Light intensity and spectrum play a major role in the regulation of the growth, development, and stress response of plants. Changes in the light conditions affect the formation of reactive oxygen species, the activity of the antioxidants, and, consequently, the redox environment in the plant tissues. Many metabolic processes, thus the biogenesis and function of miRNAs, are redox-responsive. The miRNAs, in turn, can modulate various components of the redox system, and this process is also associated with the alteration in the intensity and spectrum of the light. In this review, we would like to summarise the possible regulatory mechanisms by which the alterations in the light conditions can influence miRNAs in a redox-dependent manner. Daily and seasonal fluctuations in the intensity and spectral composition of the light can affect the expression of miRNAs, which can fine-tune the various physiological and biochemical processes due to their effect on their target genes. The interactions between the redox system and miRNAs may be modulated by light conditions, and the proposed function of this regulatory network and its effect on the various biochemical and physiological processes will be introduced in plants.
Effects of ascorbate (ASA) and hydrogen peroxide (H2O2) on metabolite profile was compared in wheat. Interestingly, the redox environment became more oxidized after ASA treatment and more reduced after H2O2 addition based on the ratios of oxidised and reduced ascorbate and glutathione. The excess of ASA could inhibit, while H2O2 could induce the oxidative pentose phosphate pathway producing reducing power as shown by the unchanged and decreased glucose-6-phosphate content, respectively. This different effect on glucose-6-phosphate content can also explain the reduced formation of several amino acids from the intermediate products of glycolysis after ASA treatment and their constant or greater levels after H2O2 addition. In contrast to most amino acids, the accumulation of Pro was greatly induced by ASA, and this change was fivefold greater than after H2O2 addition. This difference could also contribute to the distinct redox shifts after the two treatments, since NADPH is oxidised during Pro synthesis. The more oxidising environment after ASA treatment activated several transcripts related to the ascorbate–glutathione cycle and the pentose phosphate pathway. Our results indicate the overcompensating effect of ASA and H2O2 on the redox environment in leaf tissues and the subsequent different adjustment of metabolite profile and the related transcript levels.
Salicylic acid (SA) plays a crucial role not only in defence against pathogen attacks, but also in abiotic stress responses. Recently, some key steps of SA signalling outlined the importance of redox state-dependent processes. This study explores the role of glutathione transferases (GSTs) in the transcriptional reprogramming of redox status-related genes in seven-day-old wild type and Atgst mutant Arabidopsis thaliana plants. The timing of redox changes, detected by the redox-sensitive green fluorescent protein (roGFP2), differed in wild type roots treated with 10 μM or 100 μM SA. Our results verified how the applied SA concentrations had different effect on the expression of oxidative stress- and redox-related genes, among them on the expression of AtGSTF8 and AtGSTU19 genes. Lower vitality and less negative EGSH values were specific characteristics of the Atgst mutants compared to the wild type plants throughout the experiment. Changes in the redox potential were only modest in the mutants after SA treatments. A slightly modified gene expression pattern was observed in control conditions and after 1 h of SA treatments in Atgst mutants compared to Col-0 roots. These data originating from the whole roots provide indirect evidence for the role of the investigated AtGSTF8 and AtGSTU19 isoenzymes in the transduction of the redox signal. Our results demonstrate that the investigated Arabidopsis GSTs have a role in maintaining the levels of reactive oxygen species- and redox homeostasis and are involved in transcriptional reprogramming in the roots.
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