Maintain Ion Balance Research Articles

Strategies for combating plant salinity stress: the potential of plant growth-promoting microorganisms.

Global climate change and the decreasing availability of high-quality water lead to an increase in the salinization of agricultural lands. This rising salinity represents a significant abiotic stressor that detrimentally influences plant physiology and gene expression. Consequently, critical processes such as seed germination, growth, development, and yield are adversely affected. Salinity severely impacts crop yields, given that many crop plants are sensitive to salt stress. Plant growth-promoting microorganisms (PGPMs) in the rhizosphere or the rhizoplane of plants are considered the "second genome" of plants as they contribute significantly to improving the plant growth and fitness of plants under normal conditions and when plants are under stress such as salinity. PGPMs are crucial in assisting plants to navigate the harsh conditions imposed by salt stress. By enhancing water and nutrient absorption, which is often hampered by high salinity, these microorganisms significantly improve plant resilience. They bolster the plant's defenses by increasing the production of osmoprotectants and antioxidants, mitigating salt-induced damage. Furthermore, PGPMs supply growth-promoting hormones like auxins and gibberellins and reduce levels of the stress hormone ethylene, fostering healthier plant growth. Importantly, they activate genes responsible for maintaining ion balance, a vital aspect of plant survival in saline environments. This review underscores the multifaceted roles of PGPMs in supporting plant life under salt stress, highlighting their value for agriculture in salt-affected areas and their potential impact on global food security.

GmHXK2 promotes the salt tolerance of soybean seedlings by mediating AsA synthesis, and auxin synthesis and distribution

BackgroundSalt is an important factor that affects crop productivity. Plant hexokinases (HXKs) are key enzymes in the glycolytic pathway and sugar signaling transduction pathways of plants. In previous studies, we identified and confirmed the roles of GmHXK2 in salt tolerance.ResultsIn this study, we analyzed the tissue-specific expression of GmHXK2 at different growth stages throughout the plant’s life cycle. The results showed that GmHXK2 was expressed significantly in all tissues at vegetative stages, including germination and seedling. However, no expression was detected in the pods, and there was little expression in flowers during the later mature period. Arabidopsis plants overexpressing the GmHXK2 (OE) had more lateral roots. The OE seedlings also produced higher levels of auxin and ascorbic acid (AsA). Additionally, the expression levels of genes PMM, YUC4/YUC6/YUC8, and PIN/LAX1,LAX3, which are involved respectively in the synthesis of AsA and auxin, as well as polar auxin transport, were upregulated in OE plants. This upregulation occurred specifically under exogenous glucose treatment. AtHKT1, AtSOS1, and AtNHX1 were up-regulated in OE plants under salt stress, suggesting that GmHXK2 may modulate salt tolerance by maintaining ion balance within the cells and alleviating damage caused by salt stress. Additionally, we further confirmed the interaction between GmHXK2 and the protein GmPMM through yeast two-hybridization and bimolecular fluorescence complementation assays, respectively.ConclusionThe expression of GmHXK2 gene in plants is organ-specific and developmental stage specific. GmHXK2 not only regulates the synthesis of AsA and the synthesis and distribution of auxin, but also promotes root elongation and induces lateral root formation, potentially enhancing soil water absorption. This study reveals the crosstalk between sugar signaling and hormone signaling in plants, where GmHXK2 acts as a glucose sensor through its interaction with GmPMM, and sheds light on the molecular mechanism by which GmHXK2 gene is involved in salt tolerance in plants.

Silybin protected from avermectin-induced carp (Cyprinus carpio) nephrotoxicity by regulating PPAR-γ-involved inflammation, oxidative stress, ferroptosis and autophagy

Avermectin, a widely used deworming drug, poses a significant threat to fisheries. Silybin is recognized for its antioxidant and anti-inflammatory properties. The kidney, being crucial for fish survival, plays a vital role in maintaining ion balance, nitrogen metabolism, and hormone regulation. While residual avermectin in water could pose a risk to carp (Cyprinus carpio), it remains unclear whether silybin can alleviate the renal tissue toxicity induced by avermectin in this species. In current study, we developed a model of long-term exposure of carp to avermectin to investigate the potential protective effect of silybin against avermectin-induced nephrotoxicity. The results indicated that avermectin induced renal inflammation, oxidative stress, ferroptosis, and autophagy in carp. Silybin suppressed the mRNA transcript levels of pro-inflammatory factors, increased catalase (CAT) activity, reduced glutathione (GSH) activity, diminished reactive oxygen species (ROS) accumulation in renal tissues, and promoted the activation of the Nrf2-Keap1 signaling pathway. Furthermore, the transcript levels of ferroptosis-associated proteins, including gpx4 and slc7a11, were significantly reduced, while those of cox2, ftl, and ncoa4 were elevated. The transcript levels of autophagy-related genes, including p62 and atg5, were also regulated. Network pharmacological analysis revealed that silybin inhibited ROS accumulation and mitigated avermectin-induced renal inflammation, oxidative stress, ferroptosis, and autophagy in carp through the involvement of PPAR-γ. Silybin exerted its anti-inflammatory effect through the NF-κB pathway and antioxidant effect through the Nrf2-Keap1 pathway, induced renal cell iron efflux through the SLC7A11/GSH/GPX4, and suppressed autophagy initiation via the PI3K/AKT pathway. This study provides evidence of the protective effect of silybin against avermectin-induced nephrotoxicity in carp, highlighting its potential as a therapeutic agent to alleviate the adverse effects of avermectin exposure in fish.

Effects of Hydrogen-Rich Water on Postharvest Physiology in Scales of Lanzhou Lily during Storage

Hydrogen gas (H2) is considered as a signaling molecule and plays multiple roles in plant growth. However, the effect of H2 on postharvest physiology in lily scales during storage has not been reported. In this study, the regulatory roles of hydrogen-rich water (HRW, a H2 donor, a concentration of 0.45 mM for 100% HRW) in water status, ion balance, and nutrients in Lanzhou lily (Lilium davidii var. unicolor) scales were investigated. The scales were soaked in HRW for 12 d, and sampling was performed every 3 d for a total of 5 times. The results show that HRW (0, 10, 50, and 100%) increased the fresh weight, dry weight, relative water content, and water loss rate in lily scales, with maximum biological response at 50% HRW. Treatment with 50% HRW significantly increased the K+ content and K+/Na+ ratio in lily scales and decreased Na+ content. The Na+ K+-ATPase, and PM H+-ATPase activities were also increased by 50% HRW treatment. Meanwhile, 50% HRW up-regulated the expression of AKT1 and HA3 genes and down-regulated the expression of NHX2 and SOS1 genes. In addition, 50% HRW treatment significantly increased the expression level of PIP1;5, PIP2A, TIP1;3, and TIP2;2 genes. Treatment with 50% HRW significantly increased the content of water-soluble carbohydrate, sucrose, glucose, and fructose in lily scales, and decreased the content of starch. In addition, 50% HRW treatment significantly increased the activity of α-amylase, β-amylase, total amylase, sucrose synthase, and sucrose phosphate synthase. Collectively, H2 might enhance the water retention capacity and nutrient content in lily scales by maintaining ion balance, regulating aquaporin, and increasing sugar-metabolizing enzyme activity, thereby prolonging the storage period of postharvest scales of Lanzhou lily.

Deciphering salt tolerance in tetraploid honeysuckle (Lonicera japonica Thunb.) from ion homeostasis, water balance and antioxidant defense

Polyploid plants are usually salt tolerant, but the underlying mechanisms remain fragmental. This study aimed to dissect salt resistance of tetraploid honeysuckle (Lonicera japonica Thunb.) from ion balance, osmotic adjustment and antioxidant defense by contrasting with its autodiploid through pot experiments. Less salt-induced reduction in leaf and root biomass confirmed higher tolerance in tetraploid honeysuckle, and moreover, its greater stability of photosynthetic apparatus was verified by mild influence on delayed chlorophyll fluorescence transients. Compared with the diploid, greater root Na+ exclusion helped alleviate salt-induced decrease in leaf K+/Na+ for maintaining ion balance in tetraploid honeysuckle, and relied on Na+/H+ antiporter activity, because their difference of root Na+ exclusion disappeared after applying a specific inhibitor of Na+/H+ antiporter. Lower reduction in leaf relative water content suggested higher tolerance to osmotic pressure in tetraploid honeysuckle under salt stress, which hardly resulted from osmotic adjustment given the similar decrease extent of leaf osmotic potential with that in the diploid. In contrast to significant elevated leaf lipid peroxidation and superoxide dismutase and ascorbate peroxidase activities in the diploid, no obvious changes in them suggested that tetraploid honeysuckle never suffered salt-induced oxidative stress. According to more accumulated leaf chlorogenic acid and phenolics and greater elevated leaf phenylalanine ammonia-lyase activity and transcription, leaf phenolic synthesis was enhanced greater in tetraploid honeysuckle upon salt stress, which might serve to prevent oxidative threat by consuming reducing power. In conclusion, polyploidy enhanced salt tolerance in honeysuckle by maintaining ion homeostasis and water balance and preventing oxidative stress.

The apple Argonaute gene MdAGO1 modulates salt tolerance

Salinity is a significant environmental challenge that detrimentally affects the yield and quality of plants. The Argonaute (AGO) family proteins are core effectors of RNAi pathways in eukaryotes. Different AGOs bind different types of sRNAs and participate in different silencing pathways and physiological processes. The Argonaute1 (AGO1) protein binds microRNAs and post-transcriptionally inhibits gene expression in the cytoplasm. In addition, AGO1 directly binds to the promoter region of genes to promote transcription in the stress responses. In this study, we isolated the AGO family gene MdAGO1 from apple (Malus domestica). MdAGO1 encodes a protein located in the nucleus and cytoplasm. MdAGO1 expression was significantly induced by salt stress. We employed MdAGO1-RNAi transgenic apple plants, MdAGO1 overexpressing transgenic apple calli, and Arabidopsis thaliana to investigate the role of MdAGO1 in salt stress. We exposed all of the genotypes to salt stress and showed that MdAGO1 played a role in scavenging reactive oxygen species, maintaining ion balance, and increasing the accumulation of polyamines in the plants under salt stress. In addition, the MdAGO1-RNAi apple lines exhibited low photosynthetic capacity under salt stress. Taken together, these results reveal that MdAGO1 positively regulates apple salt tolerance.

Cancer as a Channelopathy-Appreciation of Complimentary Pathways Provides a Different Perspective for Developing Treatments.

Simple SummaryWhile improvements in technology have improved our ability to treat many forms of cancer when diagnosed at an early stage of the disease, the ability to improve survival and quality of life for patients with late stage disease has been limited, largely due to the ability of cancer cells to evade destruction when treatments block preferred paths for survival. Here, we review the role that ions and ion channels play in normal cell function, the development of disease and their role in the life and death of a cell. It is hoped that viewing cancer from the perspective of altered ion channel expression and ion balance may provide a novel approach for developing more effective treatments for this devastating disease.Life depends upon the ability of cells to evaluate and adapt to a constantly changing environment and to maintain internal stability to allow essential biochemical reactions to occur. Ions and ion channels play a crucial role in this process and are essential for survival. Alterations in the expression of the transmembrane proteins responsible for maintaining ion balance that occur as a result of mutations in the genetic code or in response to iatrogenically induced changes in the extracellular environment is a characteristic feature of oncogenesis and identifies cancer as one of a constellation of diseases known as channelopathies. The classification of cancer as a channelopathy provides a different perspective for viewing the disease. Potentially, it may expand opportunities for developing novel ways to affect or reverse the deleterious changes that underlie establishing and sustaining disease and developing tolerance to therapeutic attempts at treatment. The role of ions and ion channels and their interactions in the cell’s ability to maintain ionic balance, homeostasis, and survival are reviewed and possible approaches that mitigate gain or loss of ion channel function to contribute to new or enhance existing cancer therapies are discussed.

Dietary salt supplementation adversely affects thermal acclimation responses of flight ability in Drosophila melanogaster

Cold acclimation may enhance low temperature flight ability, and salt loading can alter an insects’ cold tolerance by affecting their ability to maintain ion balance in the cold. Presently however, it remains unclear if dietary salt impacts thermal acclimation of flight ability in insects. Here, we examined the effect of a combination of dietary salt loading (either NaCl or KCl) and low temperature exposure on the flight ability of Drosophila melanogaster at low (15 °C) and benign (optimal, 22 °C) temperatures. Additionally, we determined whether dietary salt supplementation translates into increased K+ and Na+ levels in the bodies of D. melanogaster. Lastly, we determined whether salt supplementation impacts body mass and wing morphology, to ascertain whether any changes in flight ability were potentially driven by flight-related morphometric variation. In control flies, we find that cold acclimation enhances low temperature flight ability over non-acclimated flies confirming the beneficial acclimation hypothesis. By contrast, flies supplemented with KCl that were cold acclimated and tested at a cold temperature had the lowest flight ability, suggesting that excess dietary KCl during development negates the beneficial cold acclimation process that would have otherwise taken place. Overall, the NaCl-supplemented flies and the control group had the greatest flight ability, whilst those fed a KCl-supplemented diet had the lowest. Dietary salt supplementation translated into increased Na+ and K+ concentration in the body tissues of flies, confirming that dietary shifts are reflected in changes in body composition and are not simply regulated out of the body by homeostasis over the course of development. Flies fed with a KCl-supplemented diet tended to be larger with larger wings, whilst those reared on the control or NaCl-supplemented diet were smaller with smaller wings. Additionally, the flies with greater flight ability tended to be smaller and have lower wing loading. In conclusion, dietary salts affected wing morphology as well as ion balance, and dietary KCl seemed to have a detrimental effect on cold acclimation responses of flight ability in D. melanogaster.

Exogenous Melatonin Promotes the Salt Tolerance by Removing Active Oxygen and Maintaining Ion Balance in Wheat (Triticum aestivum L.).

Melatonin (MT) is a small molecule indole hormone that plays an important role in the regulation of biological processes and abiotic stress resistance. Previous studies have confirmed that MT promotes the normal development of plants under stress by mediating physiological regulation mechanisms. However, the physiological mechanism of exogenous MT regulating seed germination and seedling growth of wheat under salt stress is still unclear. In this study, NaCl stress decreased germination rate and inhibited seedling growth of wheat, but shoot length, root length, and plant weight of SM15 did not change significantly. The addition of 300 μM MT in the cultivation solution directly promoted the germination rate of SM15 and ZM18, and lateral root production, but decreased the germination rate of JM22 and inhibited the length of germ and radicle of three varieties under salt stress. For wheat seedling, application of MT could increase proline content, soluble protein, soluble sugar, Ca2+ content, and vital amino acid content in leaves to keep high water content, low level of H2O2 content, and low [K+]/[Na+] ratio. MT increased root vigor and [K+]/[Na+] ratio and decreased H2O2 content in root induced by salt stress. In conclusion, MT enhanced salt tolerance in wheat seeds and seedlings by regulating the synthesis of soluble protein and sugar, ion compartmentation in roots and leaves, enhancement of enzymatic systems, and changes in amino acid levels. Salt resistance varied with different varieties under the same environmental condition. SM15 was a higher salt-resistant variety and JM22 was a salt-sensitive one. In wheat production, the application of exogenous MT should consider the differences among varieties of wheat during the sowing and seedling stages.

The Full-Length Transcriptome Sequencing and Identification of Na+/H+ Antiporter Genes in Halophyte Nitraria tangutorum Bobrov.

Nitraria tangutorum Bobrov is a halophyte that is resistant to salt and alkali and is widely distributed in northwestern China. However, its genome has not been sequenced, thereby limiting studies on this particular species. For species without a reference genome, the full-length transcriptome is a convenient and rapid way to obtain reference gene information. To better study N. tangutorum, we used PacBio single-molecule real-time technology to perform full-length transcriptome analysis of this halophyte. In this study, a total of 21.83 Gb of data were obtained, and 198,300 transcripts, 51,875 SSRs (simple sequence repeats), 55,574 CDS (coding sequence), and 74,913 lncRNAs (long non-coding RNA) were identified. In addition, using this full-length transcriptome, we identified the key Na+/H+ antiporter (NHX) genes that maintain ion balance in plants and found that these are induced to express under salt stress. The results indicate that the full-length transcriptome of N. tangutorum can be used as a database and be utilized in elucidating the salt tolerance mechanism of N. tangutorum.

Thermal acclimation alters Na+/K+-ATPase activity in a tissue-specific manner in Drosophila melanogaster

Insects, like the model species Drosophila melanogaster, lose neuromuscular function and enter a state of paralysis (chill coma) at a population- and species-specific low temperature threshold that is decreased by cold acclimation. Entry into this coma is related to a spreading depolarization in the central nervous system, while recovery involves restoration of electrochemical gradients across muscle cell membranes. The Na+/K+-ATPase helps maintain ion balance and membrane potential in both the brain and hemolymph (surrounding muscles), and changes in thermal tolerance traits have therefore been hypothesized to be closely linked to variation in the expression and/or activity of this pump in multiple tissues. Here, we tested this hypothesis by measuring activity and thermal sensitivity of the Na+/K+-ATPase at the tagma-specific level (head, thorax and abdomen) in warm- (25 °C) and cold-acclimated (15 °C) flies by measuring Na+/K+-ATPase activity at 15, 20, and 25 °C. We relate differences in pump activity to differences in chill coma temperature, spreading depolarization temperature, and thermal dependence of muscle cell polarization. Differences in pump activity and thermal sensitivity induced by cold acclimation varied in a tissue-specific manner: While thermal sensitivity remained unchanged, cold-acclimated flies had decreased Na+/K+-ATPase activity in the thorax (mainly muscle) and head (mainly composed of brain). We argue that these changes may assist in maintenance of K+ homeostasis and membrane potential across muscle membranes, and discuss how reduced Na+/K+-ATPase activity in the brain may counterintuitively help insects delay coma onset in the cold.

Arbuscular mycorrhizal fungi (AMF) species and abundance exhibit different effects on saline-alkaline tolerance in Leymus chinensis

ABSTRACT Arbuscular mycorrhizal fungi (AMF) was considered as a biotechnological tool for plant stress tolerance improvement and degraded ecosystem restoration. However, the variations in the effects of AMF species and abundance on plant performance under stress condition have to be still investigated. The study was conducted to evaluate the mechanisms of five AMF species, single or mixture, on Leymus chinensis stress tolerance along a saline-alkaline gradient. The results showed that AMF enhanced plant stress tolerance by promoting plant growth, enhancing nutrient absorption, maintaining ion balance, and improving photosynthetic efficiency. Funneliformis mosseae, Rhizophagus intraradices and the mixture treatments had more beneficial effects than Diversispora versiformis and Acaulospora scrobiculata inoculations. Plant grown under high stress level exhibited more benefits from AMF symbiosis. Our study suggests that not only presence of AMF, but also the species and abundance should be considered to reveal the exact effects of AMF on plant saline-alkaline tolerance and degraded grassland restoration.

An impressive capacity for cold tolerance plasticity protects against ionoregulatory collapse in the disease vector, Aedes aegypti

The mosquito Aedes aegypti is largely confined to tropical and subtropical regions, but its range has recently been spreading to colder climates. As insect biogeography is tied to environmental temperature, understanding the limits of A. aegypti thermal tolerance and their capacity for phenotypic plasticity is important in predicting the spread of this species. In this study, we report on the chill coma onset (CCO) and recovery time (CCRT), as well as low-temperature survival phenotypes of larvae and adults of A. aegypti that developed or were acclimated to 15°C (cold) or 25°C (warm). Cold acclimation did not affect CCO temperatures of larvae but substantially reduced CCO in adults. Temperature and the duration of exposure both affected CCRT, and cold acclimation strongly mitigated these effects and increased rates of survival following prolonged chilling. Female adults were far less likely to take a blood meal when cold acclimated, and exposing females to blood (without feeding) attenuated some of the beneficial effects of cold acclimation on CCRT. Lastly, larvae suffered from haemolymph hyperkalaemia when chilled, but cold acclimation attenuated the imbalance. Our results demonstrate that A. aegypti larvae and adults have the capacity to acclimate to low temperatures, and do so at least in part by better maintaining ion balance in the cold. This ability for cold acclimation may facilitate the spread of this species to higher latitudes, particularly in an era of climate change.

Anti-diuretic activity of a CAPA neuropeptide can compromise Drosophila chill tolerance.

For insects, chilling injuries that occur in the absence of freezing are often related to a systemic loss of ion and water balance that leads to extracellular hyperkalemia, cell depolarization and the triggering of apoptotic signalling cascades. The ability of insect ionoregulatory organs (e.g. the Malpighian tubules) to maintain ion balance in the cold has been linked to improved chill tolerance, and many neuroendocrine factors are known to influence ion transport rates of these organs. Injection of micromolar doses of CAPA (an insect neuropeptide) have been previously demonstrated to improve Drosophila cold tolerance, but the mechanisms through which it impacts chill tolerance are unclear, and low doses of CAPA have been previously demonstrated to cause anti-diuresis in insects, including dipterans. Here, we provide evidence that low (femtomolar) and high (micromolar) doses of CAPA impair and improve chill tolerance, respectively, via two different effects on Malpighian tubule ion and water transport. While low doses of CAPA are anti-diuretic, reduce tubule K+ clearance rates and reduce chill tolerance, high doses facilitate K+ clearance from the haemolymph and increase chill tolerance. By quantifying CAPA peptide levels in the central nervous system, we estimated the maximum achievable hormonal titres of CAPA and found further evidence that CAPA may function as an anti-diuretic hormone in Drosophila melanogaster We provide the first evidence of a neuropeptide that can negatively affect cold tolerance in an insect and further evidence of CAPA functioning as an anti-diuretic peptide in this ubiquitous insect model.

Solid-State Electrochemical Bidirectional Alkali Vapor Source for Cold Atom Microsystems

Cold atom microsystems have the potential to bring the precision measurement capabilities of cold atom clocks, gyroscopes, and accelerometers to portable systems and platforms (1). Trapping cold atoms in a vapor cell requires controlling alkali vapor pressure, which is a function of temperature. Using temperature control to control alkali vapor pressure is common in the lab, but requires too much power for portable microsystems. Techniques such as light-induced atomic desorption, pulsed alkali dispensers, and double MOT chambers have also been used to control alkali vapor density in the lab, but none is rapid, bidirectional, low-power, and miniaturizable as needed for portable cold atom microsystems. Solid ion conductors have been used with widely spaced Pt electrodes as alkali sources, but operate at high voltages (≥50V) and elevated temperatures (≥120°C) (2), thus requiring more power that allowable for portable microsystems applications. We present a low-power bidirectional alkali vapor source based on solid-state electrochemistry. The device comprises a solid electrolyte, beta”-alumina, in between two electrodes. One electrode contacts the alkali vapor inside the vapor cell and consists of a uniform 10nm glassy carbon layer covered with widely spaced Pt lines. The other electrode, which serves as a solid-state alkali reservoir, consists of widely space Pt lines and graphite particles. The thin glassy carbon layer getters rubidium until it becomes saturated. When a positive voltage is applied across the device electrodes, alkali atoms in the glassy carbon layer are oxidized and alkali ions transport into the solid electrolyte. This reduces the rubidium concentration in the glassy carbon and, rubidium vapor gettering resumes, causes rubidium vapor pressure reduction. Alkali ions are reduced at the other electrode and alkali atoms are intercalated in the graphite in the solid state alkali reservoir to maintain ion balance in the solid electrolyte. When a negative voltage is applied the process reverses. Alkali ions are reduced at the glassy carbon electrode, thus quickly saturating the glassy carbon with alkali atoms to stop rubidium gettering and further providing additional rubidium to evaporate and increase the rubidium vapor pressure in the vapor cell. Reversible actuation with this device has been demonstrated with voltages as low as 5 V and peak power as low as 3.4 mW. Furthermore, we will present the use of this device in a feedback loop to control Rb vapor density. The ability to electrically control alkali vapor pressure at low power is an enabling advance for cold atom microsystems. This material is based upon work supported by the Defense Advanced Research Projects Agency (DARPA) and Space and Naval Warfare Systems Center Pacific (SSC Pacific) under Contract No. N66001-15-C-4027. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of DARPA or SSC Pacific. 1. J. Kitching, S. Knappe and E. A. Donley, IEEE Sensors J, 11, 1749 (2011). 2. J. J. Bernstein, A. Whale, J. Brown, C. Johnson, E. Cook, L. Calvez, X. Zhang and S. W. Martin, in Solid-State Sensors, Actuators and Microsystems Workshop, p. 180, Hilton Head Island, South Carolina (2016).

Corticosteroid responses of snakes to toxins from toads (bufadienolides) and plants (cardenolides) reflect differences in dietary specializations

Toads are chemically defended by cardiotonic steroids known as bufadienolides. Resistance to the acute effects of bufadienolides in snakes that prey on toads is conferred by target-site insensitivity of the toxin’s target enzyme, the Na+/K+-ATPase. Previous studies have focused largely on the molecular mechanisms of resistance but have not investigated the physiological mechanisms or consequences of exposure to the toxins. Adrenal enlargement in snakes often is associated with specialization on a diet of toads. These endocrine glands are partly composed of interrenal tissue, which produces the corticosteroids corticosterone and aldosterone. Corticosterone is the main hormone released in response to stress in reptiles, and aldosterone plays an important role in maintaining ion balance through upregulation of Na+/K+-ATPase. We tested the endocrine response of select species of snakes to acute cardiotonic steroid exposure by measuring circulating aldosterone and corticosterone concentrations. We found that Rhabdophis tigrinus, which specializes on a diet of toads, responds with lower corticosterone and higher aldosterone compared to other species that exhibit target-site resistance to the toxins but do not specialize on toads. We also found differences between sexes in R. tigrinus, with males generally responding with higher corticosterone and aldosterone than females. This study provides evidence of physiological adaptations, beyond target-site resistance, associated with tolerance of bufadienolides in a specialized toad-eating snake.

Zinc as diagnostic marker of cancers

Background Zinc is a micronutrient which is essential for human health, playing a role as a cofactor of enzymes such as dehydrogenases, peptidases and component of zinc finger domains. In organism zinc is involved in metabolic pathways, immune processes, maintaining ion balance between other elements. Recently, it has been reported that zinc may play role in chemoprevention, and its level may be associated with occurrence of cancers.

Concurrent effects of cold and hyperkalaemia cause insect chilling injury.

Chilling injury and death are the ultimate consequence of low temperature exposure for chill susceptible insects, and low temperature tolerance is considered one of the most important factors determining insect distribution patterns. The physiological mechanisms that cause chilling injury are unknown, but chronic cold exposure that causes injury is consistently associated with elevated extracellular [K(+)], and cold tolerant insects possess a greater capacity to maintain ion balance at low temperatures. Here, we use the muscle tissue of the migratory locust (Locusta migratoria) to examine whether chill injury occurs during cold exposure or following return to benign temperature and we specifically examine if elevated extracellular [K(+)], low temperature, or a combination thereof causes cell death. We find that in vivo chill injury occurs during the cold exposure (when extracellular [K(+)] is high) and that there is limited capacity for repair immediately following the cold stress. Further, we demonstrate that that high extracellular [K(+)] causes cell death in situ, but only when experienced at low temperatures. These findings strongly suggest that that the ability to maintain ion (particularly K(+)) balance is critical to insect low temperature survival, and highlight novel routes of study in the mechanisms regulating cell death in insects in the cold.

海岸不同生态断带植物根叶抗逆生理变化与其Na+含量的关系

PDF HTML阅读 XML下载 导出引用 引用提醒 海岸不同生态断带植物根叶抗逆生理变化与其Na+含量的关系 DOI: 10.5846/stxb201310032406 作者: 作者单位: 鲁东大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家973课题(2009CB421303);烟台市科技局资助(2013-2H351) The relationship between concentrations of Na+ and changes of physiological response to salt in the leaves and roots of plants Author: Affiliation: Ludong University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以烟台海岸生态断带滨麦(Leymus mollis)和肾叶打碗花(Calystegia soldanella)为材料,在远离高潮线不同位置上取土样和植物材料,通过测定土壤Na+和两植物根叶Na+含量、丙二醛(MDA)含量、抗氧化酶(SOD、POD、CAT)活性和渗透调节物含量,以揭示滨麦和肾叶打碗花根叶中Na+在其适应海岸盐环境中的生理调控机制。结果表明,在高潮线土壤Na+含量最高,滨麦根叶Na+含量较高,两植物根叶中MDA和水分含量、抗氧化酶活力均较低,但渗透调节物含量均较高。随远离高潮线土壤Na+含量下降,滨麦根叶Na+含量下降,而肾叶打碗花根中Na+含量上升,其根叶Na+含量较滨麦分别高637%和319%。同时两植物根叶MDA含量、叶片含水量增加;两植物根中POD和SOD活力增加;两植物根叶可溶性糖和脯氨酸含量下降。但不同生态断带滨麦叶片平均含水量相对较低, MDA含量、POD和CAT和SOD活力、脯氨酸和可溶性糖含量相对较高。在盐土环境中滨麦通过降低Na+的吸收和提高抗氧化酶活力和有机渗透调节物含量维持氧自由基代谢平衡和水分平衡。而肾叶打碗花是泌盐植物,在不同生态断带其叶片Na+含量、平均含水量相对较高,叶MDA含量、POD和CAT活力、脯氨酸和可溶性糖含量均相对较低。泌盐植物的肾叶打碗花依赖根叶中积累的Na+作为无机渗透调节剂维护其离子平衡和水分平衡及正常生长。因此,积累在根叶中的Na+离子既作为无机渗透调节剂维护细胞离子平衡和水分平衡,又引发细胞生理干旱促进有机渗透调节物合成;另外还作为氧自由基诱发剂促使活性氧自由基(ROS)积累,通过积累的ROS激活抗氧化保护酶系统抑制膜脂过氧化、维护氧自由基代谢平衡。海岸沙地土壤中高浓度Na+是海滨滨麦和肾叶打碗花能长期在盐土环境中生存的依靠元素,其对植物的生理调控作用可能是滨麦和肾叶打碗花适应盐土生存的重要生理适应机理。 Abstract:The dominant species of the halophytes Leymus mollis(dune grass) and Calystegia soldanella (beach bindweed) grown in the coastal dunes of the coast of Yantai, China were chosen as materials for this study. Soil and plant materials were sampled from the high tide line, and 10, 20, 30, 40, and 50 metres off the high tide line of the coast. Na+ concentrations, activities of the antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and malondialdehyde (MDA), proline, soluble protein, and sugar contents in the roots and leaves of L. mollis and C. soldanella were determined to understand the role that Na+ accumulation in the roots and leaves played in the physiological adaption to saline environments. Na+ concentration in the soil was highest at high tide line, and declined with distance, with the sharpest decrease between the high tide line and 20 m further inland. L. mollis and C. soldanella both grew between 10 m and 20 m off the high tide line and further inland. At distances close to the high tide line, the roots and leaves of L. mollis had higher Na+ concentrations than did those of C. soldanella;both species had low contents of MDA and water and lower activities of antioxidant enzymes but higher concentrations of the osmoregulatory substances in leaves and roots.Farther from the high tide line, Na+ concentration also increased in the roots of C. soldanella; at 50 m, Na+ was 637% higher in roots and 319% higher in leaves than in those tissues in L. mollis. Far away from the high tide line, the contents of water and MDA increased in the leaves and roots of both plants; the activities of POD and SOD increased in the roots; and the contents of soluble sugar and proline decreased in the roots of both plants. However, at different distances from high tide, L. mollis had lower average water content, higher contents of MDA, proline, and soluble sugar, and higher POD, CAT, and SOD activity. At the saline seashore soil, L. mollis maintained free radical metabolic balance and water balance by controlling Na+ uptake and increasing the activity of antioxidant enzymes and the content of organic osmoregulatory substances. However, C. soldanella is a salt-secreting halophyte with higher Na+ and average water content in its leaves and roots, lower MDA content, activities of POD and CAT, and lower contents of proline and soluble sugar on different locations away from high tide, which indicated that the Na+ accumulated in the leaves and roots of C. soldanella played a very importance role in maintaining ion balance. Na+ accumulated in the roots and leaves of L. mollis and C. soldanella can induce the accumulation of oxygen free radicals to activate the antioxidant enzyme system which in turn would inhibit lipid peroxidation to maintain the balance of oxygen free radical metabolism. Na+ accumulated in the roots and leaves of two plants not only can be an inorganic osmotic adjustment substance to maintain cellular water balance, but plants also can increase organic osmotic adjustment substances such as proline and soluble sugars to maintain water balance. Results imply that Na+ in the leaves and roots of both plants plays a very important role in physiological regulation of the balance of oxygen free radical metabolism and water balance, allowing these two plants to survive seashore saline conditions. 参考文献 相似文献 引证文献

Cholesterol inhibits ROMK channels by holding PI(4,5)P2 in microvilli (1181.17)

The kidney plays an important role in maintaining ion balance in the blood. K+ balance is tightly regulated by a K+ channel called ROMK1. We used cultured mouse cortical collecting duct principal cells (mpkCCDc14 line) to determine how ROMK1 is regulated by cholesterol. Previous studies suggest that cholesterol inhibits ROMK channels via a direct mechanism. Surprisingly, our data demonstrate that ROMK1 channels are not located in cholesterol‐rich lipid rafts in cultured CCD cells. Patch‐clamp data demonstrated that a small‐conductance K+ (ROMK1) channel in mpkCCDc14 cells was inhibited by cholesterol and activated by extraction of cholesterol with methyl‐beta‐cyclodextrin (MbetaCD). However, confocal microscopy data showed that ROMK1 was not in the microvilli where cholesterol‐rich lipid rafts are located, but in the planar region of the apical membrane of mpkCCDc14 cells, and that phosphatidylinositol‐4,5‐bisphosphate (PI(4,5)P2), a well‐known activator of ROMK channels, was found only in the microvilli under resting conditions. Interestingly, after cholesterol synthesis was inhibited by lovastatin, PI(4,5)P2 diffused into planar region with a consequence of activation of ROMK channels. Activation of ROMK1 channels by MbetaCD was reversed by addition of exogenous cholesterol, but the activation did not occur when PI(4,5)P2 was sequestered with its antibody. These results suggest that cholesterol inhibits ROMK1 channels, at least in part, by limiting PI(4,5)P2 diffusion from microvilli to planar region of the renal CCD cell apical membrane. Since we have reported that cyclosporine A (CsA), an immunosuppressant drug which causes hyperkalemia, can alter the levels of cholesterol in renal epithelial cells, this study provides a basis for researchers to determine the mechanism of CsA‐induced hyperkalemia.Grant Funding Source: supported by NIH 5R01‐DK067110 to HPM and by NSF of China 81130028 to B‐ZS