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Much of our current knowledge on the mechanisms by which Ca²⁺ signals are generated in photosynthetic eukaryotes comes from studies of a relatively small number of model species, particularly green plants and algae, revealing some common features and notable differences between 'plant' and 'animal' systems. Physiological studies from a broad range of algal cell types have revealed the occurrence of animal-like signalling properties, including fast action potentials and fast propagating cytosolic Ca²⁺ waves. Genomic studies are beginning to reveal the widespread occurrence of conserved channel types likely to be involved in Ca²⁺ signalling. However, certain widespread 'ancient' channel types appear to have been lost by certain groups, such as the embryophytes. More recent channel gene loss is also evident from comparisons of more closely related algal species. The underlying processes that have given rise to the current distributions of Ca²⁺ channel types include widespread retention of ancient Ca²⁺ channel genes, horizontal gene transfer (including symbiotic gene transfer and acquisition of bacterial genes), gene loss and gene expansion within taxa. The assessment of the roles of Ca²⁺ channel genes in diverse physiological, developmental and life history processes represents a major challenge for future studies.

The formation of a hardened fibrous membrane through in situ degradation of polycaprolactone (PCL) in soft tissues has emerged as a promising alternative to conventional rigid bone implants for chest wall reconstruction. However, strategies to enhance the mechanical integrity and biological performance of such fibrous constructs remain limited. While nano-hydroxyapatite (nHA) is known to promote osteoblast proliferation and mineralization, its role in regulating fibroblast behavior remains unclear, particularly within a dynamically strained environment mimicking respiratory motion. In this study, we developed PCL scaffolds incorporating various concentrations of nHA using fused deposition modeling (FDM). The PCL/10 wt% nHA scaffold exhibited optimal mechanical properties and significantly enhanced fibroblast proliferation, adhesion, and extracellular matrix deposition in vitro. Notably, higher nHA content led to excessive Piezo1 activation, resulting in Ca2+ overload and increased fibroblast apoptosis. Under dynamic mechanical stimulation, the PCL/10 wt% nHA scaffold markedly promoted fibroblast functionality and tissue fibrosis, facilitating robust soft tissue hardening in vivo. Mechanistic investigations revealed that the Piezo1/TGF-β1 signaling axis plays a central role in mediating fibroblast responses to cyclic shear stress. These findings demonstrate that the PCL/10 wt% nHA scaffold effectively supports tissue-engineered structural reinforcement through fibroblast-driven fibrosis, presenting a biodegradable and mechanically adaptive approach with potential for future chest wall repair applications. In this study, PCL/nHA composite scaffolds were designed and fabricated using fused deposition modeling technology. These scaffolds not only exhibit excellent mechanical properties but also significantly promote the proliferation and fibrosis of fibroblasts. As a biodegradable implant, it supports the chest wall structure by stimulating the proliferation and fibrosis of soft tissues, providing a promising strategy for future chest wall reconstruction. [Display omitted] •PCL/nHA implants drive fibrotic integration in soft tissue, offering a degradable alternative to rigid chest wall implants.•10 wt% nHA activates Piezo1/TGF-β1 for fibrosis, while excess causes Piezo1-mediated calcium overload and apoptosis.•Dynamic respiratory shear forces synergize with PCL/nHA to enhance fibroblast function and soft tissue integrity.

• Diatoms are globally important phytoplankton that dominate coastal and polar-ice assemblages. These environments exhibit substantial changes in salinity over dynamic spatiotemporal regimes. Rapid sensory systems are vital to mitigate the harmful consequences of osmotic stress. Population-based analyses have suggested that Ca2+ signalling is involved in diatom osmotic sensing. However, mechanistic insight of the role of osmotic Ca2+ signalling is limited. • Here, we show that Phaeodactylum Ca2+ elevations are essential for surviving hypo-osmotic shock. Moreover, employing novel single-cell imaging techniques we have characterised real-time Ca2+ signalling responses in single diatom cells to environmental osmotic perturbations. • We observe that intracellular spatiotemporal patterns of osmotic-induced Ca2+ elevations encode vital information regarding the nature of the osmotic stimulus. Localised Ca2+ signals evoked by mild or gradual hypo-osmotic shocks are propagated globally from the apical cell tips, enabling fine-tuned cell volume regulation across the whole cell. • Finally, we demonstrate that diatoms adopt Ca2+-independent and dependent mechanisms for osmoregulation. We find that efflux of organic osmolytes occurs in a Ca2+-independent manner, but this response is insufficient to mitigate cell damage during hypo-osmotic shock. By comparison, Ca2+-dependent signalling is necessary to prevent cell bursting via precise coordination of K⁺ transport, and therefore is likely to underpin survival in dynamic osmotic environments.

Summary N6‐methyladenosine (m6A) is the most prevalent internal modification present in mRNAs, and is considered to participate in a range of developmental and biological processes. Drought response is highly regulated at the genomic, transcriptional and post‐transcriptional levels. However, the biological function and regulatory mechanism of m6A modification in the drought stress response is still poorly understood. We generated a transcriptome‐wide m6A map using drought‐resistant and drought‐sensitive varieties of cotton under different water deficient conditions to uncover patterns of m6A methylation in cotton response to drought stress. The results reveal that m6A represents a common modification and exhibit dramatic changes in distribution during drought stress. More 5'UTR m6A was deposited in the drought‐resistant variety and was associated with a positive effect on drought resistance by regulating mRNA abundance. Interestingly, we observed that increased m6A abundance was associated with increased mRNA abundance under drought, contributing to drought resistance, and vice versa. The demethylase GhALKBH10B was found to decrease m6A levels, facilitating the mRNA decay of ABA signal‐related genes (GhZEP, GhNCED4 and GhPP2CA) and Ca2+ signal‐related genes (GhECA1, GhCNGC4, GhANN1 and GhCML13), and mutation of GhALKBH10B enhanced drought resistance at seedling stage in cotton. Virus‐induced gene silencing (VIGS) of two Ca2+‐related genes, GhECA1 and GhCNGC4, reduced drought resistance with the decreased m6A enrichment on silenced genes in cotton. Collectively, we reveal a novel mechanism of post‐transcriptional modification involved in affecting drought response in cotton, by mediating m6A methylation on targeted transcripts in the ABA and Ca2+ signalling transduction pathways.

Background Plants are continuously exposed to changing environmental conditions and biotic attacks that affect plant growth. In crops, the inability to respond appropriately to stress has strong detrimental effects on agricultural production and yield. Ca 2+ signalling plays a fundamental role in the response of plants to most abiotic and biotic stresses. However, research on stimulus-specific Ca 2+ signals has mostly been pursued in Arabidopsis thaliana , while in other species these events are little investigated . Results In this study, we introduced the Ca 2+ reporter-encoding gene APOAEQUORIN into the crop species barley ( Hordeum vulgare ). Measurements of the dynamic changes in [Ca 2+ ] cyt in response to various stimuli such as NaCl, mannitol, H 2 O 2 , and flagellin 22 (flg22) revealed the occurrence of dose- as well as tissue-dependent [Ca 2+ ] cyt transients. Moreover, the Ca 2+ signatures were unique for each stimulus, suggesting the involvement of different Ca 2+ signalling components in the corresponding stress response. Alongside, the barley Ca 2+ signatures were compared to those produced by the phylogenetically distant model plant Arabidopsis. Notable differences in temporal kinetics and dose responses were observed, implying species-specific differences in stress response mechanisms. The plasma membrane Ca 2+ channel blocker La 3+ strongly inhibited the [Ca 2+ ] cyt response to all tested stimuli, indicating a critical role of extracellular Ca 2+ in the induction of stress-associated Ca 2+ signatures in barley. Moreover, by analysing spatio-temporal dynamics of the [Ca 2+ ] cyt transients along the developmental gradient of the barley leaf blade we demonstrate that different parts of the barley leaf show quantitative differences in [Ca 2+ ] cyt transients in response to NaCl and H 2 O 2 . There were only marginal differences in the response to flg22, indicative of developmental stage-dependent Ca 2+ responses specifically to NaCl and H 2 O 2 . Conclusion This study reveals tissue-specific Ca 2+ signals with stimulus-specific kinetics in the crop species barley, as well as quantitative differences along the barley leaf blade. A number of notable differences to the model plants Arabidopsis may be linked to different stimulus sensitivity. These transgenic barley reporter lines thus present a valuable tool to further analyse mechanisms of Ca 2+ signalling in this crop and to gain insights into the variation of Ca 2+ -dependent stress responses between stress-susceptible and -resistant species.

The sperm‐specific CatSper channel controls the intracellular Ca 2+ concentration ([Ca 2+ ] i ) and, thereby, the swimming behaviour of sperm. In humans, CatSper is directly activated by progesterone and prostaglandins—female factors that stimulate Ca 2+ influx. Other factors including neurotransmitters, chemokines, and odorants also affect sperm function by changing [Ca 2+ ] i . Several ligands, notably odorants, have been proposed to control Ca 2+ entry and motility via G protein‐coupled receptors (GPCRs) and cAMP‐signalling pathways. Here, we show that odorants directly activate CatSper without involving GPCRs and cAMP. Moreover, membrane‐permeable analogues of cyclic nucleotides that have been frequently used to study cAMP‐mediated Ca 2+ signalling also activate CatSper directly via an extracellular site. Thus, CatSper or associated protein(s) harbour promiscuous binding sites that can host various ligands. These results contest current concepts of Ca 2+ signalling by GPCR and cAMP in mammalian sperm: ligands thought to activate metabotropic pathways, in fact, act via a common ionotropic mechanism. We propose that the CatSper channel complex serves as a polymodal sensor for multiple chemical cues that assist sperm during their voyage across the female genital tract. The calcium channel CatSper governs sperm swimming behaviour in response to progesterone and prostaglandins. Surprisingly, multiple types of small molecules including odorants and nucleotides directly activate CatSper‐mediated calcium influx independent of G protein‐coupled receptor (GPCR) or cAMP signalling.

Calcium (Ca ) is an essential signaling molecule that controls a wide range of biological functions. In the immune system, calcium signals play a central role in a variety of cellular functions such as proliferation, differentiation, apoptosis, and numerous gene transcriptions. During an immune response, the engagement of T-cell and B-cell antigen receptors induces a decrease in the intracellular Ca store and then activates store-operated Ca entry (SOCE) to raise the intracellular Ca concentration, which is mediated by the Ca release-activated Ca (CRAC) channels. Recently, identification of the two critical regulators of the CRAC channel, stromal interaction molecule (STIM) and Orai1, has broadened our understanding of the regulatory mechanisms of Ca signaling in lymphocytes. Repetitive or prolonged increase in intracellular Ca is required for the calcineurin-mediated dephosphorylation of the nuclear factor of an activated T cell (NFAT). Recent data indicate that Ca -calcineurin-NFAT1 to 4 pathways are dysregulated in autoimmune diseases. Therefore, calcineurin inhibitors, cyclosporine and tacrolimus, have been used for the treatment of such autoimmune diseases as systemic lupus erythematosus and rheumatoid arthritis. Here, we review the role of the Ca -calcineurin-NFAT signaling pathway in health and diseases, focusing on the STIM and Orai1, and discuss the deregulated calcium-mediated calcineurin-NFAT pathway in autoimmune diseases.

• Plant stress signalling involves bursts of reactive oxygen species (ROS), which can be mimicked by the application of acute pulses of ozone. Such ozone-pulses inhibit photosynthesis and trigger stomatal closure in a few minutes, but the signalling that underlies these responses remains largely unknown. • We measured changes in Arabidopsis thaliana gas exchange after treatment with acute pulses of ozone and set up a system for simultaneous measurement of membrane potential and cytosolic calcium with the fluorescent reporter R-GECO1. • We show that within 1 min, prior to stomatal closure, O₃ triggered a drop in whole-plant CO₂ uptake. Within this early phase, O₃ pulses (200–1000 ppb) elicited simultaneous membrane depolarization and cytosolic calcium increase, whereas these pulses had no long-term effect on either stomatal conductance or photosynthesis. In contrast, pulses of 5000 ppb O₃ induced cell death, systemic Ca2+ signals and an irreversible drop in stomatal conductance and photosynthetic capacity. • We conclude that mesophyll cells respond to ozone in a few seconds by distinct pattern of plasma membrane depolarizations accompanied by an increase in the cytosolic calcium ion (Ca2+) level. These responses became systemic only at very high ozone concentrations. Thus, plants have rapid mechanism to sense and discriminate the strength of ozone signals.

Organelle localization is often crucial to properly modulate cellular functions and signalling cascades. For example, the distribution of organelles in axons is crucial for their function and is dysregulated in several diseases. Similarly, relative positioning of two or more organelles is also important to perform certain specialized processes. Perhaps, the best‐known form of interorganellar organization is that between endoplasmic reticulum (ER) and mitochondria. Close communication between these two compartments has been observed for a long time. Recent evidence suggests that this is the basis for a bidirectional communication regulating a number of physiological processes ranging from mitochondrial energy and lipid metabolism to Ca 2+ signalling and cell death. The recent discovery of some of the molecular mediators of the tethering already allowed to extend the function of this paradigmatic spatial organization to previously unexpected functions, and will foster future research to explore it in cellular signalling cascades as well as in disease. This review from the Scorrano lab describes how regions of close physical apposition of the ER and mitochondrial membranes result in cross‐talk between the two organelles and have a role in determining cellular decisions.

Plants are exposed to various environmental stresses. The sensing of environmental cues and the transduction of stress signals into intracellular signaling are initial events in the cellular signaling network. As a second messenger, Ca 2+ links environmental stimuli to different biological processes, such as growth, physiology, and sensing of and response to stress. An increase in intracellular calcium concentrations ([Ca 2+ ] i ) is a common event in most stress-induced signal transduction pathways. In recent years, significant progress has been made in research related to the early events of stress signaling in plants, particularly in the identification of primary stress sensors. This review highlights current advances that are beginning to elucidate the mechanisms by which abiotic environmental cues are sensed via Ca 2+ signals. Additionally, this review discusses important questions about the integration of the sensing of multiple stress conditions and subsequent signaling responses that need to be addressed in the future.