Differential Impact of Nitric Oxide and Abscisic Acid on the Cellular and Physiological Functioning of sub1A QTL Bearing Rice Genotype under Salt Stress

Exploring Aluminum Tolerance Mechanisms in Plants with Reference to Rice and Arabidopsis: A Comprehensive Review of Genetic, Metabolic, and Physiological Adaptations in Acidic Soils

Aluminum (Al) makes up a third of the Earth's crust and is a widespread toxic contaminant, particularly in acidic soils. It impacts crops at multiple levels, from cellular to whole plant systems. This review delves into Al's reactivity, including its cellular transport, involvement in oxidative redox reactions, and development of specific metabolites, as well as the influence of genes on the production of membrane channels and transporters, alongside its role in triggering senescence. It discusses the involvement of channel proteins in calcium influx, vacuolar proton pumping, the suppression of mitochondrial respiration, and the initiation of programmed cell death. At the cellular nucleus level, the effects of Al on gene regulation through alterations in nucleic acid modifications, such as methylation and histone acetylation, are examined. In addition, this review outlines the pathways of Al-induced metabolic disruption, specifically citric acid metabolism, the regulation of proton excretion, the induction of specific transcription factors, the modulation of Al-responsive proteins, changes in citrate and nucleotide glucose transporters, and overall metal detoxification pathways in tolerant genotypes. It also considers the expression of phenolic oxidases in response to oxidative stress, their regulatory feedback on mitochondrial cytochrome proteins, and their consequences on root development. Ultimately, this review focuses on the selective metabolic pathways that facilitate Al exclusion and tolerance, emphasizing compartmentalization, antioxidative defense mechanisms, and the control of programmed cell death to manage metal toxicity.

Interaction between ABA and NO in plants under abiotic stresses and its regulatory mechanisms

Abscisic acid (ABA) and nitric oxide (NO), as unique signaling molecules, are involved in plant growth, developmental processes, and abiotic stresses. However, the interaction between ABA and NO under abiotic stresses has little been worked out at present. Therefore, this paper reviews the mechanisms of crosstalk between ABA and NO in the regulation of plants in response to environmental stresses. Firstly, ABA-NO interaction can alleviate the changes of plant morphological indexes damaged by abiotic stresses, for instance, root length, leaf area, and fresh weight. Secondly, regulatory mechanisms of interaction between ABA and NO are also summarized, such as reactive oxygen species (ROS), antioxidant enzymes, proline, flavonoids, polyamines (PAs), ascorbate-glutathione cycle, water balance, photosynthetic, stomatal movement, and post-translational modifications. Meanwhile, the relationships between ABA and NO are established. ABA regulates NO through ROS at the physiological level during the regulatory processes. At the molecular level, NO counteracts ABA through mediating post-translational modifications. Moreover, we also discuss key genes related to the antioxidant enzymes, PAs biosynthesis, ABA receptor, NO biosynthesis, and flavonoid biosynthesis that are regulated by the interaction between ABA and NO under environmental stresses. This review will provide new guiding directions for the mechanism of the crosstalk between ABA and NO to alleviate abiotic stresses.

Adaptive responses of nitric oxide (NO) and its intricate dialogue with phytohormones during salinity stress

Nitric oxide (NO) is a gaseous free radical that acts as a messenger for various plant phenomena corresponding to photomorphogenesis, fertilisation, flowering, germination, growth, and productivity. Recent developments have suggested the critical role of NO in inducing adaptive responses in plants during salinity. NO minimises salinity-induced photosynthetic damage and improves plant-water relation, nutrient uptake, stomatal conductance, electron transport, and ROS and antioxidant metabolism. NO contributes active participation in ABA-mediated stomatal regulation. Similar crosstalk of NO with other phytohormones such as auxins (IAAs), gibberellins (GAs), cytokinins (CKs), ethylene (ET), salicylic acid (SA), strigolactones (SLs), and brassinosteroids (BRs) were also observed. Additionally, we discuss NO interaction with other gaseous signalling molecules such as reactive oxygen species (ROS) and reactive sulphur species (RSS). Conclusively, the present review traces critical events in NO-induced morpho-physiological adjustments under salt stress and discusses how such modulations upgrade plant resilience.

Abscisic acid priming confers salt tolerance in maize seedlings by modulating osmotic adjustment, bond energies, ROS homeostasis, and organic acid metabolism

This study aimed at investigating the influence of exogenous abscisic acid (ABA) on salt homeostasis under 100 mM NaCl stress in maize (Zea mays L. cv. Kaveri 50) through 3 and 5 days of exposure. The ratio of Na+ to K+, hydrogen peroxide (H2O2) and superoxide (O2•‒) accumulation, electrolyte leakage were the major determinants for salt sensitivity. Pretreatment with ABA [ABA (+)] had altered the salt sensitivity of plants maximally through 5 days of treatment. Plants controlled well for endogenous ABA level (92% increase) and bond energy minimization of cell wall residues to support salt tolerance proportionately to ABA (+). Salt stress was mitigated through maintenance of relative water content (RWC) (16%), glycine betaine (GB) (26%), proline (28%) and proline biosynthesis enzyme (ΔP5CS) (26%) under the application of ABA (+). Minimization of lipid peroxides (6% decrease), carbonyl content (9% decrease), acid, alkaline phosphatase activities were more tolerated under 100 mM salinity at 5 days duration. Malate metabolism for salt tolerance was dependent on the activity of the malic enzyme, malate dehydrogenase through transcript abundance in real-time manner as a function of ABA (+). Establishment of oxidative stress through days under salinity recorded by NADPH-oxidase activity (39% increase) following ROS generation as detected in tissue specific level. The ABA (+) significantly altered redox homeostasis through ratio of AsA to DHA (21% increase), GSH to GSSG (12% increase) by dehydroascorbate reductase and glutathione reductase respectively, and other enzymes like guaiacol peroxidase, catalase, glutathione reductase activities. The ABA in priming was substantially explained in stress metabolism as biomarker for salinity stress with reference to maize.

Say "NO" to plant stresses: Unravelling the role of nitric oxide under abiotic and biotic stress

Nitric oxide (NO) is a diatomic gaseous molecule, which plays different roles in different strata of organisms. Discovered as a neurotransmitter in animals, NO has now gained a significant place in plant signaling cascade. NO regulates plant growth and several developmental processes including germination, root formation, stomatal movement, maturation and defense in plants. Due to its gaseous state, it is unchallenging for NO to reach different parts of cell and counterpoise antioxidant pool. Various abiotic and biotic stresses act on plants and affect their growth and development. NO plays a pivotal role in alleviating toxic effects caused by various stressors by modulating oxidative stress, antioxidant defense mechanism, metal transport and ion homeostasis. It also modulates the activity of some transcriptional factors during stress conditions in plants. Besides its role during stress conditions, interaction of NO with other signaling molecules such as other gasotransmitters (hydrogen sulfide), phytohormones (abscisic acid, salicylic acid, jasmonic acid, gibberellin, ethylene, brassinosteroids, cytokinins and auxin), ions, polyamines, etc. has been demonstrated. These interactions play vital role in alleviating plant stress by modulating defense mechanisms in plants. Taking all these aspects into consideration, the current review focuses on the role of NO and its interaction with other signaling molecules in regulating plant growth and development, particularly under stressed conditions.

Simultaneous Action of Silymarin and Dopamine Enhances Defense Mechanisms Related to Antioxidants, Polyamine Metabolic Enzymes, and Tolerance to Cadmium Stress in Phaseolus vulgaris

Silymarin (Sm) and dopamine (DA) act synergistically as potential antioxidants, mediating many physiological and biochemical processes. As a first report, we investigated the synergistic effect of Sm and DA in mitigating cadmium stress in Phaseolus vulgaris plants. Three experiments were conducted simultaneously using 40 cm diameter pots to elucidate how Sm and DA affect cadmium tolerance traits at morphological, physiological, and biochemical levels. Cadmium stress triggered a marked reduction in growth, productivity, and physio-biochemical characteristics of common bean plants compared to unstressed plants. Seed priming (SP) and foliar spraying (FS) with silymarin (Sm) or dopamine (DA) ((DA (SP) + Sm (FS) and Sm (SP) + DA (FS)) ameliorated the damaging effects of cadmium stress. Sm seed priming + DA foliar spraying (Sm (SP) + DA (FS)) was more efficient. The treated stressed common bean plants showed greater tolerance to cadmium stress by diminishing oxidative stress biomarkers (i.e., O₂^•-, H₂O₂, and MDA) levels through enhanced enzymatic (SOD, CAT, POD, APX) and non-enzymatic (ascorbic acid, glutathione, α-tocopherol, choline, phenolics, flavonoids) antioxidant activities and osmoprotectants (proline, glycine betaine, and soluble sugars) contents, as well as through improved photosynthetic efficiency (total chlorophyll and carotenoids contents, photochemical activity, and efficiencies of carboxylation (iCE) and PSII (Fv/Fm)), polyamines (Put, Spd, and Spm), and polyamine metabolic enzymes (ADC and ODC) accumulation. These findings signify that Sm and DA have remarkable anti-stress effects, which can help regulate plant self-defense systems, reflecting satisfactory plant growth and productivity. Thus, realizing the synergistic effect of Sm and DA in cadmium tolerance confers potential new capabilities for these compounds to function in sustainable agriculture.

Plant hormones and neurotransmitter interactions mediate antioxidant defenses under induced oxidative stress in plants

Due to global climate change, abiotic stresses are affecting plant growth, productivity, and the quality of cultivated crops. Stressful conditions disrupt physiological activities and suppress defensive mechanisms, resulting in stress-sensitive plants. Consequently, plants implement various endogenous strategies, including plant hormone biosynthesis (e.g., abscisic acid, jasmonic acid, salicylic acid, brassinosteroids, indole-3-acetic acid, cytokinins, ethylene, gibberellic acid, and strigolactones) to withstand stress conditions. Combined or single abiotic stress disrupts the normal transportation of solutes, causes electron leakage, and triggers reactive oxygen species (ROS) production, creating oxidative stress in plants. Several enzymatic and non-enzymatic defense systems marshal a plant's antioxidant defenses. While stress responses and the protective role of the antioxidant defense system have been well-documented in recent investigations, the interrelationships among plant hormones, plant neurotransmitters (NTs, such as serotonin, melatonin, dopamine, acetylcholine, and γ-aminobutyric acid), and antioxidant defenses are not well explained. Thus, this review discusses recent advances in plant hormones, transgenic and metabolic developments, and the potential interaction of plant hormones with NTs in plant stress response and tolerance mechanisms. Furthermore, we discuss current challenges and future directions (transgenic breeding and genome editing) for metabolic improvement in plants using modern molecular tools. The interaction of plant hormones and NTs involved in regulating antioxidant defense systems, molecular hormone networks, and abiotic-induced oxidative stress tolerance in plants are also discussed.