pathogenic mycobacteria such as Mycobacterium tuberculosis. In this work, we examine the function and regulation of three proteins involved in regulating cell wall elongation in mycobacterial cells, which occurs at the cell tips or poles. We find that Wag31, a regulator of polar elongation, works partly through the regulation of MmpL3, a transporter of cell wall constituents and an important drug target. Our work suggests that, beyond its transport function, MmpL3 has another function in controlling cell wall synthesis broadly in response to stress.

Non-thermal plasma enhances growth and salinity tolerance of bok choy (Brassica rapa subsp. chinensis) in hydroponic culture.

In this study, we aimed to examine the growth, physiological and biochemical status, and responses to salinity stress of bok choy (Brassica rapa subsp. chinensis) cultivated in a hydroponic system with a plasma-treated solution. Plasma gas generated using a cylindrical dielectric barrier discharge or air (control) was injected into Hoagland nutrient solution once a week for different durations (0, 5, and 10 min). After 4 weeks, the length of the shoots and roots, number of leaves, and dry weight of bok choy plants significantly increased in individuals grown with Hoagland solution treated with plasma gas for 10 min. An increase in dry weight of individual plants of approximately 80.5% was observed in plants in the plasma-treated group compared to those in a control group. The levels of chlorophyll, total soluble proteins, and nitrogen uptake, and transcription of genes related to salinity stress tolerance-WRKY2, HHP3, and ABI1- were also significantly elevated in bok choy grown with plasma treated Hoagland solution. Moreover, when exposed to 20 mM NaCl, plant length and leaf number were significantly increased, in the group grown with Hoagland solution treated with plasma gas for 10 min. Level of H2O2 was significantly elevated in the treated nutrient solutions. In plants grown with the treated nutrient solution, intracellular NO was highly detected in the cell division and elongation zone of roots. Our findings suggest that plasma treatment of nutrient solutions in hydroponic culture systems may improve the growth, physiological and biochemical status, and tolerance to salinity stress in plants, and a crucial role of H2O2 generated in the treated nutrient solutions may play in this improvement.

Brassinosteroids in cotton: orchestrating fiber development.

Cotton cultivation spans over 30 million hectares across 85 countries and regions, with more than half participating in the global cotton textile trade. The elongated cotton fiber cell is an ideal model for studying cell elongation and understanding plant growth and development. Brassinosteroids (BRs), recognized for their role in cell elongation, offer the potential for improving cotton fiber quality and yield. Despite extensive research highlighting BR's positive impact on fiber development, a comprehensive review on this topic has been lacking. This review addresses this gap, providing a detailed analysis of the latest advancements in BR signaling and its effects on cotton fiber development. We explore the complex network of BR biosynthesis components, signaling molecules, and regulators, including crosstalk with other pathways and transcriptional control mechanisms. Additionally, we propose molecular strategies and highlight key genetic elements for optimizing BR-related genes to enhance fiber quality and yield. The review emphasizes the importance of BR homeostasis and the hormonal landscape during cotton fiber development, offering insights into targeted manipulation opportunities and challenges. This consolidation offers a comprehensive understanding of BR's multifaceted roles in fiber development, outlining a strategic approach for BR optimization in cotton fiber quality and yield.

Plant BCL-Domain Homologues play a conserved role in SWI/SNF complex stability.

The SWItch/Sucrose Non-Fermenting (SWI/SNF) complexes are evolutionarily conserved, ATP-dependent chromatin remodelers crucial for multiple nuclear functions in eukaryotes. Recently, plant BCL-Domain Homolog (BDH) proteins were identified as shared subunits of all plant SWI/SNF complexes, significantly impacting chromatin accessibility and various developmental processes in Arabidopsis. In this study, we performed a comprehensive characterization of bdh mutants, revealing a previously overlooked impact on hypocotyl cell elongation. Through detailed analysis of BDH domains, we identified a plant-specific N-terminal domain that facilitates the interaction between BDH and the rest of the complex. Additionally, we uncovered the critical role of the BDH β-hairpin domain, which is phylogenetically related to metazoan BCL7 SWI/SNF subunits. While phylogenetic analyses did not identify BDH/BCL7 orthologs in fungi, structure prediction modeling demonstrated strong similarities between the SWI/SNF catalytic modules of plants, animals, and fungi, and revealed the yeast Rtt102 protein as a structural homolog of BDH and BCL7. This finding is supported by the ability of Rtt102 to interact with the Arabidopsis catalytic module subunit ARP7 and partially rescue the bdh mutant phenotypes. Further experiments revealed that BDH promotes the stability of the ARP4-ARP7 heterodimer, leading to the partial destabilization of ARP4 in the SWI/SNF complexes. In summary, our study unveils the molecular function of BDH proteins in plant SWI/SNF complexes and suggests that β-hairpin-containing proteins are evolutionarily conserved subunits crucial for ARP heterodimer stability and SWI/SNF activity across eukaryotes.

Hydrodynamic hovering of swimming bacteria above surfaces

Flagellated bacteria are hydrodynamically attracted to rigid walls, yet past work shows a “hovering” state where they swim stably at a finite height above surfaces. We use numerics and theory to reveal the physical origin of hovering. Simulations first show that hovering requires an elongated cell body and results from a tilt away from the wall. Theoretical models then identify two essential asymmetries: the response of width-asymmetric cells to active flows created by length-asymmetric cells. A minimal model reconciles near- and far-field hydrodynamics, capturing all key features of hovering. Published by the American Physical Society 2024

DivIVA controls the dynamics of septum splitting and cell elongation in Streptococcus pneumoniae.

Bacterial shape and division rely on the dynamics of cell wall assembly, which involves regulated synthesis and cleavage of the peptidoglycan. In ovococci, these processes are coordinated within an annular mid-cell region with nanometric dimensions. More precisely, the cross-wall synthesized by the divisome is split to generate a lateral wall, whose expansion is insured by the insertion of the so-called peripheral peptidoglycan by the elongasome. Septum cleavage and peripheral peptidoglycan synthesis are, thus, crucial remodeling events for ovococcal cell division and elongation. The structural DivIVA protein has long been known as a major regulator of these processes, but its mode of action remains unknown. Here, we integrate click chemistry-based peptidoglycan labeling, direct stochastic optical reconstruction microscopy, and in silico modeling, as well as epifluorescence and stimulated emission depletion microscopy to investigate the role of DivIVA in Streptococcus pneumoniae cell morphogenesis. Our work reveals two distinct phases of peptidoglycan remodeling during the cell cycle that are differentially controlled by DivIVA. In particular, we show that DivIVA ensures homogeneous septum cleavage and peripheral peptidoglycan synthesis around the division site and their maintenance throughout the cell cycle. Our data additionally suggest that DivIVA impacts the contribution of the elongasome and class A penicillin-binding proteins to cell elongation. We also report the position of DivIVA on either side of the septum, consistent with its known affinity for negatively curved membranes. Finally, we take the opportunity provided by these new observations to propose hypotheses for the mechanism of action of this key morphogenetic protein.IMPORTANCEThis study sheds light on fundamental processes governing bacterial growth and division, using integrated click chemistry, advanced microscopy, and computational modeling approaches. It addresses cell wall synthesis mechanisms in the opportunistic human pathogen Streptococcus pneumoniae, responsible for a range of illnesses (otitis, pneumonia, meningitis, septicemia) and for one million deaths every year worldwide. This bacterium belongs to the morphological group of ovococci, which includes many streptococcal and enterococcal pathogens. In this study, we have dissected the function of DivIVA, which is a structural protein involved in cell division, morphogenesis, and chromosome partitioning in Gram-positive bacteria. This work unveils the role of DivIVA in the orchestration of cell division and elongation along the pneumococcal cell cycle. It not only enhances our understanding of how ovoid bacteria proliferate but also offers the opportunity to consider how DivIVA might serve as a scaffold and sensor for particular membrane regions, thereby participating in various cell cycle processes.

Enhancing Coleoptile Length of Rice Seeds under Submergence through NAL11 Knockout.

Submergence stress challenges direct seeding in rice cultivation. In this study, we identified a heat shock protein, NAL11, with a DnaJ domain, which can regulate the length of rice coleoptiles under flooded conditions. Through bioinformatics analyses, we identified cis-regulatory elements in its promoter, making it responsive to abiotic stresses, such as hypoxia or anoxia. Expression of NAL11 was higher in the basal regions of shoots and coleoptiles during flooding. NAL11 knockout triggered the rapid accumulation of abscisic acid (ABA) and reduction of Gibberellin (GA), stimulating rice coleoptile elongation and contributes to flooding stress management. In addition, NAL11 mutants were found to be more sensitive to ABA treatments. Such knockout lines exhibited enhanced cell elongation for coleoptile extension. Quantitative RT-PCR analysis revealed that NAL11 mediated the gluconeogenic pathway, essential for the energy needed in cell expansion. Furthermore, NAL11 mutants reduced the accumulation of reactive oxygen species (ROS) and malondialdehyde under submerged stress, attributed to an improved antioxidant enzyme system compared to the wild-type. In conclusion, our findings underscore the pivotal role of NAL11 knockout in enhancing the tolerance of rice to submergence stress by elucidating its mechanisms. This insight offers a new strategy for improving resilience against flooding in rice cultivation.

Endothelial cell elongation and alignment in response to shear stress requires acetylation of microtubules.

The innermost layer of the vessel wall is constantly subjected to recurring and relenting mechanical forces by virtue of their direct contact with blood flow. Endothelial cells of the vessel are exposed to distension, pressure, and shear stress; adaptation to these hemodynamic forces requires significant remodeling of the cytoskeleton which includes changes in actin, intermediate filaments, and microtubules. While much is known about the effect of shear stress on the endothelial actin cytoskeleton; the impact of hemodynamic forces on the microtubule network has not been investigated in depth. Here we used imaging techniques and protein expression analysis to characterize how pharmacological and genetic perturbations of microtubule properties alter endothelial responses to laminar shear stress. Our findings revealed that pharmacological suppression of microtubule dynamics blocked two typical responses to laminar shear stress: endothelial elongation and alignment. The findings demonstrate the essential contribution of the microtubule network to changes in cell shape driven by mechanical forces. Furthermore, we observed a flow-dependent increase in microtubule acetylation that occurred early in the process of cell elongation. Pharmacological manipulation of microtubule acetylation showed a direct and causal relationship between acetylation and endothelial elongation. Finally, genetic inactivation of aTAT1, a microtubule acetylase, led to significant loss of acetylation as well as inhibition of cell elongation in response to flow. In contrast, loss of HDAC6, a microtubule deacetylase, resulted in robust microtubule acetylation with cells displaying faster kinetics of elongation and alignment. Taken together, our findings uncovered the critical contributions of HDAC6 and aTAT1, that through their roles in the regulation of microtubule acetylation, are key mediators of endothelial mechanotransduction.

Non-linear stress-softening of the bacterial cell wall confers cell shape homeostasis.

The bacillus - or rod - is a pervasive cellular morphology among bacteria. Rod-shaped cells elongate without widening by reinforcing their cell wall anisotropically to prevent turgor pressure from inflating cell width. Here, we demonstrate that a constrictive force is also essential for avoiding pressure-driven widening in Gram-positive bacteria. Specifically, super-resolution measurements of the nonlinear mechanical properties of the cell wall revealed that across a range of turgor pressure cell elongation directly causes width constriction, similar to a "finger trap" toy. As predicted by theory, this property depends on cell-wall anisotropy and is precisely correlated with the cell's ability to maintain a rod shape. Furthermore, the acute non-linearities in the dependence between cell length and width deformation result in a negative-feedback mechanism that confers cell-width homeostasis. That is, the Gram-positive cell wall is a "smart material" whose exotic mechanical properties are exquisitely adapted to execute cellular morphogenesis.

Over-expression of LsEXPA6, a lettuce expansin gene, improves cadmium stress tolerance in transgenic Arabidopsis

Cadmium (Cd) is a harmful heavy metal that is highly toxic to plants and animals. Expansins are cell wall proteins inducing cell wall loosening and participate in all plant growth and development processes which are associated with cell wall modifications. We investigated lettuce’s expansin gene LsEXPA6 and found that LsEXPA6 overexpression Arabidopsis lines were much more resistant to cadmium stress. Our results revealed that the root system of the expa6 mutant was suppressed under cadmium stress, resulting in shorter plant height, reduced biomass, and a significant increase in cadmium content in the plants compared with wild-type plants, whereas LsEXPA6 overexpression lines had a well-developed root system and reduced cadmium accumulation in the roots and shoots of the plants. The above results indicated that overexpression of LsEXPA6 affected root development and reduced Cd absorption in Arabidopsis. In addition, the higher absorption capacity of nutrients, increased antioxidant enzymes activities, improved chlorophyll and photosynthetic function in the overexpression Arabidopsis plants, supported the Cd stress tolerance mechanism. Taken together, these results provided a new insight on the role of expansin proteins in the tolerance of plants to Cd stress by root cell elongation.

The Phyllosphere Microbiome in Tsuga canadensis: Relationships with Resistance to the Insect Adelges tsugae and Effects of the Pesticide Dinotefuran

Tsuga canadensis (eastern hemlock) is an important tree species in North America, but it has been subject to threats from invasive insects such as Adelges tsugae (hemlock woolly adelgid). A. tsugae is native to Asia, and Tsuga species from Asia are typically resistant to this insect. In this study, we examined the phyllosphere microbiome of two hemlock species native to North America and susceptible to A. tsugae ( T. canadensis and T. caroliniana) as well as two species native to Asia and resistant to A. tsugae ( T. chinensis and T. diversifolia). Because pesticide application is often used to treat native Tsuga species impacted by A. tsugae, we also examined the response of the microbiome and overall plant physiology to the pesticide dinotefuran in T. canadensis. We found significant differences in the bacterial and fungal microbiome among the four species of Tsuga. Dinotefuran also significantly affected bacterial communities, but not fungal communities, of T. canadensis. The genus Methylobacterium, which uses methanol produced during plant cell elongation and growth, was a significant indicator of trees not subject to dinotefuran. This suggests that dinotefuran may have reduced cell growth in treated trees. Despite changes in the microbiome, dinotefuran application did not significantly affect plant physiology; however, the coefficient of variation in dinotefuran-treated trees was larger than that in non-treated trees. Our results suggest that the microbiome could play a role in mediating insect resistance in Tsuga species and that pesticide application could affect the phyllosphere microbiome, with implications for plant growth and resistance. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

An outer membrane porin-lipoprotein complex modulates elongasome movement to establish cell curvature in Rhodospirillum rubrum

Curved cell shapes are widespread among bacteria and important for cellular motility, virulence and fitness. However, the underlying morphogenetic mechanisms are still incompletely understood. Here, we identify an outer-membrane protein complex that promotes cell curvature in the photosynthetic species Rhodospirillum rubrum. We show that the R. rubrum porins Por39 and Por41 form a helical ribbon-like structure at the outer curve of the cell that recruits the peptidoglycan-binding lipoprotein PapS, with PapS inactivation, porin delocalization or disruption of the porin-PapS interface resulting in cell straightening. We further demonstrate that porin-PapS assemblies act as molecular cages that entrap the cell elongation machinery, thus biasing cell growth towards the outer curve. These findings reveal a mechanistically distinct morphogenetic module mediating bacterial cell shape. Moreover, they uncover an unprecedented role of outer-membrane protein patterning in the spatial control of intracellular processes, adding an important facet to the repertoire of regulatory mechanisms in bacterial cell biology.

Influence of oipA Phase Variation on Virulence Phenotypes Related to Type IV Secretion System in Helicobacter pylori.

oipA, an outer membrane protein of Helicobacter pylori, is linked to IL-8 induction and gastric inflammation, but its role is debated due to inconsistent findings. This study aims to explore the role of oipA phase variation in modulating the virulence traits of H. pylori, a bacterium strongly associated with the development of gastric cancer. American clinical isolate AH868 strain for naturally occurring phase variations of the oipA gene, and G27 strain for invitro-induced phase variations were used to elucidate oipA's impact on key virulence phenotypes, including cell elongation, CagA phosphorylation, and IL-8 induction. Using AH868 strain, natural oipA phase variation does not affect cell elongation and IL-8 induction. Interestingly, however, invitro-induced oipA phase variations in G27 strain uncovered that 9.4% of oipA "Off" transformants exhibit reduced cell elongation while all maintaining consistent IL-8 induction levels. Additionally, complementation of oipA "Off to On" status restores the cell elongation phenotype in 12.5% of transformants, highlighting the importance of oipA in maintaining normal cell morphology. Crucially, these variations in cell elongation are not linked to changes in bacterial adherence capabilities. Furthermore, the study shows a correlation among oipA phase variation, cell elongation, and CagA phosphorylation, suggesting that oipA influences the functionality of the Type IV secretion system. Whole-genome sequencing of selected transformants reveals genetic variations in bab paralogue, cagY gene, and other genomic regions, underscoring the complex genetic interactions that shape H. pylori's virulence. Our research provides new insights into the subtle yet significant role of oipA phase variation in H. pylori pathogenicity, emphasizing the need for further studies to explore the intricate molecular mechanisms involved. This understanding could pave the way for targeted therapeutic strategies to mitigate the impact of H. pylori on human health.

Regulatory networks of coresident subgenomes during rapid fiber cell elongation in upland cotton

Cotton, an intriguing plant species shaped by polyploidization, evolution, and domestication, holds particular interest due to the complex mechanisms governing fiber traits across its two subgenomes. However, the regulatory elements or transcriptional networks between subgenomes during fiber elongation remain to be fully clarified. Here, we analyzed 1462 cotton fiber samples to reconstruct the gene-expression regulatory networks that influence fiber cell elongation. Inter-subgenome expression quantitative trait loci (eQTLs) largely dictate gene transcription, with a notable tendency for the D subgenome to regulate A-subgenome eGenes. This regulation reveals synchronized homoeologous gene expression driven by co-localized eQTLs and divergent patterns that diminish genetic correlations, thus leading to preferential expression in the A and D subgenomes. Hotspot456 emerged as a key regulator of fiber initiation and elongation, and artificial selection of trans-eQTLs in hotspot456 that positively regulate KCS1 has facilitated cell elongation. Experiments designed to clarify the roles of trans-eQTLs in improved fiber breeding confirmed the inhibition of GhTOL9 by a specific trans-eQTL via GhWRKY28, which negatively affects fiber elongation. We propose a model in which the GhWRKY28–GhTOL9 module regulates this process through the ESCRT (endosomal sorting complex required for transport) pathway. This research significantly advances our understanding of cotton’s evolutionary and domestication processes and the intricate regulatory mechanisms that underlie significant plant traits.

Plasticity variable collagen-PEG interpenetrating networks modulate cell spreading

The extracellular matrix protein collagen I has been used extensively in the field of biomaterials due to its inherent biocompatibility and unique viscoelastic and mechanical properties. Collagen I self-assembly into fibers and networks is environmentally sensitive to gelation conditions such as temperature, resulting in gels with distinct network architectures and mechanical properties. Despite this, collagen gels are not suitable for many applications given their relatively low storage modulus. We have prepared collagen-poly(ethylene glycol) [PEG] interpenetrating network (IPN) hydrogels to reinforce the collagen network, which also induces changes to network plasticity, a recent focus of study in cell-matrix interactions. Here, we prepare collagen/PEG IPNs, varying collagen concentration and collagen gelation temperature to assess changes in microarchitecture and mechanical properties of these networks. By tuning these parameters, IPNs with a range of stiffness, plasticity and pore size are obtained. Cell studies suggest that matrix plasticity is a key determinant of cell behavior, including cell elongation, on these gels. This work presents a natural/synthetic biocompatible matrix that retains the unique structural properties of collagen networks with increased storage modulus and tunable plasticity. The described IPN materials will be of use for applications in which control of cell spreading is desirable, as only minimal changes in sample preparation lead to changes in cell spreading and circularity. Additionally, this study contributes to our understanding of the connection between collagen self-assembly conditions and matrix structural and mechanical properties and presents them as useful tools for the design of other collagen based biomaterials. Statement of significanceWe developed a collagen-poly(ethylene glycol) interpenetrating network (IPN) platform that retains native collagen architecture and biocompatibility but provides higher stiffness and tunable plasticity. With minor changes in collagen gelation temperature or concentration, IPN gels with a range of plasticity, storage modulus, and pore size can be obtained. The tunable plasticity of the gels is shown to modulate cell spreading, with a greater proportion of elongated cells on the most plastic of IPNs, supporting the assertion that matrix plasticity is a key determinant of cell spreading. The material can be of use for situations where control of cell spreading is desired with minimal intervention, and the findings herein may be used to develop similar collagen based IPN platforms.

Osteogenic differentiation of bone mesenchymal stem cells on linearly aligned triangular micropatterns.

Mesenchymal stem cells (MSCs) hold promise for regenerative medicine, particularly for bone tissue engineering. However, directing MSC differentiation towards specific lineages, such as osteogenic, while minimizing undesired phenotypes remains a challenge. Here, we investigate the influence of micropatterns on the behavior and lineage commitment of rat bone marrow-derived MSCs (rBMSCs), focusing on osteogenic differentiation. Linearly aligned triangular micropatterns (TPs) and circular micropatterns (CPs) coated with fibronectin were fabricated to study their effects on rBMSC morphology and differentiation and the underlying mechanobiological mechanisms. TPs, especially TP15 (15 μm), induced the cell elongation and thinning, while CPs also promoted the cell stretching, as evidenced by the decreased circularity and increased aspect ratio. TP15 significantly promoted osteogenic differentiation, with increased expression of osteogenic genes (Runx2, Spp1, Alpl, Bglap, Col1a1) and decreased expression of adipogenic genes (Pparg, Cebpa, Fabp4). Conversely, CPs inhibited both osteogenic and adipogenic differentiation. Mechanistically, TP15 increased Piezo1 activity, cytoskeletal remodeling including the aggregates of F-actin and myosin filaments at the cell periphery, YAP1 nuclear translocation, and integrin upregulation. Piezo1 inhibition suppressed the osteogenic genes expression, myosin remodeling, and YAP1 nuclear translocation, indicating Piezo1-mediated the mechanotransduction in rBMSCs on TPs. TP15 also induced osteogenic differentiation of BMSCs from aging rats, with upregulated Piezo1 and nuclear translocation of YAP1. Therefore, triangular micropatterns, particularly TP15, promote osteogenesis and inhibit adipogenesis of rBMSCs through Piezo1-mediated myosin and YAP1 pathways. Our study provides novel insights into the mechanobiological mechanisms governing MSC behaviors on micropatterns, offering new strategies for tissue engineering and regenerative medicine.

GhEXL3 participates in brassinosteroids regulation of fiber elongation in Gossypium hirsutum.

Cotton fiber (Gossypium hirsutum) serves as an ideal model for investigating the molecular mechanisms of plant cell elongation at the single-cell level. Brassinosteroids (BRs) play a crucial role in regulating plant growth and development. However, the mechanism by which BR influences cotton fiber elongation remains incompletely understood. In this study, we identified EXORDIUM-like (GhEXL3) through transcriptome analysis of fibers from BR-deficient cotton mutant pagoda 1 (pag1) and BRI1-EMS-SUPPRESSOR 1 (GhBES1.4, encoding a central transcription factor of BR signaling) overexpression cotton lines. Knockout of GhEXL3 using CRISPR/Cas9 was found to impede cotton fiber elongation, while its overexpression promoted fiber elongation, suggesting a positive regulatory function for GhEXL3 in fiber elongation. Furthermore, in vitro ovule culture experiments revealed that the overexpression of GhEXL3 partially counteracted the inhibitory effects of brassinazole (BRZ) on cotton fiber elongation, providing additional evidence of GhEXL3 involvement in BR signaling pathways. Moreover, our findings demonstrate that GhBES1.4 directly binds to the E-box (CACGTG) motif in the GhEXL3 promoter region and enhances its transcription. RNA-seq analysis revealed that overexpression of GhEXL3 upregulated the expression of EXPs, XTHs, and other genes associated with fiber cell elongation. Overall, our study contributes to understanding the mechanism by which BR regulates the elongation of cotton fibers through the direct modulation of GhEXL3 expression by GhBES1.4.