Antioxidative Machinery for Redox Homeostasis During Abiotic Stress

Environmental stresses of (a)biotic origin induce the production of multitudinous compounds (metabolites and proteins) as protective defense mechanisms in plants. On account of the regulation of some of these compounds, arbuscular mycorrhizal fungi (AMF) reinforce the inherent tolerance of plants toward the stress of different origins and kind. This article reviews two specific fundamental mechanisms that are categorically associated with mycorrhiza in alleviating major abiotic stresses, salt, drought, and heavy metal (HM) toxicity. It puts emphasis on aquaporins (AQPs), the conduits of water and stress signals; and polyamines (PAs), the primordial stress molecules, which are regulated by AMF to assure water, nutrient, ion, and redox homeostasis. Under stressful conditions, AMF-mediated host AQP responses register distinct patterns: an upregulation to encourage water and nutrient uptake; a downregulation to restrict water loss and HM uptake; or no alterations. The patterns thereof are apparently an integrative outcome of the duration, intensity, and type of stress, AMF species, the interaction of fungal AQPs with that of plants, and the host type. However, the cellular and molecular bases of mycorrhizal influence on host AQPs are largely unexplored. The roles of PAs in augmenting the antioxidant defense system and improving the tolerance against oxidative stress are well-evident. However, the precise mechanism by which mycorrhiza accords stress tolerance by influencing the PA metabolism per se is abstruse and broadly variable under different stresses and plant species. This review comprehensively analyzes the current state-of-art of the involvement of AMF in “PA and AQP modulation” under abiotic stress and identifies the lesser-explored landscapes, gaps in understanding, and the accompanying challenges. Finally, this review outlines the prospects of AMF in realizing sustainable agriculture and provides insights into potential thrust areas of research on AMF and abiotic stress.

Download Full-text

Thiol redox-regulation for efficient adjustment of sulfur metabolism in acclimation to abiotic stress

Journal of Experimental Botany ◽

10.1093/jxb/erz118 ◽

2019 ◽

Vol 70 (16) ◽

pp. 4223-4236 ◽

Cited By ~ 3

Author(s):

Wilena Telman ◽

Karl-Josef Dietz

Keyword(s):

Abiotic Stress ◽

Redox Regulation ◽

Sulfur Metabolism ◽

Redox Homeostasis ◽

Stress Conditions ◽

Fine Tuning ◽

Sulfur Assimilation ◽

Carbon And Nitrogen ◽

Protein Functions ◽

Thiol Redox

Abstract Sulfur assimilation and sulfur metabolism are tightly controlled at the transcriptional, post-transcriptional, and post-translational levels in order to meet the demand for reduced sulfur in growth and metabolism. These regulatory mechanisms coordinate the cellular sulfhydryl supply with carbon and nitrogen assimilation in particular. Redox homeostasis is an important cellular parameter intimately connected to sulfur by means of multiple thiol modifications. Post-translational thiol modifications such as disulfide formation, sulfenylation, S-nitrosylation, persulfidation, and S-glutathionylation allow for versatile switching and adjustment of protein functions. This review focuses on redox-regulation of enzymes involved in the sulfur assimilation pathway, namely adenosine 5´-phosphosulfate reductase (APR), adenosine 5´-phosphosulfate kinase (APSK), and γ-glutamylcysteine ligase (GCL). The activity of these enzymes is adjusted at the transcriptional and post-translational level depending on physiological requirements and the state of the redox and reactive oxygen species network, which are tightly linked to abiotic stress conditions. Hormone-dependent fine-tuning contributes to regulation of sulfur assimilation. Thus, the link between oxylipin signalling and sulfur assimilation has been substantiated by identification of the so-called COPS module in the chloroplast with its components cyclophilin 20–3, O-acetylserine thiol lyase, 2-cysteine peroxiredoxin, and serine acetyl transferase. We now have a detailed understanding of how regulation enables the fine-tuning of sulfur assimilation under both normal and abiotic stress conditions.

Download Full-text

Genetic compensation of triacylglycerol biosynthesis in the green microalga Chlamydomonas reinhardtii

10.1101/2021.08.12.455529 ◽

2021 ◽

Author(s):

Yi-Ying Lee ◽

Rudolph Park ◽

Stephen Miller ◽

Yantao Li

Keyword(s):

Abiotic Stress ◽

Chlamydomonas Reinhardtii ◽

Insertional Mutagenesis ◽

Rapid Development ◽

Redox Homeostasis ◽

Model Systems ◽

Knockout Mutant ◽

Genetic Robustness ◽

Tag Biosynthesis ◽

Genetic Compensation

Genetic compensation has been proposed to explain phenotypic differences between gene knockouts and knockdowns in several metazoan and plant model systems. With the rapid development of reverse genetic tools such as CRISPR/Cas9 and RNAi in microalgae, it is increasingly important to assess whether genetic compensation affects the phenotype of engineered algal mutants. While exploring triacylglycerol (TAG) biosynthesis pathways in the model alga Chlamydomonas reinhardtii, it was discovered that knockout of certain genes catalyzing rate-limiting steps of TAG biosynthesis, type-2 diacylglycerol acyltransferase genes (DGTTs), triggered genetic compensation under abiotic stress conditions. Genetic compensation of a DGTT1 null mutation by a related PDAT gene was observed regardless of the strain background or mutagenesis approach, e.g., CRISPR/Cas 9 or insertional mutagenesis. However, no compensation was found in the PDAT knockout mutant. The effect of PDAT knockout was evaluated in a Δvtc1 mutant, in which PDAT was up-regulated under stress, resulting in a 90% increase in TAG content. Knockout of PDAT in the Δvtc1 background induced a 12.8-fold upregulation of DGTT1 and a 272.3% increase in TAG content in Δvtc1/pdat1 cells, while remaining viable. These data suggest that genetic compensation contributes to the genetic robustness of microalgal TAG biosynthetic pathways, maintaining lipid and redox homeostasis in the knockout mutants under abiotic stress. This work demonstrates examples of genetic compensation in microalgae, implies the physiological relevance of genetic compensation in TAG biosynthesis under stress, and provides guidance for future genetic engineering and mutant characterization efforts.

Download Full-text

Biostimulants in Viticulture: A Sustainable Approach against Biotic and Abiotic Stresses

Plants ◽

10.3390/plants11020162 ◽

2022 ◽

Vol 11 (2) ◽

pp. 162

Author(s):

Eleonora Cataldo ◽

Maddalena Fucile ◽

Giovan Battista Mattii

Keyword(s):

Abiotic Stress ◽

Redox Homeostasis ◽

Phenylpropanoid Pathway ◽

Soil Tillage ◽

Soil Fertilization ◽

Biotic Stresses ◽

Beneficial Effects ◽

Sustainable Products ◽

Grape Quality ◽

Resistance Inducers

Climate change and disproportionate anthropogenic interventions, such as the excess of phytopharmaceutical products and continuous soil tillage, are jeopardizing viticulture by subjecting plants to continuous abiotic stress. One of the main physiological repercussions of abiotic stress is represented by the unbalanced redox homeostasis due to the overproduction of reactive oxygen species (ROS), ultimately leading to a state of oxidative stress (detrimental to grape quality). To these are added the direct and indirect damages caused by pathogens (biotic stresses). In light of this scenario, it is inevitable that sustainable techniques and sensitivity approaches for environmental and human health have to be applied in viticulture. Sustainable viticulture can only be made with the aid of sustainable products. Biostimulant (PB) applications (including resistance inducers or elicitors) in the vineyard have become interesting maneuvers for counteracting vine diseases and improving grape quality. These also represent a partial alternative to soil fertilization by improving nutrient absorption and avoiding its leaching into the groundwater. Their role as elicitors has important repercussions in the stimulation of the phenylpropanoid pathway by triggering the activation of several enzymes, such as polyphenol oxidase, lipoxygenase, phenylalanine ammonia-lyase, and peroxidase (with the accumulation of phenolic compounds). The present review paper summarizes the PBs’ implications in viticulture, gathering historical, functional, and applicative information. This work aims to highlight the innumerable beneficial effects on vines brought by these products. It also serves to spur the scientific community to a greater contribution in investigating the response mechanisms of the plant to positive inductions.

Download Full-text

Structural and functional characterisation of two novel durum wheat annexin genes in response to abiotic stress

Functional Plant Biology ◽

10.1071/fp17212 ◽

2018 ◽

Vol 45 (5) ◽

pp. 542 ◽

Cited By ~ 3

Author(s):

Marwa Harbaoui ◽

Rania Ben Saad ◽

Nihed Ben Halima ◽

Mouna Choura ◽

Faiçal Brini

Keyword(s):

Abiotic Stress ◽

Durum Wheat ◽

Stress Responses ◽

Triticum Turgidum ◽

Expression Patterns ◽

Redox Homeostasis ◽

Heavy Metal Stress ◽

Active Role ◽

Crop Productivity ◽

Wheat Varieties

Abiotic stress results in massive loss of crop productivity throughout the world. Understanding the plant gene regulatory mechanisms involved in stress responses is very important. Annexins are a conserved multigene family of Ca-dependent, phospholipid-binding proteins with suggested functions in response to environmental stresses and signalling during plant growth and development. Annexins function to counteract oxidative stress, maintain cell redox homeostasis and enhance drought tolerance. A full-length cDNA of two genes (TdAnn6 and TdAnn12) encoding annexin proteins were isolated and characterised from Tunisian durum wheat varieties (Triticum turgidum L. subsp. durum cv. Mahmoudi). Analyses of the deduced proteins encoded by annexin cDNAs (TdAnn6 and TdAnn12) indicate the presence of the characteristic four repeats of 70–75 amino acids and the motifs proposed to be involved in Ca2+ binding. Gene expression patterns obtained by real-time PCR revealed differential temporal and spatial regulation of the two annexin genes in durum wheat under different abiotic stress conditions such as salt (NaCl 150 mM), osmotic (10% polyethylene glycol 8000), ionic (LiCl 10 mM), oxidative (H2O2), ABA (100 µM), salicylic acid (10 mM), cold (4°C) and heat (37°C) stress. The two annexin genes were not regulated by heavy metal stress (CdCl2 150 µM). Moreover, heterologous expression of TdAnn6 and TdAnn12 in yeast improves its tolerance to abiotic stresses, suggesting annexin’s involvement in theses stress tolerance mechanisms. Taken together, our results show that the two newly isolated wheat annexin might play an active role in modulating plant cell responses to abiotic stress responses.

Download Full-text