Accumulation Of Glycine Betaine Research Articles

Exogenous Root Uptake of Glycine Betaine Mitigates Improved Tolerance to Salinity Stress in Avicenna germinans under Ambient and Elevated CO2 Conditions

In recent years, climate change has caused unpredictable variations in sea levels and an increase in atmospheric CO2 levels. Increasing temperatures and subsequent rates of evaporation have been demonstrated to cause increased coastal salinity in certain areas, which induces abiotic stress, in mangroves systems. The osmolyte, glycine betaine, has been shown in numerous studies to increase the tolerance of plants to environmental stressors, including salt stress. A handful of studies have demonstrated that increased CO2 concentrations confer increased salt tolerance and photosynthetic productivity of different mangrove species. Avicenna germinans, commonly referred to as the black mangrove, is native to Pacific and Atlantic coasts, and produces glycine betaine endogenously. This study sought to characterize the response of A. germinans exposed to increasing saline conditions, grown under normal and high CO2 concentrations. Elucidation of the role glycine betaine accumulation plays in tolerance to abiotic stress was investigated. A. germinans seedlings were subjected to increasing levels of salt stress (15–90 ppt) and treated with a dose response of glycine betaine (0–50 μM). Half of the seedlings were grown under ambient (400 ppm) CO2 conditions, and the other half were grown under elevated (800 ppm) CO2 conditions. Increased salinity tolerance and higher photosynthetic rates were observed among seedlings exposed to elevated CO2 conditions, as indicated by increased survival rates and qualitative health observations. This research may provide insights into potential consequences posed by climate change, as well as characterizing the glycine betaine signaling pathway in this mangrove species. Looking into the future, the knowledge obtained through this study may potentially contribute to our predictions of mangrove adaptability and therefore conferred protection of our coastlines in an ever‐changing world.

Nitric Oxide Stimulates Antioxidant System and Osmotic Adjustment in Soybean Under Drought Stress

The target of the present study was to determine the effect of nitric oxide (NO) on drought stress amelioration in soybean plant. Plants were treated with different polyethylene glycol (PEG) concentrations (0, 5, 10, and 15%) without or with NO (100 μM). Based on our results, drought stress significantly decreased growth in soybean plants. Increase in hydrogen peroxide, malondialdehyde, and aldehyde content indicated drought-induced oxidative stress in soybean plants. Drought stress enhanced the activities of catalase, ascorbate peroxidase, accumulation of proline and glycine betaine, and lipoxygenase activity as well as total phenol and tocopherol content. NO had a beneficial effect on drought tolerance and promoted growth in soybean plants. NO treatment maintained soybean against drought-induced oxidative hurt, thereby improving the antioxidant defense mechanism (enzymatic and non-enzymatic antioxidants). NO application caused osmotic adjustment by up-regulation accumulation of compatible solutes in stressed plants. Enhanced plant growth was linked with induction of phenylalanine ammonia-lyase and tyrosine ammonia-lyase activity and decrease in electrolyte leakage by NO application. Our results revealed that NO had ability to alleviate the destructive effects in soybean plants under drought stress.

Physiological changes of Mentha pulegium in response to exogenous salicylic acid under salinity

Plant productivity could be largely limited by salt stress. Thus, a pot experiment was conducted to evaluate the response of Mentha pulegium to foliar spray of salicylic acid (SA) (0, 0.5, 1 and 1.5 mM) under different salinity levels (0, 25, 50 and 75 mM NaCl). The results revealed that accumulation of malondialdehyde, H2O2, proline, glycine betaine and total phenol as well as the activities of catalase, peroxidase, ascorbate peroxidase, superoxide dismutase and phenylalanine ammonia-lyase were increased with increasing salinity level. However, leaf water content and photosynthetic pigments were significantly decreased by salt stress. SA treatment had no significant effect on glycine betaine, total phenol content and phenylalanine ammonia-lyase activity in salt-stressed plants, while this treatment enhanced proline content via increasing pyrroline-5-carboxylate reductase activity and decreasing proline oxidase activity. Foliar spray of SA also stimulated the activities of catalase, ascorbate peroxidase and superoxide dismutase enzymes and thereby limited H2O2 accumulation and lipid peroxidation. Application of 1 and 1.5 mM SA considerably improved leaf water content and chlorophyll content of M. pulegium under different levels of salinity. These results suggest that exogenous application of 1 and 1.5 mM SA could mitigate salt toxicity and improve antioxidant capacity of M. pulegium under different levels of salinity.

Effects of Climate Temperature and Water Stress on Plant Growth and Accumulation of Antioxidant Compounds in Sweet Basil (Ocimum basilicum L.) Leafy Vegetable.

The effects of climate temperature and water stress on growth and several stress markers were investigated in sweet basil plants. Some growth parameters (shoot length and number of leaves) and photosynthetic chlorophyll contents were determined every two days during plant growth, and foliage leaf material was collected after 15 and 21 days of treatment. Both climate temperature and water stress inhibited sweet basil plant growth; especially, total chlorophyll levels were decreased significantly in response to high-temperature treatments. Under strong stresses, basil plants induced the synthesis and accumulation of glycine betaine (GB) as a secondary osmolyte, although at less content when compared with the proline content under the same stress conditions. Proline concentrations particularly increased in leaves of both basil stressed plants, accomplishing levels high enough to play a crucial role in cellular osmoregulation adjustment. Stress-induced accumulation of these antioxidant compounds was detected in sweet basil. Therefore, it appears that sweet basil-treated plants are able to synthesize antioxidant compounds under strong stress conditions. On the other hand, total sugar concentrations decreased in stress-treated basil plants. Both temperature and water stress treatments caused oxidative stress in the treated plants, as indicated by a significant increment in malondialdehyde (MDA) concentrations. An increase in total phenolic and flavonoid concentrations in response to water stress and a highly significant decrease in carotenoid concentrations in basil leaves were observed; flavonoids also increased under high climate temperature conditions.

Use of Nitric Oxide and Hydrogen Peroxide for Better Yield of Wheat (Triticum aestivum L.) under Water Deficit Conditions: Growth, Osmoregulation, and Antioxidative Defense Mechanism.

The present experiment was carried out to study the influences of exogenously-applied nitric oxide (NO) donor sodium nitroprusside (SNP) and hydrogen peroxide (H2O2) as seed primers on growth and yield in relation with different physio-biochemical parameters, antioxidant activities, and osmolyte accumulation in wheat plants grown under control (100% field capacity) and water stress (60% field capacity) conditions. During soaking, the seeds were covered and kept in completely dark. Drought stress markedly reduced the plant growth, grain yield, leaf photosynthetic pigments, total phenolic content (TPC), total soluble proteins (TSP), leaf water potential (Ψw), leaf turgor potential (Ψp), osmotic potential (Ψs), and leaf relative water content (LRWC), while it increased the activities of enzymatic antioxidants and the accumulation of leaf ascorbic acid (AsA), proline (Pro), glycine betaine (GB), malondialdehyde (MDA), and H2O2. However, seed priming with SNP and H2O2 alone and in combination mitigated the deleterious effects of water stress on growth and yield by improving the Ψw, Ψs, Ψp, photosynthetic pigments, osmolytes accumulation (GB and Pro), TSP, and the antioxidative defense mechanism. Furthermore, the application of NO and H2O2 as seed primers also reduced the accumulation of H2O2 and MDA contents. The effectiveness was treatment-specific and the combined application was also found to be effective. The results revealed that exogenous application of NO and H2O2 was effective in increasing the tolerance of wheat plants under drought stress in terms of growth and grain yield by regulating plant–water relations, the antioxidative defense mechanism, and accumulation of osmolytes, and by reducing the membrane lipid peroxidation.

Intracellular osmoprotectant concentrations determine Propionibacterium freudenreichii survival during drying

Propionibacterium freudenreichii is a beneficial bacterium widely used in food as a probiotic and as a cheese-ripening starter. In these different applications, it is produced, dried, and stored before being used. Both freeze-drying and spray-drying were considered for this purpose. Freeze-drying is a discontinuous process that is energy-consuming but that allows high cell survival. Spray-drying is a continuous process that is more energy-efficient but that can lead to massive bacterial death related to heat, osmotic, and oxidative stresses. We have shown that P. freudenreichii cultivated in hyperconcentrated rich media can be spray-dried with limited bacterial death. However, the general stress tolerance conferred by this hyperosmotic constraint remained a black box. In this study, we modulated P. freudenreichii growth conditions and monitored both osmoprotectant accumulation and stress tolerance acquisition. Changing the ratio between the carbohydrates provided and non-protein nitrogen during growth under osmotic constraint modulated osmoprotectant accumulation. This, in turn, was correlated with P. freudenreichii tolerance towards different stresses, on the one hand, and towards freeze-drying and spray-drying, on the other. Surprisingly, trehalose accumulation correlated with spray-drying survival and glycine betaine accumulation with freeze-drying. This first report showing the ability to modulate the trehalose/GB ratio in osmoprotectants accumulated by a probiotic bacterium opens new perspectives for the optimization of probiotics production.

Glycinebetaine Enhances Osmotic Adjustment of Ryegrass under Cold Temperatures

Perennial (Lolium perenne L.) and annual (L. multiflorum) ryegrass are important species for landscape (e.g., turf) and agricultural (e.g., pasture systems) uses. Abiotic stresses limit the survival, growth, and/or appearance of these species. The synthesis and accumulation of quaternary ammonium compounds (QACs) such as glycinebetaine (GB) are an adaptive response to abiotic environmental stresses in some species. Both L. perenne and L. multiflorum are GB-accumulating species, and exogenous application of GB may enhance growth under less-than-optimal environmental conditions. We tested the effects of exogenous application of GB on growth and water relations of annual and perennial ryegrass growing under temperatures at the lower limits of their optimal growth. Osmotic stress resulted in increased GB accumulation in L. perenne, but exposure to cold temperatures did not result in increased GB accumulation in either species. Both species accumulated higher concentrations of GB in leaf and stem tissues when exogenous GB was supplied, regardless of growing temperature. Exogenous GB did contribute to lower osmotic potential in both species, but did not affect relative water content, although succulence was higher in some cases. Overall, exogenous GB did not affect growth under optimal growing temperatures, but did enhance growth of L. perenne growing under low temperatures.

Amelioration of drought stress in Foxtail millet (Setaria italica L.) by P-solubilizing drought-tolerant microbes with multifarious plant growth promoting attributes

Drought is the most limiting factors affecting plant development. It severely affects the crops and leads to serious reductions in yield. There are certain nutrients which also act as limiting factor for plants such as phosphorus and nitrogen. Under the conditions of nutrient limitations, growth is greatly reduced. Plant associated microbiome are gaining attention as they help the host (plant) to combat stress conditions. In the present study, stress-adaptive and phosphorus-solubilizing microbes were isolated from rhizosphere of different crops such as wheat, maize, foxtail millet, and finger millet growing in NW Indian Himalayas. A total of 70 microbes were isolated using different defined and selective growth media. The isolated microbes were screened for plant growth promoting (PGP) ability of phosphate solubilization using three different insoluble phosphorus (P) substrates (apatite, tricalcium phosphate and rock phosphate) under the drought stress conditions (5–8% PEG-8000). Among isolated microbes 27 isolates exhibited P-solubilizing attribute under the water deficient conditions. The two efficient drought-adaptive and P-solubilizing isolates were identified as Acinetobacter calcoaceticus EU- LRNA-72 and Penicillium sp. EU-FTF-6, respectively, by 16S rRNA and 18S rRNA gene sequencing. The isolates EU- LRNA-72 and EU-FTF-6 were evaluated for plant growth promoting (PGP) traits and mitigation of drought stress in foxtail millet under the controlled and natural conditions. The isolates A. calcoaceticus EU- LRNA-72 and Penicillium sp. EU-FTF-6 efficiently mitigated the adverse effects of drought in foxtail millet by enhancing the accumulation of glycine betaine, proline, sugars, and decreasing lipid peroxidation. The drought tolerant P-solubilizing microbes could be useful for plant growth promotion and mitigation of drought stress for crops growing under the water deficient conditions.

Unveiling salinity effects on photo-bioelectrocatalysis through combination of bioinformatics and electrochemistry

Little is known about the adaptation strategies utilized by photosynthetic microorganisms to cope with salinity changes happening in the environment, and the effects on microbial electrochemical technologies. Herein, bioinformatics analysis revealed a metabolism shift in Rhodobacter capsulatus resulting from salt stress, with changes in gene expression allowing accumulation of compatible solutes to balance osmotic pressure, together with the up-regulation of the nitrogen fixation cycle, an electron sink of the photosynthetic electron transfer chain. Using the transcriptome evidence of hindered electron transfer in the photosynthetic electron transport chain induced by adaption to salinity, increased understanding of photo-bioelectrocatalysis under salt stress is achieved. Accumulation of glycine-betaine allows immediate tuning of salinity tolerance but does not provide cell stabilization, with a 40 ± 20% loss of photo-bioelectrocatalysis in a 60 min time scale. Conversely, exposure to or inducing the expression of the Rhodobacter capsulatus gene transfer agent tunes salinity tolerance and increases cell stability. This work provides a proof of concept for the combination of bioinformatics and electrochemical tools to investigate microbial electrochemical systems, opening exciting future research opportunities.

Important roles of glycinebetaine in stabilizing the structure and function of the photosystem II complex under abiotic stresses.

The molecular and physiological mechanisms of glycinebetaine stabilizing photosystem II complex under abiotic stresses are discussed, helping to address food shortage problems threatening the survival of growing population. In the backdrop of climate change, the frequency, dimensions and duration of extreme events have increased sharply, which may have unintended consequences for agricultural. The acclimation of plants to a constantly changing environment involves the accumulation of compatible solutes. Various compatible solutes enable plants to tolerate abiotic stresses, and glycinebetaine (GB) is one of the most-studied. The biosynthesis and accumulation of GB appear in numerous plant species, especially under environmental stresses. The exogenous application of GB and GB-accumulating transgenic plants have been proven to further promote plant development under stresses. Early research on GB focused on the maintenance of osmotic potential in plants. Subsequent experimental evidence demonstrated that it also protects proteins including the photosystem II complex (PSII) from denaturation and deactivation. As reviewed here, multiple experimental evidences have indicated considerable progress in the roles of GB in stabilizing PSII under abiotic stresses. Based on these advances, we've concluded two effects of GB on PSII: (1) it stabilizes the structure of PSII by protecting extrinsic proteins from dissociation or by promoting protein synthesize; (2) it enhances the oxygen-evolving activity of PSII or promotes the repair of the photosynthetic damage of PSII.

Endogenous accumulation of glycine betaine confers improved low temperature resistance on transplastomic potato plants.

Glycine betaine (GB) plays a crucial role in plant response to abiotic stress, and its accumulation in chloroplasts is more effective than in the cytosol in improving the resistance of transgenic plants. Here, we report that the codA gene from Arthrobacter globiformis, which encodes a choline oxidase catalysing the conversion of choline to GB, was successfully introduced into the plastid genome of potato (Solanum tuberosum L.). Transgenic plants with plastid expression of codA showed increased tolerance to low temperature stress compared with the wild type (WT). Further studies revealed that under low temperature stress condition, transgenic plants presented a significantly higher photosynthetic performance by regulating the electron transport and energy distribution in PSII, and higher antioxidant enzyme activities and lower O2- and H2O2 accumulation than did the WT plants. A higher expression of the COR genes was also observed in transgenic plants. Our results suggest that chloroplast biosynthesis of GB could be an effective strategy for the engineering of plants with increased resistance to low temperature stress.

Effect of water stress on the physiological and biochemical responses of two different Coleus (Plectranthus) species.

Effect of water stress on the physiology and biochemistry of two different Coleus species, Coleus forskholii and Coleus amboinicus, was studied. Drought stress was imposed by withholding the water supply until leaf water potentials reached -0.4, -0.8, and -1.2 MPa. Physiological parameters such as relative water content and water uptake capacity were studied along with lipid peroxidation, superoxide, H2O2, and •OH accumulation-, l-diphenyl-2-picrylhydrazyl radical (DPPH) scavenging assays. Antioxidant defense system in Coleus under drought stress was studied by quantifying the Trolox equivalent antioxidant capacity, ascorbic acid, reduced glutathione-, and α-tocopherol content as well as activities of superoxide dismutase, catalase, ascorbate peroxidase, peroxidase, and glutathione reductase. Accumulation of osmolytes proline, glycine betaine, and phytohormone abscisic acid was also used as key parameters for assessing their performance. There was a marked variation in the antioxidative defense system and osmolyte accumulation in these two species under drought stress. Relative water content was reduced and water uptake capacity was increased. A comparative study in the perspectives of osmolyte accumulation, antioxidant, and physiological responses inferred C. amboinicus as a drought stress-tolerant species when compared to C. forskholii.

Metabolic responses of wheat seedlings to osmotic stress induced by various osmolytes under iso-osmotic conditions.

Many environmental stresses cause osmotic stress which induces several metabolic changes in plants. These changes often vary depending on the genotype, type and intensity of stress or the environmental conditions. In the current experiments, metabolic responses of wheat to osmotic stress induced by different kinds of osmolytes were studied under iso-osmotic stress conditions. A single wheat genotypes was treated with PEG-6000, mannitol, sorbitol or NaCl at such concentrations which reduce the osmotic potential of the culture media to the same level (-0.8MPa). The metabolic changes, including the accumulation of proline, glycine betaine (GB) and sugar metabolites (glucose, fructose, galactose, maltose and sucrose) were studied both in the leaves and roots together with monitoring the plant growth, changes in the photosynthetic activity and chlorophyll content of the leaves. In addition, the polyamine metabolism was also investigated. Although all osmolytes inhibited growth similarly, they induced different physiological and metabolic responses: the CO2 assimilation capacity, RWC content and the osmotic potential (ψπ) of the leaves decreased intensively, especially after mannitol and sorbitol treatments, followed by NaCl treatment, while PEG caused only a slight modification in these parameters. In the roots, the most pronounced decrease of ψπ was found after salt-treatments, followed by PEG treatment. Osmotic stress induced the accumulation of proline, glycine betaine and soluble sugars, such as fructose, glucose, sucrose and galactose in both the root and leaf sap. Specific metabolic response of roots and leaves under PEG included accumulation of glucose, fructose and GB (in the roots); sucrose, galactose and proline synthesis were dominant under NaCl stress while exposure to mannitol and sorbitol triggered polyamine metabolism and overproduction of maltose. The amount of those metabolites was time-dependent in the manner that longer exposure to iso-osmotic stress conditions stimulated the sugar metabolic routes. Our results showed that the various osmolytes activated different metabolic processes even under iso-osmotic stress conditions and these changes also differed in the leaves and roots.

Exogenous Nitric Oxide Mitigates Nickel-Induced Oxidative Damage in Eggplant by Upregulating Antioxidants, Osmolyte Metabolism, and Glyoxalase Systems.

Nitric oxide (NO) at optimal levels is considered beneficial to plant functioning. The present study was carried out to investigate the role of exogenously applied NO (100 and 150 µM sodium nitropurusside, SNP) in amelioration of nickel (Ni)-mediated oxidative effects in eggplant. Ni stress declined growth and biomass production, relative water content (RWC), and chlorophyll pigment synthesis, thereby affecting the photosynthetic efficiency. Exogenously applied SNP proved beneficial in mitigating the Ni-mediated growth restrictions. NO-treated seedlings exhibited improved photosynthesis, stomatal conductance, and chlorophyll content with the effect of being apparent at lower concentration (100 µM SNP). SNP upregulated the antioxidant system mitigating the oxidative damage on membranes due to Ni stress. The activity of superoxide dismutase, catalase, glutathione S-transferase, ascorbate peroxidase, and glutathione reductase was upregulated due to SNP which also increased the ascorbate and reduced glutathione content. SNP-supplied seedlings also showed higher proline and glycine betaine accumulation, thereby improving RWC and antioxidant system. Glyoxalase I activity was induced due to SNP application declining the accumulation of methylglyoxal. NO-mediated mitigation of Ni toxicity was confirmed using NO scavenger (PTIO, 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), which reversed the influence of SNP almost entirely on the parameters studied. Uptake of nitrogen (N), potassium (K), and calcium (Ca) was increased due to SNP application and Ni was reduced significantly. Therefore, this study revealed the efficiency of exogenous SNP in enhancing Ni stress tolerance through upregulating antioxidant and glyoxalase systems.

24-Epibrassinolide (EBR) Confers Tolerance against NaCl Stress in Soybean Plants by Up-Regulating Antioxidant System, Ascorbate-Glutathione Cycle, and Glyoxalase System.

The present research was performed to assess the effect of 24-epibrassinolide (EBR) on salt-stressed soybean plants. Salt stress suppressed growth, biomass yield, gas exchange parameters, pigment content, and chlorophyll fluorescence, but all these parameters were up-regulated by EBR supply. Moreover, salt stress increased hydrogen peroxide, malondialdehyde, and electrolyte leakage. EBR supplementation reduced the accumulation of oxidative stress biomarkers. The activities of superoxide dismutase and catalase, and the accumulation of proline, glycinebetaine, total phenols, and total flavonoids increased with NaCl stress, but these attributes further increased with EBR supplementation. The activities of enzymes and the levels of non-enzymatic antioxidants involved in the Asc-Glu cycle also increased with NaCl stress, and further enhancement in these attributes was recorded by EBR supplementation. Salinity elevated the methylglyoxal content, but it was decreased by the EBR supplementation accompanying with up-regulation of the glyoxalase cycle (GlyI and GlyII). Salinity enhanced the Na+ uptake in root and shoot coupled with a decrease in uptake of Ca2+, K+, and P. However, EBR supplementation declined Na+ accumulation and promoted the uptake of the aforementioned nutrients. Overall, EBR supplementation regulated the salt tolerance mechanism in soybean plants by modulating osmolytes, activities of key enzymes, and the levels of non-enzymatic antioxidants.

Silicon Priming Regulates Morpho-Physiological Growth and Oxidative Metabolism in Maize under Drought Stress.

Seed priming with silicon (Si) is an efficient and easy method to regulate plant tolerance against different abiotic stresses. A pot experiment was conducted to examine the Si-mediated changes in oxidative defense and some vital physio-biochemical parameters of maize under a limited water supply. For this purpose, two maize varieties (Pearl and Malka) with different Si priming treatments (0, 4 mM, 6 mM) were grown under a control and 60% field capacity for three weeks. At 60% field capacity, significant reductions in plant growth attributes and chlorophyll contents were recorded compared with the control. The negative effects of drought stress were more severe for Malka compared with Pearl. Drought stress increased the malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents, altered the activities of antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)), and triggered the accumulation of soluble sugars, glycine betaine, proline, and phenolics contents. Nevertheless, seed priming with silicon at 4 or 6 mM was effective in alleviating the detrimental effects of drought stress in both cultivars. Si priming particularly at 6 mM significantly enhanced the shoot and root lengths as well as their biomass and improved the levels of photosynthetic pigments. Moreover, Si treatments enhanced the activities of antioxidant enzymes (SOD, POD, and CAT) while it reduced the MDA and H2O2 contents in both cultivars under stress conditions. In crux, the present investigation suggests that Si priming mitigates the harmful effects of drought stress and contributes to the recovery of maize growth.

Involvement of abscisic acid-responsive element-binding factors in cassava (Manihot esculenta) dehydration stress response

Cassava (Manihot esculenta) is a major staple food, animal feed and energy crop in the tropics and subtropics. It is one of the most drought-tolerant crops, however, the mechanisms of cassava drought tolerance remain unclear. Abscisic acid (ABA)-responsive element (ABRE)-binding factors (ABFs) are transcription factors that regulate expression of target genes involved in plant tolerance to drought, high salinity, and osmotic stress by binding ABRE cis-elements in the promoter regions of these genes. However, there is little information about ABF genes in cassava. A comprehensive analysis of Manihot esculenta ABFs (MeABFs) described the phylogeny, genome location, cis-acting elements, expression profiles, and regulatory relationship between these factors and Manihot esculenta betaine aldehyde dehydrogenase genes (MeBADHs). Here we conducted genome-wide searches and subsequent molecular cloning to identify seven MeABFs that are distributed unevenly across six chromosomes in cassava. These MeABFs can be clustered into three groups according to their phylogenetic relationships to their Arabidopsis (Arabidopsis thaliana) counterparts. Analysis of the 5′-upstream region of MeABFs revealed putative cis-acting elements related to hormone signaling, stress, light, and circadian clock. MeABF expression profiles displayed clear differences among leaf, stem, root, and tuberous root tissues under non-stress and drought, osmotic, or salt stress conditions. Drought stress in cassava leaves and roots, osmotic stress in tuberous roots, and salt stress in stems induced expression of the highest number of MeABFs showing significantly elevated expression. The glycine betaine (GB) content of cassava leaves also was elevated after drought, osmotic, or salt stress treatments. BADH1 is involved in GB synthesis. We show that MeBADH1 promoter sequences contained ABREs and that MeBADH1 expression correlated with MeABF expression profiles in cassava leaves after the three stress treatments. Taken together, these results suggest that in response to various dehydration stresses, MeABFs in cassava may activate transcriptional expression of MeBADH1 by binding the MeBADH1 promoter that in turn promotes GB biosynthesis and accumulation via an increase in MeBADH1 gene expression levels and MeBADH1 enzymatic activity. These responses protect cells against dehydration stresses by preserving an osmotic balance that enhances cassava tolerance to dehydration stresses.

Transformation of wheat Triticum aestivum with the HvBADH1 transgene from hulless barley improves salinity-stress tolerance

Studies have shown that the stress tolerance of cereal plants to osmotic or salinity stresses can be improved to varying degrees by the overexpression of an introduced betaine aldehyde dehydrogenase (BADH) gene. In the present study, the HvBADH1 gene from Hordeum vulgare L. var. nudum Hook. f., encoding a cytosolic BADH, was transferred into Triticum aestivum via traditional Agrobacterium tumefaciens-mediated transformation. Molecular methods, such as PCR, Southern blot analysis, and real-time quantitative RT-PCR were used to identify the successful integration and expression of the HvBADH1 transgene in genetically transformed wheat lines. To detect the efficacy of the HvBADH1 transgene in the transformants, some pivotal physiological indicators that reflected abiotic stress tolerance were measured in individual transgenic plant lines. These indicators included intracellular K+ and Na+ contents or K+/Na+ ratio, relative conductivity, and malondialdehyde and glycine betaine (GB) concentrations in cells. The results revealed that all the tested transgenic lines could significantly increase the recruitments of K+ in their cytosol than the wild-type seedlings. Similarly, 11.59- to 21.82-fold greater accumulation of GB, 2.11–2.56 times higher calli relative growth rates, and 26.2–29.1% seedling survival rates were found in transgenic lines under 150 mM NaCl stressed conditions. Our results demonstrated that by overexpressing the HvBADH1 transgene in genetically transformed wheat, the overall salt tolerance of the target plants was significantly increased, and the damaging effects of high salinity were significantly reduced.

The role of glycine betaine in range expansions; protecting mangroves against extreme freeze events

Abstract Due to a warming climate, mangrove populations within the Gulf of Mexico and along the Florida Atlantic coastline are expanding their range poleward. As mangroves expand their range limit, leading edge individuals are more likely to experience an increased incidence of freeze events. However, we still lack a clear understanding of the mechanisms used by mangroves to survive freezing conditions. Here, we conducted common garden experiments at different locations experiencing variable winter freeze conditions to show glycine betaine, an organic osmolyte, increases significantly with freeze exposure, playing an important role in the freeze tolerance of Avicennia germinans, a widespread Neotropical mangrove. We found glycine betaine accumulation was similar across all source populations and freeze exposure locations, suggesting glycine betaine is not a range limit adaptation and is instead used for freeze tolerance by A. germinans irrespective of source population. Plants sourced from populations that experience freezing conditions exhibited greater rates of survival, indicating range edge populations of A. germinans have other heritable adaptations in addition to glycine betaine for freeze tolerance. Synthesis. Continued mangrove expansion poleward will result in a greater incidence of freeze events for individuals at the leading edge. Our findings suggest freeze tolerance in this species may be genetically based and that leading edge A. germinans have the potential to survive extreme freeze events and recover post‐freeze, allowing for their continued expansion poleward. This process of selective survival may act to promote adaptation of freeze tolerance in range edge populations.

Physiological and transcriptional variations inducing complex adaptive mechanisms in grapevine by salt stress

Salinity is an omnipresent stressor, depleting osmotic potential and affecting the vineyard development and productivity. It is indispensable to screen the grapevine genetic resources for possibilities to mitigate and adapt to the stress conditions. This paper describes the distinct response of the grapevine under progressive salt stress duration (0, 24, 48, and 72 h). Intriguingly, besides the adverse effect of salt stress on grapevine growth, the findings exhibit significant levels of stress responses to diminish the impact of salinity. Discerned are the accumulation of glycine betaine (GB) and trehalose, which can be supposed as distinct grapevine responses associated with the maintenance of high K+ level and, consequently, lower K+/Na+ ratios, with an excellent performance of cell water status and photosynthetic activity as compared to the controls. Moreover, an alleviated level of the oxidative stress marker (MDA) gives rise to superoxide radicals (O2−) and hydrogen peroxide (H2O2), while the antioxidative scavenging system is activated to counter the synthesis of reactive oxygen species (ROS). Principal component analysis (PCA) distinguished several salt prediction candidate markers based on physiological and transcriptional indexes in four different clusters. Current findings have elucidated new and fascinating responses of the grapevine to lengthy salt-stress period and provide a list of intended enzymatic targets for candidate gene selection to uplift the abiotic stress tolerance in horticultural crops.