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1.
The Adaptation and Tolerance of Major Cereals and Legumes to Important Abiotic Stresses.
Rane, J, Singh, AK, Kumar, M, Boraiah, KM, Meena, KK, Pradhan, A, Prasad, PVV
International journal of molecular sciences. 2021;(23)
Abstract
Abiotic stresses, including drought, extreme temperatures, salinity, and waterlogging, are the major constraints in crop production. These abiotic stresses are likely to be amplified by climate change with varying temporal and spatial dimensions across the globe. The knowledge about the effects of abiotic stressors on major cereal and legume crops is essential for effective management in unfavorable agro-ecologies. These crops are critical components of cropping systems and the daily diets of millions across the globe. Major cereals like rice, wheat, and maize are highly vulnerable to abiotic stresses, while many grain legumes are grown in abiotic stress-prone areas. Despite extensive investigations, abiotic stress tolerance in crop plants is not fully understood. Current insights into the abiotic stress responses of plants have shown the potential to improve crop tolerance to abiotic stresses. Studies aimed at stress tolerance mechanisms have resulted in the elucidation of traits associated with tolerance in plants, in addition to the molecular control of stress-responsive genes. Some of these studies have paved the way for new opportunities to address the molecular basis of stress responses in plants and identify novel traits and associated genes for the genetic improvement of crop plants. The present review examines the responses of crops under abiotic stresses in terms of changes in morphology, physiology, and biochemistry, focusing on major cereals and legume crops. It also explores emerging opportunities to accelerate our efforts to identify desired traits and genes associated with stress tolerance.
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2.
The Roots of Plant Frost Hardiness and Tolerance.
Ambroise, V, Legay, S, Guerriero, G, Hausman, JF, Cuypers, A, Sergeant, K
Plant & cell physiology. 2020;(1):3-20
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Abstract
Frost stress severely affects agriculture and agroforestry worldwide. Although many studies about frost hardening and resistance have been published, most of them focused on the aboveground organs and only a minority specifically targets the roots. However, roots and aboveground tissues have different physiologies and stress response mechanisms. Climate models predict an increase in the magnitude and frequency of late-frost events, which, together with an observed loss of soil insulation, will greatly decrease plant primary production due to damage at the root level. Molecular and metabolic responses inducing root cold hardiness are complex. They involve a variety of processes related to modifications in cell wall composition, maintenance of the cellular homeostasis and the synthesis of primary and secondary metabolites. After a summary of the current climatic models, this review details the specificity of freezing stress at the root level and explores the strategies roots developed to cope with freezing stress. We then describe the level to which roots can be frost hardy, depending on their age, size category and species. After that, we compare the environmental signals inducing cold acclimation and frost hardening in the roots and aboveground organs. Subsequently, we discuss how roots sense cold at a cellular level and briefly describe the following signal transduction pathway, which leads to molecular and metabolic responses associated with frost hardening. Finally, the current options available to increase root frost tolerance are explored and promising lines of future research are discussed.
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3.
Does Dehydration Affect the Adaptations of Plasma Volume, Heart Rate, Internal Body Temperature, and Sweat Rate During the Induction Phase of Heat Acclimation?
Sekiguchi, Y, Filep, EM, Benjamin, CL, Casa, DJ, DiStefano, LJ
Journal of sport rehabilitation. 2020;(6):847-850
Abstract
Clinical Scenario: Exercise in the heat can lead to performance decrements and increase the risk of heat illness. Heat acclimation refers to the systematic and gradual increase in exercise in a controlled, laboratory environment. Increased duration and intensity of exercise in the heat positively affects physiological responses, such as higher sweat rate, plasma volume expansion, decreased heart rate, and lower internal body temperature. Many heat acclimation studies have examined the hydration status of the subjects exercising in the heat. Some of the physiological responses that are desired to elicit heat acclimation (ie, higher heart rate and internal body temperature) are exacerbated in a dehydrated state. Thus, euhydration (optimal hydration) and dehydration trials during heat acclimation induction have been conducted to determine if there are additional benefits to dehydrated exercise trials on physiological adaptations. However, there is still much debate over hydration status and its effect on heat acclimation. Clinical Question: Does dehydration affect the adaptations of plasma volume, heart rate, internal body temperature, skin temperature, and sweat rate during the induction phase of heat acclimation? Summary of Findings: There were no observed differences in plasma volume, internal body temperature, and skin temperature following heat acclimation in this critically appraised topic. One study found an increase in sweat rate and another study indicated greater changes in heart rate following heat acclimation with dehydration. Aside from these findings, all 4 trials did not observe statistically significant differences in euhydrated and dehydrated heat acclimation trials. Clinical Bottom Line: There is minimal evidence to suggest that hydration status affects heat acclimation induction. In the studies that met the inclusion criteria, there were no differences in plasma volume concentrations, internal body temperature, and skin temperature. Strength of Recommendation: Based on the Oxford Centre for Evidence-Based Medicine Scale, Level 2 evidence exists.
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4.
Seed Priming: A Feasible Strategy to Enhance Drought Tolerance in Crop Plants.
Marthandan, V, Geetha, R, Kumutha, K, Renganathan, VG, Karthikeyan, A, Ramalingam, J
International journal of molecular sciences. 2020;(21)
Abstract
Drought is a serious threat to the farming community, biasing the crop productivity in arid and semi-arid regions of the world. Drought adversely affects seed germination, plant growth, and development via non-normal physiological processes. Plants generally acclimatize to drought stress through various tolerance mechanisms, but the changes in global climate and modern agricultural systems have further worsened the crop productivity. In order to increase the production and productivity, several strategies such as the breeding of tolerant varieties and exogenous application of growth regulators, osmoprotectants, and plant mineral nutrients are followed to mitigate the effects of drought stress. Nevertheless, the complex nature of drought stress makes these strategies ineffective in benefiting the farming community. Seed priming is an alternative, low-cost, and feasible technique, which can improve drought stress tolerance through enhanced and advanced seed germination. Primed seeds can retain the memory of previous stress and enable protection against oxidative stress through earlier activation of the cellular defense mechanism, reduced imbibition time, upsurge of germination promoters, and osmotic regulation. However, a better understanding of the metabolic events during the priming treatment is needed to use this technology in a more efficient way. Interestingly, the review highlights the morphological, physiological, biochemical, and molecular responses of seed priming for enhancing the drought tolerance in crop plants. Furthermore, the challenges and opportunities associated with various priming methods are also addressed side-by-side to enable the use of this simple and cost-efficient technique in a more efficient manner.
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Tolerance of roots to low oxygen: 'Anoxic' cores, the phytoglobin-nitric oxide cycle, and energy or oxygen sensing.
Armstrong, W, Beckett, PM, Colmer, TD, Setter, TL, Greenway, H
Journal of plant physiology. 2019;:92-108
Abstract
Acclimation by plants to hypoxia and anoxia is of importance in various ecological systems, and especially for roots in waterlogged soil. We present evidence for acclimation by roots via 'anoxic' cores rather than being triggered by O2 sensors. The evidence for 'anoxic' cores comes from radial O2 profiles across maize roots and associated metabolic changes such as increases in the 'anaerobic enzymes' ADH and PDC in the 'anoxic' core, and inhibition of Cl- transport to the xylem. These cores are predicted to develop within 15-20 min after sudden transfer of a root to hypoxia, so that the cores are 'anoxically-shocked'. We suggest that 'anoxic' cores could emanate a signal(s), such as ACC the precursor of ethylene and/or propagation of a 'Ca2+ wave', to other tissue zones. There, the signalling would result in acclimation of the tissues to energy crisis metabolism. An O2 diffusion model for tissues with an 'anoxic' core, indicates that the phytoglobin-nitric oxide (Pgb-NO) cycle would only be engaged in a thin 'shell' (annulus) of tissue surrounding the 'anoxic' core, and so would only contribute small amounts of ATP on a whole organ basis (e.g. whole roots). A key feature within this annulus of tissue, where O2 is likely to be limiting, is that the ratio (ATP formed) / (O2 consumed) is 5-6, both when the NAD(P)H of glycolysis is converted to NAD(P)+ by the Pgb-NO cycle or by the TCA cycle linked to the electron transport chain. The main function of the Pgb-NO cycle may be the modulating of NO levels and O2 scavenging, thus preventing oxidative damage. We speculate that an 'anoxic' core in hypoxic plant organs may have a particularly high tolerance to anoxia because cells might receive a prolonged supply of carbohydrates and/or ATP from the regions still receiving sufficient O2 for oxidative phosphorylation. Severely hypoxic or 'anoxic' cores are well documented, but much research on responses of roots to hypoxia is still based on bulk tissue analyses. More research is needed on the interaction between 'anoxic' cores and tissues still receiving sufficient O2 for oxidative phosphorylation, both during a hypoxic exposure and during subsequent anoxia of the tissue/organ as a whole.
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6.
Maximizing Cellular Adaptation to Endurance Exercise in Skeletal Muscle.
Hawley, JA, Lundby, C, Cotter, JD, Burke, LM
Cell metabolism. 2018;(5):962-976
Abstract
The application of molecular techniques to exercise biology has provided novel insight into the complexity and breadth of intracellular signaling networks involved in response to endurance-based exercise. Here we discuss several strategies that have high uptake by athletes and, on mechanistic grounds, have the potential to promote cellular adaptation to endurance training in skeletal muscle. Such approaches are based on the underlying premise that imposing a greater metabolic load and provoking extreme perturbations in cellular homeostasis will augment acute exercise responses that, when repeated over months and years, will amplify training adaptation.
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7.
Using genomic information to improve soybean adaptability to climate change.
Li, MW, Xin, D, Gao, Y, Li, KP, Fan, K, Muñoz, NB, Yung, WS, Lam, HM
Journal of experimental botany. 2017;(8):1823-1834
Abstract
Climate change has brought severe challenges to agriculture. It is anticipated that there will be a drop in crop yield - including that of soybean - due to climatic stress factors that include drastic fluctuations in temperature, drought, flooding and high salinity. Genomic information on soybean has been accumulating rapidly since initial publication of its reference genome, providing a valuable tool for the improvement of cultivated soybean. Not only are many molecular markers that are associated with important quantitative trait loci now identified, but we also have a more detailed picture of the genomic variations among soybean germplasms, enabling us to utilize these as tools to assist crop breeding. In this review, we will summarize and discuss the currently available soybean genomic approaches, including whole-genome sequencing, sequencing-based genotyping, functional genomics, proteomics, and epigenomics. The information uncovered through these techniques will help further pinpoint important gene candidates and genomic loci associated with adaptive traits, as well as achieving a better understanding of how soybeans cope with the changing climate.
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8.
Muscle Protein Turnover and the Molecular Regulation of Muscle Mass during Hypoxia.
Pasiakos, SM, Berryman, CE, Carrigan, CT, Young, AJ, Carbone, JW
Medicine and science in sports and exercise. 2017;(7):1340-1350
Abstract
: Effects of environmental hypoxia on fat-free mass are well studied. Negative energy balance, increased nitrogen excretion, and fat-free mass loss are commonly observed in lowlanders sojourning at high altitude. Reductions in fat-free mass can be minimized if energy consumption matches energy expenditure. However, in nonresearch settings, achieving energy balance during high-altitude sojourns is unlikely, and myofibrillar protein mass is usually lost, but the mechanisms accounting for the loss of muscle mass are not clear. At sea level, negative energy balance reduces basal and blunts postprandial muscle protein synthesis, with no relevant change in muscle protein breakdown. Downregulations in muscle protein synthesis and loss of fat-free mass during energy deficit at sea level are largely overcome by consuming at least twice the recommended dietary allowance for protein. Hypoxia may increase or not affect resting muscle protein synthesis, blunt postexercise muscle protein synthesis, and markedly increase proteolysis independent of energy status. Hypoxia-induced mTORC1 dysregulation and an upregulation in calpain- and ubiquitin proteasome-mediated proteolysis may drive catabolism in lowlanders sojourning at high altitude. However, the combined effects of energy deficit, exercise, and dietary protein manipulations on the regulation of muscle protein turnover have never been studied at high altitude. This article reviews the available literature related to the effects of high altitude on fat-free mass, highlighting contemporary studies that assessed the influence of altitude exposure (or hypoxia) on muscle protein turnover and intramuscular regulation of muscle mass. Knowledge gaps are addressed, and studies to identify effective and feasible countermeasures to hypoxia-induced muscle loss are discussed.
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9.
Bicarbonate Values for Healthy Residents Living in Cities Above 1500 Meters of Altitude: A Theoretical Model and Systematic Review.
Ramirez-Sandoval, JC, Castilla-Peón, MF, Gotés-Palazuelos, J, Vázquez-García, JC, Wagner, MP, Merelo-Arias, CA, Vega-Vega, O, Rincón-Pedrero, R, Correa-Rotter, R
High altitude medicine & biology. 2016;(2):85-92
Abstract
Ramirez-Sandoval, Juan C., Maria F. Castilla-Peón, José Gotés-Palazuelos, Juan C. Vázquez-García, Michael P. Wagner, Carlos A. Merelo-Arias, Olynka Vega-Vega, Rodolfo Rincón-Pedrero, and Ricardo Correa-Rotter. Bicarbonate values for healthy residents living in cities above 1500 m of altitude: a theoretical model and systematic review. High Alt Med Biol. 17:85-92, 2016.-Plasma bicarbonate (HCO3(-)) concentration is the main value used to assess the metabolic component of the acid-base status. There is limited information regarding plasma HCO3(-) values adjusted for altitude for people living in cities at high altitude defined as 1500 m (4921 ft) or more above sea level. Our aim was to estimate the plasma HCO3(-) concentration in residents of cities at these altitudes using a theoretical model and compare these values with HCO3(-) values found on a systematic review, and with those venous CO2 values obtained in a sample of 633 healthy individuals living at an altitude of 2240 m (7350 ft). We calculated the PCO2 using linear regression models and calculated plasma HCO3(-) according to the Henderson-Hasselbalch equation. Results show that HCO3(-) concentration falls as the altitude of the cities increase. For each 1000 m of altitude above sea level, HCO3(-) decreases to 0.55 and 1.5 mEq/L in subjects living at sea level with acute exposure to altitude and in subjects acclimatized to altitude, respectively. Estimated HCO3(-) values from the theoretical model were not different to HCO3(-) values found in publications of a systematic review or with venous total CO2 measurements in our sample. Altitude has to be taken into consideration in the calculation of HCO3(-) concentrations in cities above 1500 m to avoid an overdiagnosis of acid-base disorders in a given individual.
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Plant responses to ambient temperature fluctuations and water-limiting conditions: A proteome-wide perspective.
Johnová, P, Skalák, J, Saiz-Fernández, I, Brzobohatý, B
Biochimica et biophysica acta. 2016;(8):916-31
Abstract
BACKGROUND Every year, environmental stresses such as limited water and nutrient availability, salinity, and temperature fluctuations inflict significant losses on crop yields across the globe. Recently, developments in analytical techniques, e.g. mass spectrometry, have led to great advances towards understanding how plants respond to environmental stresses. These processes are mediated by many molecular pathways and, at least partially, via proteome-environment interactions. SCOPE OF REVIEW This review focuses on the current state of knowledge about interactions between the plant proteome and the environment, with a special focus on drought and temperature responses of plant proteome dynamics, and subcellular and organ-specific compartmentalization, in Arabidopsis thaliana and crop species. MAJOR CONCLUSIONS Correct plant development under non-optimal conditions requires complex self-protection mechanisms, many of them common to different abiotic stresses. Proteome analyses of plant responses to temperature and drought stresses have revealed an intriguing interplay of modifications, mainly affecting the photosynthetic machinery, carbohydrate metabolism, and ROS activation and scavenging. Imbalances between transcript-level and protein-level regulation observed during adaptation to abiotic stresses suggest that many of the regulatory processes are controlled at translational and post-translational levels; proteomics is thus essential in revealing important regulatory networks. GENERAL SIGNIFICANCE Because information from proteomic data extends far beyond what can be deduced from transcriptome analysis, the results of proteome studies have substantially deepened our understanding of stress adaptation in plants; this is clearly a prerequisite for designing strategies to improve the yield and quality of crops grown under unfavorable conditions brought about by ongoing climatic change. This article is part of a Special Issue entitled: Plant Proteomics--a bridge between fundamental processes and crop production, edited by Dr. Hans-Peter Mock.