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1.
Ca 2+ is a ubiquitous second messenger in plant cell signalling. In this review we consider the role of Ca 2+-based signal transduction in stomatal guard cells focusing on three important areas: (1) the regulation of guard cell turgor relations and the control of gene expression in guard cells, (2) the control of specificity in Ca 2+ signalling, (3) emerging technologies and new approaches for studying intracellular signalling. Stomatal apertures alter in response to a wide array of environmental stimuli as a result of changes in guard cell turgor. For example, the plant hormone abscisic acid (ABA) stimulates a reduction in stomatal aperture through a decrease in guard cell turgor. Furthermore, guard cells have been shown to be competent to relay an ABA signal from its site of perception to the nucleus. An increase in the concentration of cytosolic free Ca 2+ ([Ca 2+] 1) is central to the mechanisms underlying ABA-induced changes in guard cell turgor. We describe a possible model of Ca 2+-based ABA signal transduction during stomatal closure and discuss recent evidence which suggests that Ca 2+ is also involved in ABA nuclear signal transduction. Many other environmental stimuli which affect stomatal apertures, in addition to ABA, induce an increase in guard cell [Ca 2+] 1) This raises questions regarding how increases in [Ca 2+] 1) can be a common component in the signal transduction pathways by which stimuli cause both stomatal opening and closure. We discuss several mechanisms of increasing the amount of information contained within the Ca 2+ signal, including encoding information in a stimulus-specific Ca 2+ signal or Ca 2+ signature', the concept of the ‘physiological address’ of the cell, and the use of other second messengers. We conclude by addressing the emerging technologies and new approaches which can be used in conjunction with guard cells to dissect further the molecular mechanisms of Ca 2+-mediated signalling in plants. 相似文献
2.
Plant cells maintain high Ca 2+ concentration gradients between the cytosol and the extracellular matrix, as well as intracellular compartments. During evolution, the regulatory mechanisms, maintaining low cytosolic free Ca 2+ concentrations, most likely provided the backbone for the development of Ca 2+‐dependent signalling pathways. In this review, the current understanding of molecular mechanisms involved in Ca 2+ homeostasis of plants cells is evaluated. The question is addressed to which extent the mechanisms, controlling the cytosolic Ca 2+ concentration, are linked to Ca 2+‐based signalling. A large number of environmental stimuli can evoke Ca 2+ signals, but the Ca 2+‐induced responses are likely to differ depending on the stimulus applied. Two mechanisms are put forward to explain signal specificity of Ca 2+‐dependent responses. A signal may evoke a specific Ca 2+ signature that is recognized by downstream signalling components. Alternatively, Ca 2+ signals are accompanied by Ca 2+‐independent signalling events that determine the specificity of the response. The existence of such parallel‐acting pathways explains why guard cell responses to abscisic acid (ABA) can occur in the absence, as well as in the presence, of Ca 2+ signals. Future research may shed new light on the relation between parallel acting Ca 2+‐dependent and ‐independent events, and may provide insights in their evolutionary origin. 相似文献
3.
Ca 2+ is a ubiquitous intracellular messenger in malaria parasites with important functions in asexual blood stages responsible for malaria symptoms, the preceding liver‐stage infection and transmission through the mosquito. Intracellular messengers amplify signals by binding to effector molecules that trigger physiological changes. The characterisation of some Ca 2+ effector proteins has begun to provide insights into the vast range of biological processes controlled by Ca 2+ signalling in malaria parasites, including host cell egress and invasion, protein secretion, motility and cell cycle regulation. Despite the importance of Ca 2+ signalling during the life cycle of malaria parasites, little is known about Ca 2+ homeostasis. Recent findings highlighted that upstream of stage‐specific Ca 2+ effectors is a conserved interplay between second messengers to control critical intracellular Ca 2+ signals throughout the life cycle. The identification of the molecular mechanisms integrating stage‐transcending mechanisms of Ca 2+ homeostasis in a network of stage‐specific regulator and effector pathways now represents a major challenge for a meaningful understanding of Ca 2+ signalling in malaria parasites. 相似文献
4.
Cancer involves defects in the mechanisms underlying cell proliferation, death and migration. Calcium ions are central to these phenomena, serving as major signalling agents with spatial localization, magnitude and temporal characteristics of calcium signals ultimately determining cell''s fate. Cellular Ca 2+ signalling is determined by the concerted action of a molecular Ca 2+-handling toolkit which includes: active energy-dependent Ca 2+ transporters, Ca 2+-permeable ion channels, Ca 2+-binding and storage proteins, Ca 2+-dependent effectors. In cancer, because of mutations, aberrant expression, regulation and/or subcellular targeting of Ca 2+-handling/transport protein(s) normal relationships among extracellular, cytosolic, endoplasmic reticulum and mitochondrial Ca 2+ concentrations or spatio-temporal patterns of Ca 2+ signalling become distorted. This causes deregulation of Ca 2+-dependent effectors that control signalling pathways determining cell''s behaviour in a way to promote pathophysiological cancer hallmarks such as enhanced proliferation, survival and invasion. Despite the progress in our understanding of Ca 2+ homeostasis remodelling in cancer cells as well as in identification of the key Ca 2+-transport molecules promoting certain malignant phenotypes, there is still a lot of work to be done to transform fundamental findings and concepts into new Ca 2+ transport-targeting tools for cancer diagnosis and treatment. 相似文献
6.
The central role of Ca 2+ signalling in plants is now well established. Much of our recent research has been based on the premise that the direct demonstration of signal-response coupling via Ca 2+ requires the imaging or measurement of cytosolic free Ca 2+ in living cells. Methods (confocal microscopy, fluorescence ratio imaging and photon counting imaging) which we use for imaging Ca 2+ with fluorescent dyes or recombinant aequorin, are described. Approaches for using dyes are now routine for many plant cells. However, the imaging Ca 2+ in whole tissues of plants genetically transformed with the aequorin gene is a very new development. We predict that this method, first employed in our laboratory, will bring about a revolution in our understanding of Ca 2+ signalling at the multicellular level. 相似文献
7.
The role of Ca 2+ in the initiation and maintenance of contraction has been extensively studies. Many of these studies have focused on how Ca 2+ influx and efflux affect cytoplasmic Ca 2+ (Ca i) and, therefore, contraction in cardiac muscle. However, it has recently become apparent that Ca i itself may play a major role in the control of Ca 2+ influx and efflux from cardiac muscle. Here we review current ideas on the mechanisms underlying Ca 2+ homeostasis in cardiac muscle, with specific attention to how Ca i may control Ca 2+ influx, both under normal and pathological conditions. 相似文献
8.
Nutrients have been known to affect stress conditions, in fact, nutrient deprivations are stress conditions for plants itself. Likewise, three important nutrients Nitrogen (N), Phosphorus (P) and Potassium (K) mediates major stress responses in plants. Here, involvement of K has been discussed briefly in plant stress response along with its impact on plant development. K has been regarded as immensely important nutrient in agriculture, hence, its deficiency triggers various signaling cascades, finally enabling plants to activate stress adaptation responses. So far, K+ has been reported to play pivotal role in various abiotic stresses such as drought, cold, water stresses etc. However, the exact mechanism and interplay of these different abiotic stress regulation by K+ is not completely explored and demand further functional investigations. The in-depth understanding of components involved in K+ sensing, transport, and homeostasis will enable plant biologist to engineer crop varieties tolerant to abiotic stresses and nutrient deficient soil in near future. 相似文献
9.
This review portrays the plant vacuole as both a source and a target of Ca 2+ signals. In plants, the vacuole represents a Ca 2+ store of enormous size and capacity. Total and free Ca 2+ concentrations in the vacuole vary with plant species, cell type, and environment, which is likely to have an impact on vacuolar function and the release of vacuolar Ca 2+. It is known that cytosolic Ca 2+ signals are often generated by release of the ion from internal stores, but in very few cases has a role of the vacuole been directly demonstrated. Biochemical and electrophysical studies have provided evidence for the operation of ligand- and voltage-gated Ca 2+-permeable channels in the vacuolar membrane. The underlying molecular mechanisms are largely unknown with one exception: the slow vacuolar channel, encoded by TPC1, is the only vacuolar Ca 2+-permeable channel cloned to date. However, due to its complex regulation and its low selectivity amongst cations, the role of this channel in Ca 2+ signalling is still debated. Many transport proteins at the vacuolar membrane are also targets of Ca 2+ signals, both by direct binding of Ca 2+ and by Ca 2+-dependent phosphorylation. This enables the operation of feedback mechanisms and integrates vacuolar transport systems in the wider signalling network of the plant cell. 相似文献
11.
Many signals that modify plant cell growth and development initiate changes in cytoplasmic Ca 2+. The subsequent movement of Ca 2+ in the cytoplasm is thought to take place via waves of free Ca 2+. These waves may be initiated at defined regions of the cell and movement requires release from a reticulated endoplasmic reticulum and the vacuole. The mechanism of wave propagation is outlined and the possible basis of repetitive reticulum wave formation, Ca 2+ oscillations and capacitative Ca 2+ signalling is discussed. Evidence for the presence of Ca 2+ waves in plant cells is outlined, and from studies on raphides it is suggested that the capabilities for capacitative Ca 2+ signalling are also present. The paper finishes with an outline of the possible interrelation between Ca 2+ waves and organelles and describes the intercellular movement of Ca 2+ waves and the relevance of such information communication to plant development. 相似文献
12.
Biochar is a carbon (C)-rich solid formed when biomass is used to produce bioenergy. This ‘black carbon’ has been suggested as a solution to climate change, potentially reducing global anthropogenic emissions of greenhouse gases by 12%, as well as promoting increased crop growth. How biochar application to soil leads to better crop yields remains open to speculation. Using the model plant Arabidopsis and the crop plant lettuce ( Lactuca sativa L.), we found increased plant growth in both species following biochar application. Statistically significant increases for Arabidopsis in leaf area (130%), rosette diameter (61%) and root length (100%) were observed with similar findings in lettuce, where biochar application also increased leaf cell expansion. For the first time, global gene expression arrays were used on biochar-treated plants, enabling us to identify the growth-promoting plant hormones, brassinosteroid and auxin, and their signalling molecules, as key to this growth stimulation, with limited impacts on genes controlling photosynthesis. In addition, genes for cell wall loosening were promoted as were those for increased activity in membrane transporters for sugar, nutrients and aquaporins for better water and nutrient uptake and movement of sugars for metabolism in the plant. Positive growth effects were accompanied by down-regulation of a large suite of plant defence genes, including the jasmonic acid biosynthetic pathway, defensins and most categories of secondary metabolites. Such genes are critical for plant protection against insect and pathogen attack, as well as defence against stresses including drought. We propose a conceptual model to explain these effects in this biochar type, hypothesizing a role for additional K + supply in biochar amended soils, leading to Ca 2+ and Reactive Oxygen Species (ROS) –mediated signalling underpinning growth and defence signalling responses. 相似文献
13.
Oxidative stress is a major challenge for all cells living in an oxygen‐based world. Among reactive oxygen species, H 2O 2, is a well known toxic molecule and, nowadays, considered a specific component of several signalling pathways. In order to gain insight into the roles played by H 2O 2 in plant cells, it is necessary to have a reliable, specific and non‐invasive methodology for its in vivo detection. Hence, the genetically encoded H 2O 2 sensor HyPer was expressed in plant cells in different subcellular compartments such as cytoplasm and peroxisomes. Moreover, with the use of the new green fluorescent protein (GFP)‐based Cameleon Ca 2+ indicator, D3cpv–KVK–SKL, targeted to peroxisomes, we demonstrated that the induction of cytoplasmic Ca 2+ increase is followed by Ca 2+ rise in the peroxisomal lumen. The analyses of HyPer fluorescence ratios were performed in leaf peroxisomes of tobacco and pre‐ and post‐bolting Arabidopsis plants. These analyses allowed us to demonstrate that an intraperoxisomal Ca 2+ rise in vivo stimulates catalase activity, increasing peroxisomal H 2O 2 scavenging efficiency. 相似文献
14.
Cation/proton exchangers (CAXs) are a class of secondary energised ion transporter that are being implicated in an increasing range of cellular and physiological functions. CAXs are primarily Ca 2+ efflux transporters that mediate the sequestration of Ca 2+ from the cytosol, usually into the vacuole. Some CAX isoforms have broad substrate specificity, providing the ability to transport trace metal ions such as Mn 2+ and Cd 2+, as well as Ca 2+. In recent years, genomic analyses have begun to uncover the expansion of CAXs within the green lineage and their presence within non‐plant species. Although there appears to be significant conservation in tertiary structure of CAX proteins, there is diversity in function of CAXs between species and individual isoforms. For example, in halophytic plants, CAXs have been recruited to play a role in salt tolerance, while in metal hyperaccumulator plants CAXs are implicated in cadmium transport and tolerance. CAX proteins are involved in various abiotic stress response pathways, in some cases as a modulator of cytosolic Ca 2+ signalling, but in some situations there is evidence of CAXs acting as a pH regulator. The metal transport and abiotic stress tolerance functions of CAXs make them attractive targets for biotechnology, whether to provide mineral nutrient biofortification or toxic metal bioremediation. The study of non‐plant CAXs may also provide insight into both conserved and novel transport mechanisms and functions. 相似文献
15.
We show here that both salinity and osmotic stress trigger transient increases in intracellular free Ca 2+ concentration ([Ca 2+] i) in cells of the nitrogen‐fixing filamentous cyanobacterium Anabaena sp. PCC7120, which constitutively expresses apoaequorin. Isoosmolar concentrations of salt (NaCl) and osmoticum (sucrose) induced calcium transients of similar magnitude and shape, suggesting that cells sense, via Ca 2+ signalling, mostly osmotic stress. The Ca 2+ transients induced by NaCl and sucrose were completely blocked by the calcium chelator ethylene glycol‐bis(b‐aminoethylether)N,N,N¢,N¢‐tetraacetic acid (EGTA) and were partially inhibited by the calcium channel blocker verapamil. Increased external Ca 2+ and the Ca 2+ ionophore calcimycin (compound A23187) enhanced Ca 2+ influx further, suggesting the involvement of extracellular Ca 2+ in the observed response to salinity and osmotic stress. However, the plant hormone abscisic acid (ABA) did not provoke any effect on the Ca 2+ transients induced by both stresses, indicating that it may not be acting upstream of Ca 2+ in the signalling of salinity and/or osmotic stress in Anabaena sp. PCC7120. 相似文献
16.
Calcium (Ca 2+), as a second messenger, is crucial for signal transduction processes during many biotic interactions. We demonstrate that cellular [Ca 2+] elevations are early events in the interaction between the plant growth‐promoting fungus Piriformospora indica and Arabidopsis thaliana. A cell wall extract (CWE) from the fungus promotes the growth of wild‐type seedlings but not of seedlings from P. indica‐insensitive mutants. The extract and the fungus also induce a similar set of genes in Arabidopsis roots, among them genes with Ca 2+ signalling‐related functions. The CWE induces a transient cytosolic Ca 2+ ([Ca 2+] cyt) elevation in the roots of Arabidopsis and tobacco ( Nicotiana tabacum) plants, as well as in BY‐2 suspension cultures expressing the Ca 2+ bioluminescent indicator aequorin. Nuclear Ca 2+ transients were also observed in tobacco BY‐2 cells. The Ca 2+ response was more pronounced in roots than in shoots and involved Ca 2+ uptake from the extracellular space as revealed by inhibitor studies. Inhibition of the Ca 2+ response by staurosporine and the refractory nature of the Ca 2+ elevation suggest that a receptor may be involved. The CWE does not stimulate H 2O 2 production and the activation of defence gene expression, although it led to phosphorylation of mitogen‐activated protein kinases (MAPKs) in a Ca 2+‐dependent manner. The involvement of MAPK6 in the mutualistic interaction was shown for an mpk6 line, which did not respond to P. indica. Thus, Ca 2+ is likely to be an early signalling component in the mutualistic interaction between P. indica and Arabidopsis or tobacco. 相似文献
17.
Soil salinity adversely affects plant growth, crop yield and the composition of ecosystems. Salinity stress impacts plants by combined effects of Na + toxicity and osmotic perturbation. Plants have evolved elaborate mechanisms to counteract the detrimental consequences of salinity. Here we reflect on recent advances in our understanding of plant salt tolerance mechanisms. We discuss the embedding of the salt tolerance‐mediating SOS pathway in plant hormonal and developmental adaptation. Moreover, we review newly accumulating evidence indicating a crucial role of a transpiration‐dependent salinity tolerance pathway, that is centred around the function of the NADPH oxidase RBOHF and its role in endodermal and Casparian strip differentiation. Together, these data suggest a unifying and coordinating role for Ca 2+ signalling in combating salinity stress at the cellular and organismal level. 相似文献
18.
Peripheral sensory nervous system is comprised of neurones with their axons and neuroglia that includes satellite glial cells in sensory ganglia, myelinating, non-myelinating and perisynaptic Schwann cells. Pathogenesis of peripheral diabetic polyneuropathies is associated with aberrant function of both neurones and glia. Deregulated Ca 2+ homoeostasis and aberrant Ca 2+ signalling in neuronal and glial elements contributes to many forms of neuropathology and is fundamental to neurodegenerative diseases. In diabetes both neurones and glia experience metabolic stress and mitochondrial dysfunction which lead to deregulation of Ca 2+ homeostasis and Ca 2+ signalling, which in their turn lead to pathological cellular reactions contributing to development of diabetic neuropathies. Molecular cascades responsible for Ca 2+ homeostasis and signalling, therefore, can be regarded as potential therapeutic targets. 相似文献
19.
Salinity reduces Ca 2+ availability, transport, and mobility to growing regions of the plant and supplemental Ca 2+ is known to reduce salinity damages. This study was undertaken to unravel some of the ameliorative mechanisms of Ca 2+ on salt stress at the cellular and tissue levels. Zea mays L. plants were grown in nutrient solution containing 1 or 80 mM NaCl with various Ca 2+ levels. Measurements of growth and physiological parameters, such as ion imbalance, indicated that the Ca 2+-induced alleviation mechanisms differed between plant organs. Under salinity, H 2O 2 levels increased in the leaf-growing tissue with increasing levels of supplemental Ca 2+ and reached the levels of control plants, whereas superoxide levels remained low at all Ca 2+ levels, indicating that Ca 2+ affected growth by increasing H 2O 2 but not superoxide levels. Salinity completely abolished apoplastic peroxidase activity. Supplemental Ca 2+ increased its activity only slightly. However, under salinity, polyamine oxidase (PAO) activity was shifted toward the leaf base probably as an adaptive mechanism aimed at restoring normal levels of reactive oxygen species (ROS) at the expansion zone where NADPH oxidase could no longer provide the required ROS for growth. Interestingly, addition of Ca 2+ shifted the PAO-activity peak back to its original location in addition to its enhancement. The increase in PAO activity in conjunction with low levels of apoplastic peroxidase is supportive of cellular growth via nonenzymatic wall loosening derived by the increase in H 2O 2 and less supportive of the peroxidase-mediated cross-linking of wall material. Thus extracellular Ca 2+ can modulate ROS levels at specific tissue localization and developmental stages thereby affecting cellular extension. 相似文献
20.
The physiology of paracellular permeation of ions and solutes in the kidney is pivotally important but poorly understood. Claudins are the key components of the paracellular pathway. Defects in claudin function result in a broad range of renal diseases, including hypomagnesemia, hypercalciuria and nephrolithiasis. This review describes recent findings on the physiological function of claudins underlying paracellular transport mechanisms with a focus on renal Ca 2+ handling. We have uncovered a molecular mechanism underlying paracellular Ca 2+ transport in the thick ascending limb of Henle (TAL) that involves the functional interplay of three important claudin genes: claudin-14, -16 and -19, all of which are associated with human kidney diseases with hypercalciuria, nephrolithiasis and bone mineral loss. The Ca 2+ sensing receptor (CaSR) signaling in the kidney has long been a mystery. By analyzing small non-coding RNA molecules in the kidney, we have uncovered a novel microRNA based signaling pathway downstream of CaSR that directly regulates claudin-14 gene expression and establishes the claudin-14 molecule as a key regulator for renal Ca 2+ homeostasis. The molecular cascade of CaSR-microRNAs-claudins forms a regulatory loop to maintain proper Ca 2+ homeostasis in the kidney. 相似文献
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