scholarly journals Plant transporters involved in combating boron toxicity: beyond 3D structures

2020 ◽  
Vol 48 (4) ◽  
pp. 1683-1696
Author(s):  
Maria Hrmova ◽  
Matthew Gilliham ◽  
Stephen D. Tyerman

Membrane transporters control the movement and distribution of solutes, including the disposal or compartmentation of toxic substances that accumulate in plants under adverse environmental conditions. In this minireview, in the light of the approaching 100th anniversary of unveiling the significance of boron to plants (K. Warington, 1923; Ann. Bot.37, 629) we discuss the current state of the knowledge on boron transport systems that plants utilise to combat boron toxicity. These transport proteins include: (i) nodulin-26-like intrinsic protein-types of aquaporins, and (ii) anionic efflux (borate) solute carriers. We describe the recent progress made on the structure–function relationships of these transport proteins and point out that this progress is integral to quantitative considerations of the transporter's roles in tissue boron homeostasis. Newly acquired knowledge at the molecular level has informed on the transport mechanics and conformational states of boron transport systems that can explain their impact on cell biology and whole plant physiology. We expect that this information will form the basis for engineering transporters with optimised features to alleviate boron toxicity tolerance in plants exposed to suboptimal soil conditions for sustained food production.

2021 ◽  
Author(s):  
Yuriy Lykholat

The book contains the study results of the environmental and soil conditions of the transformed territories, the ecological patterns of woody plants natural communities’ formation as well as the features of the herbaceous communities’ succession in flooded areas. The current state of forest areas is highlighted, the problems of forest management and their exploitation in Ukraine are outlined. Aspects of anthropogenic impact on natural aquatic ecosystems are shown and various biotesting methods of negative effects are characterized. The relationship between the presence of exogenous biologically active chemical compounds in the environment and damage to the endocrine system of animals has been revealed. The scientific manuscript is intended for ecologists, specialists interested in environmental management and environmental protection. The book may be useful for graduate students and scientific researchers.


2011 ◽  
Vol 2011 ◽  
pp. 1-13 ◽  
Author(s):  
Gretchen J. Mahler ◽  
Jonathan T. Butcher

Heart valve disease is unique in that it affects both the very young and very old, and does not discriminate by financial affluence, social stratus, or global location. Research over the past decade has transformed our understanding of heart valve cell biology, yet still more remains unclear regarding how these cells respond and adapt to their local microenvironment. Recent studies have identified inflammatory signaling at nearly every point in the life cycle of heart valves, yet its role at each stage is unclear. While the vast majority of evidence points to inflammation as mediating pathological valve remodeling and eventual destruction, some studies suggest inflammation may provide key signals guiding transient adaptive remodeling. Though the mechanisms are far from clear, inflammatory signaling may be a previously unrecognized ally in the quest for controlled rapid tissue remodeling, a key requirement for regenerative medicine approaches for heart valve disease. This paper summarizes the current state of knowledge regarding inflammatory mediation of heart valve remodeling and suggests key questions moving forward.


2003 ◽  
Vol 83 (2) ◽  
pp. 633-671 ◽  
Author(s):  
Michael Trauner ◽  
James L. Boyer

Molecular medicine has led to rapid advances in the characterization of hepatobiliary transport systems that determine the uptake and excretion of bile salts and other biliary constituents in the liver and extrahepatic tissues. The bile salt pool undergoes an enterohepatic circulation that is regulated by distinct bile salt transport proteins, including the canalicular bile salt export pump BSEP (ABCB11), the ileal Na+-dependent bile salt transporter ISBT (SLC10A2), and the hepatic sinusoidal Na+- taurocholate cotransporting polypeptide NTCP (SLC10A1). Other bile salt transporters include the organic anion transporting polypeptides OATPs (SLC21A) and the multidrug resistance-associated proteins 2 and 3 MRP2,3 (ABCC2,3). Bile salt transporters are also present in cholangiocytes, the renal proximal tubule, and the placenta. Expression of these transport proteins is regulated by both transcriptional and posttranscriptional events, with the former involving nuclear hormone receptors where bile salts function as specific ligands. During bile secretory failure (cholestasis), bile salt transport proteins undergo adaptive responses that serve to protect the liver from bile salt retention and which facilitate extrahepatic routes of bile salt excretion. This review is a comprehensive summary of current knowledge of the molecular characterization, function, and regulation of bile salt transporters in normal physiology and in cholestatic liver disease and liver regeneration.


1981 ◽  
Vol 29 (9) ◽  
pp. 1043-1052 ◽  
Author(s):  
E R Weibel

The current state of the art in morphometric cell biology is reviewed by looking at the developmental state of stereological methods, and at the approaches used to arrive at quantitative structure-function correlation. Stereological methods have reached a fairly advanced level of sophistication since mathematical stereology has been developed as a branch of geometric probability theory. The application of these methods in cell biology lags behind, both quantitatively and qualitatively. Among the strategies used in exploiting stereological methods in cell biology the physiological approach (where a change is induced experimentally and its effect on the cells is followed by biochemical and morphometric methods) ranks highest and is still valid. More analytical approaches, such as combining stereology and biochemistry in cell fraction studies, are fraught with difficulties. In considering future developments of stereological methods, the emphasis will have to be 1) on developing procedures for eliminating biases such as section thickness or resolution effects, and 2) on increasing the efficiency of the methods by better sampling rules and improved instrumentation. The future trends in morphometric cell biology might best be served by exploiting the potentials of histochemistry and stereology by combining them with a view to 1) establishing procedures for cell-specific sampling and 2) developing methods towards "molecular morphometry" on the basis of immunocytochemical labeling.


2006 ◽  
Vol 401 (2) ◽  
pp. 365-375 ◽  
Author(s):  
Wouter F. Visser ◽  
Carlo W. T. van Roermund ◽  
Lodewijk Ijlst ◽  
Hans R. Waterham ◽  
Ronald J. A. Wanders

In recent years, much progress has been made with respect to the unravelling of the functions of peroxisomes in metabolism, and it is now well established that peroxisomes are indispensable organelles, especially in higher eukaryotes. Peroxisomes catalyse a number of essential metabolic functions including fatty acid β-oxidation, ether phospholipid biosynthesis, fatty acid α-oxidation and glyoxylate detoxification. The involvement of peroxisomes in these metabolic pathways necessitates the transport of metabolites in and out of peroxisomes. Recently, considerable progress has been made in the characterization of metabolite transport across the peroxisomal membrane. Peroxisomes posses several specialized transport systems to transport metabolites. This is exemplified by the identification of a specific transporter for adenine nucleotides and several half-ABC (ATP-binding cassette) transporters which may be present as hetero- and homo-dimers. The nature of the substrates handled by the different ABC transporters is less clear. In this review we will describe the current state of knowledge of the permeability properties of the peroxisomal membrane.


2017 ◽  
Vol 50 (5) ◽  
pp. 1700754 ◽  
Author(s):  
Andrea Olschewski ◽  
Emma L. Veale ◽  
Bence M. Nagy ◽  
Chandran Nagaraj ◽  
Grazyna Kwapiszewska ◽  
...  

TWIK-related acid-sensitive potassium channel 1 (TASK-1 encoded by KCNK3) belongs to the family of two-pore domain potassium channels. This gene subfamily is constitutively active at physiological resting membrane potentials in excitable cells, including smooth muscle cells, and has been particularly linked to the human pulmonary circulation. TASK-1 channels are sensitive to a wide array of physiological and pharmacological mediators that affect their activity such as unsaturated fatty acids, extracellular pH, hypoxia, anaesthetics and intracellular signalling pathways. Recent studies show that modulation of TASK-1 channels, either directly or indirectly by targeting their regulatory mechanisms, has the potential to control pulmonary arterial tone in humans. Furthermore, mutations in KCNK3 have been identified as a rare cause of both familial and idiopathic pulmonary arterial hypertension. This review summarises our current state of knowledge of the functional role of TASK-1 channels in the pulmonary circulation in health and disease, with special emphasis on current advancements in the field.


2013 ◽  
Vol 57 (11) ◽  
pp. 5457-5461 ◽  
Author(s):  
Dong H. Kwon ◽  
Saboor Hekmaty ◽  
Gomattie Seecoomar

ABSTRACTGlutathione is a tripeptide (l-γ-glutamyl–l-cysteinyl–glycine) thiol compound existing in many bacteria and maintains a proper cellular redox state, thus protecting cells against toxic substances such as reactive oxygen species. Polyamines (spermine and spermidine) are low-molecular-weight aliphatic polycations ubiquitously presenting in all living cells and modulate many cellular functions. We previously reported that exogenous polyamines significantly enhanced β-lactam susceptibility of β-lactam-associated multidrug-resistantAcinetobacter baumannii. In this study, three genes differentially associated with the polyamine effects on β-lactam susceptibility were identified by transposon mutagenesis ofA. baumanniiATCC 19606. All three genes encoded components of membrane transport systems. Inactivation of one of the genes encoding a putative glutathione transport ATP-binding protein increased the accumulation of intracellular glutathione (∼150 to ∼200%) and significantly decreased the polyamine effects on β-lactam susceptibility inA. baumanniiATCC 19606. When the cells were grown with polyamines, the levels of intracellular glutathione inA. baumanniiATCC 19606 significantly decreased from ∼0.5 to ∼0.2 nmol, while the levels of extracellular glutathione were correspondingly increased. However, the levels of total glutathione (intra- plus extracellular) were unchanged when the cells were grown with or without polyamines. Overall, these results suggest that exogenous polyamines induce glutathione export, resulting in decreased levels of intracellular glutathione, which may produce an improper cellular redox state that is associated with the polyamine-mediated β-lactam susceptibility ofA. baumannii. This finding may provide a clue for development of new antimicrobial agents and/or novel strategies to treat multidrug-resistantA. baumannii.


2004 ◽  
Vol 28 (4) ◽  
pp. 143-154 ◽  
Author(s):  
George R. Dubyak

The steady-state maintenance of highly asymmetric concentrations of the major inorganic cations and anions is a major function of both plasma membranes and the membranes of intracellular organelles. Homeostatic regulation of these ionic gradients is critical for most functions. Due to their charge, the movements of ions across biological membranes necessarily involves facilitation by intrinsic membrane transport proteins. The functional characterization and categorization of membrane transport proteins was a major focus of cell physiological research from the 1950s through the 1980s. On the basis of these functional analyses, ion transport proteins were broadly divided into two classes: channels and carrier-type transporters (which include exchangers, cotransporters, and ATP-driven ion pumps). Beginning in the mid-1980s, these functional analyses of ion transport and homeostasis were complemented by the cloning of genes encoding many ion channels and transporter proteins. Comparison of the predicted primary amino acid sequences and structures of functionally similar ion transport proteins facilitated their grouping within families and superfamilies of structurally related membrane proteins. Postgenomics research in ion transport biology increasingly involves two powerful approaches. One involves elucidation of the molecular structures, at the atomic level in some cases, of model ion transport proteins. The second uses the tools of cell biology to explore the cell-specific function or subcellular localization of ion transport proteins. This review will describe how these approaches have provided new, and sometimes surprising, insights regarding four major questions in current ion transporter research. 1) What are the fundamental differences between ion channels and ion transporters? 2) How does the interaction of an ion transport protein with so-called adapter proteins affect its subcellular localization or regulation by various intracellular signal transduction pathways? 3) How does the specific lipid composition of the local membrane microenvironment modulate the function of an ion transport protein? 4) How can the basic functional properties of a ubiquitously expressed ion transport protein vary depending on the cell type in which it is expressed?


2003 ◽  
pp. 85-89
Author(s):  
Kamilla Taraczközi

The soil constitutes the basis of the food chain. To keep soil conditions in a good trim is very important, it’s part of the sustainable development and of producing food supply harmless to health.In some cases, soil productivity is the only important part, qualitative requirements or economical characteristics can improve it. The soil is threatened by two danger factors: the soil degradation and the soil pollution. The accumulation of different harmful and/or toxic substances in the soil is well known. Heavy metals constitute a part of it. Metals in the soil and in the soil-solution are balanced. This balance depends on the type of the metal, on the pH, on the cation-band capacity of the soil, on the redox relations and the concentration of cations in the soil.To be able to handle the metal contamination of the soil, it is important to estimate the form, the possible extension and the concentration of metals.Of course, the different types of soils have different physical-chemical, biological and buffer capacity, they can moderate or reinforce the harmful effects of heavy metals. To draw general conclusion of the dispersion and quantitative relations on the metals originated from different contamination sources is hard, because in some emissive sources contamination is limited in small areas but on a high level, some others usually expand on larger areas, and as a result of equal dispersion, the contamination’s level is lower.Heavy metals – unlike alkali ions – strongly bond to organic materials, or infiltrate in a kelát form. Their outstanding characteristic is the tendency to create metal-complex forms. Kelats take part in the uptaking and transportation of heavy metals. Heavy metals exert their effects mostly as enzyme-activators.The metals cannot degrade in an organic way, they accumulate in living organisms, and they can form toxic compounds through biochemical reactions.Lot of the heavy metals accumulate on the boundaries of the abiotic systems (air/soil, water/sediment), when physical or chemical parameters change, and this influences their remobilization.Human activity plays a great part in heavy metal mobilization, results in the human origin of most biochemical process of metals.To understand the toxic influence of accumulated metals of high concentration, their transportation from soils to plants or their damage in human health, must clearly defined and investigated.For effective protection against soil pollution, the types and levels of harmful pollution to soil must identified, regarding legal, technical and soil-science aspects, preferable in a single way. Difficulties in this area mean that toxicity depends on loading, uptake, soil characteristics and living organisms (species, age, condition etc.), furthermore, local and economic conditions considerably differ.


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