Maintain Ion Homeostasis Research Articles

The Sweetpotato Voltage-Gated K+ Channel β Subunit, KIbB1, Positively Regulates Low-K+ and High-Salinity Tolerance by Maintaining Ion Homeostasis.

Voltage-gated K+ channel β subunits act as a structural component of Kin channels in different species. The β subunits are not essential to the channel activity but confer different properties through binding the T1 domain or the C-terminal of α subunits. Here, we studied the physiological function of a novel gene, KIbB1, encoding a voltage-gated K+ channel β subunit in sweetpotato. The transcriptional level of this gene was significantly higher in the low-K+-tolerant line than that in the low-K+-sensitive line under K+ deficiency conditions. In Arabidopsis, KIbB1 positively regulated low-K+ tolerance through regulating K+ uptake and translocation. Under high-salinity stress, the growth conditions of transgenic lines were obviously better than wild typr (WT). Enzymatic and non-enzymatic reactive oxygen species (ROS) scavenging were activated in transgenic plants. Accordingly, the malondialdehyde (MDA) content and the accumulation of ROS such as H2O2 and O2− were lower in transgenic lines under salt stress. It was also found that the overexpression of KIbB1 enhanced K+ uptake, but the translocation from root to shoot was not affected under salt stress. This demonstrates that KIbB1 acted as a positive regulator in high-salinity stress resistance through regulating Na+ and K+ uptake to maintain K+/Na+ homeostasis. These results collectively suggest that the mechanisms of KIbB1 in regulating K+ were somewhat different between low-K+ and high-salinity conditions.

Heterologous expression of Arabidopsis SOS3 increases salinity tolerance in Petunia.

Salinity stress is one of the most important rising problems worldwide. It significantly reduces plant growth and development, mainly by provoking excessive uptake of ions such as Na+. The Salt Overly Sensitive (SOS) machinery is a well-known signaling pathway that help plants to maintain ion homeostasis by reducing Na+ accumulation in plant cells. Overexpression of key components of this pathway has been reported to increase salinity stress tolerance in some plant species. In this study, SOS3 cDNA isolated from Arabidopsis seedlings was transferred into the Petunia genome by two common plant transformation methods, Agrobacterium and biolistic gun. Transgene integration and expression in putative lines were evaluated by PCR and RT-PCR techniques. In vitro and greenhouse evaluation of transgenic plants for salt tolerance showed that, compared to the wild type, transgenic plants overexpressing AtSOS3 gene exhibit enhanced salt tolerance in response to high NaCl concentrations. These results not only demonstrate the potential of SOS pathway components to improve salt tolerance in Petunia, but also provide more evidence for functional conservation of the SOS salt tolerance signaling pathway among different plant families.

Endogenous hormones improve the salt tolerance of maize (Zea mays L.) by inducing root architecture and ion balance optimizations

AbstractThe growth and development of maize is affected in a crucial way by the salinity of the soil it grows in. Therefore, if we want to improve the salt tolerance of maize, it is of paramount importance to understand how it responds to salt stress. To explore how maize adapts to a saline environment, we chose one salt‐tolerant maize variety, Jingnongyu 658 (JNY658), and one salt‐sensitive variety, Yunyu7 (YY7), and treated the seedlings of both varieties with a 100 mM NaCl solution. After harvesting them, we analysed the adaptive responses to salt stress with respect to various characteristics of the root architecture and water and nutrient acquisition. We found that when subjected to salt stress, both varieties exhibited a reduction in biomass, root activity, 15N and H218O uptake amount, lateral root branching density, lateral root length, total root length, root surface area and root volume, where the YY7 suffered a greater reduction than the JNY658. Salt stress also induced a decreased absorption of K+, passively promoted the absorption of Na+ and gave rise to an increased Na+/K+ ratio in the roots of both varieties. It should be noted that JNY658 exposed to salt stress developed a lower Na+/K+ ratio than YY7. Compared with the control group, the expression of ZmSOS1, ZmSOS2 and ZmNHX genes in the roots of JNY658 subjected to salt stress was significantly upregulated, which enabled them to maintain a lower Na+ content. In both varieties, the salicylic acid (SA) and gibberellin19 acid (GA19) content increased significantly, but the auxin (IAA), jasmonic acid (JA) and trans‐zeatin (TZ) content was reduced. In addition, JNY658 in salt stress significantly increased their abscisic acid (ABA) content, due to the increased expression of its key biosynthesis genes, NCED. Compared with JNY658, the reductions in IAA, JA and TZ content in YY7 were greater, while the increases in ABA and SA content were smaller. The varieties in the ABA, JA, SA and IAA of roots subjected to salt stress significantly or extremely significantly correlated with the lateral root branching density, lateral root length, root surface area, Na+ content, K+ content and Na+/K+ ratio. We conclude that the salt‐tolerant maize variety mitigated the toxic effect of salinity on maize root growth and development by regulating the hormone content and enhancing its expression of stress‐responsive genes while maintaining ion homeostasis and promoting water and nutrient acquisition, which ultimately resulted in a less pronounced decrease in plant biomass.

Elucidating the role of adenine nucleotide transporter in mitochondrial swelling: an experimental and computational approaches

Mitochondria produce over 90% of cellular ATP and actively participate in maintaining ion homeostasis, redox status, lipid metabolism, and cell growth. Changes in the matrix volume of mitochondria affect their functional and structural integrity. Modest volume increases associated with modulation of the inner mitochondrial membrane can activate electron transfer chain and oxidative phosphorylation, whereas excessive swelling impairs structural organization of the membrane and initiate mitochondria‐mediated cell death mechanisms. Therefore, clarifying the precise mechanisms of excessive mitochondrial swelling is important for regulation of mitochondria‐mediated cell death pathways in response to energy and oxidative stresses. Opening of non‐selective mitochondrial permeability transition pores (mPTP) is the primary cause of excessive matrix swelling. The molecular identity remains unknown and recent studies suggest the existence of two or more types of mPTP that can be composed of different protein(s). The adenine nucleotide translocator (ANT) and FOF1‐ATP synthase were proposed to be potential mPTP core components that can act together or independently each other. Here, we elucidated the role of ANT in mPTP opening by applying both experimental and computational approaches. mPTP opening was evaluated in cardiac mitochondria that were exposed to moderate and high Ca2+ concentrations in the absence and presence of respiratory substrates and ADP. We developed a detailed model of the ANT transport mechanism including the matrix (ANTM), cytosolic (ANTC), and pore (ANTP) states of the transporter that was able to simulate our experimental data. In addition, we corroborated and simulated our ANT model based on previous ANT kinetics data. The model was successful not only in simulating ANT pore state transition, but also explained the potential role of ANT in mPTP opening in cardiac mitochondria.

Ion transporters and their regulatory signal transduction mechanisms for salinity tolerance in plants.

Soil salinity is one of the most serious threats to plant growth and productivity. Due to global climate change, burgeoning population and shrinking arable land, there is an urgent need to develop crops with minimum reduction in yield when cultivated in salt-affected areas. Salinity stress imposes osmotic stress as well as ion toxicity, which impairs major plant processes such as photosynthesis, cellular metabolism, and plant nutrition. One of the major effects of salinity stress in plants includes the disturbance of ion homeostasis in various tissues. In the present study, we aimed to review the regulation of uptake, transport, storage, efflux, influx, and accumulation of various ions in plants under salinity stress. We have summarized major research advancements towards understanding the ion homeostasis at both cellular and whole-plant level under salinity stress. We have also discussed various factors regulating the function of ion transporters and channels in maintaining ion homeostasis and ionic interactions under salt stress, including plant antioxidative defense, osmo-protection, and osmoregulation. We further elaborated on stress perception at extracellular and intracellular levels, which triggers downstream intracellular-signaling cascade, including secondary messenger molecules generation. Various signaling and signal transduction mechanisms under salinity stress and their role in improving ion homeostasis in plants are also discussed. Taken together, the present review focuses on recent advancements in understanding the regulation and function of different ion channels and transporters under salt stress, which may pave the way for crop improvement.

An Insight into Abiotic Stress and Influx Tolerance Mechanisms in Plants to Cope in Saline Environments.

Simple SummaryThis review focuses on plant growth and development harmed by abiotic stress, primarily salt stress. Salt stress raises the intracellular osmotic pressure, leading to hazardous sodium buildup. Plants react to salt stress signals by regulating ion homeostasis, activating the osmotic stress pathway, modulating plant hormone signaling, and altering cytoskeleton dynamics and cell wall composition. Understanding the processes underlying these physiological and biochemical responses to salt stress could lead to more effective agricultural crop yield measures. In this review, researchers outline recent advances in plant salt stress control. The study of plant salt tolerance processes is essential, both theoretically and practically, to improve agricultural output, produce novel salt-tolerant cultivars, and make full use of saline soil. Based on past research, this paper discusses the adverse effects of salt stress on plants, including photosynthesis suppression, ion homeostasis disturbance, and membrane peroxidation. The authors have also covered the physiological mechanisms of salt tolerance, such as the scavenging of reactive oxygen species and osmotic adjustment. This study further identifies specific salt stress-responsive mechanisms linked to physiological systems. Based on previous studies, this article reviews the current methodologies and techniques for improving plant salt tolerance. Overall, it is hoped that the above-mentioned points will impart helpful background information for future agricultural and crop plant production.Salinity is significant abiotic stress that affects the majority of agricultural, irrigated, and cultivated land. It is an issue of global importance, causing many socio-economic problems. Salt stress mainly occurs due to two factors: (1) soil type and (2) irrigation water. It is a major environmental constraint, limiting crop growth, plant productivity, and agricultural yield. Soil salinity is a major problem that considerably distorts ecological habitats in arid and semi-arid regions. Excess salts in the soil affect plant nutrient uptake and osmotic balance, leading to osmotic and ionic stress. Plant adaptation or tolerance to salinity stress involves complex physiological traits, metabolic pathways, the production of enzymes, compatible solutes, metabolites, and molecular or genetic networks. Different plant species have different salt overly sensitive pathways and high-affinity K+ channel transporters that maintain ion homeostasis. However, little progress has been made in developing salt-tolerant crop varieties using different breeding approaches. This review highlights the interlinking of plant morpho-physiological, molecular, biochemical, and genetic approaches to produce salt-tolerant plant species. Most of the research emphasizes the significance of plant growth-promoting rhizobacteria in protecting plants from biotic and abiotic stressors. Plant growth, survival, and yield can be stabilized by utilizing this knowledge using different breeding and agronomical techniques. This information marks existing research areas and future gaps that require more attention to reveal new salt tolerance determinants in plants—in the future, creating genetically modified plants could help increase crop growth and the toleration of saline environments.

Ion homeostasis in differently adapted populations of Suaeda vera Forssk. ex J.F. Gmel. for phytoremediation of hypersaline soils

Salt-accumulator species are of great interest for the phytoremediation of salt-affected soils to reclaim soil salinization, a major constraints causing germination retardation and growth restriction of plants as well as habitat degradation. Higher biomass production at ECe 23–36 dS m−1 indicated that this species grows better in high to moderate salinity that was linked to osmotic adjustment through higher ion accumulation (Na+, Cl‒, and Ca2+) and organic osmolytes (free amino acids and proline). Plants from highly and moderately saline habitats exhibited broader metaxylem vessels, which was associated with eased conduction of solutes leading to better growth. Leaf anatomical characteristics generally increased with increasing salinity except at the highest ECe 55 dS m−1. The increased leaf lamina thickness contributed to succulence because of increased storage parenchymatous spongy tissues (that can store high amounts of water), water contents and it is a reflection of maintaining ion homeostasis and colonizing hyper-saline soil. Reduced stomatal density and area under high salinity are critical to cope with environmental hazards. Under high salinity, compartmentalization of excessive Na+ and Cl− ions and accumulation of compatible osmolytes are directly related to high degree of salinity tolerance, and hence are useful for phyto-amelioration of salinity-impacted lands.

Mechanistic Insights of Plant Growth Promoting Bacteria Mediated Drought and Salt Stress Tolerance in Plants for Sustainable Agriculture.

Climate change has devastating effects on plant growth and yield. During ontogenesis, plants are subjected to a variety of abiotic stresses, including drought and salinity, affecting the crop loss (20–50%) and making them vulnerable in terms of survival. These stresses lead to the excessive production of reactive oxygen species (ROS) that damage nucleic acid, proteins, and lipids. Plant growth-promoting bacteria (PGPB) have remarkable capabilities in combating drought and salinity stress and improving plant growth, which enhances the crop productivity and contributes to food security. PGPB inoculation under abiotic stresses promotes plant growth through several modes of actions, such as the production of phytohormones, 1-aminocyclopropane-1-carboxylic acid deaminase, exopolysaccharide, siderophore, hydrogen cyanide, extracellular polymeric substances, volatile organic compounds, modulate antioxidants defense machinery, and abscisic acid, thereby preventing oxidative stress. These bacteria also provide osmotic balance; maintain ion homeostasis; and induce drought and salt-responsive genes, metabolic reprogramming, provide transcriptional changes in ion transporter genes, etc. Therefore, in this review, we summarize the effects of PGPB on drought and salinity stress to mitigate its detrimental effects. Furthermore, we also discuss the mechanistic insights of PGPB towards drought and salinity stress tolerance for sustainable agriculture.

Plant Salinity Stress Response and Nano-Enabled Plant Salt Tolerance.

The area of salinized land is gradually expanding cross the globe. Salt stress seriously reduces the yield and quality of crops and endangers food supply to meet the demand of the increased population. The mechanisms underlying nano-enabled plant tolerance were discussed, including (1) maintaining ROS homeostasis, (2) improving plant’s ability to exclude Na+ and to retain K+, (3) improving the production of nitric oxide, (4) increasing α-amylase activities to increase soluble sugar content, and (5) decreasing lipoxygenase activities to reduce membrane oxidative damage. The possible commonly employed mechanisms such as alleviating oxidative stress damage and maintaining ion homeostasis were highlighted. Further, the possible role of phytohormones and the molecular mechanisms in nano-enabled plant salt tolerance were discussed. Overall, this review paper aims to help the researchers from different field such as plant science and nanoscience to better understand possible new approaches to address salinity issues in agriculture.

Thellungiella halophila ST5 improves salt tolerance in cotton

BackgroundSalinity is a major abiotic stress to global agriculture which hampers crop growth and development, and eventually reduces yield. Transgenic technology is an effective and efficient approach to improve crop salt tolerance but depending on the availability of effective genes. We previously isolated Salt Tolerance5 (ThST5) from the halophyte Thellungiella halophila, an ortholog of Arabidopsis SPT4-2 which encodes a transcription elongation factor. However, SPT4-2-confered salt tolerance has not been evaluated in crops yet. Here we report the evaluation of ThST5-conferred salt tolerance in cotton (Gossypium hirsutum L.).ResultsThe ThST5 overexpression transgenic cotton plants displayed enhanced tolerance to salt stress during seed germination and seedling stage compared with wild type. Particularly, the transgenic plants showed improved salinity tolerance as well as yield under saline field conditions. Comparative transcriptomic analysis showed that ThST5 improved salt tolerance of transgenic cotton mainly by maintaining ion homeostasis. In addition, ThST5 also orchestrated the expression of genes encoding antioxidants and salt-responsive transcription factors.ConclusionOur results demonstrate that ThST5 is a promising candidate to improve salt tolerance in cotton.

Methyl jasmonate increases aluminum tolerance in rice by augmenting the antioxidant defense system, maintaining ion homeostasis, and increasing nonprotein thiol compounds.

Aluminum (Al) stress is known as a serious threat to the growth and production of crops in acidic soils. Here, the effects of different concentrations of methyl jasmonate (MJ, 0.5 and 1µM) on rice plants were investigated hydroponically under different concentrations of Al (0.5 and 1mM). Aluminum treatments injured membrane lipids and photosynthetic apparatus by reducing the leaf contents of mineral nutrients and increasing the accumulation of free radicals (hydrogen peroxide, methylglyoxal, and superoxide anion), resulting in reduced growth and biomass of rice. In comparison to control plants, 0.5 and 1μM Al treatments lowered height by 21 and 37% and total dry weight by 24 and 41%, respectively. Exogenously added methyl diminished the inhibitory effects of Al stress on growth and photosynthetic apparatus by restoring ion homeostasis and improving chlorophyll metabolism. The application of MJ, by inducing the activity of antioxidant enzymes and the glyoxalase cycle, lessened the levels of the toxic compounds hydrogen peroxide, methylglyoxal, and superoxide anion and, as a result, dwindled the toxic Al-induced oxidative stress. Methyl jasmonate enhanced the leaf accumulation of nonprotein thiol compounds and improved plant tolerance under Al stress by increasing the activity of enzymes involved in the synthesis of thiol compounds. Methyl jasmonate increased the leaf accumulation of glutathione and phytochelatins in Al-stressed plants by increasing the expression of GSH1, PCS, and ABCC1, which reduced the toxicity of toxic Al accumulated in leaves by sequestering toxic Al in vacuoles. Together, the results revealed that MJ increased the tolerance of rice under Al toxicity by maintaining ion homeostasis, improving the activity of antioxidant enzymes and the glyoxalase system, and increasing the level of non-protein thiol compounds. This research adds to our understanding of how MJ may be used in the future to improve Al stress tolerance in sustainable agriculture.

Polyamine oxidase 3 is involved in salt tolerance at the germination stage in rice

Soil salinity inhibits seed germination and reduces seedling survival rate, resulting in significant yield reductions in crops. Here, we report the identification of a polyamine oxidase, OsPAO3, conferring salt tolerance at the germination stage in rice (Oryza sativa L.), through map-based cloning approach. OsPAO3 is up-regulated under salt stress at the germination stage and highly expressed in various organs. Overexpression of OsPAO3 increases activity of polyamine oxidases, enhancing the polyamine content in seed coleoptiles. Increased polyamine may lead to the enhance of the activity of ROS-scavenging enzymes to eliminate over-accumulated H2O2 and to reduce Na+ content in seed coleoptiles to maintain ion homeostasis and weaken Na+ damage. These changes resulted in stronger salt tolerance at the germination stage in rice. Our findings not only provide a unique gene for breeding new salt-tolerant rice cultivars but also help to elucidate the mechanism of salt tolerance in rice.

Effects of Phytohormone-Producing Rhizobacteria on Casparian Band Formation, Ion Homeostasis and Salt Tolerance of Durum Wheat

Inoculation with plant growth-promoting rhizobacteria can increase plant salt resistance. We aimed to reveal bacterial effects on the formation of apoplastic barriers and hormone concentration in relation to maintaining ion homeostasis and growth of salt-stressed plants. The rhizosphere of a durum wheat variety was inoculated with cytokinin-producing Bacillus subtilis and auxin-producing Pseudomonas mandelii strains. Plant growth, deposition of lignin and suberin and concentrations of sodium, potassium, phosphorus and hormones were studied in the plants exposed to salinity. Accumulation of sodium inhibited plant growth accompanied by a decline in potassium in roots and phosphorus in shoots of the salt-stressed plants. Inoculation with both bacterial strains resulted in faster appearance of Casparian bands in root endodermis and an increased growth of salt-stressed plants. B. subtilis prevented the decline in both potassium and phosphorus concentrations and increased concentration of cytokinins in salt-stressed plants. P. mandelii decreased the level of sodium accumulation and increased the concentration of auxin. Growth promotion was greater in plants inoculated with B. subtilis. Increased ion homeostasis may be related to the capacity of bacteria to accelerate the formation of Casparian bands preventing uncontrolled diffusion of solutes through the apoplast. We discuss the relative impacts of the decline in Na accumulation and maintenance of K and P content for growth improvement of salt-stressed plants and their possible relation to the changes in hormone concentration in plants.

Response of MaHMA2 gene expression and stress tolerance to zinc stress in mulberry (Morus alba L.)

HMA2 (heavy metal ATPase 2) plays a crucial role in extracellular and intracellular Zn2+ transport across biomembranes, maintaining ion homeostasis, and playing an important role in the normal physiological metabolism, growth, and development of plants. In our study, a novel HMA2 gene, named MaHMA2, was isolated and cloned from white mulberry (Morus alba L.). The gene sequence obtained was 1,342 bp long, with an open reading frame of 1,194 bp, encoding a protein of 397 amino acids, with a predicted molecular mass of 42.852 kD and an isoelectric point of 7.53. This protein belonged to the PIB-type ATPase transport protein family. We analyzed the expression of the MaHMA2 gene by quantitative real-time PCR. The results showed that the level of MaHMA2 gene expression decreased to a Zn concentration of 800 mg/kg. Malondialdehyde and proline levels increased and responded to increasing Zn when the MaHMA2 gene was silenced, whereas the activities of peroxidase and superoxide dismutase tended to increase in response to increasing Zn2+ ion stress concentrations but were lower in the gene-silenced plants. These findings suggested that the MaHMA2 gene played an active role in the tolerance response of mulberry to Zn stress.

A proteomic approach to understand the impact of nodulation on salinity stress response in alfalfa (Medicago sativa L.).

Symbiotic nitrogen fixation in legumes is an important source of nitrogen supply in sustainable agriculture. Salinity is a key abiotic stress that negatively affects host plant growth, rhizobium-legume symbiosis and nitrogen fixation. This work investigates how the symbiotic relationship impacts plant response to salinity stress. We assayed the physiological changes and the proteome profile of alfalfa plants with active nodules (NA), inactive nodules (NI) or without nodules (NN) when plants were subjected to salinity stress. Our data suggest that NA plants respond to salinity stress through some unique signalling regulations. NA plants showed upregulation of proteins related to cell wall remodelling and reactive oxygen species scavenging, and downregulation of proteins involved in protein synthesis and degradation. The data also show that NA plants, together with NI plants, upregulated proteins involved in photosynthesis, carbon fixation and respiration, anion transport and plant defence against pathogens. The study suggests that the symbiotic relationship gave the host plant a better capacity to adjust key processes, probably to more efficiently use energy and resources, deal with oxidative stress, and maintain ion homeostasis and health during salinity stress.

Importance of hydrogen sulfide as the molecular basis of heterosis in hybrid Brassica napus: A case study in salinity response

Heterosis or hybrid vigor is a phenomenon that a heterozygote is superior to two parental lines in one or more traits, or even responses against stresses. However, related molecular mechanism is still not fully elucidated. In this paper, we investigated whether hydrogen sulfide (H2S), a universal signaling molecule in both mammals and plants, participates in heterosis. When upon salinity stress, two parents of Brassica napus (NJ4375 and MB1894) were more sensitive to salinity compared to the hybrid (F1, NJ4375×MB1894), evaluated by the improving effects on the reduction in shoot length, root length, fresh weight of root parts, and chlorophyll content. It was further observed that the increased endogenous H2S synthesis was more pronounced in the hybrid than those of two parental lines when stressed with salinity, suggesting the important roles of endogenous H2S. The removal of endogenous H2S by its biosynthesis inhibitor (PAG) and scavenger (HT) could differentially abolish the salinity tolerance observed in the hybrid. Subsequent experiments showed that the hybrid could maintain ion homeostasis by regulating the sodium and potassium transporters, which was confirmed by modulating NHX1, SOS2, AKT1 and HAK5 transcripts. Proline content was also significantly increased and lipid peroxidation was obviously alleviated in the hybrid plants compared to those in both NJ4375 and MB1894. Above responses in hybrid were sensitive to the inhibition of endogenous H2S synthesis or its scavenging. Overall, our results clearly provided the evidence that salt-tolerant heterosis of hybrid might be closely associated with endogenous H2S signaling.

Harnessing an arbuscular mycorrhizal fungus to improve the adaptability of a facultative metallophytic poplar (Populus yunnanensis) to cadmium stress: Physiological and molecular responses

Populus yunnanensis Dode, a facultative metallophytic poplar, exhibits afforestation potential in barren mine tailing areas. However, the interactions and functional roles of arbuscular mycorrhizal fungus (AMF) in P. yunnanensis adaptability to heavy metal stress remain unclear. Physiological and molecular responses of P. yunnanensis plantlets to AMF (Funneliformis mosseae) under cadmium (Cd) stress (50 mg kg−1) were investigated. Results showed attenuation of Cd phytotoxicity effects on cell organelles upon AMF inoculation, which also reduced the Cd concentration in the poplar leaves, stems, and roots. Under Cd stress, AMF-blocking of metal transporter (e.g., Ca2+ channel) activity occurred, decreasing root cell Cd influx by reducing H+ efflux. Bioaugmentation of rhizosphere sediments by AMF to stabilize metals with a decreasing DTPA-extractable Cd also occurred. The AMF inoculation promoted Cd conversion into inactive, less phytotoxic forms, and helped to maintain ion homeostasis and relieve nutritional ion (e.g., Ca, Mg) disorders caused by excessive Cd. Leaf enzyme and non-enzyme antioxidant systems were triggered. Root and leaf physiological response patterns differed. The AMF regulated the poplar functional genes, and nine metal-responsive gene clusters were identified. We suggest that AMF is a functional component of P. yunnanensis phenotype extension, contributing to strong adaptability to unfavorable mine tailings conditions.

Analysis of toxicity effects of delta-9-tetrahydrocannabinol on isolated rat heart mitochondria

Mitochondria have the main roles in myocardial tissue homeostasis, through providing ATP for the vital enzymes in intermediate metabolism, contractile apparatus and maintaining ion homeostasis. Mitochondria-related cardiotoxicity results from the exposure with illicit drugs have previously reported. These illicit drugs interference with processes of normal mitochondrial homeostasis and lead to mitochondrial dysfunction and mitochondrial-related oxidative stress. Cannabis consumption has been shown to cause ventricular tachycardia, to increase the risk of myocardial infarction (MI) and potentially sudden death. Here, we investigated this hypothesis that delta-9-tetrahydrocannabinol (Delta-9-THC) as a main cannabinoid found in cannabis could directly cause mitochondrial dysfunction. Cardiac mitochondria were isolated with mechanical lysis and differential centrifugation form rat heart. The isolated cardiac mitochondria were treated with different concentrations of THC (1, 5, 10, 50, 100 and 500 µM) for 1 hour at 37 °C. Then, succinate dehydrogenase (SDH) activity, mitochondrial swelling, reactive oxygen species (ROS) formation, mitochondrial membrane potential (MMP) collapse and lipid peroxidation were measured in the treated and nontreated isolated cardiac mitochondria. Our observation showed that THC did not cause a deleterious alteration in mitochondrial functions, ROS production, MMP collapse, mitochondrial swelling, oxidative stress and lipid peroxidation in used concentrations (5–100 µM), even in several tests, toxicity showed a decreasing trend. Altogether, the results of the current study showed that THC is not directly toxic in isolated cardiac mitochondria, and even may be helpful in reducing mitochondrial toxicity.

NtCycB2 gene knockout enhances resistance to high salinity stress in Nicotiana tabacum

High salinity-induced Na+ toxicity and osmotic stress in the rhizosphere environment seriously jeopardize and limit plant growth and development and crop productivity. Trichomes are epidermal outgrowths that contribute to plant defense responses against abiotic stresses. Here, we showed that the expression of NtCycB2 gene in wild flue-cured K326, a B-type cyclin involved in the negative regulation of trichomes density, was induced by NaCl stress. Enhanced high salinity-resistance was observed in NtCycB2 knockout (ko) lines with high-density glandular trichomes, whereas it was the opposite in an NtCycB2 overexpression (OE) line with low-density glandular trichomes. NtCycB2 gene knockout reduced cell death, O2− accumulation, and water loss ratio after different concentrations of NaCl treatments, caused by upregulation of superoxide dismutase (SOD), peroxidase (POD), proline (Pro), higher expression levels of ABA-meditated salinity stress responsive genes, and downregulation of malondialdehyde (MDA). Additionally, NtCycB2 gene knockout had a crucial capacity to reduce Na+ content and improve the K+/Na+ ratio for maintaining ion homeostasis with more intact glandular trichomes under NaCl stress. Increased expression levels of Na+ and K+ uptake or transport genes were positively correlated with NaCl resistance. Together, these data suggested that NtCycB2 acted as a negative regulator and conferred high salinity-resistance. High-density glandular trichomes be an important botanical trait to improve plant resistance.

Dynamic changes of phosphatidylinositol and phosphatidylinositol 4-phosphate levels modulate H+-ATPase and Na+/H+ antiporter activities to maintain ion homeostasis in Arabidopsis under salt stress

Plant metabolites are dynamically modified and distributed in response to environmental changes. However, it is poorly understood how metabolic change functions in plant stress responses. Maintaining ion homeostasis under salt stress requires coordinated activation of two types of central regulators: plasma membrane (PM) H+-ATPase and Na+/H+ antiporter. In this study, we used a bioassay-guided isolation approach to identify endogenous small molecules that affect PM H+-ATPase and Na+/H+ antiporter activities and identified phosphatidylinositol (PI), which inhibits PM H+-ATPase activity under non-stress conditions in Arabidopsis by directly binding to the C terminus of the PM H+-ATPase AHA2. Under salt stress, the phosphatidylinositol 4-phosphate-to-phosphatidylinositol (PI4P-to-PI) ratio increased, and PI4P bound and activated the PM Na+/H+ antiporter. PI prefers binding to the inactive form of PM H+-ATPase, while PI4P tends to bind to the active form of the Na+/H+ antiporter. Consistent with this, pis1 mutants, with reduced levels of PI, displayed increased PM H+-ATPase activity and salt stress tolerance, while the pi4kβ1 mutant, with reduced levels of PI4P, displayed reduced PM Na+/H+ antiporter activity and salt stress tolerance. Collectively, our results reveal that the dynamic change between PI and PI4P in response to salt stress in Arabidopsis is crucial for maintaining ion homeostasis to protect plants from unfavorable environmental conditions.