![]() ![]() Specifically, the conversion of VXC pigments under increased light conditions was studied to determine the relationship between AOX and VDE activities, and to estimate whether this connection is mediated by Asc level. thaliana transformed plant lines on the state of chloroplast photoprotective systems. In the current study, we examined the previously unknown effects of AOX1a expression in A. As a result, the ROS concentrations in AS-12 cells were decreased in comparison with the wild type. ![]() thaliana line for AOX1a (AS-12) displayed a compensatory upregulation of the majority of AOX-encoding genes and genes of other respiratory process components when exposed to moderately high light (400 μmol m −2 s −1). thaliana is the most stress-responsive gene based on the highest variety of stress-inducing factors affecting its expression and the magnitude of the expression response, e.g. In particular, the inhibition of the AOX pathway by salicylhydroxamic acid (SHAM) in Rumex K-1 leaves treated with intense light (600 μmol m −2 s −1) caused a restriction in photosynthetic linear electron flow and decreased xanthophyll cycle (VXC) de-epoxidation and the induction of NPQ. A possible relationship between mETC functioning and the activity of xanthophyll pigment conversion has already been noted. The last step in Asc synthesis is linked with mETC activity thus, this association can connect functioning AOX and VDE. The de-epoxidation of Vx is catalysed by violaxanthin de-epoxidase (VDE), which is activated by low pH in the thylakoid lumen of chloroplasts and uses ascorbate (Asc) as a reductant. Zx is capable of absorbing and dissipating energy from excited Chl. One component of NPQ is pH-dependent and involves zeaxanthin (Zx) formation from the de-epoxidation of violaxanthin (Vx) under the action of light. It is shown that aox1a mutants can respond to high light, particularly in the presence of CP inhibitors, by increasing non-photochemical quenching of Chl fluorescence (NPQ). In addition, AOX gene expression is light-induced and mediated through photoreceptor control. It is also considered that in illuminated green plant tissues, functioning AOX aids in the utilisation of the excessive reducing equivalents transported from the chloroplasts, preventing oxidative damage to photosynthetic organelles and whole cells. ![]() AOX function is important for mitochondrial redox balance maintenance and limiting the formation of ROS. The AOX is capable of shunting electrons from ubiquinone directly to oxygen, bypassing proton-pumping complexes III and IV thus, the total efficiency of respiration is reduced. In addition to the main cytochrome pathway (CP) for electron transport from ubiquinone to O 2, the mETC in higher plants contains the cyanide-insensitive alternative pathway (AP) catalysing by the terminal alternative oxidase (AOX). The involvement of components of the mitochondrial electron transport chain (mETC) is considered to optimize photosynthetic processes in plants. This study emphasizes the role played by AOX in modulating the photoprotection processes and in the maintenance of relationships between mitochondria and chloroplasts by influencing ascorbate content.Ĭhloroplasts and mitochondria, the main organelles that provide energy to plant cells, are in contact at the metabolic and signalling levels, and their relationship maintains homeostasis in photosynthetic cells. Simultaneously, gene expression and the activity of ascorbate peroxidase in the antisense line increased after 8 h of MHL, supporting the compensatory effect of the antioxidant system when AOX1a expression is suppressed. The decline in DEPS in AS-12 plants was attributed to an insufficient violaxanthin de-epoxidase activity, which in turn was associated with a decrease in reduced ascorbate levels in the chloroplasts and leaves. Antisense plants displayed the lowest level of qN and a lower de-epoxidation state (DEPS) relative to plants of the same line after 4–6 h MHL, as well as compared to WT and XX-2 plants after 8 h MHL. After 8 h of MHL, the WT and XX-2 plants showed stable non-photochemical quenching (qN) and violaxanthin cycle activity. Arabidopsis thaliana plants (4 weeks old), comprising three genotypes (wild type, overexpressing and antisense lines for AOX1a), were exposed to moderately high light conditions (MHL, 400 μmol m −2 s −1) in a short-term experiment (8 h). Here, we examined the effects of the AOX pathway on the state of chloroplast photoprotective systems. Alternative oxidase (AOX) in the mitochondrial electron transport chain is considered important for sustaining photosynthesis under high light conditions. ![]()
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