Light-harvesting complexes in photosystem II regulate glutathione-induced sensitivity of Arabidopsis guard cells to abscisic acid

Multi-omics insights into the positive role of strigolactone perception in barley drought response

BACKGROUND

Drought is a major environmental stress that affects crop productivity worldwide. Although previous research demonstrated links between strigolactones (SLs) and drought, here we used barley (Hordeum vulgare) SL-insensitive mutant hvd14 (dwarf14) to scrutinize the SL-dependent mechanisms associated with water deficit response.

RESULTS

We have employed a combination of transcriptomics, proteomics, phytohormonomics analyses, and physiological data to unravel differences between wild-type and hvd14 plants under drought. Our research revealed that drought sensitivity of hvd14 is related to weaker induction of abscisic acid-responsive genes/proteins, lower jasmonic acid content, higher reactive oxygen species content, and lower wax biosynthetic and deposition mechanisms than wild-type plants. In addition, we identified a set of transcription factors (TFs) that are exclusively drought-induced in the wild-type barley.

CONCLUSIONS

Critically, we resolved a comprehensive series of interactions between the drought-induced barley transcriptome and proteome responses, allowing us to understand the profound effects of SLs in alleviating water-limiting conditions. Several new avenues have opened for developing barley more resilient to drought through the information provided. Moreover, our study contributes to a better understanding of the complex interplay between genes, proteins, and hormones in response to drought, and underscores the importance of a multidisciplinary approach to studying plant stress response mechanisms.

The impact of engineered nickel oxide nanoparticles on ascorbate glutathione cycle in Allium cepa L

Engineered nickel oxide nanoparticle (NiO-NP) can inflict significant damages on exposed plants, even though very little is known about the modus operandi. The present study investigated effects of NiO-NP on the crucial stress alleviation mechanism Ascorbate-Glutathione Cycle (Asa-GSH cycle) in the model plant Allium cepa. Cellular contents of reduced glutathione (GSH) and oxidised glutathione (GSSG), was disturbed upon NiO-NP exposure. The ratio of GSH to GSSG changed from 20:1 in NC to 4:1 in roots exposed to 125 mg L-1 NiO-NP. Even the lowest treatments of NiO-NP (10 mg L-1) increased ascorbic acid (2.9-folds) and cysteine contents (1.6-folds). Enzymes like glutathione reductase, ascorbate peroxidase, glutathione peroxidase and glutathione-S-transferase also showed altered activities in the affected tissues. Further, intracellular methylglyoxal, a harbinger of ROS (Reactive oxygen species), increased significantly (~ 26 to 65-fold) across different concentrations NiO-NP. Intracellular H2O2 (hydrogen peroxide) and ROS levels increased with NiO-NP doses, as did electrolytic leakage from damaged cells. The present work indicated that multiple pathways were compromised in NiO-NP affected plants and this information can bolster our general understanding of the actual mechanism of its toxicity on living cells, and help formulate strategies to thwart ecological pollution.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-023-01314-8.

Integration of Electrical Signals and Phytohormones in the Control of Systemic Response

Plants are constantly exposed to environmental stresses. Local stimuli sensed by one part of a plant are translated into long-distance signals that can influence the activities in distant tissues. Changes in levels of phytohormones in distant parts of the plant occur in response to various local stimuli. The regulation of hormone levels can be mediated by long-distance electrical signals, which are also induced by local stimulation. We consider the crosstalk between electrical signals and phytohormones and identify interaction points, as well as provide insights into the integration nodes that involve changes in pH, Ca²⁺ and ROS levels. This review also provides an overview of our current knowledge of how electrical signals and hormones work together to induce a systemic response.

Structure-function correlations and system dynamics in oxygenic photosynthesis: classical perspectives and murburn precepts

HIGHLIGHTS

Contemporary beliefs on oxygenic photosynthesis are critiqued.Murburn model is suggested as an alternative explanation.In the new model, diffusible reactive species are the main protagonists.All pigments are deemed photo-redox active in the new stochastic mechanism.NADPH synthesis occurs via simple electron transfers, not via elaborate ETC.Oxygenesis is delocalized and not just centered at Mn-Complex.Energetics of murburn proposal for photophosphorylation is provided.The proposal ushers in a paradigm shift in photosynthesis research.

Roles of Glutathione in Mediating Abscisic Acid Signaling and Its Regulation of Seed Dormancy and Drought Tolerance

Plant growth and development and interactions with the environment are regulated by phytohormones and other signaling molecules. During their evolution, plants have developed strategies for efficient signal perception and for the activation of signal transduction cascades to maintain proper growth and development, in particular under adverse environmental conditions. Abscisic acid (ABA) is one of the phytohormones known to regulate plant developmental events and tolerance to environmental stresses. The role of ABA is mediated by both its accumulated level, which is regulated by its biosynthesis and catabolism, and signaling, all of which are influenced by complex regulatory mechanisms. Under stress conditions, plants employ enzymatic and non-enzymatic antioxidant strategies to scavenge excess reactive oxygen species (ROS) and mitigate the negative effects of oxidative stress. Glutathione (GSH) is one of the main antioxidant molecules playing a critical role in plant survival under stress conditions through the detoxification of excess ROS, maintaining cellular redox homeostasis and regulating protein functions. GSH has recently emerged as an important signaling molecule regulating ABA signal transduction and associated developmental events, and response to stressors. This review highlights the current knowledge on the interplay between ABA and GSH in regulating seed dormancy, germination, stomatal closure and tolerance to drought.

Abscisic acid modulates differential physiological and biochemical responses of roots, stems, and leaves in mung bean seedlings to cadmium stress

Experiments were conducted to determine how exogenous abscisic acid (ABA) mediates the tolerance of plants to cadmium (Cd) exposure. Cd stress strongly reduced all the growth parameters of mung bean seedlings. Cd significantly increased ascorbate peroxidase (APX) and catalase (CAT) activities in roots and stems, and peroxidase (POD) activities in roots, stems, and leaves of mung bean seedlings. Cd caused remarkable increases in the levels of leaf chlorophyll and carotenoid, root polyphenols, and malondialdehyde (MDA) and proline in the three organs. However, Cd greatly decreased leaf CAT activity, root and leaf ascorbic acid (AsA) levels, and stem and leaf polyphenol levels. Foliar application of ABA partially alleviated Cd toxicity on the seedlings. ABA could restore most of the changed biochemical parameters caused by Cd, suggesting that ABA played roles in the protection of membrane lipid peroxidation and the modulation of antioxidative defense systems in response to Cd stress. Our results also implied the differential physiological and biochemical responsive patterns of roots, stems, and leaves to Cd and ABA in mung bean seedlings. The great changes in many biochemical parameters in roots suggested that roots were the first to be affected by Cd and play pivotal roles in response to Cd, especially in chelating Cd and reducing Cd absorption.

Lower cadmium accumulation and higher antioxidative capacity in edible parts of Brassica campestris L. seedlings applied with glutathione under cadmium toxicity

Glutathione (GSH) is involved in not only plant developmental processes but also plant responses to abiotic stresses. A hydroponic experiment was performed to explore the protective roles of exogenous GSH in mitigating cadmium (Cd) stress in Brassica campestris L. seedlings by analyzing the morphological and physiological parameters. Results showed that Cd caused severe growth inhibition and Cd accumulation. However, application of GSH significantly mitigated toxic symptoms induced by Cd, including the improvement of the photosynthesis-, plant growth-, and root morphology-related parameters in seedlings under Cd stress. These responses were associated with a striking increase in activities of representative antioxidative enzymes and contents of corresponding non-enzymatic antioxidants. In vivo imaging of O₂^.- and H₂O₂, and the detection of lipid peroxidation further demonstrated that increased ability by GSH for Brassica campestris L. seedlings to endure Cd stress was consistent with a striking elevation of ratios of reduced to oxidized glutathione (GSH/GSSG) and ascorbic acid to dehydroascorbic acid (AsA/DHA). Additionally, GSH application increased Cd retained in roots, thus significantly decreased its translocation from root to shoot, ultimately decreased Cd accumulation in shoots. Taken together, our results proved evidence for GSH in ameliorating Cd toxicity via reducing Cd accumulation in shoots and increasing oxidation resistance. Accordingly, application of GSH could be a high-efficiency and promising strategy to decrease Cd concentration in edible parts of Brassica campestris L. in agricultural production.

Stomata control is changed in a chlorophyll b-free barley mutant

The barley (Hordeum vulgare L.) chlorina f2 3613 mutant exhibits low photosynthesis and slow growth. This results from downregulation of the levels of photosynthetic antenna proteins caused by the absence of chl b, the major regulator of photosynthetic antennae in land plants. Here, we demonstrate that, when grown in the field in full sunlight, this mutant displays a changed pattern of stomatal responses compared with the parental wild-type cultivar Donaria. However, stomatal regulation of chlorina f2 3613 plants was restored when plants were placed under a shade cover for several days. The shade cover reduced incident PAR from 2000-2200μmolm-2s-1 to 800-880μmolm-2s-1 as measured at noon. Contents of ABA, the xanthophyll precursors of ABA biosynthesis and minor antenna proteins, as well as reactive oxygen species levels in stomata and the sensitivity of stomata to exogenously supplied ABA, were determined in leaves of wild-type Donaria and chlorina f2 3613 before and after shading. The results support the view that the restoration of stomatal control in barley chlorina f2 3613 is correlated with an increase in the levels of the minor antenna protein Lhcb6, which has recently been implicated in the enhancement of stomatal sensitivity to ABA in Arabidopsis thaliana (L.) Heynh.