scholarly journals A Quest for Mechanisms of Plant Root Exudation Brings New Results and Models, 300 Years after Hales

Plants ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 38
Author(s):  
Vadim Volkov ◽  
Heiner Schwenke
Keyword(s):  
Water Transport ◽  
18Th Century ◽  
Current Knowledge ◽  
Experimental Testing ◽  
Plant Root ◽  
Root Exudation ◽  
Channel Blockers ◽  
Root Cells ◽  
Ion Channel Blockers ◽  
Cation Chloride Cotransporters

The review summarizes some of our current knowledge on the phenomenon of exudation from the cut surface of detached roots with emphasis on results that were mostly established over the last fifty years. The phenomenon is quantitatively documented in the 18th century (by Hales in 1727). By the 19th century, theories mainly ascribed exudation to the secretion of living root cells. The 20th century favored the osmometer model of root exudation. Nevertheless, growing insights into the mechanisms of water transport and new or rediscovered observations stimulated the quest for a more adequate exudation model. The historical overview shows how understanding of exudation changed with time following experimental opportunities and novel ideas from different areas of knowledge. Later theories included cytoskeleton-dependent micro-pulsations of turgor in root cells to explain the observed water exudation. Recent progress in experimental biomedicine led to detailed study of channels and transporters for ion transport via cellular membranes and to the discovery of aquaporins. These universal molecular entities have been incorporated to the more complex models of water transport via plant roots. A new set of ideas and explanations was based on cellular osmoregulation by mechanosensitive ion channels. Thermodynamic calculations predicted the possibility of water transport against osmotic forces based on co-transport of water with ions via cation-chloride cotransporters. Recent observations of rhizodermis exudation, exudation of roots without an external aqueous medium, segments cut from roots, pulses of exudation, a phase shifting of water uptake and exudation, and of effects of physiologically active compounds (like ion channel blockers, metabolic agents, and cytoskeletal agents) will likely refine our understanding of the phenomenon. So far, it seems that more than one mechanism is responsible for root pressure and root exudation, processes which are important for refilling of embolized xylem vessels. However, recent advances in ion and water transport research at the molecular level suggest potential future directions to understanding of root exudation and new models awaiting experimental testing.

scholarly journals A novel putative microtubule-associated protein is involved in arbuscule development during arbuscular mycorrhiza formation

2021 ◽  
Author(s):  
Tania Ho-Plágaro ◽  
Raúl Huertas ◽  
María I Tamayo-Navarrete ◽  
Elison Blancaflor ◽  
Nuria Gavara ◽  
...  
Keyword(s):  
Plant Root ◽  
Arbuscular Mycorrhizal ◽  
Host Cells ◽  
Root Cells ◽  
Filament Dynamics ◽  
Fungal Structure ◽  
Genes Encoding ◽  
Associated Proteins ◽  
Mycorrhizal Development

Abstract The formation of arbuscular mycorrhizal (AM) symbiosis requires plant root host cells to undergo major structural and functional reprogramming in order to house the highly branched AM fungal structure for the reciprocal exchange of nutrients. These morphological modifications are associated with cytoskeleton remodelling. However, molecular bases and the role of microtubules (MTs) and actin filament dynamics during AM formation are largely unknown. In this study, the tomato tsb gene, belonging to a Solanaceae group of genes encoding MT-associated proteins for pollen development, was found to be highly expressed in root cells containing arbuscules. At earlier stages of mycorrhizal development, tsb overexpression enhanced the formation of highly developed and transcriptionally active arbuscules, while tsb silencing hampers the formation of mature arbuscules and represses arbuscule functionality. However, at later stages of mycorrhizal colonization, tsb OE roots accumulate fully developed transcriptionally inactive arbuscules, suggesting that the collapse and turnover of arbuscules might be impaired by TSB accumulation. Imaging analysis of the MT cytoskeleton in cortex root cells overexpressing tsb revealed that TSB is involved in MT-bundling. Taken together, our results provide unprecedented insights into the role of novel MT-associated protein in MT rearrangements throughout the different stages of the arbuscule life cycle.

scholarly journals Pulmonary Hypertension in Acute and Chronic High Altitude Maladaptation Disorders

2021 ◽  
Vol 18 (4) ◽  
pp. 1692
Author(s):  
Akylbek Sydykov ◽  
Argen Mamazhakypov ◽  
Abdirashit Maripov ◽  
Djuro Kosanovic ◽  
Norbert Weissmann ◽  
...  
Keyword(s):  
Pulmonary Hypertension ◽  
High Altitude ◽  
Clinical Experience ◽  
Current Knowledge ◽  
Hypoxic Pulmonary Vasoconstriction ◽  
Treatment Options ◽  
Right Heart Failure ◽  
Channel Blockers ◽  
The Right ◽  
Extensive Clinical Experience

Alveolar hypoxia is the most prominent feature of high altitude environment with well-known consequences for the cardio-pulmonary system, including development of pulmonary hypertension. Pulmonary hypertension due to an exaggerated hypoxic pulmonary vasoconstriction contributes to high altitude pulmonary edema (HAPE), a life-threatening disorder, occurring at high altitudes in non-acclimatized healthy individuals. Despite a strong physiologic rationale for using vasodilators for prevention and treatment of HAPE, no systematic studies of their efficacy have been conducted to date. Calcium-channel blockers are currently recommended for drug prophylaxis in high-risk individuals with a clear history of recurrent HAPE based on the extensive clinical experience with nifedipine in HAPE prevention in susceptible individuals. Chronic exposure to hypoxia induces pulmonary vascular remodeling and development of pulmonary hypertension, which places an increased pressure load on the right ventricle leading to right heart failure. Further, pulmonary hypertension along with excessive erythrocytosis may complicate chronic mountain sickness, another high altitude maladaptation disorder. Importantly, other causes than hypoxia may potentially underlie and/or contribute to pulmonary hypertension at high altitude, such as chronic heart and lung diseases, thrombotic or embolic diseases. Extensive clinical experience with drugs in patients with pulmonary arterial hypertension suggests their potential for treatment of high altitude pulmonary hypertension. Small studies have demonstrated their efficacy in reducing pulmonary artery pressure in high altitude residents. However, no drugs have been approved to date for the therapy of chronic high altitude pulmonary hypertension. This work provides a literature review on the role of pulmonary hypertension in the pathogenesis of acute and chronic high altitude maladaptation disorders and summarizes current knowledge regarding potential treatment options.

Fluorescence-Based High Throughput Screening Technologies for Natural Chloride Ion Channel Blockers

2018 ◽  
Vol 31 (12) ◽  
pp. 1332-1338 ◽  
Author(s):  
Rong Xu ◽  
Yuan Xiao ◽  
Yan Liu ◽  
Bo Wang ◽  
Xing Li ◽  
...  
Keyword(s):  
Ion Channel ◽  
High Throughput ◽  
High Throughput Screening ◽  
Chloride Ion ◽  
Channel Blockers ◽  
Ion Channel Blockers

scholarly journals Is Lipid Bilayer Binding a Common Property of Inhibitor Cysteine Knot Ion-Channel Blockers?

2007 ◽  
Vol 93 (4) ◽  
pp. L20-L22 ◽  
Author(s):  
Yevgen O. Posokhov ◽  
Philip A. Gottlieb ◽  
Michael J. Morales ◽  
Frederick Sachs ◽  
Alexey S. Ladokhin
Keyword(s):  
Ion Channel ◽  
Lipid Bilayer ◽  
Common Property ◽  
Channel Blockers ◽  
Ion Channel Blockers

Compartmental Model of Vertebrate Motoneurons for Ca2+-Dependent Spiking and Plateau Potentials Under Pharmacological Treatment

1997 ◽  
Vol 78 (6) ◽  
pp. 3371-3385 ◽  
Author(s):  
Victoria Booth ◽  
John Rinzel ◽  
Ole Kiehn
Keyword(s):  
Ion Channel ◽  
Compartmental Model ◽  
Ionic Currents ◽  
Channel Blockers ◽  
Spinal Motoneurons ◽  
Plateau Potentials ◽  
Firing Patterns ◽  
Calcium Dependent ◽  
Ion Channel Blockers ◽  
Experimental Effect

Booth, Victoria, John Rinzel, and Ole Kiehn. Compartmental model of vertebrate motoneurons for Ca2+-dependent spiking and plateau potentials under pharmacological treatment. J. Neurophysiol. 78: 3371–3385, 1997. In contrast to the limited response properties observed under normal experimental conditions, spinal motoneurons generate complex firing patterns, such as Ca2+-dependent regenerative spiking and plateaus, in the presence of certain neurotransmitters and ion-channel blockers. We have developed a quantitative motoneuron model, based on turtle motoneuron data, toinvestigate the roles of specific ionic currents and the effects of their soma and dendritic distribution in generating these complex firing patterns. In addition, the model is used to explore the effects of multiple ion channel blockers and neurotransmitters that are known to modulate motoneuron firing patterns. To represent the distribution of ionic currents across the soma and dendrites, the model contains two compartments. The soma compartment, representing the soma and proximal dendrites, contains Hodgkin-Huxley-like sodium ( I Na) and delayed rectifier K+ ( I K−dr) currents, an N-like Ca2+ current ( I Ca−N), and a calcium-dependent K+ current [ I K(Ca)]. The dendritic compartment, representing the lumped distal dendrites, contains, in addition to I Ca−N and I K(Ca) as in the soma, a persistent L-like calcium current ( I Ca−L). We determined kinetic parameters for I Na, I K−dr, I Ca−N, and I K(Ca) in order to reproduce normal action-potential firing observed in turtle spinal motoneurons, including fast and slow afterhyperpolarizations (AHPs) and a linear steady-state frequency-current relation. With this parameter set as default, a sequence of pharmacological manipulations were systematically simulated. A small reduction of I K−dr [mimicking the experimental effect of tetraethylammonium (TEA) in low concentration] enhanced the slow AHP and caused calcium spiking (mediated by I Ca−N) when I Na was blocked. Firing patterns observed experimentally in high TEA [and tetrodotoxin (TTX)], namely calcium spikes riding on a calcium plateau, were reproduced only when both I K−dr and I K(Ca) were reduced. Dendritic plateau potentials, mediated by I Ca−L, were reliably unmasked when I K(Ca) was reduced, mimicking the experimental effect of the bee venom apamin. The effect of 5-HT, which experimentally induces the ability to generate calcium-dependent plateau potentials but not calcium spiking, was reproduced in the model by reducing I K(Ca) alone. The plateau threshold current level, however, was reduced substantially if a simultaneous increase in I Ca−L was simulated, suggesting that serotonin (5-HT) induces plateau potentials by regulating more than one conductance. The onset of the plateau potential showed significant delays in response to near-threshold, depolarizing current steps. In addition, the delay times were sensitive to the current step amplitude. The delay and its sensitivity were explained by examining the model's behavior near the threshold for plateau onset. This modeling study thus accurately accounts for the basic firing behavior of vertebrate motoneurons as well as a range of complex firing patterns invoked by ion-channel blockers and 5-HT. In addition, our computational results support the hypothesis that the electroresponsiveness of motoneurons depends on a nonuniform distribution of ionic conductances, and they predict modulatory effects of 5-HT and properties of plateau activation that have yet to be tested experimentally.

scholarly journals Mathematical Model and Simulation for Nutrient-Plant Interaction Analysis

2020 ◽  
Author(s):  
Byunghyun Ban
Keyword(s):  
Cell Membrane ◽  
Interaction Analysis ◽  
Plant Root ◽  
Gene Expression Pattern ◽  
Root Cell ◽  
Ion Concentration ◽  
Absorption Model ◽  
Membrane Flow ◽  
Root Cells ◽  
Model And Simulation

Differential equation models to understand interaction between plant and nutrient solution are presented. The root cells selectively emit H+ ions with active transport consuming ATPs to establish electrical gradient along the cell membrane. It establishes electrical field with Nernst potential to make positively charged ions outside the cell membrane flow into the root cell. Anion influx is also modulated by H+ ion concentration because plant root cell absorbs negatively charged particles with symport. If an anion collides with H+ cell to make net charge as neutral, at symport channel, it can flow through. In this paper, mathematical models for cation and anion absorption are introduced. Cation absorption model was induced from Ohm's law combined with Goldman's equation. Anion absorption model is similar to chemical reaction rate model. Both models have physiological terms influenced by gene expression pattern, species or phenotypes. Cation model also includes terms for ion's kinetic and electrical properties, growth of plant and interaction between the root and the surroundings. Simulation for 20 different sets of coefficients showed that the physiology-related coefficient has important role on nutrition absorption tendencies of plants.

scholarly journals Phospholipid Fatty Acid (PLFA) Analysis of Rhizosphere Bacterial Communities in a Peat Soil

2002 ◽  
Vol 51 (1-2) ◽  
pp. 123-128 ◽  
Author(s):  
András Halbritter ◽  
T. Mogyoróssy
Keyword(s):  
Fatty Acid ◽  
Bacterial Communities ◽  
Phospholipid Fatty Acid ◽  
Plant Root ◽  
Peat Soil ◽  
Total Lipid Content ◽  
Gas Chromatography Mass Spectrometry ◽  
Root Cells ◽  
Plfa Analysis ◽  
Rhizosphere Bacterial Communities

To analyze the rhizosphere bacterial communities in wetlands, the total lipid content was extracted from a peat soil and 4 abundant wetland plant roots ( Typha angustifolia L., Salix cinerea L., Carex pseudocyperus L., Thelypteris palustris Salisb.). The separated phospholipid fraction was further fractionated and deriva­tized prior to gas chromatography-mass spectrometry (GC-MS) measurement. In the evaluation only the bacteria-specific fatty acids were used in order to neglect fatty acid information derived from plant root cells. Based on these analyses, a high level bacterial concentration was demonstrated in the rhizosphere, and the relative occurrence of aerobe and anaerobe, Gram positive and negative bacteria, methanotrophs, sulphate reducers and Actinobacteria was determined. Through the PLFA analysis the study of bacteria regardless of culturability was possible.

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