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1.
Boron toxicity in higher plants: an update.
Landi, M, Margaritopoulou, T, Papadakis, IE, Araniti, F
Planta. 2019;(4):1011-1032
Abstract
In this review, emphasis is given to the most recent updates about morpho-anatomical, physiological, biochemical and molecular responses adopted by plants to cope with B excess. Boron (B) is a unique micronutrient for plants given that the range of B concentration from its essentiality to toxicity is extremely narrow, and also because it occurs as an uncharged molecule (boric acid) which can pass lipid bilayers without any degree of controls, as occurs for other ionic nutrients. Boron frequently exceeds the plant's requirement in arid and semiarid environments due to poor drainage, and in agricultural soils close to coastal areas due to the intrusion of B-rich seawater in fresh aquifer or because of dispersion of seawater aerosol. Global releases of elemental B through weathering, volcanic and geothermal processes are also relevant in enriching B concentration in some areas. Considerable progress has been made in understanding how plants react to B toxicity and relevant efforts have been made to investigate: (I) B uptake and in planta partitioning, (II) physiological, biochemical, and molecular changes induced by B excess, with particular emphasis to the effects on the photosynthetic process, the B-triggered oxidative stress and responses of the antioxidant apparatus to B toxicity, and finally (III) mechanisms of B tolerance. Recent findings addressing the effects of B toxicity are reviewed here, intending to clarify the effect of B excess and to propose new perspectives aimed at driving future researches on the topic.
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2.
Nitric oxide signaling, metabolism and toxicity in nitrogen-fixing symbiosis.
Berger, A, Boscari, A, Frendo, P, Brouquisse, R
Journal of experimental botany. 2019;(17):4505-4520
Abstract
Interactions between legumes and rhizobia lead to the establishment of a symbiotic relationship characterized by the formation of a new organ, the nodule, which facilitates the fixation of atmospheric nitrogen (N2) by nitrogenase through the creation of a hypoxic environment. Significant amounts of nitric oxide (NO) accumulate at different stages of nodule development, suggesting that NO performs specific signaling and/or metabolic functions during symbiosis. NO, which regulates nodule gene expression, accumulates to high levels in hypoxic nodules. NO accumulation is considered to assist energy metabolism within the hypoxic environment of the nodule via a phytoglobin-NO-mediated respiration process. NO is a potent inhibitor of the activity of nitrogenase and other plant and bacterial enzymes, acting as a developmental signal in the induction of nodule senescence. Hence, key questions concern the relative importance of the signaling and metabolic functions of NO versus its toxic action and how NO levels are regulated to be compatible with nitrogen fixation functions. This review analyses these paradoxical roles of NO at various stages of symbiosis, and highlights the role of plant phytoglobins and bacterial hemoproteins in the control of NO accumulation.
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3.
A critical review on the effects of zinc at toxic levels of cadmium in plants.
Rizwan, M, Ali, S, Rehman, MZU, Maqbool, A
Environmental science and pollution research international. 2019;(7):6279-6289
Abstract
Increasing cadmium (Cd) pollution in agricultural soils has raised serious concerns worldwide. Several exogenous substances can be used to mitigate the toxic effects of Cd in plants. Zinc (Zn) is one of the essential plant micronutrients and is involved in several physiological functions in plants. Zn may alleviate Cd toxicity in plants owing to the chemical similarity of Zn with Cd. Published reports demonstrated that Zn can alleviate toxic effects of Cd in plants by increasing plant growth, regulating Cd uptake, increasing photosynthesis, and reducing oxidative stress. Literature demonstrated that the role of Zn on Cd accumulation by plants is very controversial and depends upon several factors including concentrations of Cd and Zn in the medium, exposure duration, plant species and genotypes, and growth conditions. This review highlights the role of Zn in reducing Cd toxicity in plants and provides new insight that proper level of Zn in plants may enhance plant resistance to excess Cd.
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4.
PRRs and NB-LRRs: From Signal Perception to Activation of Plant Innate Immunity.
Noman, A, Aqeel, M, Lou, Y
International journal of molecular sciences. 2019;(8)
Abstract
To ward off pathogens and pests, plants use a sophisticated immune system. They use pattern-recognition receptors (PRRs), as well as nucleotide-binding and leucine-rich repeat (NB-LRR) domains, for detecting nonindigenous molecular signatures from pathogens. Plant PRRs induce local and systemic immunity. Plasma-membrane-localized PRRs are the main components of multiprotein complexes having additional transmembrane and cytosolic kinases. Topical research involving proteins and their interactive partners, along with transcriptional and posttranscriptional regulation, has extended our understanding of R-gene-mediated plant immunity. The unique LRR domain conformation helps in the best utilization of a surface area and essentially mediates protein-protein interactions. Genome-wide analyses of inter- and intraspecies PRRs and NB-LRRs offer innovative information about their working and evolution. We reviewed plant immune responses with relevance to PRRs and NB-LRRs. This article focuses on the significant functional diversity, pathogen-recognition mechanisms, and subcellular compartmentalization of plant PRRs and NB-LRRs. We highlight the potential biotechnological application of PRRs and NB-LRRs to enhance broad-spectrum disease resistance in crops.
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5.
Bioactive compounds in plant materials for the prevention of diabetesand obesity.
Kato, E
Bioscience, biotechnology, and biochemistry. 2019;(6):975-985
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Abstract
Plant materials have been widely studied for their preventive and therapeutic effects for type 2 diabetes mellitus (T2DM) and obesity. The effect of a plant material arises from its constituents, and the study of these bioactive compounds is important to achieve a deeper understanding of its effect at the molecular level. In particular, the study of the effects of such bioactive compounds on various biological processes, from digestion to cellular responses, is required to fully understand the overall effects of plant materials in these health contexts. In this review, I summarize the bioactive compounds we have recently studied in our research group that target digestive enzymes, dipeptidyl peptidase-4, myocyte glucose uptake, and lipid accumulation in adipocytes. Abbreviations: AC: adenylyl cyclase; AMPK AMP-activated protein kinase; βAR: β-adrenergic receptor; CA: catecholamine; cAMP: cyclic adenosine monophosphate; cGMP: cyclic guanosine monophosphate; DPP-4: dipeptidyl peptidase-4; ERK: extracellular signal-regulated kinase; GC: guanylyl cyclase; GH: growth hormone; GLP-1: glucagon-like peptide-1; GLUT glucose transporter; HSL: hormone-sensitive lipase; IR: insulin receptor; IRS: insulin receptor substrate; MAPK mitogen-activated protein kinase; MEK: MAPK/ERK kinase; MG: maltase-glucoamylase; NP: natriuretic peptide; NPR: natriuretic peptide receptor; mTORC2: mechanistic target of rapamycin complex-2; PC: proanthocyanidin; PI3K: phosphoinositide 3-kinase; PKA: cAMP-dependent protein kinase; PKB (AKT): protein kinase B; PKG: cGMP-dependent protein kinase; PPARγ: peroxisome proliferator-activated receptor-γ; SGLT1: sodium-dependent glucose transporter 1; SI: sucrase-isomaltase; T2DM: type 2 diabetes mellitus; TNFα: tumor necrosis factor-α.
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6.
Dual Role of Metallic Trace Elements in Stress Biology-From Negative to Beneficial Impact on Plants.
Muszyńska, E, Labudda, M
International journal of molecular sciences. 2019;(13)
Abstract
Heavy metals are an interesting group of trace elements (TEs). Some of them are minutely required for normal plant growth and development, while others have unknown biological actions. They may cause injury when they are applied in an elevated concentration, regardless of the importance for the plant functioning. On the other hand, their application may help to alleviate various abiotic stresses. In this review, both the deleterious and beneficial effects of metallic trace elements from their uptake by roots and leaves, through toxicity, up to the regulation of physiological and molecular mechanisms that are associated with plant protection against stress conditions have been briefly discussed. We have highlighted the involvement of metallic ions in mitigating oxidative stress by the activation of various antioxidant enzymes and emphasized the phenomenon of low-dose stimulation that is caused by non-essential, potentially poisonous elements called hormesis, which is recently one of the most studied issues. Finally, we have described the evolutionary consequences of long-term exposure to metallic elements, resulting in the development of unique assemblages of vegetation, classified as metallophytes, which constitute excellent model systems for research on metal accumulation and tolerance. Taken together, the paper can provide a novel insight into the toxicity concept, since both dose- and genotype-dependent response to the presence of metallic trace elements has been comprehensively explained.
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7.
Chloride as a Beneficial Macronutrient in Higher Plants: New Roles and Regulation.
Colmenero-Flores, JM, Franco-Navarro, JD, Cubero-Font, P, Peinado-Torrubia, P, Rosales, MA
International journal of molecular sciences. 2019;(19)
Abstract
Chloride (Cl-) has traditionally been considered a micronutrient largely excluded by plants due to its ubiquity and abundance in nature, its antagonism with nitrate (NO3-), and its toxicity when accumulated at high concentrations. In recent years, there has been a paradigm shift in this regard since Cl- has gone from being considered a harmful ion, accidentally absorbed through NO3- transporters, to being considered a beneficial macronutrient whose transport is finely regulated by plants. As a beneficial macronutrient, Cl- determines increased fresh and dry biomass, greater leaf expansion, increased elongation of leaf and root cells, improved water relations, higher mesophyll diffusion to CO2, and better water- and nitrogen-use efficiency. While optimal growth of plants requires the synchronic supply of both Cl- and NO3- molecules, the NO3-/Cl- plant selectivity varies between species and varieties, and in the same plant it can be modified by environmental cues such as water deficit or salinity. Recently, new genes encoding transporters mediating Cl- influx (ZmNPF6.4 and ZmNPF6.6), Cl- efflux (AtSLAH3 and AtSLAH1), and Cl- compartmentalization (AtDTX33, AtDTX35, AtALMT4, and GsCLC2) have been identified and characterized. These transporters have proven to be highly relevant for nutrition, long-distance transport and compartmentalization of Cl-, as well as for cell turgor regulation and stress tolerance in plants.
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8.
Nanoparticles: biosynthesis, translocation and role in plant metabolism.
Faraz, A, Faizan, M, Sami, F, Siddiqui, H, Pichtel, J, Hayat, S
IET nanobiotechnology. 2019;(4):345-352
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Abstract
Nanotechnology is an emerging field of science that applies particles between 1 and 100 nm in size for a range of practical uses. Nano-technological discoveries have opened novel applications in biotechnology and agriculture. Many reactions involving nanoparticles (NPs) are more efficient compared to those of their respective bulk materials. NPs obtained from plant material, denoted as biogenic or phytosynthesised NPs, are preferred over chemically synthesised NPs due to their low toxicity, rapid reactions and cost-effective production. NPs impart both positive and negative impacts on plant growth and development. NPs exhibit their unique actions as a function of their size, reactivity, surface area and concentration. An insight into NP biosynthesis and translocation within the plant system will shed some light on the roles and mechanisms of NP-mediated regulation of plant metabolism. This review is a step towards that goal.
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The Caucasian flora: a still-to-be-discovered rich source of antioxidants.
Sahakyan, N, Petrosyan, M, Koss-Mikołajczyk, I, Bartoszek, A, Sad, TG, Nasim, MJ, Vanidze, M, Kalandia, A, Jacob, C, Trchounian, A
Free radical research. 2019;(sup1):1153-1162
Abstract
Cellular redox homeostasis is a state of balance between the formation of Usually Reactive Oxygen and / or Nitrogen Species (ROS/RNS), endogenous antioxidant defence systems, and exogenous dietary antioxidants. The disturbance of redox homeostasis, by the overproduction of endogenous ROS/RNS, may increase the risk of development of so-called civilisation diseases. The solution seems to be either the increased production of endogenous or consumption of exogenous antioxidants. Plant-borne antioxidants act via different chemical and molecular mechanisms, such as decreasing the level of oxidative damage in cells directly by reacting with ROS/RNS or indirectly - by inhibition of the activity and expression of free radical generating enzymes or by enhancing the activity or expression of intracellular antioxidant defence enzymes. Despite the fact that the Caucasian flora is rich of health promoting edible/medicinal plants, recent studies concerning the biological activity of these plants are very scarce. This review is summarising the state-of-art on the health-promoting potential of plants representing the Caucasian flora, whose antioxidant capacity have been investigated in various in vitro models.
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10.
Hydrogen peroxide metabolism and functions in plants.
Smirnoff, N, Arnaud, D
The New phytologist. 2019;(3):1197-1214
Abstract
Contents Summary 1197 I. Introduction 1198 II. Measurement and imaging of H2 O2 1198 III. H2 O2 and O2·- toxicity 1199 IV. Production of H2 O2 : enzymes and subcellular locations 1200 V. H2 O2 transport 1205 VI. Control of H2 O2 concentration: how and where? 1205 VII. Metabolic functions of H2 O2 1207 VIII. H2 O2 signalling 1207 IX. Where next? 1209 Acknowledgements 1209 References 1209 SUMMARY Hydrogen peroxide (H2 O2 ) is produced, via superoxide and superoxide dismutase, by electron transport in chloroplasts and mitochondria, plasma membrane NADPH oxidases, peroxisomal oxidases, type III peroxidases and other apoplastic oxidases. Intracellular transport is facilitated by aquaporins and H2 O2 is removed by catalase, peroxiredoxin, glutathione peroxidase-like enzymes and ascorbate peroxidase, all of which have cell compartment-specific isoforms. Apoplastic H2 O2 influences cell expansion, development and defence by its involvement in type III peroxidase-mediated polymer cross-linking, lignification and, possibly, cell expansion via H2 O2 -derived hydroxyl radicals. Excess H2 O2 triggers chloroplast and peroxisome autophagy and programmed cell death. The role of H2 O2 in signalling, for example during acclimation to stress and pathogen defence, has received much attention, but the signal transduction mechanisms are poorly defined. H2 O2 oxidizes specific cysteine residues of target proteins to the sulfenic acid form and, similar to other organisms, this modification could initiate thiol-based redox relays and modify target enzymes, receptor kinases and transcription factors. Quantification of the sources and sinks of H2 O2 is being improved by the spatial and temporal resolution of genetically encoded H2 O2 sensors, such as HyPer and roGFP2-Orp1. These H2 O2 sensors, combined with the detection of specific proteins modified by H2 O2 , will allow a deeper understanding of its signalling roles.