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Regulation and Function of Defense-Related Callose Deposition in Plants.
Wang, Y, Li, X, Fan, B, Zhu, C, Chen, Z
International journal of molecular sciences. 2021;(5)
Abstract
Plants are constantly exposed to a wide range of potential pathogens and to protect themselves, have developed a variety of chemical and physical defense mechanisms. Callose is a β-(1,3)-D-glucan that is widely distributed in higher plants. In addition to its role in normal growth and development, callose plays an important role in plant defense. Callose is deposited between the plasma membrane and the cell wall at the site of pathogen attack, at the plasmodesmata, and on other plant tissues to slow pathogen invasion and spread. Since it was first reported more than a century ago, defense-related callose deposition has been extensively studied in a wide-spectrum of plant-pathogen systems. Over the past 20 years or so, a large number of studies have been published that address the dynamic nature of pathogen-induced callose deposition, the complex regulation of synthesis and transport of defense-related callose and associated callose synthases, and its important roles in plant defense responses. In this review, we summarize our current understanding of the regulation and function of defense-related callose deposition in plants and discuss both the progresses and future challenges in addressing this complex defense mechanism as a critical component of a plant immune system.
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A Report on Fungal (1→3)-α-d-glucans: Properties, Functions and Application.
Złotko, K, Wiater, A, Waśko, A, Pleszczyńska, M, Paduch, R, Jaroszuk-Ściseł, J, Bieganowski, A
Molecules (Basel, Switzerland). 2019;(21)
Abstract
The cell walls of fungi are composed of glycoproteins, chitin, and α- and β-glucans. Although there are many reports on β-glucans, α-glucan polysaccharides are not yet fully understood. This review characterizes the physicochemical properties and functions of (1→3)-α-d-glucans. Particular attention has been paid to practical application and the effect of glucans in various respects, taking into account unfavourable effects and potential use. The role of α-glucans in plant infection has been proven, and collected facts have confirmed the characteristics of Aspergillus fumigatus infection associated with the presence of glucan in fungal cell wall. Like β-glucans, there are now evidence that α-glucans can also stimulate the immune system. Moreover, α-d-glucans have the ability to induce mutanases and can thus decompose plaque.
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Emerging models on the regulation of intercellular transport by plasmodesmata-associated callose.
Amsbury, S, Kirk, P, Benitez-Alfonso, Y
Journal of experimental botany. 2017;(1):105-115
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The intercellular transport of molecules through membranous channels that traverse the cell walls-so-called plasmodesmata-is of fundamental importance for plant development. Regulation of plasmodesmata aperture (and transport capacity) is mediated by changes in the flanking cell walls, mainly via the synthesis/degradation (turnover) of the (1,3)-β-glucan polymer callose. The role of callose in organ development and in plant environmental responses is well recognized, but detailed understanding of the mechanisms regulating its accumulation and its effects on the structure and permeability of the channels is still missing. We compiled information on the molecular components and signalling pathways involved in callose turnover at plasmodesmata and, more generally, on the structural and mechanical properties of (1,3)-β-glucan polymers in cell walls. Based on this revision, we propose models integrating callose, cell walls, and the regulation of plasmodesmata structure and intercellular communication. We also highlight new tools and interdisciplinary approaches that can be applied to gain further insight into the effects of modifying callose in cell walls and its consequences for intercellular signalling.
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Cellulose and callose synthesis and organization in focus, what's new?
Schneider, R, Hanak, T, Persson, S, Voigt, CA
Current opinion in plant biology. 2016;:9-16
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Abstract
Plant growth and development are supported by plastic but strong cell walls. These walls consist largely of polysaccharides that vary in content and structure. Most of the polysaccharides are produced in the Golgi apparatus and are then secreted to the apoplast and built into the growing walls. However, the two glucan polymers cellulose and callose are synthesized at the plasma membrane by cellulose or callose synthase complexes, respectively. Cellulose is the most common cell wall polymer in land plants and provides strength to the walls to support directed cell expansion. In contrast, callose is integral to specialized cell walls, such as the cell plate that separates dividing cells and growing pollen tube walls, and maintains important functions during abiotic and biotic stress responses. The last years have seen a dramatic increase in our understanding of how cellulose and callose are manufactured, and new factors that regulate the synthases have been identified. Much of this knowledge has been amassed via various microscopy-based techniques, including various confocal techniques and super-resolution imaging. Here, we summarize and synthesize recent findings in the fields of cellulose and callose synthesis in plant biology.
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Callose synthesis during reproductive development in monocotyledonous and dicotyledonous plants.
Shi, X, Han, X, Lu, TG
Plant signaling & behavior. 2016;(2):e1062196
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Callose, a linear β-1,3-glucan molecule, plays important roles in a variety of processes in angiosperms, including development and the response to biotic and abiotic stress. Despite the importance of callose deposition, our understanding of the roles of callose in rice reproductive development and the regulation of callose biosynthesis is limited. GLUCAN SYNTHASE-LIKE genes encode callose synthases (GSLs), which function in the production of callose at diverse sites in plants. Studies have shown that callose participated in plant reproductive development, and that the timely deposition and degradation of callose were essential for normal male gametophyte development. In this mini-review, we described conserved sequences found in GSL family proteins from monocotyledonous (Oryza sativa and Zea mays) and dicotyledonous (Arabidopsis thaliana and Glycine max) plants. We also describe the latest findings on callose biosynthesis and deposition during reproductive development and discuss future challenges in unraveling the mechanism of callose synthesis and deposition in higher plants.
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Effect of Polydextrose on Subjective Feelings of Appetite during the Satiation and Satiety Periods: A Systematic Review and Meta-Analysis.
Ibarra, A, Astbury, NM, Olli, K, Alhoniemi, E, Tiihonen, K
Nutrients. 2016;(1)
Abstract
INTRODUCTION Subjective feelings of appetite are measured using visual analogue scales (VAS) in controlled trials. However, the methods used to analyze VAS during the Satiation (pre- to post-meal) and Satiety (post-meal to subsequent meal) periods vary broadly, making it difficult to compare results amongst independent studies testing the same product. This review proposes a methodology to analyze VAS during both the Satiation and Satiety periods, allowing us to compare results in a meta-analysis. METHODS A methodology to express VAS results as incremental areas under the curve (iAUC) for both the Satiation and Satiety periods is proposed using polydextrose as a case study. Further, a systematic review and meta-analysis on subjective feelings of appetite was conducted following the PRISMA methodology. Meta-analyses were expressed as Standardized Mean Difference (SMD). RESULTS Seven studies were included in the meta-analysis. There were important differences in the methods used to analyze appetite ratings amongst these studies. The separate subjective feelings of appetite reported were Hunger, Satisfaction, Fullness, Prospective Food Consumption, and the Desire to Eat. The method proposed here allowed the results of the different studies to be homogenized. The meta-analysis showed that Desire to Eat during the Satiation period favors polydextrose for the reduction of this subjective feeling of appetite (SMD = 0.24, I² < 0.01, p = 0.018); this effect was also significant in the sub-analysis by sex for the male population (SMD = 0.35, I² < 0.01, p = 0.015). There were no other significant results. CONCLUSION It is possible to compare VAS results from separate studies. The assessment of iAUC for both the Satiation and Satiety periods generates results of homogeneous magnitudes. This case study demonstrates, for the first time, that polydextrose reduces the Desire to Eat during the Satiation period. This may explain, at least in part, the observed effects of polydextrose on the reduction of levels of energy intake at subsequent meals.
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Effects of polydextrose on different levels of energy intake. A systematic review and meta-analysis.
Ibarra, A, Astbury, NM, Olli, K, Alhoniemi, E, Tiihonen, K
Appetite. 2015;:30-7
Abstract
INTRODUCTION Dietary fibers help to control energy intake and reduce the risk of developing obesity. Recent studies show that the consumption of polydextrose reduces energy intake at a subsequent meal. In this systematic review and meta-analysis we examine the subsequent effects of polydextrose on different levels of energy intake (EI). METHOD The review followed the PRISMA methodology. Meta-analyses were expressed as Standardized Mean Difference (SMD). A linear regression approach was used to model the relationship between the polydextrose dose and the different levels of EI expressed as a relative change (%). RESULTS All the studies included in this review administered polydextrose as part of a mid-morning snack. Six studies were included in the analysis of EI at an ad libitum lunch; and three were included in the analysis of EI during the rest of the day, as well as total daily EI. The meta-analysis showed that the consumption of polydextrose is associated with a reduction in EI at lunch time (SMD = 0.35; P <0.01; I(2) = 0). The dose of polydextrose consumed correlated significantly with this reduction in EI, EILunch (%) = -0.67 Polydextrose (g/day) (R(2) = 0.80; P <0.01). The meta-analysis of EI during the rest of the day and daily EI did not show any difference. Nevertheless, the regression equation indicates that there is a dose-dependent effect on the reduction of daily EI, EIDaily (%) = -0.35 × Polydextrose (g/day) (R(2) = 0.68; P <0.05). Sex-specific results are consistent with results for the whole group. CONCLUSION The studies included in this meta-analysis support the notion that the consumption of polydextrose reduces voluntary energy intake at a subsequent meal. Furthermore, this reduction in energy intake occurs in a dose-dependent manner.
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New insights into the biological role of the osmoregulated periplasmic glucans in pathogenic and symbiotic bacteria.
Bontemps-Gallo, S, Lacroix, JM
Environmental microbiology reports. 2015;(5):690-7
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This review emphasizes the biological roles of the osmoregulated periplasmic glucans (OPGs). Osmoregulated periplasmic glucans occur in almost all α-, β- and γ-Proteobacteria. This polymer of glucose is required for full virulence. The roles of the OPGs are complex and vary depending on the species. Here, we outline the four major roles of the OPGs through four different pathogenic and one symbiotic bacterial models (Dickeya dadantii, Salmonella enterica, Pseudomonas aeruginosa, Brucella abortus and Sinorhizobium meliloti). When periplasmic, the OPGs are a part of the signal transduction pathway and indirectly regulate genes involved in virulence. The OPGs can also be secreted. When outside of the cell, they interact directly with antibiotics to protect the bacterial cell or interact with the host cell to facilitate the invasion process. When OPGs are not found, as in the ε-Proteobacteria, OPG-like oligosaccharides are present. Their presence strengthens the evidence that OPGs play an important role in virulence.
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Practical considerations when prescribing icodextrin: a narrative review.
Silver, SA, Harel, Z, Perl, J
American journal of nephrology. 2014;(6):515-27
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BACKGROUND Icodextrin is a peritoneal dialysis solution that is commonly used to increase ultrafiltration during the long dwell. The other major clinical benefit of icodextrin is that it is glucose-sparing, which may help preserve peritoneal membrane function. Since it has a different chemical composition than dextrose, and with its increasing use, there are several clinical considerations healthcare providers must familiarize themselves with prior to prescribing icodextrin. SUMMARY Failure to recognize these special properties of icodextrin can lead to adverse events reaching patients. This narrative review explores the hemodynamic, metabolic, and idiopathic effects of icodextrin to facilitate the safe use of icodextrin in peritoneal dialysis. KEY MESSAGES Hemodynamic effects include hypotension from enhanced ultrafiltration contributing to loss of residual kidney function. Metabolic effects include the chemical structure of icodextrin interfering with biochemical assays, resulting in misleading glucose readings on non-specific glucometers. Idiopathic adverse effects include a diffuse rash and sterile peritonitis. It is also important to remember that not all antibiotic combinations have undergone stability testing in icodextrin. This narrative review will help healthcare providers to confidently prescribe icodextrin to maximize its benefit in peritoneal dialysis patients.
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Callose biosynthesis in Arabidopsis with a focus on pathogen response: what we have learned within the last decade.
Ellinger, D, Voigt, CA
Annals of botany. 2014;(6):1349-58
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BACKGROUND (1,3)-β-Glucan callose is a cell wall polymer that is involved in several fundamental biological processes, ranging from plant development to the response to abiotic and biotic stresses. Despite its importance in maintaining plant integrity and plant defence, knowledge about the regulation of callose biosynthesis at its diverse sites of action within the plant is still limited. The moderately sized family of GSL (GLUCAN SYNTHASE-LIKE) genes is predicted to encode callose synthases with a specific biological function and subcellular localization. Phosphorylation and directed translocation of callose synthases seem to be key post-translational mechanisms of enzymatic regulation, whereas transcriptional control of GSL genes might only have a minor function in response to biotic or abiotic stresses. SCOPE AND CONCLUSIONS Among the different sites of callose biosynthesis within the plant, particular attention has been focused on the formation of callose in response to pathogen attack. Here, callose is deposited between the plasma membrane and the cell wall to act as a physical barrier to stop or slow invading pathogens. Arabidopsis (Arabidopsis thaliana) is one of the best-studied models not only for general plant defence responses but also for the regulation of pathogen-induced callose biosynthesis. Callose synthase GSL5 (GLUCAN SYNTHASE-LIKE5) has been shown to be responsible for stress-induced callose deposition. Within the last decade of research into stress-induced callose, growing evidence has been found that the timing of callose deposition in the multilayered system of plant defence responses could be the key parameter for optimal effectiveness. This timing seems to be achieved through co-ordinated transport and formation of the callose synthase complex.