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Signaling in plants
Tony Fordham-Skelton, Keith Lindsey
Genome Biology , 2001, DOI: 10.1186/gb-2000-2-1-reports4001
Abstract: This meeting was organized jointly between The Biochemical Society and The New Phytologist and brought together an international field of plant scientists to discuss some of the latest advances in the study of signal transduction in plants. In this short report we have highlighted only some of the areas reported. It became increasingly evident during the meeting that 'cross-talk' and integration between plant signaling pathways will become an even more important theme in the future.There is now good evidence that plant cells not only contain key components of the calcium-mediated signaling pathways found in animal cells but also use them. One powerful experimental system to study calcium signaling mechanisms has been the stomatal guard cell complex, which can be induced to open by various effectors such as high light levels, low CO2 concentrations, auxins, cytokinins and fusicoccin, and can be induced to close by abscisic acid (ABA), high CO2 and inositol trisphosphate (InsP3). A common feature of these activities is the involvement of calcium ions. For example, the experimental addition of ABA to guard cells leads to a heterogeneity in calcium levels across the cell - a 'calcium signature' - that can be visualized by confocal microscopical imaging techniques (Alistair Hetherington, Lancaster University, UK). Hetherington argued that it is the uniqueness of each signature that represents the cellular expression of calcium signaling specificity. A number of interesting questions were raised at the conference. What range of molecules act as effectors of calcium signatures? How are distinctive calcium signatures generated? And how do cells interpret or decode different calcium signatures?Charles Brearley (University of Cambridge, UK) showed evidence for the role of inositol hexakisphosphate (InsP6) as an intermediate component in the ABA-induced calcium transients and guard cell closure of the potato (Solanum tuberosum). InsP6 is very effective (more so than InsP3) at
The Language of Reactive Oxygen Species Signaling in Plants  [PDF]
Soumen Bhattacharjee
Journal of Botany , 2012, DOI: 10.1155/2012/985298
Abstract: Reactive oxygen species (ROS) are astonishingly versatile molecular species and radicals that are poised at the core of a sophisticated network of signaling pathways of plants and act as core regulator of cell physiology and cellular responses to environment. ROS are continuously generated in plants as an inevitable consequence of redox cascades of aerobic metabolism. In one hand, plants are surfeited with the mechanism to combat reactive oxygen species, in other circumstances, plants appear to purposefully generate (oxidative burst) and exploit ROS or ROS-induced secondary breakdown products for the regulation of almost every aspect of plant biology, from perception of environmental cues to gene expression. The molecular language associated with ROS-mediated signal transduction, leading to modulation in gene expression to be one of the specific early stress response in the acclamatory performance of the plant. They may even act as “second messenger” modulating the activities of specific proteins or expression of genes by changing redox balance of the cell. The network of redox signals orchestrates metabolism for regulating energy production to utilization, interfering with primary signaling agents (hormones) to respond to changing environmental cues at every stage of plant development. The oxidative lipid peroxidation products and the resulting generated products thereof (associated with stress and senescence) also represent “biological signals,” which do not require preceding activation of genes. Unlike ROS-induced expression of genes, these lipid peroxidation products produce nonspecific response to a large variety of environmental stresses. The present review explores the specific and nonspecific signaling language of reactive oxygen species in plant acclamatory defense processes, controlled cell death, and development. Special emphasis is given to ROS and redox-regulated gene expression and the role of redox-sensitive proteins in signal transduction event. It also describes the emerging complexity of apparently contradictory roles that ROS play in cellular physiology to ascertain their position in the life of the plant. 1. Introduction Environmental stresses such as extremes of temperature, salinity, drought, heavy metals, herbicides and pathogens greatly affect plant metabolism and productivity [1]. Because of environmental stress, the yield potential of the crops is hardly realized. It has been estimated that a country like USA is being able to harvest approximately one fourth of the genetic potential of the crop [1, 2]. To survive plant have
Lipid Rafts and Caveolae in Signaling by Growth Factor Receptors
Angela de Laurentiis, Lorna DonovanAlexandre Arcaro
The Open Biochemistry Journal , 2007, DOI: 10.2174/1874091X00701010012]
Abstract: Angela de Laurentiis, Lorna Donovan and Alexandre Arcaro Publ(13 September, 2007) Lipid rafts and caveolae are microdomains of the plasma membrane enriched in sphingolipids and cholesterol, and hence are less fluid than the remainder of the membrane. Caveolae have an invaginated structure, while lipid rafts are flat regions of the membrane. The two types of microdomains have different protein compositions (growth factor receptors and their downstream molecules) suggesting that lipid rafts and caveolae have a role in the regulation of signaling by these receptors. The purpose of this review is to discuss this model, and the implications that it might have regarding a potential role for lipid rafts and caveolae in human cancer. Particular attention will be paid to the epidermal growth factor receptor, for which the largest amount of information is available. It has been proposed that caveolins act as tumor suppressors. The role of lipid rafts is less clear, but they seem to be capable of acting as ‘signaling platforms’, in which signal initiation and propagation can occur efficiently.
Cold Signaling and Cold Response in Plants  [PDF]
Kenji Miura,Tsuyoshi Furumoto
International Journal of Molecular Sciences , 2013, DOI: 10.3390/ijms14035312
Abstract: Plants are constantly exposed to a variety of environmental stresses. Freezing or extremely low temperature constitutes a key factor influencing plant growth, development and crop productivity. Plants have evolved a mechanism to enhance tolerance to freezing during exposure to periods of low, but non-freezing temperatures. This phenomenon is called cold acclimation. During cold acclimation, plants develop several mechanisms to minimize potential damages caused by low temperature. Cold response is highly complex process that involves an array of physiological and biochemical modifications. Furthermore, alterations of the expression patterns of many genes, proteins and metabolites in response to cold stress have been reported. Recent studies demonstrate that post-transcriptional and post-translational regulations play a role in the regulation of cold signaling. In this review article, recent advances in cold stress signaling and tolerance are highlighted.
SEC14 Phospholipid Transfer Protein Is Involved in Lipid Signaling-Mediated Plant Immune Responses in Nicotiana benthamiana  [PDF]
Akinori Kiba, Ivan Galis, Yuko Hojo, Kouhei Ohnishi, Hirofumi Yoshioka, Yasufumi Hikichi
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0098150
Abstract: We previously identified a gene related to the SEC14-gene phospholipid transfer protein superfamily that is induced in Nicotiana benthamiana (NbSEC14) in response to infection with Ralstonia solanacearum. We here report that NbSEC14 plays a role in plant immune responses via phospholipid-turnover. NbSEC14-silencing compromised expression of defense–related PR-4 and accumulation of jasmonic acid (JA) and its derivative JA-Ile. Transient expression of NbSEC14 induced PR-4 gene expression. Activities of diacylglycerol kinase, phospholipase C and D, and the synthesis of diacylglycerol and phosphatidic acid elicited by avirulent R. solanacearum were reduced in NbSEC14-silenced plants. Accumulation of signaling lipids and activation of diacylglycerol kinase and phospholipases were enhanced by transient expression of NbSEC14. These results suggest that the NbSEC14 protein plays a role at the interface between lipid signaling-metabolism and plant innate immune responses.
Lipid rafts: cell surface platforms for T cell signaling
MAGEE,TONY; PIRINEN,NIINA; ADLER,JEREMY; PAGAKIS,STAMATIS N; PARMRYD,INGELA;
Biological Research , 2002, DOI: 10.4067/S0716-97602002000200003
Abstract: the src family tyrosine kinase lck is essential for t cell development and t cell receptor (tcr)* signaling. lck is post-translationally fatty acylated at its n-terminus conferring membrane targeting and concentration in plasma membrane lipid rafts, which are lipid-based organisational platforms. confocal fluorescence microscopy shows that lck colocalises in rafts with gpi-linked proteins, the adaptor protein lat and ras, but not with non-raft membrane proteins including the protein tyrosine phosphatase cd45. the tcr also associates with lipid rafts and its cross-linking causes coaggregation of raft-associated proteins including lck, but not of cd45. cross-linking of either the tcr or rafts strongly induces specific tyrosine phosphorylation of the tcr in the rafts. remarkably, raft patching alone induces signalling events analogous to tcr stimulation, with the same dependence on expression of key tcr signalling molecules. our results indicate a mechanism whereby tcr engagement promotes aggregation of lipid rafts, which facilitates colocalisation of signaling proteins including lck, lat, and the tcr, while excluding cd45, thereby potentiating protein tyrosine phosphorylation and downstream signaling. we are currently testing this hypothesis as well as using imaging techniques such as fluorescence resonance energy transfer (fret) microscopy to study the dynamics of proteins and lipids in lipid rafts in living cells undergoing signaling events. recent data show that the key phosphoinositide pi(4,5)p2 is concentrated in t cell lipid rafts and that on stimulation of the cells it is rapidly converted to pi(3,4,5)p3 and diacylglycerol within rafts. thus rafts are hotspots for both protein and lipid signalling pathways.
Lipid rafts: cell surface platforms for T cell signaling  [cached]
TONY MAGEE,NIINA PIRINEN,JEREMY ADLER,STAMATIS N PAGAKIS
Biological Research , 2002,
Abstract: The Src family tyrosine kinase Lck is essential for T cell development and T cell receptor (TCR)* signaling. Lck is post-translationally fatty acylated at its N-terminus conferring membrane targeting and concentration in plasma membrane lipid rafts, which are lipid-based organisational platforms. Confocal fluorescence microscopy shows that Lck colocalises in rafts with GPI-linked proteins, the adaptor protein LAT and Ras, but not with non-raft membrane proteins including the protein tyrosine phosphatase CD45. The TCR also associates with lipid rafts and its cross-linking causes coaggregation of raft-associated proteins including Lck, but not of CD45. Cross-linking of either the TCR or rafts strongly induces specific tyrosine phosphorylation of the TCR in the rafts. Remarkably, raft patching alone induces signalling events analogous to TCR stimulation, with the same dependence on expression of key TCR signalling molecules. Our results indicate a mechanism whereby TCR engagement promotes aggregation of lipid rafts, which facilitates colocalisation of signaling proteins including Lck, LAT, and the TCR, while excluding CD45, thereby potentiating protein tyrosine phosphorylation and downstream signaling. We are currently testing this hypothesis as well as using imaging techniques such as fluorescence resonance energy transfer (FRET) microscopy to study the dynamics of proteins and lipids in lipid rafts in living cells undergoing signaling events. Recent data show that the key phosphoinositide PI(4,5)P2 is concentrated in T cell lipid rafts and that on stimulation of the cells it is rapidly converted to PI(3,4,5)P3 and diacylglycerol within rafts. Thus rafts are hotspots for both protein and lipid signalling pathways.
PPARs Mediate Lipid Signaling in Inflammation and Cancer  [PDF]
Liliane Michalik,Walter Wahli
PPAR Research , 2008, DOI: 10.1155/2008/134059
Abstract: Lipid mediators can trigger physiological responses by activating nuclear hormone receptors, such as the peroxisome proliferator-activated receptors (PPARs). PPARs, in turn, control the expression of networks of genes encoding proteins involved in all aspects of lipid metabolism. In addition, PPARs are tumor growth modifiers, via the regulation of cancer cell apoptosis, proliferation, and differentiation, and through their action on the tumor cell environment, namely, angiogenesis, inflammation, and immune cell functions. Epidemiological studies have established that tumor progression may be exacerbated by chronic inflammation. Here, we describe the production of the lipids that act as activators of PPARs, and we review the roles of these receptors in inflammation and cancer. Finally, we consider emerging strategies for therapeutic intervention.
Cysteine–based redox regulation and signaling in plants  [PDF]
Jérémy Couturier,Kamel Chibani,Jean-Pierre Jacquot,Nicolas Rouhier
Frontiers in Plant Science , 2013, DOI: 10.3389/fpls.2013.00105
Abstract: Living organisms are subjected to oxidative stress conditions which are characterized by the production of reactive oxygen, nitrogen, and sulfur species. In plants as in other organisms, many of these compounds have a dual function as they damage different types of macromolecules but they also likely fulfil an important role as secondary messengers. Owing to the reactivity of their thiol groups, some protein cysteine residues are particularly prone to oxidation by these molecules. In the past years, besides their recognized catalytic and regulatory functions, the modification of cysteine thiol group was increasingly viewed as either protective or redox signaling mechanisms. The most physiologically relevant reversible redox post-translational modifications (PTMs) are disulfide bonds, sulfenic acids, S-glutathione adducts, S-nitrosothiols and to a lesser extent S-sulfenyl-amides, thiosulfinates and S-persulfides. These redox PTMs are mostly controlled by two oxidoreductase families, thioredoxins and glutaredoxins. This review focuses on recent advances highlighting the variety and physiological roles of these PTMs and the proteomic strategies used for their detection.
Effect of docosahexaenoic acid on interleukin-2 receptor signaling pathway in lipid rafts
Qiurong Li,Jian Ma,Li Tan,Chang Wang,Ning Li,Yousheng Li,Guowang Xu,Jieshou Li
Science China Life Sciences , 2006, DOI: 10.1007/s11427-005-0014-1
Abstract: Recent studies have shown that polyunsaturated fatty acids (PUFA) regulated the functions of membrane receptors in T cells and suppressed T cell-mediated immune responses. But the molecular mechanisms of immune regulation are not yet elucidated. Lipid rafts are plasma membrane microdomains, in which many receptors localized. The purpose of this study was to investigate the effect of DHA on IL-2R signaling pathway in lipid rafts. We isolated lipid rafts by discontinuous sucrose density gradient ultracentrifugation, and found that DHA could change the composition of lipid rafts and alter the distribution of key molecules of IL-2R signaling pathway, which transferred from lipid rafts to detergent-soluble membrane fractions. These results revealed that DHA treatment increased the proportion of polyunsaturated fatty acids especially n 3 polyunsaturated fatty acids in lipid rafts and changed the lipid environment of membrane microdomains in T cells. Compared with controls, DHA changed the localization of IL-2R, STAT5a and STAT5b in lipid rafts and suppressed the expression of JAK1, JAK3 and tyrosine phosphotyrosine in soluble membrane fractions. Summarily, this study concluded the effects of DHA on IL-2R signaling pathway in lipid rafts and explained the regulation of PUFAs in T cell-mediated immune responses.
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