Gross morphology and adhesion-associated physical properties of Drosophila larval salivary gland glue secretion.

One of the major functions of the larval salivary glands (SGs) of many Drosophila species is to produce a massive secretion during puparium formation. This so-called proteinaceous glue is exocytosed into the centrally located lumen, and subsequently expectorated, serving as an adhesive to attach the puparial case to a solid substrate during metamorphosis. Although this was first described almost 70 years ago, a detailed description of the morphology and mechanical properties of the glue is largely missing. Its main known physical property is that it is released as a watery liquid that quickly hardens into a solid cement. Here, we provide a detailed morphological and topological analysis of the solidified glue. We demonstrated that it forms a distinctive enamel-like plaque that is composed of a central fingerprint surrounded by a cascade of laterally layered terraces. The solidifying glue rapidly produces crystals of KCl on these alluvial-like terraces. Since the properties of the glue affect the adhesion of the puparium to its substrate, and so can influence the success of metamorphosis, we evaluated over 80 different materials for their ability to adhere to the glue to determine which properties favor strong adhesion. We found that the alkaline Sgs-glue adheres strongly to wettable and positively charged surfaces but not to neutral or negatively charged and hydrophobic surfaces. Puparia formed on unfavored materials can be removed easily without leaving fingerprints or cascading terraces. For successful adhesion of the Sgs-glue, the material surface must display a specific type of triboelectric charge. Interestingly, the expectorated glue can move upwards against gravity on the surface of freshly formed puparia via specific, unique and novel anatomical structures present in the puparial's lateral abdominal segments that we have named bidentia.

Janus adhesive microneedle patch loaded with exosomes for intrauterine adhesion treatment.

Intrauterine adhesions (IUAs) are common sequelae of cervical mucosa damage caused by uterine curettage. Establishing an anti-adhesion barrier between the damaged endometrium with a sustained-release drug capability and hence promoting endogenous regeneration of the endometrium is an available treatment for IUA. However, current therapy lacks long-term intracavitary residence, drug-delivery permeability, and tissue anti-adhesion to the endometrium. Here, we report the design of a Janus microneedle patch consisting of two layers: an adhesive inner layer with an exosomes-loaded microneedle, which endows the patch with a tissue adhesive capability as well as transdermal drug-delivery capability; and an anti-adhesion outer layer, which prevents the intrauterine membrane from postoperative adhesion. This Janus adhesive microneedle patch firmly adhered to uterine tissue, and sustainedly released ∼80% of the total loaded exosomes in 7 days, hence promoting the expression of vascular- and endothelial-related cell signals. Furthermore, the anti-adhesive layer of the microneedle patch exhibited low cell and protein adhesion performance. In rats, the microneedle patch successfully prevented uterine adhesions, improved endometrial angiogenesis, proliferation, and hormone response levels. This study provides a stable anti-adhesion barrier as well as efficient drug-release capability treatment for intrauterine adhesion treatment.

Specification of distinct cell types in a sensory-adhesive organ important for metamorphosis in tunicate larvae.

The papillae of tunicate larvae contribute sensory, adhesive, and metamorphosis-regulating functions that are crucial for the biphasic lifestyle of these marine, non-vertebrate chordates. We have identified additional molecular markers for at least 5 distinct cell types in the papillae of the model tunicate Ciona, allowing us to further study the development of these organs. Using tissue-specific CRISPR/Cas9-mediated mutagenesis and other molecular perturbations, we reveal the roles of key transcription factors and signaling pathways that are important for patterning the papilla territory into a highly organized array of different cell types and shapes. We further test the contributions of different transcription factors and cell types to the production of the adhesive glue that allows for larval attachment during settlement, and to the processes of tail retraction and body rotation during metamorphosis. With this study, we continue working towards connecting gene regulation to cellular functions that control the developmental transition between the motile larva and sessile adult of Ciona.

Enhancing Transdermal Delivery: Investigating the Impact of Permeation Promoters on Ibuprofen Release and Penetration from Medical Patches-In Vitro Research.

This study investigated the impact of various enhancers on permeation through the skin and accumulation in the skin from acrylic pressure-sensitive adhesive-based drug-in-adhesives matrix-type transdermal patches. Eleven patches, each containing a 5% enhancer of permeation, encompassing compounds such as salicylic acid, menthol, urea, glycolic acid, allantoin, oleic acid, Tween 80, linolenic acid, camphor, N-dodecylcaprolactam, and glycerin, were developed. Ibuprofen (IBU) was the model active substance, a widely-used non-steroidal anti-inflammatory drug. The results were compared to patches without enhancers and commercial preparations. The study aimed to assess the effect of enhancers on IBU permeability. The adhesive properties of the patches were characterised, and active substance permeability was tested. The findings revealed that patches with 5% allantoin exhibited the highest IBU permeability, approximately 2.8 times greater than patches without enhancers after 24 h. These patches present a potential alternative to commercial preparations, highlighting the significant impact of enhancers on transdermal drug delivery efficiency.

Adaptive Adhesions of Barnacle-Inspired Adhesive Peptides.

The strategy of robust adhesion employed by barnacles renders them fascinating biomimetic candidates for developing novel wet adhesives. Particularly, barnacle cement protein 19k (cp19k) has been speculated to be the key adhesive protein establishing the priming layer in the initial barnacle cement construction. In this work, we systematically studied the sequence design rationale of cp19k by designing adhesive peptides inspired by the low-complexity STGA-rich and the charged segments of cp19k. Combining structure analysis and the adhesion performance test, we found that cp19k-inspired adhesive peptides possess excellent disparate adhesion strategies for both hydrophilic mica and hydrophobic self-assembled monolayer surfaces. Specifically, the low-complexity STGA-rich segment offers great structure flexibility for surface adhesion, while the hydrophobic and charged residues can contribute to the adhesion of the peptides on hydrophobic and charged surfaces. The adaptive adhesion strategy identified in this work broadens our understanding of barnacle adhesion mechanisms and offers valuable insights for designing advanced wet adhesives with exceptional performance on various types of surfaces.

Diatom adhesive trail proteins acquired by horizontal gene transfer from bacteria serve as primers for marine biofilm formation.

Biofilm-forming benthic diatoms are key primary producers in coastal habitats, where they frequently dominate sunlit intertidal substrata. The development of gliding motility in raphid diatoms was a key molecular adaptation that contributed to their evolutionary success. However, the structure-function correlation between diatom adhesives utilized for gliding and their relationship to the extracellular matrix that constitutes the diatom biofilm is unknown. Here, we have used proteomics, immunolocalization, comparative genomics, phylogenetics and structural homology analysis to investigate the evolutionary history and function of diatom adhesive proteins. Our study identified eight proteins from the adhesive trails of Craspedostauros australis, of which four form a new protein family called Trailins that contain an enigmatic Choice-of-Anchor A (CAA) domain, which was acquired through horizontal gene transfer from bacteria. Notably, the CAA-domain shares a striking structural similarity with one of the most widespread domains found in ice-binding proteins (IPR021884). Our work offers new insights into the molecular basis for diatom biofilm formation, shedding light on the function and evolution of diatom adhesive proteins. This discovery suggests that there is a transition in the composition of biomolecules required for initial surface colonization and those utilized for 3D biofilm matrix formation.

Preclinical Investigation of Transdermal Route for Enhanced Bio-performance of Duloxetine HCl.

The aim of the study was to develop and optimise drug-in-adhesive (DIA) transdermal patch of duloxetine HCl for enhanced drug delivery. DIA patch so developed reduced the dose and dosing frequency by enhancing bio-performance of the drug. A transdermal DIA patch having Duro-Tak 87-2287 as DIA polymer and Transcutol P as permeation enhancer loaded with 40% drug previously complexed with MeßCD duly characterised (FTIR, DSC, and SEM) was developed for in vivo study. Pharmacokinetic parameters of developed formulation were assessed and compared with oral route of administration. Among various permeation enhancers (PEs), Transcutol P exhibited most enhanced permeation (ER ≈ 1.99) in terms of flux and Q24 compared to control group having. Mean of maximum plasma concentration (Cmax) and area under time-concentration curve (AUC0-72) in Wistar rats (n = 6) for transdermal patch (10 mg/kg) was found to be 70.31 ± 11.2 ng/ml and 2997.29 ± 387.4 ng/ml*h, respectively, and were considerably higher than oral dose of DLX (20 mg/kg and 10 mg/kg). Albeit, T1/2 was higher in case of transdermal delivery, but this was due to sustained behaviour of delivery system. These findings highlight the significance of both inclusion complexation and transdermal delivery of DLX using DIA patch for efficient drug absorption.

Continuous removal of single cell layers by tape stripping the stratum corneum - a histological study.

Studies on the penetration of toxicologically or pharmaceutically relevant substances through the skin and, more specifically, through the stratum corneum (s.c.) often rely on the well-established method of tape stripping. Tape stripping involves the removal of skin layers by means of adhesive tape, which is usually followed by quantification of dermally applied substances in these layers. However, the amount of s.c. removed by each individual tape strip is still a matter of scientific debate. While some studies imply that the amount of s.c. adhering to each tape strip decreases with increasing depth into the s.c., others observed a constant removal rate. All these studies rely on the quantification of the amount of s.c. captured on individual or pooled tape strips. Here, we present an approach whereby we measured the amount of s.c. remaining on excised porcine skin in the process of tape stripping. Staining and bloating of the s.c. allowed to measure its thickness and to count individual s.c. layers, respectively. Histologically, we show that the s.c. remaining on the skin decreased linearly as a function of strips taken. We found that each tape strip removes about 0.4 µm of s.c., which corresponds to approximately one cellular layer. With a high coefficient of determination (r2 > 0.95), we were able to linearly correlate the thickness of the remaining s.c., the number of remaining cell layers and the number of tape strips applied. Furthermore, we elaborate on possible reasons for the discrepancies reported in the scientific literature regarding the amount of s.c. removed by each tape strip.

Functional modification of mussel adhesive protein to control solubility and adhesion property.

Marine mussels produce strong underwater adhesives called mussel adhesive proteins (MAPs) that can adhere to a variety of surfaces under physiological conditions. Thus, MAPs have been investigated as a potentially sustainable alternative to conventional petrochemical-based adhesives. Recombinant MAPs would be promising for large-scale production and commercialization; however, MAPs are intrinsically adhesive, aggregative, and insoluble in water. In this study, we have developed a solubilization method for the control of MAP adhesion by fusion protein technique. Foot protein 1 (Fp1), a kind of MAP, was fused with the highly water-soluble protein, which is the C-terminal domain of ice-nucleation protein K (InaKC), separated by a protease cleaving site. The fusion protein exhibited low adhesion but high solubility and stability. Notably, Fp1 recovered its adhesive property after removal from the InaKC moiety by protease cleaving, which was evaluated and confirmed by the agglomeration of magnetite particles in water. The ability to control adhesion and agglomeration makes MAPs favorable prospects for bio-based adhesives.

Bristles formation in adhesive pads and sensilli of the gecko Tarentola mauritanica derive from a massive accumulation of corneous material in Oberhautchen cells of the epidermis.

Among lizards, geckos possess special digital scales modified as hairy-like lamellae that allow attachment to vertical substrates for the movement using adhesive nanoscale filaments called setae. The present study shows new ultrastructural details on setae formation in the gecko Tarentula mauritanica. Setae derive from the special differentiation of an epidermal layer termed Oberhauchen and can reach 30-60 µm in length. Oberhautchen cells in the adhesive pad lamellae becomes hypertrophic and rest upon 2 layers of non-corneous and pale cells instead of beta-cells like in the other scales. Only 1-2 beta-layers are formed underneath the pale layer. Setae derive from the accumulation of numerous roundish and heterogenous beta-packets with variable electron-density in Oberhautchen cells, possibly indicating a mixed protein composition. Immunofluorescence and immunogold labeling for CBPs show that beta-packets merge at the base of the growing setae forming long corneous bundles. Pale cells formed underneath the Oberhautchen layer contain small vesicles or tubules with a likely lipid content, sparse keratin filaments and ribosomes. In mature lamellae these cells merge with Oberhautchen and beta-cells forming a thin electron-paler layer located between the Oberhautchen and the thin beta-layer, a variation of the typical sequence of epidermal layers present in other scales. The formation of a softer pale layer and of a thin beta-layer likely determines a flexible corneous support for the adhesive setae. The specific molecular mechanism that stimulates the cellular changes observed during Oberhautchen hypertrophy and the alteration of the typical epidermal stratification in the pad epidermis remains unknown.

Glycoproteins Involved in Sea Urchin Temporary Adhesion.

Biomedical adhesives, despite having been used increasingly in recent years, still face a major technological challenge: strong adhesion in wet environments. In this context, biological adhesives secreted by marine invertebrates have appealing characteristics to incorporate into new underwater biomimetic adhesives: water resistance, nontoxicity and biodegradability. Little is still known about temporary adhesion. Recently, a transcriptomic differential analysis of sea urchin Paracentrotus lividus tube feet pinpointed 16 adhesive/cohesive protein candidates. In addition, it has been demonstrated that the adhesive secreted by this species is composed of high molecular weight proteins associated with N-Acetylglucosamine in a specific chitobiose arrangement. As a follow-up, we aimed to investigate which of these adhesive/cohesive protein candidates were glycosylated through lectin pulldowns, protein identification by mass spectroscopy and in silico characterization. We demonstrate that at least five of the previously identified protein adhesive/cohesive candidates are glycoproteins. We also report the involvement of a third Nectin variant, the first adhesion-related protein to be identified in P. lividus. By providing a deeper characterization of these adhesive/cohesive glycoproteins, this work advances our understanding of the key features that should be replicated in future sea urchin-inspired bioadhesives.

Electrostatic Assembly of Multiarm PEG-Based Hydrogels as Extracellular Matrix Mimics: Cell Response in the Presence and Absence of RGD Cell Adhesive Ligands.

Synthetic hydrogels have been used widely as extracellular matrix (ECM) mimics due to the ability to control and mimic physical and biochemical cues observed in natural ECM proteins such as collagen, laminin, and fibronectin. Most synthetic hydrogels are formed via covalent bonding resulting in slow gelation which is incompatible with drop-on-demand 3D bioprinting of cells and injectable hydrogels for therapeutic delivery. Herein, we developed an electrostatically crosslinked PEG-based hydrogel system for creating high-throughput 3D in vitro models using synthetic hydrogels to mimic the ECM cancer environment. A 3-arm PEG-based polymer backbone was first modified with either permanent cationic charged moieties (2-(methacryloyloxy)ethyl trimethylammonium) or permanent anionic charged moieties (3-sulfopropyl methacrylate potassium salt). The resulting charged polymers can be conjugated further with various amounts of cell adhesive RGD motifs (0, 25, 75, and 98%) to study the influences of RGD motifs on breast cancer (MCF-7) spheroid formation. Formation, stability, and mechanical properties of hydrogels were tested with, and without, RGD to evaluate the cellular response to material parameters in a 3D environment. The hydrogels can be degraded in the presence of salts at room temperature by breaking the interaction of oppositely charged polymer chains. MCF-7 cells could be released with high viability through brief exposure to NaCl solution. Flow cytometry characterization demonstrated that embedded MCF-7 cells proliferate better in a softer (60 Pa) 3D hydrogel environment compared to those that are stiffer (1160 Pa). As the stiffness increases, the RGD motif plays a role in promoting cell proliferation in the stiffer hydrogel. Flow cytometry characterization demonstrated that embedded MCF-7 cells proliferate better in a softer (60 Pa) 3D hydrogel environment compared to those that are stiffer (1160 Pa). As the stiffness increases, the RGD motif plays a role in promoting cell proliferation in the stiffer hydrogel. Additionally, cell viability was not impacted by the tested hydrogel stiffness range between 60 to 1160 Pa. Taken together, this PEG-based tuneable hydrogel system shows great promise as a 3D ECM mimic of cancer extracellular environments with controllable biophysical and biochemical properties. The ease of gelation and dissolution through salt concentration provides a way to quickly harvest cells for further analysis at any given time of interest without compromising cell viability.

Penetration of Cell Surface Glycocalyx by Enveloped Viruses Is Aided by Weak Multivalent Adhesive Interaction.

Viral infection usually begins with adhesion between the viral particle and viral receptors displayed on the cell membrane. The exterior surface of the cell membrane is typically coated with a brush-like layer of molecules, the glycocalyx, that the viruses need to penetrate. Although there is extensive literature on the biomechanics of virus-cell adhesion, much of it is based on continuum-level models that do not address the question of how virus/cell-membrane adhesion occurs through the glycocalyx. In this work, we present a simulation study of the penetration mechanism. Using a coarse-grained molecular model, we study the force-driven and diffusive penetration of a brush-like glycocalyx by viral particles. For force-driven penetration, we find that viral particles smaller than the spacing of molecules in the brush reach the membrane surface readily. For a given maximum force, viral particles larger than the minimum spacing of brush molecules arrest at some distance from the membrane, governed by the balance of elastic and applied forces. For the diffusive case, we find that weak but multivalent attraction between the glycocalyx molecules and the virus effectively leads to its engulfment by the glycocalyx. Our finding provides potential guidance for developing glycocalyx-targeting drugs and therapies by understanding how virus-cell adhesion works.

Growth phase-dependent production of the adhesive nanofiber protein AtaA in Acinetobacter sp. Tol 5.

AtaA, the sticky, long, and peritrichate nanofiber protein from Acinetobacter sp. Tol 5, mediates autoagglutination and is highly adhesive to various material surfaces, resulting in a biofilm. Although the production of the adhesive nanofiber protein is likely to require a large amount of energy and material sources, the relationship between AtaA fiber production and cell growth remains unknown. Here, we report the growth phase-dependent AtaA fiber production in Tol 5. We examined the ataA gene expression in different growth phases using a reporter gene assay with an originally developed reporter plasmid and using reverse transcription-quantitative polymerase chain reaction. Bacterial cells with surface-displayed AtaA at different growth phases were immunostained and analyzed using fluorescence flow cytometry and confocal laser scanning microscopy. The results indicate that Tol 5 modulated the amount of surface-displayed AtaA at the transcriptional level. AtaA production was low in the early growth phase but remarkably increased in the late growth phase, covering the whole bacterial cell with AtaA fibers in the stationary phase. Tol 5 displayed AtaA fibers poorly in the early growth phase and showed less autoagglutination and adhesiveness than those in the stationary phase. Although Tol 5 grew as fast as its ataA-deficient mutant in the early growth phase, the optical density of Tol 5 culture was slightly lower than that of the ataA-deficient mutant in the late growth phase. Based on these experimental results, we propose the growth-phase-dependent production of AtaA fiber for efficient and fast cell growth.

Promoting soluble expression of hybrid mussel foot proteins by SUMO-TrxA tags for production of mussel glue.

Mussel foot proteins (Mfps) display application potential with strong adhesion, enabling mussels to adhere firmly to various surfaces. Mytilus galloprovincialis foot protein 3B (Mgfp-3B) exhibits this characteristic remarkably. However, it remains a challenge for further research due to the low soluble expression of heterologous production. In this study, a small ubiquitin-related modifier (SUMO) and thioredoxin A (TrxA), which catalyzed the proper folding of disulfide bridges, were selected to increase the soluble expression of mfps. An additional ribosome binding site was introduced between the molecular chaperones and Mgfp-3B (fp-3) to form a bicistronic translation-coupled expression vector for co-expression. The results revealed that the combination of SUMO-TrxA increased the soluble expression of fp-3 by 18.07 %. Furthermore, the SUMO-TrxA also boosted the soluble expression of hybrid mfps Mgfp-3B-Mfp-1 (fp-3-1) by 11.29 %, Mgfp-3B-Mgfp-3B (fp-3-3) by 19.91 %, and Mgfp-3B-Mgfp-5 (fp-3-5) by 14.03 %. Ultimately, by high cell density cultivation in a 5 L bioreactor, the yields of fp-3, fp-3-3, and fp-3-5 co-expressed with SUMO-TrxA reached 217.75 mg/L, 127.2 mg/L, and 97.28 mg/L, respectively. Consequently, soluble production of mfps holds great potential for the sustainable supply of protein adhesive materials.

Semi-Biosynthetic Production of Surface-Binding Adhesive Antimicrobial Peptides Using Intein-Mediated Protein Ligation.

Microbial infections remain a global health concern, calling for the urgent need to implement effective prevention measures. Antimicrobial peptides (AMPs) have been extensively studied as potential antimicrobial coating agents. However, an efficient and economical method for AMP production is lacking. Here, we synthesized the direct coating adhesive AMP, NKC-DOPA5, composed of NKC, a potent AMP, and repeats of the adhesive amino acid 3,4-dihydroxyphenylalanine (DOPA) via an intein-mediated protein ligation strategy. NKC was expressed as a soluble fusion protein His-NKC-GyrA (HNG) in Escherichia coli, comprising an N-terminal 6× His-tag and a C-terminal Mxe GyrA intein. The HNG protein was efficiently produced in a 500-L fermenter, with a titer of 1.63 g/L. The NKC-thioester was released from the purified HNG fusion protein by thiol attack and subsequently ligated with chemically synthesized Cys-DOPA5. The ligated peptide His-NKC-Cys-DOPA5 was obtained at a yield of 88.7%. The purified His-NKC-Cys-DOPA5 possessed surface-binding and antimicrobial properties identical to those of the peptide obtained via solid-phase peptide synthesis. His-NKC-Cys-DOPA5 can be applied as a practical and functional antimicrobial coating to various materials, such as medical devices and home appliances.

Programmable integrin and N-cadherin adhesive interactions modulate mechanosensing of mesenchymal stem cells by cofilin phosphorylation.

During mesenchymal development, the sources of mechanical forces transduced by cells transition over time from predominantly cell-cell interactions to predominantly cell-extracellular matrix (ECM) interactions. Transduction of the associated mechanical signals is critical for development, but how these signals converge to regulate human mesenchymal stem cells (hMSCs) mechanosensing is not fully understood, in part because time-evolving mechanical signals cannot readily be presented in vitro. Here, we established a DNA-driven cell culture platform that could be programmed to present the RGD peptide from fibronectin, mimicking cell-ECM interactions, and the HAVDI peptide from N-cadherin, mimicking cell-cell interactions, through DNA hybridization and toehold-mediated strand displacement reactions. The platform could be programmed to mimic the evolving cell-ECM and cell-cell interactions during mesenchymal development. We applied this platform to reveal that RGD/integrin ligation promoted cofilin phosphorylation, while HAVDI/N-cadherin ligation inhibited cofilin phosphorylation. Cofilin phosphorylation upregulated perinuclear apical actin fibers, which deformed the nucleus and thereby induced YAP nuclear localization in hMSCs, resulting in subsequent osteogenic differentiation. Our programmable culture platform is broadly applicable to the study of dynamic, integrated mechanobiological signals in development, healing, and tissue engineering.

Development and evaluation of a drug-in-adhesive transdermal delivery system for delivery of olanzapine.

OBJECTIVES: Olanzapine (OZP) is a safe and effective atypical antipsychotic drug used in treating schizophrenia and bipolar disorders. The dosage forms currently on the market for OZP are administered via oral or intramuscular routes. However, there are many problems associated with oral and intramuscular routes of drug administration. Thus, our aim was to develop a drug-in-adhesive transdermal delivery system (TDS) that can deliver OZP for 3 days. METHODS: We determined passive permeation, effect of oleic acid as chemical enhancer, and delivery of OZP across different skin types. Based on preliminary studies and saturation solubility of OZP in different pressure-sensitive adhesives (PSAs), we formulated and characterized solution-based TDS in acrylate PSA and suspension-based TDS in silicone and PIB PSA, with oleic acid as chemical enhancer. RESULTS: Acrylate solution-based TDS, silicone, and PIB suspension-based TDS delivered 58.97 ± 6.59 µg/sq.cm, 129.34 ± 16.59 µg/sq.cm, and 245.00 ± 2.51 µg/sq.cm, respectively, using in vitro permeation testing. PIB PSA suspension-based TDS met the 3 days desired target delivery. Skin irritation testing using In vitro EpiDermTM skin irritation test (EPI-200-SIT) kit found PIB TDS to be nonirritant. CONCLUSION: The PIB PSA suspension-based TDS could serve as a potentially effective transdermal delivery system for olanzapine.

The conidial coin toss: A polarized conidial adhesive in Colletotrichum graminicola.

Colletotrichum graminicola is an economically significant fungal pathogen of maize. The primary infective conidia of the fungus, falcate conidia, are splash-dispersed during rain events. The adhesion of the falcate conidia triggers germination and is required for the development of infection structures. Falcate conidia are capable of immediate adhesion upon encountering the substrate. We report that rapid adhesion in C. graminicola is polarized, with a single-sided strip of adhesive material running the length of a single side (or face) of the conidium between the tips. This strip of adhesive is co-localized with dynamic transverse actin cables, and both the adhesive strip and actin cables are formed after liberation of the conidium from its conidiogenous cell but prior to adhesion to the infection court. Orientation of conidia upon contact with substrate determines whether they will rapidly adhere, and those which do not initially adhere can be induced to do so by applying force to reorient or "flip" the conidia. We propose that C. graminicola possesses an adhesive mechanism resulting in an adhesion efficiency of approximately 50% upon initial contact with substrata, and that an increase in adhesion efficiency can be induced by disturbance.

Filopodial adhesive force in discrete nodes revealed by integrin molecular tension imaging.

Filopodia are narrow cell extensions involved in various physiological processes. Integrins mediate filopodia adhesion and likely transmit adhesive force to regulate filopodia formation and functions, but the force is extremely weak to study and remains poorly understood. Using integrative tension sensor (ITS), we imaged filopodia adhesive force at the single molecular tension level and investigated the force dynamics and sources. Results show that filopodia integrin tension (FIT) is generated in discrete foci (force nodes) along single filopodia with a spacing of ∼1 µm. Inhibitions of actin polymerization or myosin II activity markedly reduced FIT signals in force nodes at filopodia tips and at filopodia bases, respectively, suggesting differential force sources of FIT in the distal force nodes and proximal ones in filopodia. Using two ITS constructs with different force thresholds for activation, we showed that the molecular force level of FIT is greater at filopodia bases than that at filopodia tips. We also tested the role of vinculin and myosin X in the FIT transmission. With vinculin knockout in cells, filopodia and associated force nodes were still formed normally, suggesting that vinculin is dispensable for the formation of filopodia and force nodes. However, vinculin is indeed required for the transmission of strong FIT (capable of rupturing DNA in a shear conformation), as the strong FIT vanished in filopodia with vinculin knockout. Co-imaging of FIT and myosin X shows no apparent co-localization, demonstrating that myosin X is not directly responsible for generating FIT, despite its prominent role in filopodium elongation.