The oxidative damage induced by abiotic stress factors such as salinity, drought, extreme temperatures, heavy metals, pollution, and high irradiance has been studied in Arabidopsis thaliana. Ultra-weak photon emission (UPE) is presented as a signature reflecting the extent of the oxidation process and/or damage. It can be used to predict the physiological state and general health of plants. This study presents an overview of a potential research platform where the technique can be applied. The results presented can aid in providing invaluable information for developing strategies to mitigate abiotic stress in crops by improving plant breeding programs with a focus on enhancing tolerance. This study evaluates the applicability of charged couple device (CCD) imaging in evaluating plant stress and degree of damage and to discuss the advantages and limitations of the claimed non-invasive label-free tool.

• Keywords
• Antioxidants, Reactive oxygen species, Stress imaging, Two-dimensional photon emission imaging, Wounding,
• MeSH
• Arabidopsis * physiology   MeSH
• Photons * MeSH
• Stress, Physiological * MeSH
• Publication type
• Journal Article MeSH
• Review MeSH

Photosystem II (PSII) represents the most vulnerable component of the photosynthetic machinery and its response in plants subjected to abiotic stress has been widely studied over many years. PSII is a thylakoid membrane-located multiprotein pigment complex that catalyses the light-induced electron transfer from water to plastoquinone with the concomitant production of oxygen. PSII is rich in intrinsic (PsbA and PsbD, namely D1 and D2, CP47 or PsbB and CP43 or PsbC) but also extrinsic proteins. The first ones are more largely conserved from cyanobacteria to higher plants while the extrinsic proteins are different among species. It has been found that extrinsic proteins involved in oxygen evolution change dramatically the PSII efficiency and PSII repair systems. However, little information is available on the effects of abiotic stress on their function and structure.

• Keywords
• abiotic stress, extrinsic protein, intrinsic protein, photosynthesis, photosystem II,
• Publication type
• Journal Article MeSH
• Review MeSH

Products of lipid peroxidation induce detrimental structural changes in cell membranes, such as the formation of water pores, which occur in the presence of lipids with partially oxidized chains. However, the influence of another class of products, dicarboxylic acids, is still unclear. These products have greater mobility in the lipid bilayer, which enables their aggregation and the formation of favorable sites for the appearance of pores. Therefore, dodecanedioic acid (DDA) was selected as a model product. Additionally, the influence of several structurally different flavonoids on DDA aggregation via formation of hydrogen bonds with carboxyl groups was investigated. The molecular dynamics of DDA in DOPC lipid bilayer revealed the formation of aggregates extending over the hydrophobic region of the bilayer and increasing its polarity. Consequently, water penetration and the appearance of water wires was observed, representing a new step in the mechanism of pore formation. Furthermore, DDA molecules were found to interact with lipid polar groups, causing them to be buried in the bilayer. The addition of flavonoids to the system disrupted aggregate formation, resulting in the displacement of DDA molecules from the center of the bilayer. The placement of DDA and flavonoids in the lipid bilayer was confirmed by small-angle X-ray scattering. Atomic force microscopy and electron paramagnetic resonance were used to characterize the structural properties. The presence of DDA increased bilayer roughness and decreased the ordering of lipid chains, confirming its detrimental effects on the membrane surface, while flavonoids were found to reduce or reverse these changes.

• Keywords
• antioxidant, dicarboxylic acid, flavone, flavonol, lipid/peroxidation, oxidized lipid, phospholipid/phosphatidylcholine, physical biochemistry,
• Publication type
• Journal Article MeSH

Deg proteases play critical roles in photoprotection and PSII-repair circle, which remains elusive in cereal crops including wheat. Here, a Deg7-encoding gene TaDeg7 was silenced in wheat via a Barley stripe mosaic virus-induced gene-silencing system (BSMV-VIGS). When the expression level of TaDeg7 was downregulated, the photosynthetic activity including CO2 assimilation rate, actual photochemical efficiency of PSII, and electron transport rate declined while the nonphotochemical quenching increased significantly. When grown in high light, the BSMV:TaDeg7 plants accumulated more soluble sugar, malondialdehyde, and superoxide anion but had lower superoxide dismutase activity and less ascorbic acid. Additionally, the expression levels of TaPsbA and TarbcS were repressed in the BSMV:TaDeg7 plants in high light. The BSMV:TaDeg7 plants also were more sensitive to high-light stress. Collectively, it appeared that TaDeg7 may be a potential target for wheat radiation-use efficiency improvement against high light stress.

• Keywords
• Deg7 protease, high light, photosynthetic efficiency, virus-induced gene silencing, wheat,
• Publication type
• Journal Article MeSH

Reactive oxygen species (ROS) are formed in photosystem II (PSII) under various types of abiotic and biotic stresses. It is considered that ROS play a role in chloroplast-to-nucleus retrograde signaling, which changes the nuclear gene expression. However, as ROS lifetime and diffusion are restricted due to the high reactivity towards biomolecules (lipids, pigments, and proteins) and the spatial specificity of signal transduction is low, it is not entirely clear how ROS might transduce signal from the chloroplasts to the nucleus. Biomolecule oxidation was formerly connected solely with damage; nevertheless, the evidence appears that oxidatively modified lipids and pigments are be involved in chloroplast-to-nucleus retrograde signaling due to their long diffusion distance. Moreover, oxidatively modified proteins show high spatial specificity; however, their role in signal transduction from chloroplasts to the nucleus has not been proven yet. The review attempts to summarize and evaluate the evidence for the involvement of ROS in oxidative signaling in PSII.

• Keywords
• Chloroplast-to-nucleus retrograde signaling, Lipid peroxidation, Protein oxidation, Reactive oxygen species,
• MeSH
• Chloroplasts * metabolism   MeSH
• Photosystem II Protein Complex * metabolism   MeSH
• Lipids MeSH
• Oxidative Stress MeSH
• Reactive Oxygen Species metabolism   MeSH
• Signal Transduction physiology   MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Photosystem II Protein Complex * MeSH
• Lipids MeSH
• Reactive Oxygen Species MeSH

Formation of singlet oxygen (1O2) was reported to accompany light stress in plants, contributing to cell signaling or oxidative damage. So far, Singlet Oxygen Sensor Green (SOSG) has been the only commercialized fluorescent probe for 1O2 imaging though it suffers from several limitations (unequal penetration and photosensitization) that need to be carefully considered to avoid misinterpretation of the analysed data. Herein, we present results of a comprehensive study focused on the appropriateness of SOSG for 1O2 imaging in three model photosynthetic organisms, unicellular cyanobacteria Synechocystis sp. PCC 6803, unicellular green alga Chlamydomonas reinhardtii and higher plant Arabidopsis thaliana. Penetration of SOSG differs in both unicellular organisms; while it is rather convenient for Chlamydomonas it is restricted by the presence of mucoid sheath of Synechocystis, which penetrability might be improved by mild heating. In Arabidopsis, SOSG penetration is limited due to tissue complexity which can be increased by pressure infiltration using a shut syringe. Photosensitization of SOSG and SOSG endoperoxide formed by its interaction with 1O2 might be prevented by illumination of samples by a red light. When measured under controlled conditions given above, SOSG might serve as specific probe for detection of intracellular 1O2 formation in photosynthetic organisms.

• MeSH
• Arabidopsis metabolism   MeSH
• Color MeSH
• Chlamydomonas reinhardtii metabolism   MeSH
• Fluorescent Dyes metabolism   MeSH
• Photosynthesis physiology   MeSH
• Oxygen metabolism   MeSH
• Oxidation-Reduction MeSH
• Singlet Oxygen metabolism   MeSH
• Light MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Fluorescent Dyes MeSH
• Oxygen MeSH
• Singlet Oxygen MeSH

Singlet oxygen (1O2) is formed by triplet-triplet energy transfer from triplet chlorophyll to O2 via Type II photosensitization reaction in photosystem II (PSII). Formation of triplet chlorophyll is associated with the change in spin state of the excited electron and recombination of triplet radical pair in the PSII antenna complex and reaction center, respectively. Here, we have provided evidence for the formation of 1O2 by decomposition of protein hydroperoxide in PSII membranes deprived of Mn4O5Ca complex. Protein hydroperoxide is formed by protein oxidation initiated by highly oxidizing chlorophyll cation radical and hydroxyl radical formed by Type I photosensitization reaction. Under highly oxidizing conditions, protein hydroperoxide is oxidized to protein peroxyl radical which either cyclizes to dioxetane or recombines with another protein peroxyl radical to tetroxide. These highly unstable intermediates decompose to triplet carbonyls which transfer energy to O2 forming 1O2. Data presented in this study show for the first time that 1O2 is formed by decomposition of protein hydroperoxide in PSII membranes deprived of Mn4O5Ca complex.

• MeSH
• Chlorophyll metabolism   MeSH
• Electron Spin Resonance Spectroscopy methods   MeSH
• Photosystem II Protein Complex metabolism   MeSH
• Oxygen metabolism   MeSH
• Oxidation-Reduction MeSH
• Hydrogen Peroxide metabolism   MeSH
• Peroxides metabolism   MeSH
• Energy Transfer physiology   MeSH
• Singlet Oxygen metabolism   MeSH
• Light MeSH
• Light-Harvesting Protein Complexes metabolism   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Chlorophyll MeSH
• Photosystem II Protein Complex MeSH
• Oxygen MeSH
• perhydroxyl radical MeSH Browser
• Hydrogen Peroxide MeSH
• Peroxides MeSH
• Singlet Oxygen MeSH
• Light-Harvesting Protein Complexes MeSH