Carbonylation of proteins-an element of plant ageing

Nitric oxide action in the digestive fluid of Nepenthes × ventrata is linked to the modulation of ROS level

Nepenthes are carnivorous plants with photoactive leaves converted into jug-shaped containers filled with the digestive fluid. The digestion requires various enzymes and reactive oxygen species (ROS) that facilitate proteolysis. Reactive nitrogen species are present in the digestive fluid of Nepenthes × ventrata, and the increased nitric oxide (NO) formation is associated with protein degradation. The aim of the work was to verify the beneficial effect of NO application into the trap on the dynamics of protein digestion and ROS homeostasis. Measurements were done using the digestive fluid or the tissue collected from the mature pitcher plants (fed) grown in a greenhouse. Two independent methods confirmed NO formation in the digestive fluid of fed and non-fed traps. NO supplementation with food into the trap accelerated protein degradation in the digestive fluid by increasing the proteolytic activity. NO modulated free radical formation (as the result of direct impact on NADPH oxidase), stimulated ROS scavenging capacity, increased -SH groups and flavonoids content, particularly at the beginning of the digestion. In non-fed traps, the relatively high level of protein nitration in the digestive fluid may prevent self-protein proteolysis. Whereas, after initiation of the digestion decreasing level of nitrated proteins in the fluid may indicate their accelerated degradation. Therefore, it can be assumed that NO exhibits a protective effect on the fluid and the trap tissue before digestion, while during digestion, NO is an accelerator of protein decomposition and the ROS balance keeper.

Screening clusters of charged residues in plants' mitochondrial proteins and biological significance

Protein function is dependent on charge interactions and charge biased regions, which are involved in a wide range of cellular and biochemical processes. We report the development of a new algorithm implemented in Python and its use to identify charge clusters CC (NegativeCC: NCC, PositiveCC: PCC and MixedCC: MCC) and compare their presence in mitochondrial proteins of plant groups. To characterize the resulting CC, statistical, structural and functional analyses were conducted. The screening of 105 399 protein sequences showed that 2.6 %, 0.48 % and 0.03 % of the proteins contain NCC, PCC and MCC, respectively. Mitochondrial proteins encoded by the nuclear genome of green algae have the biggest proportion of both PCC (1.6 %) and MCC (0.4 %) and mitochondrial proteins coded by the nuclear genome of other plants group have the highest portion of NCC (7.5 %). The mapping of the identified CC showed that they are mainly located in the terminal regions of the protein. Annotation showed that proteins with CC are classified as binding proteins, are included in the transmembrane transport processes, and are mainly located in the membrane. The CC scanning revealed the presence of 2373 and 784 sites and 192 and 149 motif profiles within NCC and PCC, respectively. The investigation of CC within pentatricopeptide repeat-containing proteins revealed that they are involved in correct and specific RNA editing. CC were proven to play a key role in providing insightful structural and functional information of complex protein assemblies which could be useful in biotechnological applications.

Reactive nitrogen species act as the enhancers of glutathione pool in embryonic axes of apple seeds subjected to accelerated ageing

MAIN CONCLUSION

Reactive nitrogen species mitigate the deteriorative effect of accelerated seed ageing by affecting the glutathione concentration and activities of GR and GPX-like. The treatment of apple (Malus domestica Borkh.) embryos isolated from accelerated aged seeds with nitric oxide-derived compounds increases their vigour and is linked to the alleviation of the negative effect of excessive oxidation processes. Reduced form of glutathione (GSH) is involved in the maintenance of redox potential. Glutathione peroxidase-like (GPX-like) uses GSH and converts it to oxidised form (GSSG), while glutathione reductase (GR) reduces GSSG into GSH. The aim of this work was to investigate the impact of the short-time NOx treatment of embryos isolated from apple seeds subjected to accelerated ageing on glutathione-related parameters. Apple seeds were subjected to accelerated ageing for 7, 14 or 21 days. Isolated embryos were shortly treated with NOx and cultured for 48 h. During ageing, in the axes of apple embryos, GSH and GSSG levels as well as half-cell reduction potential remained stable, while GR and GPX-like activities decreased. However, the positive effect of NOx in the vigour preservation of embryos isolated from prolonged aged seeds is linked to the increased total glutathione pool, and above all, higher GSH content. Moreover, NOx increased the level of transcripts encoding GPX-like and stimulated enzymatic activity. The obtained results indicate that high seed vigour related to the mode of action of NO and its derivatives is closely linked to the maintenance of higher GSH levels.

Response to Cadmium in Silene vulgaris Ecotypes Is Distinctly Affected by Priming-Induced Changes in Oxidation Status of Macromolecules

This study investigated the impact of several priming agents on metal-tolerant and sensitive Silene vulgaris ecotypes exposed to environmentally relevant cadmium dose. We analyzed how priming-induced changes in the level of lipid, protein, and DNA oxidation contribute to calamine (Cal) and non-calamine (N-Cal) ecotype response to Cd toxicity, and whether the oxidative modifications interrelate with Cd tolerance. In non-primed ecotypes, the levels of DNA and protein oxidation were similar whereas Cal Cd tolerance was manifested in reduced lipid peroxidation. In both ecotypes protective action of salicylic acid (SA) and nitric oxide (NO) priming was observed. SA stimulated growth and reduced lipid and DNA oxidation at most, while NO protected DNA from fragmentation. Priming with hydrogen peroxide reduced biomass and induced DNA oxidation. In N-Cal, priming diminished Cd accumulation and oxidative activity, whereas in Cal, it merely affected Cd uptake and induced protein carbonylation. The study showed that priming did not stimulate extra stress resistance in the tolerant ecotype but induced metabolic remodeling. In turn, the lack of adaptive tolerance made the sensitive ecotype more responsive to the benefits of the primed state. These findings could facilitate priming exploitation with a view of enhancing metallophyte and non-metallophyte suitability for phytoremediation and land revegetation.

Do Reactive Oxygen and Nitrogen Species Have a Similar Effect on Digestive Processes in Carnivorous Nepenthes Plants and Humans?

Carnivorous plants attract animals, trap and kill them, and absorb nutrients from the digested bodies. This unusual (for autotrophs) type of nutrient acquisition evolved through the conversion of photosynthetically active leaves into specialised organs commonly called traps. The genus Nepenthes (pitcher plants) consists of approximately 169 species belonging to the group of carnivorous plants. Pitcher plants are characterised by specialised passive traps filled with a digestive fluid. The digestion that occurs inside the traps of carnivorous plants depends on the activities of many enzymes. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) also participate in the digestive process, but their action is poorly recognised. ROS and RNS, named together as RONS, exhibit concentration-dependent bimodal functions (toxic or signalling). They act as antimicrobial agents, participate in protein modification, and are components of signal transduction cascades. In the human stomach, ROS are considered as the cause of different diseases. RNS have multifaceted functions in the gastrointestinal tract, with both positive and negative impacts on digestion. This review describes the documented and potential impacts of RONS on the digestion in pitcher plant traps, which may be considered as an external stomach.

Interaction of heavy metals in Drosophila melanogaster larvae: Fourier transform infrared spectroscopy and single-cell electrophoresis study

The present study evaluates the Murraya Koenigii (CuLE) and Tinospora Crispa (TiSE) antimutagenic effect and the impact of industrial soil and solid waste leachate on Drosophila larvae. Larvae were exposed to leachate prepared at different pH (7, 4.93, 2.88) and treated with TiSE and CuLE at different concentration (4 g/L and 6 g/L) mixed with standard Drosophila medium. Emphasis was given to the binding interaction of heavy metals with proteins in Drosophila. The change in structure and molecular composition in Drosophila by leachate containing heavy metals induced toxicity has been studied by using Fourier transform infrared (FTIR) spectroscopy. Results from the study demonstrated that CuLE/TiSE administration restored the level of oxidative stress as evidenced by an enhanced antioxidant system and a decrease in lipid peroxidation and protein oxidation. The amide I and amide II bands spectral shifting revealed the binding interaction. The shift in the peak of PO2- asymmetric stretching might be due to compositional changes in nucleic acids. Single-cell electrophoresis was performed to detect the DNA damage which also proved to be ameliorated by administration of CuLE/TiSE. The result concludes that CuLE/TiSE may have great potential in the protection of Drosophila larvae from leachate induced oxidative stress through antioxidant and antimutagenic mechanisms this might help to cope with environmental toxicants.Communicated by Ramaswamy H. Sarma.

Selenate triggers diverse oxidative responses in Astragalus species with diverse selenium tolerance and hyperaccumulation capacity

Selenium (Se) hyperaccumulators are capable of uptake and tolerate high Se dosages. Excess Se-induced oxidative responses were compared in Astragalus bisulcatus and Astragalus cicer. Plants were grown on media supplemented with 0, 25 or 75 μM selenate for 14 days. Both A. bisulcatus and A. cicer accumulated >2000 μg/g dry weight Se to the shoot but the translocation factors of A. cicer were below 1 suggesting its non hyperaccumulator nature. A. cicer showed Se sensitivity indicated by reduced seedling fresh weight, root growth and root apical meristem viability, altered element homeostasis in the presence of Se. In Se-exposed A. bisulcatus, less toxic organic Se forms (mainly MetSeCys, γ-Glu-MetSeCys, and a selenosugar) dominated, while these were absent from A. cicer suggesting that the majority of the accumulated Se may be present as inorganic forms. The glutathione-dependent processes were more affected, while ascorbate levels were not notably influenced by Se in either species. Exogenous Se triggered more intense accumulation of malondialdehyde in the sensitive A. cicer compared with the tolerant A. bisulcatus. The extent of protein carbonylation in the roots of the 75 μM Se-exposed A. cicer exceeded that of A. bisulcatus indicating a correlation between selenate sensitivity and the degree of protein carbonylation. Overall, our results reveal connection between oxidative processes and Se sensitivity/tolerance/hyperaccumulation and contribute to the understanding of the molecular responses to excess Se.

Effect of the metal ion-induced carbonylation modification of mitochondrial membrane channel protein VDAC on cell vitality, seedling growth and seed aging

Introduction

Seeds are the most important carrier of germplasm preservation. However, an irreversible decrease in vigor can occur after the maturation of seeds, denoted as seed aging. Mitochondrion is a crucial organelle in initiation programmed cell death during seed aging. However, the underlying mechanism remains unclear.

Methods

Our previous proteome study found that 13 mitochondria proteins underwent carbonylation modification during the aging of Ulmus pumila L. (Up) seeds. This study detected metal binding proteins through immobilized metal affinity chromatography (IMAC), indicating that metal binding proteins in mitochondria are the main targets of carbonization during seed aging. Biochemistry, molecular and cellular biology methods were adopted to detect metal-protein binding, protein modification and subcellular localization. Yeast and Arabidopsis were used to investigate the biological functions in vivo.

Results and discussion

In IMAC assay, 12 proteins were identified as Fe²+/Cu²+/Zn²+ binding proteins, including mitochondrial voltage dependent anion channels (VDAC). UpVDAC showed binding abilities to all the three metal ions. His204Ala (H204A) and H219A mutated UpVDAC proteins lost their metal binding ability, and became insensitive to metal-catalyzed oxidation (MCO) induced carbonylation. The overexpression of wild-type UpVDAC made yeast cells more sensitive to oxidative stress, retarded the growth of Arabidopsis seedlings and accelerated the seed aging, while overexpression of mutated UpVDAC weakened these effects of VDAC. These results reveal the relationship between the metal binding ability and carbonylation modification, as well as the probable function of VDAC in regulating cell vitality, seedling growth and seed aging.

The transcription factor GhWRKY70 from gossypium hirsutum enhances resistance to verticillium wilt via the jasmonic acid pathway

BACKGROUND

The WRKY transcription factors play significant roles in plant growth, development, and defense responses. However, in cotton, the molecular mechanism of most WRKY proteins and their involvement in Verticillium wilt tolerance are not well understood.

RESULTS

GhWRKY70 is greatly up-regulated in cotton by Verticillium dahliae. Subcellular localization suggests that GhWRKY70 is only located in the nucleus. Transcriptional activation of GhWRKY70 further demonstrates that GhWRKY70 function as a transcriptional activator. Transgenic Arabidopsis plants overexpressing GhWRKY70 exhibited better growth performance and higher lignin content, antioxidant enzyme activities and jasmonic acid (JA) levels than wild-type plants after infection with V. dahliae. In addition, the transgenic Arabidopsis resulted in an enhanced expression level of AtAOS1, a gene related to JA synthesis, further leading to a higher JA accumulation compared to the wild type. However, the disease index (DI) values of the VIGS-treated cotton plants with TRV:WRKY70 were also significantly higher than those of the VIGS-treated cotton plants with TRV:00. The chlorophyll and lignin contents of TRV:WRKY70 plants were significantly lower than those of TRV:00 plants. GhAOS1 expression and JA abundance in TRV:WRKY70 plants were decreased. The GhWRKY70 protein was confirmed to bind to the W-box element in the promoter region of GhAOS by yeast one-hybrid assay and transient expression.

CONCLUSION

These results indicate that the GhWRKY70 transcription factor is a positive regulator in Verticillium wilt tolerance of cotton, and may promote the production of JA via regulation of GhAOS1 expression.

Recent progress in molecular genetics and omics-driven research in seed biology

Elucidating the mechanisms that control seed development, metabolism, and physiology is a fundamental issue in biology. Michel Caboche had long been a catalyst for seed biology research in France up until his untimely passing away last year. To honour his memory, we have updated a review written under his coordination in 2010 entitled "Arabidopsis seed secrets unravelled after a decade of genetic and omics-driven research". This review encompassed different molecular aspects of seed development, reserve accumulation, dormancy and germination, that are studied in the lab created by M. Caboche. We have extended the scope of this review to highlight original experimental approaches implemented in the field over the past decade such as omics approaches aimed at investigating the control of gene expression, protein modifications, primary and specialized metabolites at the tissue or even cellular level, as well as seed biodiversity and the impact of the environment on seed quality.

A deeply conserved protease, acylamino acid-releasing enzyme (AARE), acts in ageing in Physcomitrella and Arabidopsis

Reactive oxygen species (ROS) are constant by-products of aerobic life. In excess, ROS lead to cytotoxic protein aggregates, which are a hallmark of ageing in animals and linked to age-related pathologies in humans. Acylamino acid-releasing enzymes (AARE) are bifunctional serine proteases, acting on oxidized proteins. AARE are found in all domains of life, albeit under different names, such as acylpeptide hydrolase (APEH/ACPH), acylaminoacyl peptidase (AAP), or oxidized protein hydrolase (OPH). In humans, AARE malfunction is associated with age-related pathologies, while their function in plants is less clear. Here, we provide a detailed analysis of AARE genes in the plant lineage and an in-depth analysis of AARE localization and function in the moss Physcomitrella and the angiosperm Arabidopsis. AARE loss-of-function mutants have not been described for any organism so far. We generated and analysed such mutants and describe a connection between AARE function, aggregation of oxidized proteins and plant ageing, including accelerated developmental progression and reduced life span. Our findings complement similar findings in animals and humans, and suggest a unified concept of ageing may exist in different life forms.

Free Radicals Mediated Redox Signaling in Plant Stress Tolerance

Abiotic and biotic stresses negatively affect plant cellular and biological processes, limiting their growth and productivity. Plants respond to these environmental cues and biotrophic attackers by activating intricate metabolic-molecular signaling networks precisely and coordinately. One of the initial signaling networks activated is involved in the generation of reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive sulfur species (RSS). Recent research has exemplified that ROS below the threshold level can stimulate plant survival by modulating redox homeostasis and regulating various genes of the stress defense pathway. In contrast, RNS regulates the stress tolerance potential of crop plants by modulating post-translation modification processes, such as S-nitrosation and tyrosine nitration, improving the stability of protein and DNA and activating the expression of downstream stress-responsive genes. RSS has recently emerged as a new warrior in combating plant stress-induced oxidative damage by modulating various physiological and stress-related processes. Several recent findings have corroborated the existence of intertwined signaling of ROS/RNS/RSS, playing a substantial role in crop stress management. However, the molecular mechanisms underlying their remarkable effect are still unknown. This review comprehensively describes recent ROS/RNS/RSS biology advancements and how they can modulate cell signaling and gene regulation for abiotic stress management in crop plants. Further, the review summarizes the latest information on how these ROS/RNS/RSS signaling interacts with other plant growth regulators and modulates essential plant functions, particularly photosynthesis, cell growth, and apoptosis.

Proteome-wide analysis of hydrogen peroxide-induced protein carbonylation in Arabidopsis thaliana

INTRODUCTION

Protein carbonylation is a non-enzymatic and irreversible post-translational modification that occurs naturally in living organisms under the direct or indirect effect of reactive oxygen species (ROS). In animals, signaling pathways involving numerous carbonylated proteins have been identified, highlighting the dual role of these molecules in ROS signal transduction. In plants, studies on phytohormone signaling (auxin, methyl jasmonate, abscisic acid) have shown that reactive carbonyl species (RCS: acrolein, malondialdehyde, 4-hydroxynonenal, etc.), derived from the action of ROS on lipids, play important roles in secondary root formation and stomatal closure. However, the carbonylated proteins involved in these signaling pathways remain to be identified.

METHODS

In this study, we analyzed proteins responsive to carbonylation by exogenous hydrogen peroxide (H2O2) by profiling the carbonyl proteome extracted from Arabidopsis thaliana leaves after H2O2 treatment. Carbonylated proteins were enriched at the peptide level and analyzed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS).

RESULTS AND DISCUSSION

We identified 35 and 39 uniquely carbonylated proteins in the untreated and the H2O2-treated plant samples, respectively. In comparison to the control treatment, gene ontology enrichment analysis revealed that most of the carbonylated proteins identified in the H2O2-treated plant samples are related to sulfate adenylyl transferases and amidophosphoribosyl transferases involved in the immune system response, defense response, and external stimulus-response. These results indicated that exogenous H2O2 caused a change in the pattern of protein carbonylation in A. thaliana leaves. Protein carbonylation may thus influence the plant transcriptome and metabolism in response to H2O2 and ROS-triggering external stimuli.

ROS and RNS Alterations in the Digestive Fluid of Nepenthes × ventrata Trap at Different Developmental Stages

The carnivorous pitcher plant, Nepenthes × ventrata (Hort. ex Fleming = N. ventricosa Blanco × N. alata Blanco), produces passive traps containing digestive fluid. Although reactive oxygen species (ROS) in the fluid were detected in some pitcher plants, the participation of reactive nitrogen species (RNS) in the digestion process has not yet been examined. The aim of this work was to investigate the production of superoxide anion (O2•-), nitric oxide (NO) and peroxynitrite (ONOO-) levels in the digestive fluid of traps throughout organ development. We revealed the ROS and RNS occurrence in the digestive fluid, linked to the ROS-scavenging capacity and total phenolics content. In digestive fluid from the fed traps, NO emission was higher than in the fluid from the developed unfed pitcher. The concentration of nitrite (NO2-) decreased in the fluid from the fed traps in comparison to the unfed ones, pointing at NO2- as the key source of NO. The enhanced emission of NO was associated with lowered content of ONOO- in the fluid, probably due to lower production of O2•-. At the same time, despite a decline in total phenolics, the maximum ROS scavenging capacity was detected. In addition, ROS and RNS were noted even in closed traps, suggesting their involvement not only in digestion per se but also their action as signaling agents in trap ontogeny.

Nitric Oxide in Seed Biology

Nitric oxide (NO) has been recognized as a gasotransmitter in the mainstream of plant research since the beginning of the 21st century. It is produced in plant tissue and the environment. It influences plant physiology during every ontogenetic stage from seed germination to plant senescence. In this review, we demonstrate the increased interest in NO as a regulatory molecule in combination with other signalling molecules and phytohormones in the information network of plant cells. This work is a summary of the current knowledge on NO action in seeds, starting from seed pretreatment techniques applied to increase seed quality. We describe mode of action of NO in the regulation of seed dormancy, germination, and aging. During each stage of seed physiology, NO appears to act as a key agent with a predominantly beneficial effect.

Kilning invokes oxidative changes in malt proteins

Beneath glycation, oxidation reactions may take place at cereal proteins during production of malt. The extent of oxidative chemical changes at malt proteins has not yet been studied. In the present short communication, malt protein was characterized by the determination of free thiol groups and degree of methionine oxidation as well as the sites that are reactive to covalent modification by 2,4-dinitrophenylhydrazine (DNPH, “protein carbonylation”). Protein carbonylation in pale malts was around 1.5 nmol/mg protein and increased with increasing malt colour. Investigations on the protein pellet isolated for determination of carbonylation revealed that solubility and colour may disturb the quantification of carbonyl sites in roasted malts. Free thiols decreased with increasing malt colour already in pale malts (EBC < 10). The formation of methionine sulfoxide (MetSO) was intensified with increasing malt colour. An amount of 7–20% of methionine was converted to MetSO in pale and dark malt, whereas nearly 60% of methionine was oxidized to MetSO in roasted malts. The formation of methionine sulfone was negligible. This study shows that malt proteins suffer from oxidation during kilning, and future studies will have to show whether this supports the pro- or antioxidant activity of malt.

The Effect of Leaf Wounding on Basil Plants of Different Developmental Stages

Leaf wounding is a common stress that triggers a great number of plant mechanisms, while the overall plant status and age could also be critical for these mechanisms. However, there are not sufficient data about plants' physiological responses after leaf wounding that has been imposed at different developmental stages. In this study, physiological parameters, such as photosynthesis, transpiration, and stomatal conductance, as well as the chlorophyll and anthocyanin leaf contents, of Ocimum basilicum var. minimum L. plants were measured for seven days on wounded plants during three different developmental stages (vegetative, budding, and flowering). All of the measurements were conducted on control and wounded plants, while on the latter they were conducted on both wounded and intact leaves. The physiological parameters mentioned above revealed a remarkable decrease in wounded leaves of the budding and flowering plants, while they seemed to be only partially affected on the leaves of vegetative plants. The physiological parameters' decrease was not only an immediate plant response that was observed 1-2 h after wounding, but, in general, it was constant (during the seven days of treatments) and diurnal (from 8 a.m. to 8 p.m.). The wounded leaves revealed an immediate and constant anthocyanin content decrease during all of the developmental stages, while the corresponding chlorophyll decrease was mainly evident in the flowering plants. Regarding the intact leaves, they exhibited, in general, a similar profile to that of the control ones. The results above reveal that at the vegetative stage, basil plants are more tolerant to leaf wounding than those at the budding and flowering stages, implying that the plant's response to wounding is a phenomenon that depends on the plant's developmental stage.

The RPN12a proteasome subunit is essential for the multiple hormonal homeostasis controlling the progression of leaf senescence

The 26S proteasome is a conserved multi-subunit machinery in eukaryotes. It selectively degrades ubiquitinated proteins, which in turn provides an efficient molecular mechanism to regulate numerous cellular functions and developmental processes. Here, we studied a new loss-of-function allele of RPN12a, a plant ortholog of the yeast and human structural component of the 19S proteasome RPN12. Combining a set of biochemical and molecular approaches, we confirmed that a rpn12a knock-out had exacerbated 20S and impaired 26S activities. The altered proteasomal activity led to a pleiotropic phenotype affecting both the vegetative growth and reproductive phase of the plant, including a striking repression of leaf senescence associate cell-death. Further investigation demonstrated that RPN12a is involved in the regulation of several conjugates associated with the auxin, cytokinin, ethylene and jasmonic acid homeostasis. Such enhanced aptitude of plant cells for survival in rpn12a contrasts with reports on animals, where 26S proteasome mutants generally show an accelerated cell death phenotype.

Cold stratification-induced dormancy removal in apple (Malus domestica Borkh.) seeds is accompanied by an increased glutathione pool in embryonic axes

A reduced form of glutathione (GSH) is an essential metabolite that participates in the control of reactive oxygen species (ROS) levels in cells. GSH plays a pivotal role in seed biology as a modulator of seed viability and germination. The GSH:GSSG ratio and half-cell reduction potential (E_GSSG/2GSH) serve as indicators of the oxidative status in seeds. Apple (Malus domestica Borkh.) seeds are deeply dormant, and this state is removed by long-term cold stratification. The aim of our work was to examine the modification of GSH and GSSG content, GSH:GSSG ratio and E_GSSG/2GSH in the embryonic axes isolated from apple seeds subjected to cold stratification for 7, 14, 21 and 40 d. Our data indicated that cold stratification increased the generation of free radicals in the embryonic axes, which correlated with an alteration in the expression of genes encoding Rboh, particularly RbohC. GSH and GSSG levels increased during prolonged cold stratification of apple seeds. This was accompanied by the modification of glutathione reductase and glutathione peroxidase-like activities, which did not match their transcript levels. The steady-state GSH:GSSG ratio and E_GSSG/2GSH in the axes of embryos subjected to cold stratification indicated no impact of the dormancy removal treatment on apple seed viability. We suggest that the glutathione system is an important component of the redox network and is involved in the management of the seed transition from dormant to nondormant states.

Enhanced Carbonylation of Photosynthetic and Glycolytic Proteins in Antibiotic Timentin-Treated Tobacco In Vitro Shoot Culture

Antibiotics are used in plant in vitro tissue culture to eliminate microbial contamination or for selection in genetic transformation. Antibiotic timentin has a relatively low cytotoxic effect on plant tissue culture; however, it could induce an enduring growth-inhibiting effect in tobacco in vitro shoot culture that persists after tissue transfer to a medium without antibiotic. The effect is associated with an increase in oxidative stress injury in plant tissues. In this study, we assessed changes of reactive oxygen species accumulation, protein expression, and oxidative protein modification response associated with enduring timentin treatment-induced growth suppression in tobacco (Nicotiana tabacum L.) in vitro shoot culture. The study revealed a gradual 1.7 and 1.9-fold increase in superoxide (O₂^•−) content at the later phase of the propagation cycle for treatment control (TC) and post-antibiotic treatment (PA) shoots; however, the O₂^•− accumulation pattern was different. For PA shoots, the increase in O₂^•− concentration occurred several days earlier, resulting in 1.2 to 1.4-fold higher O₂^•− concentration compared to TC during the period following the first week of cultivation. Although no protein expression differences were detectable between the TC and PA shoots by two-dimensional electrophoresis, the increase in O₂^•− concentration in PA shoots was associated with a 1.5-fold increase in protein carbonyl modification content after one week of cultivation, and protein carbonylation analysis revealed differential modification of 26 proteoforms involved in the biological processes of photosynthesis and glycolysis. The results imply that the timentin treatment-induced oxidative stress might be implicated in nontranslational cellular redox balance regulation, accelerates the development of senescence of the shoot culture, and contributes to the shoot growth-suppressing effect of antibiotic treatment.

Graphene oxide influence in soil bacteria is dose dependent and changes at osmotic stress: growth variation, oxidative damage, antioxidant response, and plant growth promotion traits of a Rhizobium strain

Climate change events, such as drought, are increasing and soil bacteria can be severely affected. Moreover, the accumulation of emerging pollutants is expected to rapidly increase, and their impact on soil organisms, their interactions, and the services they provide is poorly known. The use of graphene oxide (GO) has been increasing due to its enormous potential for application in several areas and it is expected that concentration in soil will increase in the future, potentially causing disturbances in soil microorganisms not yet identified.Here we show the effects that GO nanosheets can cause on soil bacteria, in particular those that promote plant growth, in control and 10% polyethylene glycol (PEG) conditions. Low concentrations of GO nanosheets did not affect the growth of Rhizobium strain E20-8, but under osmotic stress (PEG) GO decreased bacterial growth even at lower concentrations. GO caused oxidative stress, with antioxidant mechanisms being induced to restrain damage, effectively at lower concentrations, but less effective at higher concentrations, and oxidative damage overcame. Under osmotic stress, alginate and glycine betaine osmoregulated the bacteria. Simultaneous exposure to PEG and GO induced oxidative damage. Plant growth promotion traits (indole acetic acid and siderophores production) were increased by osmotic stress and GO did not disturb these abilities. In the context of climate change, our findings might be relevant as they can form the premises for the implementation of crop production methodologies adapted to the new prevailing conditions, which include the presence of nanoparticles in the soil and more frequent and severe drought.

Cellular senescence, rejuvenation and potential immortality

Ageing, death, and potential immortality lie at the heart of biology, but two seemingly incompatible paradigms coexist in different research communities and have done since the nineteenth century. The universal senescence paradigm sees senescence as inevitable in all cells. Damage accumulates. The potential immortality paradigm sees some cells as potentially immortal, especially unicellular organisms, germ cells and cancerous cells. Recent research with animal cells, yeasts and bacteria show that damaged cell constituents do in fact build up, but can be diluted by growth and cell division, especially by asymmetric cell division. By contrast, mammalian embryonic stem cells and many cancerous and 'immortalized' cell lines divide symmetrically, and yet replicate indefinitely. How do they acquire their potential immortality? I suggest they are rejuvenated by excreting damaged cell constituents in extracellular vesicles. If so, our understanding of cellular senescence, rejuvenation and potential immortality could be brought together in a new synthesis, which I call the cellular rejuvenation hypothesis: damaged cell constituents build up in all cells, but cells can be rejuvenated either by growth and cell division or, in 'immortal' cell lines, by excreting damaged cell constituents. In electronic supplementary material, appendix, I outline nine ways in which this hypothesis could be tested.

Reactive Oxygen Species, Antioxidant Responses and Implications from a Microbial Modulation Perspective

Simple Summary

Environmental conditions are subject to unprecedented changes due to recent progressive anthropogenic activities on our planet. Plants, as the frontline of food security, are susceptible to these changes, resulting in the generation of unavoidable byproducts of metabolism (ROS), which eventually affect their productivity. The response of plants to these unfavorable conditions is highly intricate and depends on several factors, among them are the species/genotype tolerance level, intensity, and duration of stress factors. Defensive mechanisms in plant systems, by nature, are concerned primarily with generating enzymatic and non-enzymatic antioxidants. In addition to this, plant-microbe interactions have been found to improve immune systems in plants suffering from drought and salinity stress.

Abstract

Plants are exposed to various environmental stresses in their lifespan that threaten their survival. Reactive oxygen species (ROS), the byproducts of aerobic metabolism, are essential signalling molecules in regulating multiple plant developmental processes as well as in reinforcing plant tolerance to biotic and abiotic stimuli. However, intensified environmental challenges such as salinity, drought, UV irradiation, and heavy metals usually interfere with natural ROS metabolism and homeostasis, thus aggravating ROS generation excessively and ultimately resulting in oxidative stress. Cellular damage is confined to the degradation of biomolecular structures, including carbohydrates, proteins, lipids, pigments, and DNA. The nature of the double-edged function of ROS as a secondary messenger or harmful oxidant has been attributed to the degree of existing balance between cellular ROS production and ROS removal machinery. The activities of enzyme-based antioxidants, catalase (CAT, EC 1.11.1.6), monodehydroascorbate reductase (MDHAR, E.C.1.6.5.4), dehydroascorbate reductase (DHAR, EC 1.8.5.1), superoxide dismutase (SOD, EC 1.15.1.1), ascorbate peroxidase (APX, EC 1.11.1.11), glutathione reductase (GR, EC 1.6.4.2), and guaiacol peroxidase (GPX, EC 1.11.1.7); and non-enzyme based antioxidant molecules, ascorbate (AA), glutathione (GSH), carotenoids, α-tocopherol, prolines, flavonoids, and phenolics, are indeed parts of the defensive strategies developed by plants to scavenge excess ROS and to maintain cellular redox homeostasis during oxidative stress. This review briefly summarises current knowledge on enzymatic and non-enzymatic antioxidant machinery in plants. Moreover, additional information about the beneficial impact of the microbiome on countering abiotic/biotic stresses in association with roots and plant tissues has also been provided.

A Simplified Method to Assay Protein Carbonylation by Spectrophotometry

Protein carbonylation is an irreversible oxidation process leading to a loss of function of carbonylated proteins. Carbonylation is largely considered as a hallmark of oxidative stress, the level of protein carbonylation being an indicator of the oxidative cellular status. The method described herein represents an adaptation to the commonly used 2,4-dinitrophenylhydrazine (DNPH)-based spectrophotometric method to monitor protein carbonylation level. The classical final sample precipitation was replaced by a gel filtration step avoiding the tedious and repetitive washings of the protein pellet to remove free DNPH while allowing optimal protein recovery.This improved protocol here implemented to assay protein carbonylation in plant leaves can potentially be used with any cellular extract.

Melatonin treatment improves postharvest quality and regulates reactive oxygen species metabolism in "Feizixiao" litchi based on principal component analysis

Postharvest quality of litchi reduces rapidly during storage at room temperature. This study aimed to investigate the effect of melatonin treatment on postharvest quality and oxidative stress markers of litchi fruit during cold storage. The "Feizixiao" litchi was treated with melatonin solution concentrations of 0.2 and 0.6 mmol·L^-1 and then stored at 4°C for 12 days. The results confirmed that the melatonin treatment effectively maintained the appearance and color of the litchi fruit, suppressed the peel browning, and improved the litchi quality. The treatment also significantly enhanced the levels of endogenous melatonin, antioxidant components (total phenolics, flavonoids, and anthocyanin), and antioxidant enzyme activities of the fruit. It also inhibited the other oxidative stress markers, such as O 2 - , H₂O₂, MDA, and protein carbonyl content, and upregulated the expressions of antioxidant and Msr-related genes. Correlation and principal component analyses further confirmed that the melatonin treatment effectively delayed the fruit senescence by enhancing the antioxidant enzyme activities and modulating peel browning and reactive oxygen species metabolism of the litchi fruit via regulating gene expression of the related enzymes (SOD and PPO). These findings suggested that the exogenous application of melatonin to litchi during the postharvest is an ideal way to preserve the fruit quality and delay fruit senescence.

Nitric Oxide as a Remedy against Oxidative Damages in Apple Seeds Undergoing Accelerated Ageing

Seed ageing is associated with a high concentration of reactive oxygen species (ROS). Apple (Malus domestica Borkh.) seeds belong to the orthodox type. Due to a deep dormancy, they may be stored in dry condition at 5 °C for a long time, without viability loss. In the laboratory, artificial ageing of apple seeds is performed by imbibition in wet sand at warm temperature (33 °C). The aim of the work was to study nitric oxide (NO) as a seed vigour preservation agent. Embryos isolated from apple seeds subjected to accelerated ageing for 7, 14, 21 or 40 days were fumigated with NO. Embryo quality was estimated by TTC and MDA tests. ROS level was confirmed by NBT staining. We analysed the alteration in transcript levels of CAT, SOD and POX. NO fumigation of embryos of seeds aged for 21 days stimulated germination and increased ROS level which correlated to the elevated expression of RBOH. The increased total antioxidant capacity after NO fumigation was accompanied by the increased transcript levels of genes encoding enzymatic antioxidants, that could protect against ROS overaccumulation. Moreover, post-aged NO application diminished the nitro-oxidative modification of RNA, proving NO action as a remedy in oxidative remodelling after seeds ageing.

Toxicity of meta-Tyrosine

L-Tyrosine (Tyr) is one of the twenty proteinogenic amino acids and also acts as a precursor for secondary metabolites. Tyr is prone to modifications, especially under conditions of cellular redox imbalance. The oxidation of Tyr precursor phenylalanine leads to the formation of Tyr non-proteinogenic isomers, including meta-Tyr (m-Tyr), a marker of oxidative stress. The aim of this review is to summarize the current knowledge on m-Tyr toxicity. The direct m-Tyr mode of action is linked to its incorporation into proteins, resulting in their improper conformation. Furthermore, m-Tyr produced by some plants as an allelochemical impacts the growth and development of neighboring organisms. In plants, the direct harmful effect of m-Tyr is due to its modification of the proteins structure, whereas its indirect action is linked to the disruption of reactive oxygen and nitrogen species metabolism. In humans, the elevated concentration of m-Tyr is characteristic of various diseases and ageing. Indeed, m-Tyr is believed to play an important role in cancer physiology. Thus, since, in animal cells, m-Tyr is formed directly in response to oxidative stress, whereas, in plants, m-Tyr is also synthesized enzymatically and serves as a chemical weapon in plant-plant competition, the general concept of m-Tyr role in living organisms should be specified.

Altitudinal Variation of Metabolites, Mineral Elements and Antioxidant Activities of Rhodiola crenulata (Hook.f. & Thomson) H.Ohba

Rhodiolacrenulata (Hook.f. & Thomson) H.Ohba is an alpine medicinal plant that can survive in extreme high altitude environments. However, its changes to extreme high altitude are not yet clear. In this study, the response of Rhodiola crenulata to differences in altitude gradients was investigated through chemical, ICP-MS and metabolomic methods. A targeted study of Rhodiola crenulata growing at three vertical altitudes revealed that the contents of seven elements Ca, Sr, B, Mn, Ni, Cu, and Cd, the phenolic components, the ascorbic acid, the ascorbic acid/dehydroascorbate ratio, and the antioxidant capacity were positively correlated with altitude, while the opposite was true for total ascorbic acid content. Furthermore, 1165 metabolites were identified: flavonoids (200), gallic acids (30), phenylpropanoids (237), amino acids (100), free fatty acids and glycerides (56), nucleotides (60), as well as other metabolites (482). The differential metabolite and biomarker analyses suggested that, with an increasing altitude: (1) the shikimic acid-phenylalanine-phenylpropanoids-flavonoids pathway was enhanced, with phenylpropanoids upregulating biomarkers much more than flavonoids; phenylpropanes and phenylmethanes upregulated, and phenylethanes downregulated; the upregulation of quercetin was especially significant in flavonoids; upregulation of condensed tannins and downregulation of hydrolyzed tannins; upregulation of shikimic acids and amino acids including phenylalanine. (2) significant upregulation of free fatty acids and downregulation of glycerides; and (3) upregulation of adenosine phosphates. Our findings provide new insights on the responses of Rhodiola crenulata to extreme high altitude adversity.

Nitrate alleviates ammonium toxicity in wheat (Triticum aestivum L.) by regulating tricarboxylic acid cycle and reducing rhizospheric acidification and oxidative damage

Ammonium (NH₄⁺) is one of the most important nutrients required by plants. However, a high concentration of NH₄⁺ as the sole nitrogen source suppresses plant growth. Although nitrate (NO₃^-) can alleviate NH₄⁺ toxicity, the mechanisms underlying this ability have not been fully elucidated. In this study, wheat plants were cultivated in hydroponic solution with 7.5 mM NO₃^- (control), 7.5 mM NH₄⁺ (sole ammonium, SA) or 7.5 mM NH₄⁺ plus 1.0 mM NO₃^- (ammonium and nitrate, AN). The results showed that compared with the control, the SA treatment significantly decreased root growth, protein content and the concentrations of most intermediates and the activity of enzymes from the tricarboxylic acid (TCA) cycle. Moreover, increased the activity of plasma membrane H⁺-ATPase and the rate of H⁺ efflux along roots, caused solution acidification, and increased the activity of mitochondrial respiratory chain complexes I-IV and the contents of protein-bound carbonyls and malondialdehyde in roots. SA treatment induced ultrastructure disruption and reduced the viability of root cells. Compared with the SA treatment, the AN treatment increased root growth, protein content, the concentrations of most intermediates and the activity of enzymes from the TCA cycle. Furthermore, AN treatment decreased the rate of H⁺ efflux, retarded medium acidification, decreased protein carbonylation and lipid peroxidation in roots and relieved ultrastructure disruption and increased the viability of root cells. Taken together, these results indicate that NO₃^--dependent alleviation of NH₄⁺ toxicity in wheat seedlings is closely associated with physiological processes that mediate TCA cycle, relieve rhizospheric acidification and decrease the production of ROS and oxidative damage.

Measuring ROS and redox markers in plant cells

Reactive oxygen species (ROS) are produced throughout plant cells as a by-product of electron transfer processes. While highly oxidative and potentially damaging to a range of biomolecules, there exists a suite of ROS-scavenging antioxidant strategies that maintain a redox equilibrium. This balance can be disrupted in the event of cellular stress leading to increased ROS levels, which can act as a useful stress signal but, in excess, can result in cell damage and death. As crop plants become exposed to greater degrees of multiple stresses due to climate change, efforts are ongoing to engineer plants with greater stress tolerance. It is therefore important to understand the pathways underpinning ROS-mediated signalling and damage, both through measuring ROS themselves and other indicators of redox imbalance. The highly reactive and transient nature of ROS makes this challenging to achieve, particularly in a way that is specific to individual ROS species. In this review, we describe the range of chemical and biological tools and techniques currently available for ROS and redox marker measurement in plant cells and tissues. We discuss the limitations inherent in current methodology and opportunities for advancement.

Heat stress-mediated effects on the morphophysiological, biochemical, and ultrastructural parameters of germinating Melanoxylon brauna Schott. seeds

The present study showed that the heat stress (40 °C) caused changes in morphophysiological, biochemical, and ultrastructural parameters to the seeds Melanoxylon brauna, ultimately leading to loss of germination capacity. Temperature is an abiotic factor that influences seed germination. In the present study, we investigated morphophysiological, biochemical, and ultrastructural changes during the germination of Melanoxylon brauna seeds under heat stress. Seed germination was evaluated at constant temperatures of 25 and 40 °C. The samples consisted of seeds soaked in distilled and ionized water for 48 and 96 h at both temperatures. For the evaluation of internal morphology, the seeds were radiographed. Ultrastructural parameters were assessed using transmission electron microscopy (TEM). The production of reactive oxygen species (ROS), content of malondialdehyde (MDA) and glucose, carbonylated proteins, and activity of the enzymes (superoxide dismutase-SOD, ascorbate peroxidase-APX, catalase-CAT, peroxidase-POX, glucose-6-phosphate dehydrogenase-G6PDH, lipase, α- and β-amylase, and protease) were measured by spectrophotometric analysis. An 82% reduction in the germination of M. brauna seeds was observed at 25 °C, and 0% at 40 °C. TEM showed that seeds submitted to heat stress (40 °C) had poorly developed mitochondria and significantly reduced respiration rates. The content of ROS and protein carbonylation in seeds subjected to 40 °C increased compared to that at 25 °C. The activity of antioxidant enzymes, namely SOD, APX, CAT, and POX, was significantly reduced in seeds subjected to heat stress. Glucose content, G6PDH, and lipase activity also decreased when the seeds were exposed to heat stress. Conversely, α- and β-amylase enzymes and the protease increased due to the increase in temperature. Our data showed that the increase in temperature caused an accumulation of ROS, increasing the oxidative damage to the seeds, which led to mitochondrial dysfunction, ultimately leading to loss of germination.

Reactive oxygen species (ROS) constitute an additional player in regulating epithelial development

Reactive oxygen species (ROS) are highly reactive molecules produced in cells. So far, they have mostly been connected to diseases and pathological conditions. More recent results revealed a somewhat unexpected role of ROS in control of developmental processes. In this review, we elaborate on ROS in development, focussing on their connection to epithelial tissue morphogenesis. After briefly summarising unique characteristics of epithelial cells, we present some characteristic features of ROS species, their production and targets, with a focus on proteins important for epithelial development and function. Finally, we provide examples of regulation of epithelial morphogenesis by ROS, and also of developmental genes that regulate the overall redox status. We conclude by discussing future avenues of research that will further elucidate ROS regulation in epithelial development.

Is protein carbonylation a biomarker of seed priming and ageing?

For a long time, it has been known that seed priming allows the improvement of plant production and tolerance to abiotic stresses. However, a negative effect on the longevity of the seeds thus primed was observed; these mechanisms are still poorly understood. In addition, it has been shown by several authors that seed ageing is associated with the oxidation and particularly with carbonylation of protein. Our work consisted in studying the AOPP and carbonyl protein at the different parts of the embryo from freshly primed seeds and from those that have been primed for 4 years (after storage). We subjected Vigna unguiculata (L.) Walp. seeds to a single or double hydropriming. Our study showed that hydropriming, and more particularly a double cycle of hydration-dehydration, makes it possible to attenuate the oxidation of the protein while it favours a certain threshold of carbonylation in the freshly dehydrated seeds in order to better trigger the germination process. On the other hand, after a storage period of 4 years, these dehydrated seeds are characterised by a strong accumulation of the products of oxidation and especially carbonylated protein, compared with the untreated seeds, which could explain the decrease of the longevity of these seeds.

Neuroprotective Effects of Acrocomia aculeata Pulp Oil Microcapsules on Rats Subjected to Chronic Stress

Acrocomia aculeata fruits are rich in monounsaturated fatty acid, β-carotene, tocopherol, and other antioxidant compounds. The aim of our study was to investigate and compare the protective effects of A. aculeata pulp oil and microencapsulated pulp oil on brain oxidative damage induced by chronic restraint stress (CRS) in rats (cortex, hippocampus, and striatum). Thirty-six Wistar rats were divided into six treatment groups: C, P, and M groups received 1 μL/g of body weight of distilled water, pulp oil, and pulp oil microcapsules by daily gavage, respectively. The SC, SP, and SM groups received 1 μL/g of body weight of distilled water, pulp oil, and pulp oil microcapsules by daily gavage, respectively, and were then subjected to uninterrupted 6 h of CRS. After 21 days of testing, the rats were euthanized and the brain tissue of the groups was removed for evaluation for oxidative damage markers and antioxidant enzymes. Endpoints of oxidative stress (OS) markers (lipid peroxidation, protein carbonylation, and reduced glutathione [GSH]) and antioxidant enzymes (superoxide dismutase and catalase) were evaluated. By imposing chronic stress on rats, pulp oil and microcapsules of pulp oil induced positive antioxidant responses, mainly by increasing the GSH content, increasing the ability of neural tissues to deal with inherent OS, thus protecting against neurodegenerative diseases. The administration of A. aculeata pulp oil and microencapsulated pulp oil made the reversal of the oxidant parameters, which may protect the brain tissue of rats altered by CRS. The Clinical Trial Registration number: n° 1.008/2018 CEUA/UFMS.

Signaling Toward Reactive Oxygen Species-Scavenging Enzymes in Plants

Reactive oxygen species (ROS) are signaling molecules essential for plant responses to abiotic and biotic stimuli as well as for multiple developmental processes. They are produced as byproducts of aerobic metabolism and are affected by adverse environmental conditions. The ROS content is controlled on the side of their production but also by scavenging machinery. Antioxidant enzymes represent a major ROS-scavenging force and are crucial for stress tolerance in plants. Enzymatic antioxidant defense occurs as a series of redox reactions for ROS elimination. Therefore, the deregulation of the antioxidant machinery may lead to the overaccumulation of ROS in plants, with negative consequences both in terms of plant development and resistance to environmental challenges. The transcriptional activation of antioxidant enzymes accompanies the long-term exposure of plants to unfavorable environmental conditions. Fast ROS production requires the immediate mobilization of the antioxidant defense system, which may occur via retrograde signaling, redox-based modifications, and the phosphorylation of ROS detoxifying enzymes. This review aimed to summarize the current knowledge on signaling processes regulating the enzymatic antioxidant capacity of plants.

Jasmonic Acid Impairs Arabidopsis Seedling Salt Stress Tolerance Through MYC2-Mediated Repression of CAT2 Expression

High salinity causes ionic, osmotic, and oxidative stresses to plants, and the antioxidant enzyme Catalase2 (CAT2) plays a vital role in this process, while how CAT2 expression is regulated during plant response to high salinity remains elusive. Here, we report that phytohormone jasmonic acid (JA) impairs plant salt stress tolerance by repressing CAT2 expression in an MYC2-dependent manner. Exogenous JA application decreased plant salt stress tolerance while the jar1 mutant with reduced bioactive JA-Ile accumulation showed enhanced salt stress tolerance. JA enhanced salt-induced hydrogen peroxide (H₂O₂) accumulation, while treatment with H₂O₂-scavenger glutathione compromised such effects of JA on plant H₂O₂ accumulation and salt stress tolerance. In addition, JA repressed CAT2 expression in salt-stressed wild-type plant but not in myc2, a mutant of the master transcriptional factor MYC2 in JA signaling, therefore, the myc2 mutant exhibited increased salt stress tolerance. Further study showed that mutation of CAT2 largely reverted lower reactive oxygen species (ROS) accumulation, higher CAT activity, and enhanced salt stress tolerance of the myc2 mutant in myc2 cat2-1 double mutant, revealing that CAT2 functions downstream JA-MYC2 module in plant response to high salinity. Together, our study reveals that JA impairs Arabidopsis seedling salt stress tolerance through MYC2-mediated repression of CAT2 expression.