Overexpression of MdATG18a enhances alkaline tolerance and GABA shunt in apple through increased autophagy under alkaline conditions

Abstract Soil alkalization affects apple production in northwest China. Autophagy is a highly conserved degradative protein pathway in eukaryotes. Autophagy in plants can be activated by various abiotic factors. We previously identified the positive role of the autophagy-related gene MdATG18a in drought, nitrogen deficiency and resistance to Diplocarpon mali infection in apple. However, it is still unclear whether ATG18a is related to alkaline stress. In this study, we used hydroponic culture to simulate alkaline stress and found that the overexpression of MdATG18a significantly improved the tolerance of apple to alkaline stress. The overexpression of MdATG18a increased biomass, photosynthetic rate and antioxidant capacity of transgenic plants compared with wild-type plants under alkaline stress. The overexpression of MdATG18a promoted γ-aminobutyric acid (GABA) shunt via an increase in glutamate (GABA precursor) and GABA contents and upregulation of GABA shunt-related genes. In addition, the overexpression of MdATG18a significantly upregulated the expression of other core ATG genes and increased the formation of autophagosomes under alkaline stress. In conclusion, these results suggest that the overexpression of MdATG18a in apple enhances alkaline tolerance and the GABA shunt, which may be owing to the increase in autophagic activity.

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Abscisic Acid Priming Creates Alkaline Tolerance in Alfalfa Seedlings (Medicago sativa L.)

Agriculture ◽

10.3390/agriculture11070608 ◽

2021 ◽

Vol 11 (7) ◽

pp. 608

Author(s):

Tian-Jiao Wei ◽

Ming-Ming Wang ◽

Yang-Yang Jin ◽

Guo-Hui Zhang ◽

Miao Liu ◽

...

Keyword(s):

Abscisic Acid ◽

Molecular Mechanisms ◽

Leaf Damage ◽

Alkaline Stress ◽

Acid Pretreatment ◽

Solution Ph ◽

Expression Of Genes ◽

Alkaline Tolerance ◽

Alkaline Conditions ◽

Medicago Sativa L

Soil alkalization triggers ion toxicity and osmotic and alkaline (high pH) stresses in plants, damaging their growth and productivity. Therefore, we investigated whether priming with abscisic acid (ABA) increases the tolerance of alfalfa seedlings to alkaline stress, and then examined the underlying molecular mechanisms. Alfalfa seedlings were pretreated with ABA (10 μM) for 16 h and then subjected to alkaline stress using a 15 mM Na2CO3 solution (pH 10.87). Compared with the control, ABA pretreatment significantly alleviated leaf damage and improved the fresh weight, water content, and survival rate of alfalfa seedlings under alkaline conditions. Abscisic acid pretreatment reduced accumulation of reactive oxygen species (ROS), increased activities of the antioxidant enzymes superoxide dismutase (SOD) and peroxidase (POD), maintained higher ratios of K+/Na+, Ca2+/Na+, and Mg2+/Na+, and increased accumulation of proline. In addition, ABA upregulated the expression of genes involved in proline biosynthesis (P5CS) and the sequestration of Na+ in vacuoles (NHX1 and AVP) under alkaline conditions. Abscisic acid priming increased tolerance to alkaline stress by maintaining homeostasis of ROS and metal ions and upregulating osmoprotection and the expression of stress tolerance-related genes.

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Characterization of alkaline stress tolerance mechanisms in Lotus forage species modulated by Pantoea eucalypti

10.1101/2020.06.06.138230 ◽

2020 ◽

Author(s):

Maria Paula Campestre ◽

Nazareno Luis Castagno ◽

Cristian Javier Antonelli ◽

Vanina Giselle Maguire ◽

Francisco Jose Escaray ◽

...

Keyword(s):

Considerable Increase ◽

Physiological Responses ◽

Dry Mass ◽

Alkaline Treatment ◽

Alkaline Stress ◽

Tolerance Mechanisms ◽

Alkaline Tolerance ◽

Forage Species ◽

Alkaline Conditions

AbstractThis study was designed to elucidate the physiological responses of three Lotus forage accessions to alkaline stress and the influence of the inoculation of a Pantoea eucalypti endophyte strain on its mitigation. One-month-old diploid accessions of Lotus corniculatus (Lc) and Lotus tenuis (Lt), and the interspecific hybrid LtxLc obtained from these parental accessions, were exposed to alkaline stress (pH 8.2) by the addition of NaHCO3 10 mM to the nutrient solution for 2 weeks. The results indicated that Lt and the LtxLc hybrid are alkaline-tolerant compared to Lc, based on the observation that their dry mass is not reduced under stress, and symptoms of chlorosis do not appear on leaf blades, in contrast to observations of the Lc accession subjected to identical growth and stress conditions. In Lc and LtxLc accessions, the Fe2+ concentration decreased in the aerial part under stress and increased in the roots. Interveinal chlorosis observed in the youngest leaves of Lc during alkaline treatment was accompanied with a higher reduction of Fe2+ levels in shoots and a higher increment of Fe2+ in roots, compared to the other accession. Plant inoculation also tended to acidify the medium under alkalinity, contributing to Fe accumulation in the roots. Moreover, the inoculation caused a considerable increase in Fe2+ content in shoots in all three Lotus forage species under alkaline treatment.Fv/Fm and PIABS were only reduced in Lc under alkaline treatment. Inoculation reverted this effect and improved the ABS/RC and DIo/RC ratios in all three accessions. In addition, under alkaline conditions, Lc dissipated more energy than control plants. Expression of the metal-transporting gene NRAMP1 increased in the inoculated Lc accession under stress, while remaining unmodified in Lt and LtxLc hybrid.Altogether, the results obtained make clear the importance of inoculation with P. eucalypti, which contributed significantly to the mitigation of alkaline stress. Thus, all the results provide useful information for improving alkaline tolerance traits in Lotus forage species and their interspecific hybrids.

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The Lysine 299 Residue Endows the Multisubunit Mrp1 Antiporter with Dominant Roles in Na+Resistance and pH Homeostasis inCorynebacterium glutamicum

Applied and Environmental Microbiology ◽

10.1128/aem.00110-18 ◽

2018 ◽

Vol 84 (10) ◽

Cited By ~ 6

Author(s):

Ning Xu ◽

Yingying Zheng ◽

Xiaochen Wang ◽

Terry A. Krulwich ◽

Yanhe Ma ◽

...

Keyword(s):

Corynebacterium Glutamicum ◽

Expression Patterns ◽

Alkaline Stress ◽

Alkaline Ph ◽

Ph Homeostasis ◽

Conserved Residues ◽

Content Type ◽

Ion Translocation ◽

Alkaline Tolerance ◽

Alkaline Conditions

ABSTRACTCorynebacterium glutamicumis generally regarded as a moderately salt- and alkali-tolerant industrial organism. However, relatively little is known about the molecular mechanisms underlying these specific adaptations. Here, we found that the Mrp1 antiporter played crucial roles in conferring both environmental Na+resistance and alkali tolerance whereas the Mrp2 antiporter was necessary in coping with high-KCl stress at alkaline pH. Furthermore, the Δmrp1Δmrp2double mutant showed the most-severe growth retardation and failed to grow under high-salt or alkaline conditions. Consistent with growth properties, the Na+/H+antiporters ofC. glutamicumwere differentially expressed in response to specific salt or alkaline stress, and an alkaline stimulus particularly induced transcript levels of the Mrp-type antiporters. When the major Mrp1 antiporter was overwhelmed,C. glutamicummight employ alternative coordinate strategies to regulate antiport activities. Site-directed mutagenesis demonstrated that several conserved residues were required for optimal Na+resistance, such as Mrp1A K299, Mrp1C I76, Mrp1A H230, and Mrp1D E136. Moreover, the chromosomal replacement of lysine 299 in the Mrp1A subunit resulted in a higher intracellular Na+level and a more alkaline intracellular pH value, thereby causing a remarkable growth attenuation. Homology modeling of the Mrp1 subcomplex suggested two possible ion translocation pathways, and lysine 299 might exert its effect by affecting the stability and flexibility of the cytoplasm-facing channel in the Mrp1A subunit. Overall, these findings will provide new clues to the understanding of salt-alkali adaptation duringC. glutamicumstress acclimatization.IMPORTANCEThe capacity to adapt to harsh environments is crucial for bacterial survival and product yields, including industrially usefulCorynebacterium glutamicum. AlthoughC. glutamicumexhibits a marked resistance to salt-alkaline stress, the possible mechanism for these adaptations is still unclear. Here, we present the physiological functions and expression patterns ofC. glutamicumputative Na+/H+antiporters and conserved residues of Mrp1 subunits, which respond to different salt and alkaline stresses. We found that the Mrp-type antiporters, particularly the Mrp1 antiporter, played a predominant role in maintaining intracellular nontoxic Na+levels and alkaline pH homeostasis. Loss of the major Mrp1 antiporter had a profound effect on gene expression of other antiporters under salt or alkaline conditions. The lysine 299 residue may play its essential roles in conferring salt and alkaline tolerance by affecting the ion translocation channel of the Mrp1A subunit. These findings will contribute to a better understanding of Na+/H+antiporters in sodium antiport and pH regulation.

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Physiological and transcriptomic analyses reveal novel insights into the cultivar-specific response to alkaline stress in alfalfa (Medicago sativa L.)

10.21203/rs.3.rs-292953/v1 ◽

2021 ◽

Author(s):

Tian-Jiao Wei ◽

Guang Li ◽

Ming-Ming Wang ◽

Yang-Yang Jin ◽

Guo-Hui Zhang ◽

...

Keyword(s):

Medicago Sativa ◽

Chlorophyll Content ◽

Soluble Sugar ◽

Alkaline Treatment ◽

Redox Status ◽

Mapk Signaling ◽

Specific Response ◽

Alkaline Stress ◽

Alkaline Tolerance ◽

Alkaline Conditions

Abstract Key message Candidate pathways for alkaline tolerance in alfalfa seedlings were identified; these included those for homeostasis of ions and redox status, biosynthesis of phenylpropanoids, flavonoids, and amino acids, and MAPK signaling.Abstract Soil alkalization severely limits plant growth and development; however, the mechanisms of alkaline response remain largely unknown. In this study, we performed physiological and transcriptomic analyses using two alfalfa cultivars (Medicago sativa L.) with different sensitivities to alkaline conditions. The chlorophyll content and shoot fresh weight drastically declined in the alkaline-sensitive cultivar Algonquin (AG) following alkaline treatment (0-25 mM Na2CO3 solution), while the alkaline-tolerant cultivar Gongnong NO.1 (GN) maintained relatively stable growth and chlorophyll content. Physiological analysis revealed that compared with AG, GN had higher contents of Ca2+ and Mg2+; the ratios of Ca2+ and Mg2+ to Na+, proline and soluble sugar, and enzyme activities of peroxidase (POD) and catalase (CAT) decreased under the alkaline conditions. Further, transcriptomic analysis identified three categories of alkaline-responsive differentially expressed genes (DEGs) between the two cultivars: 48 genes commonly induced in both the cultivars (CAR), 574 genes from the tolerant cultivar (TAR), and 493 genes from the sensitive cultivar (SAR). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that CAR genes were mostly involved in phenylpropanoid biosynthesis, lipid metabolism, and DNA replication and repair; TAR genes were significantly enriched in metabolic pathways, biosynthesis of secondary metabolites, MAPK signaling pathway, and flavonoid and amino acid biosynthesis; the SAR genes were specifically enriched in vitamin B6 metabolism. Taken together, the results identified candidate pathways associated with genetic variation in response to alkaline stress, providing novel insights into the mechanisms underlying alkaline tolerance in alfalfa.

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Validation of Analytical Methods for Tacrolimus Determination in Poly(ε-caprolactone) Nanocapsules and Identification of Drug Degradation Products

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2021.19500 ◽

2021 ◽

Vol 21 (12) ◽

pp. 5920-5928

Author(s):

Guilherme A. Camargo ◽

Amanda M. Lyra ◽

Fernanda M. Barboza ◽

Barbara C. Fiorin ◽

Flávio L. Beltrame ◽

...

Keyword(s):

Liquid Chromatography ◽

High Performance ◽

Degradation Products ◽

Multiple Reaction Monitoring ◽

Forced Degradation ◽

Alkaline Stress ◽

Drug Degradation ◽

Relative Standard ◽

Polymeric Nanocapsules ◽

Alkaline Conditions

The aim of this paper was to use chromatographic tools for validating an analytical method for the tacrolimus (TAC) determination in polymeric nanocapsules and for identifying the drug degradation products after alkaline stress. A rapid Ultra-High-Performance Liquid Chromatography coupled with photo-diode array (UHPLC-PDA) method was successfully performed using the following chromatographic conditions: the Shimadzu Shim-pack XR-ODS III C18 column (100 mm×2.00 mm, 2.2 μm), the mobile phase consisting of methanol and acidified ultrapure water (89:11 v/v), the flow rate of 0.55 mL·min−1, and the ultraviolet (UV) detection at 235 nm. This method was validated as per International Council for Harmonisation (ICH) guidelines. In addition, a TAC forced degradation assay was carried out after alkaline stress and its degradation products were investigated using Liquid Chromatography coupled tandem mass spectroscopy (LC-MS/MS). The calibration curve was linear in the range of 100.0–300.0 μg·mL−1 (r >0.9999). Accuracy was confirmed by the TAC recovery of 96.55 to 98.19%. Precision (intraday and interday) were demonstrated by relative standard deviation lower than 0.89% and 3.25%, respectively. Selectivity and robustness were also proved. The method developed it was successfully applied to quantify TAC from polymeric nanocapsules, showing a high loading efficiency rate (>96.47%). The main drug degradation product observed in a multiple reaction monitoring (MRM) experiment was m/z 844, confirming the susceptibility of TAC under alkaline conditions; this finding was first time described.

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Physiological and Biochemical Responses of Jerusalem Artichoke Seedlings to Mixed Salt-Alkali Stress Conditions

Notulae Botanicae Horti Agrobotanici Cluj-Napoca ◽

10.15835/nbha43210154 ◽

2015 ◽

Vol 43 (2) ◽

pp. 473-478 ◽

Cited By ~ 2

Author(s):

Shuai SHAO ◽

Mingming QI ◽

Shuang TAO ◽

Jixiang LIN ◽

Yingnan WANG ◽

...

Keyword(s):

Seedling Growth ◽

Jerusalem Artichoke ◽

Soil Salinization ◽

Stress Conditions ◽

Energy Crop ◽

Alkaline Stress ◽

Alkali Stress ◽

Mixed Salt ◽

Effective Utilization ◽

Alkaline Conditions

Soil salinization and alkalization frequently co-occur in the grassland, but little information exists concerning the mixed effects of salt-alkaline stress on plant. Jerusalem artichoke is an economically and ecologically important energy crop and also considered as a salt-tolerant species. In this study, we investigated the effects of 12 mixed salt-alkaline conditions on the seedling growth and responses of Jerusalem artichoke to such conditions. The results showed that the seedling growth decreased with the increasing salinity and pH, and the destructive effects were more markedly under the interactions of highest salinity and pH. The Na+, Mg2+ and Ca2+ concentrations were all increased with the increasing salinity and pH, but the K+ kept stable. The Cl- concentration increased when the treatment without alkali salts, and the NO3â€“ and H2PO4- concentrations were decreased with the increasing salinity. Jerusalem artichoke seedlings enhanced organic acids and proline to supply the shortage of inorganic anions and cope with osmotic stress from the high Na+ concentration. Above results show that the toxicity effects of the interactions of salt stress and alkali stress on plant is much greater than that only salt or alkali stress. A better understanding of the seedlings of Jerusalem artichoke under mixed salt-alkali stress conditions should facilitate the effective utilization of this species under such complex environment in Northeast China.

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Beneficial Effects of Biochar-Based Organic Fertilizer on Nitrogen Assimilation, Antioxidant Capacities, and Photosynthesis of Sugar Beet (Beta vulgaris L.) under Saline-Alkaline Stress

Agronomy ◽

10.3390/agronomy10101562 ◽

2020 ◽

Vol 10 (10) ◽

pp. 1562

Author(s):

Pengfei Zhang ◽

Fangfang Yang ◽

He Zhang ◽

Lei Liu ◽

Xinyu Liu ◽

...

Keyword(s):

Sugar Beet ◽

Nitrogen Assimilation ◽

Organic Fertilizer ◽

Root Activity ◽

Alkaline Stress ◽

Alkaline Soil ◽

Chemical Fertilizers ◽

Alkaline Conditions ◽

Negative Effect ◽

Antioxidant Enzymes Activities

The Songnen Plain, whose climatic conditions are perfectly suited to sugar beet growth, is located in northeastern China. Unfortunately, this region has a lot of saline-alkaline land, which is the most important factor limiting sugar beet production. This study was undertaken to determine whether biochar-based organic fertilizer could alleviate the negative effect of saline-alkaline soil on sugar beet yield and whether such an effect correlated with changes in nitrogen assimilation, antioxidant system, root activity, and photosynthesis. Three treatments were established: Chemical fertilizers were applied to neutral soil (CK), chemical fertilizers were applied to saline-alkaline soil (SA), and biochar-based organic fertilizer was applied to saline-alkaline soil (SA + B). Our results showed that saline-alkaline stress significantly inhibited the nitrogen assimilation and antioxidant enzymes activities in root, root activity, and photosynthesis, thus significantly reducing the yield and sugar content of sugar beet. Under saline-alkaline conditions, the application of biochar-based organic fertilizer improved the activities of nitrogen assimilation enzymes in the root; at the same time, the antioxidant enzymes activities of the root were significantly increased for improving root activity in this treatment. Moreover, the application of biochar-based organic fertilizer could improve the synthesis of photosynthetic pigments, PSII (Photosystem II) activity, stomatal opening, and photosynthesis of sugar beet under saline-alkaline conditions. Hence, the growth and yield of sugar beet were improved by applying biochar-based organic fertilizer to saline-alkaline soil. These results proved the significance of biochar-based organic fertilizer in alleviating the negative effect of saline-alkaline stress on sugar beet. The results obtained in the pot experiment may not be viable in field conditions. Therefore, in the future, we will verify whether biochar-based organic fertilizer could alleviate the adverse effects of saline-alkaline stress on sugar beets yield under field conditions.

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Identification of Quantitative Trait Loci for Alkaline Tolerance at Early Seedling Stage of Japonica Rice Under Alkaline Stress

Acta Agronomica Sinica ◽

10.1016/s1875-2780(08)60062-0 ◽

2009 ◽

Vol 35 (2) ◽

pp. 301-308

Author(s):

Dong-Ling QI ◽

Gui-Zhen GUO ◽

Myung-Chul LEE ◽

Chun-Gang YANG ◽

Jun-Guo ZHANG ◽

...

Keyword(s):

Quantitative Trait Loci ◽

Quantitative Trait ◽

Seedling Stage ◽

Alkaline Stress ◽

Japonica Rice ◽

Alkaline Tolerance ◽

Trait Loci ◽

Early Seedling

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Silicon and salicylic acid confer high-pH stress tolerance in tomato seedlings

Scientific Reports ◽

10.1038/s41598-019-55651-4 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 13

Author(s):

Adil Khan ◽

Muhammad Kamran ◽

Muhammad Imran ◽

Ahmed Al-Harrasi ◽

Ahmed Al-Rawahi ◽

...

Keyword(s):

Salicylic Acid ◽

Oxidative Damage ◽

Stress Tolerance ◽

Alkaline Stress ◽

Alkaline Soil ◽

Antioxidant Defence ◽

High Ph ◽

Tomato Seedlings ◽

Alkaline Conditions ◽

Key Genes

AbstractAlkalinity is a known threat to crop plant growth and production, yet the role of exogenous silicon (Si) and salicylic acid (SA) application has been largely unexplored. Here, we sought to understand the beneficial impacts of Si and SA on tomato seedlings during high-pH (9.0) stress. Results showed that Si- and SA-treated plants displayed higher biomass, chlorophyll contents, relative leaf water and better root system than none-treated plants under alkaline conditions. Both Si and SA counteracted the alkaline stress-induced oxidative damage by lowering the accumulation of reactive oxygen species and lipid peroxidation. The major antioxidant defence enzyme activities were largely stimulated by Si and SA, and these treatments caused significantly increased K+ and lowered Na+ concentrations in shoot and root under stress. Moreover, Si and SA treatments modulated endogenous SA levels and dramatically decreased abscisic acid levels in both shoot and root. Additionally, key genes involved in Si uptake, SA biosynthesis, the antioxidant defence system and rhizosphere acidification were up-regulated in Si and SA treatments under alkaline conditions. These results demonstrate that Si and SA play critical roles in improving alkaline stress tolerance in tomato seedlings, by modifying the endogenous Na+ and K+ contents, regulating oxidative damage and key genes and modulating endogenous hormone levels. These findings will help to broaden our understanding regarding the physiological and molecular mechanisms associated with the alkaline soil tolerance in plants.

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Effects of Arbuscular Mycorrhiza Fungi on the Growth Characteristics, Root Morphology, and Ion Distribution of Pyrus betulaefolia Bunge under Saline-Alkaline Stress

Forest Science ◽

10.1093/forsci/fxz047 ◽

2019 ◽

Author(s):

Xiuyan Yang ◽

Huanyong Li ◽

Lei Jiang ◽

Xiaoqian Tang ◽

Xiaowei Liu ◽

...

Keyword(s):

Arbuscular Mycorrhiza ◽

Root Morphology ◽

Biomass Accumulation ◽

Growth Characteristics ◽

Alkaline Stress ◽

Alkaline Soil ◽

Ion Distribution ◽

Funneliformis Mosseae ◽

Arbuscular Mycorrhiza Fungi ◽

Alkaline Tolerance

Abstract In this study, Pyrus betulaefolia Bunge seedlings were used to investigate the effects of an arbuscular mycorrhiza fungus (AMF; Funneliformis mosseae) on plant-growth characteristics, root morphology, salt tolerance, and ion distribution under saline-alkaline stress. An indoor pot experiment was conducted in which seedlings were inoculated with Funneliformis mosseae under treatments of four different concentrations of Na2CO3 solution. The results show that AMF could establish symbiotic relations with the P. betulaefolia root system under Na2CO3 stress. Under the same Na2CO3 stress, AMF significantly increased the height growth and biomass accumulation of P. betulaefolia seedlings. AMF also promoted the root growth of P. betulaefolia seedlings. AMF inoculation significantly affected the absorption and distribution of K+ and Na+ in P. betulaefolia. The K/Na ratios in the roots and leaves of seedlings inoculated with AMF were higher than those of seedlings without inoculation. The results of this study show that inoculation with AMF had a positive effect on enhancing the saline-alkaline tolerance of P. betulaefolia, and root treatment of P. betulaefolia seedlings with Funneliformis mosseae has the potential for application in the development of saline-alkaline soil vegetation.

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