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Plants can experience a variety of environmental stresses that significantly impact their fitness and survival. Additionally, biotic stress can harm agriculture, leading to reduced crop yields and economic losses worldwide. As a result, plants have developed defense strategies to combat potential invaders. These strategies involve regulating redox homeostasis. Several studies have documented the positive role of plant antioxidants, including Ascorbate (Asc), under biotic stress conditions. Asc is a multifaceted antioxidant that scavenges ROS, acts as a co‐factor for different enzymes, regulates gene expression, and facilitates iron transport. However, little attention has been given to Asc and its transport, regulatory effects, interplay with phytohormones, and involvement in defense processes under biotic stress. Asc interacts with other components of the redox system and phytohormones to activate various defense responses that reduce the growth of plant pathogens and promote plant growth and development under biotic stress conditions. Scientific reports indicate that Asc can significantly contribute to plant resistance against biotic stress through mutual interactions with components of the redox and hormonal systems. This review focuses on the role of Asc in enhancing plant resistance against pathogens. Further research is necessary to gain a more comprehensive understanding of the molecular and cellular regulatory processes involved. [ABSTRACT FROM AUTHOR]

We assumed that miRNAs might regulate the physiological and biochemical processes in plants through their effects on the redox system and phytohormones. To check this hypothesis, the transcriptome profile of wild‐type Arabidopsis and lines with decreased ascorbate (Asc), glutathione (GSH), or salicylate (Sal) levels were compared. GSH deficiency did not influence the miRNA expression, whereas lower levels of Asc and Sal reduced the accumulation of 9 and 44 miRNAs, respectively, but only four miRNAs were upregulated. Bioinformatics analysis revealed that their over‐represented target genes are associated with the synthesis of nitrogen‐containing and aromatic compounds, nucleic acids, and sulphate assimilation. Among them, the sulphate reduction‐related miR395 – ATP‐sulfurylase couple was selected to check the assumed modulating role of the light spectrum. A greater induction of the Asc‐ and Sal‐responsive miR395 was observed under sulphur starvation in far‐red light compared to white and blue light in wild‐type and GSH‐deficient Arabidopsis lines. Sal deficiency inhibited the induction of miR395 by sulphur starvation in blue light, whereas Asc deficiency greatly reduced it independently of the spectrum. Interestingly, sulphur starvation decreased only the level of ATP sulfurylase 4 among the miR395 target genes in far‐red light. The expression level of ATP sulfurylase 3 was higher in far‐red light than in blue light in wild‐type and Asc‐deficient lines. The results indicate the coordinated control of miRNAs by the redox and hormonal system since 11 miRNAs were affected by both Asc and Sal deficiency. This process can be modulated by light spectrum, as shown for miR395. [ABSTRACT FROM AUTHOR]

Light‐dependent (250 or 500 µmol/m2/s, red/far‐red: 15/1; 250 µmol/m2/s and red/far‐red: 10/1) adjustment of glutathione metabolism during cold acclimation (5°C, 7 d) was compared in four wheat genotypes (14‐day‐old) differing in freezing tolerance. Only the shoot fresh weight of the two tolerant genotypes increased during cold, regardless of light conditions. Their electrolyte leakage was decreased in high light intensity. Cold greatly increased both the amount of γ‐glutamylcysteine (glutathione precursor) and cysteinylglycine (degradation product) in all genotypes grown in high intensity and far‐red lights, and consequently, the ratio of their oxidised forms exhibited a great decrease. However, cold induced a fivefold increase in the amount of glutathione and hydroxymethylglutathione disulphides only in the two sensitive genotypes grown in far‐red light. In general, the activities of the four enzymes of ascorbate–glutathione cycle were decreased by cold, except for the two tolerant genotypes cultivated in high light intensity. The gene expression studies did not reveal any transcriptional control of the changes observed at metabolite and activity levels. Our results show that both high intensity and far‐red lights are involved in the control of the cold‐induced changes in the amount/activity of the studied antioxidants, and some of these alterations have positive correlation with the level of freezing tolerance. [ABSTRACT FROM AUTHOR]

Reactive oxygen species and antioxidants have an important role in the regulation of plant growth and development under both optimal and stress conditions. In this study, we investigate a possible redox control of miRNAs in wheat (Triticum aestivum ssp. aestivum). Treatment of seedlings with 10 mM H2O2 via the roots for 24 h resulted in decreased glutathione content, increased half-cell reduction potential of the glutathione disulphide/glutathione redox pair, and greater ascorbate peroxidase activity compared to the control plants. These changes were accompanied by alterations in the miRNA transcript profile, with 70 miRNAs being identified with at least 1.5-fold difference in their expression between control and treated (0, 3, 6 h) seedlings. Degradome sequencing identified 86 target genes of these miRNAs, and 6722 possible additional target genes were identified using bioinformatics tools. The H2O2-responsiveness of 1647 target genes over 24 h of treatment was also confirmed by transcriptome analysis, and they were mainly found to be related to the control of redox processes, transcription, and protein phosphorylation and degradation. In a time-course experiment (0–24 h of treatment) a correlation was found between the levels of glutathione, other antioxidants, and the transcript levels of the H2O2-responsive miRNAs and their target mRNAs. This relationship together with bioinformatics modelling of the regulatory network indicated glutathione-related redox control of miRNAs and their targets, which allows the adjustment of the metabolism to changing environmental conditions. [ABSTRACT FROM AUTHOR]