Oxidative Stress and Heavy Metals in Plants

Health Risk Assessment for Potentially Toxic Elements Accumulation in Amaranthaceae Family Cultivars and their Correlation with Antioxidants and Antinutrients

Delhi's agricultural hub, nestled along the Yamuna floodplains, faces soil and water contamination issues. Utilizing organic waste composts is gaining traction to improve soil quality, but uncertainties remain about their efficacy in reducing harmful elements. The study examined three Amaranthaceae cultivars, comparing organic waste composts with chemical fertilizer to evaluate correlations between heavy metals, antioxidants, and antinutrients to assess their bioremediation potential. "Heavy metals" or "potentially toxic elements (PTE)" levels in soil and leaves were measured by ICP-MS, while antioxidants and antinutrients were analyzed with UV-VIS spectroscopy. The study revealed higher PTE levels in floodplain soil, with Cr, Ni, and Cd exceeding safe limits in all cultivars. Compost amendments reduced these pollutants by 28% compared to chemical fertilizers, decreasing bioaccumulation by 20%. Health risk assessments showed lower risks in compost-amended cultivars. Additionally, compost amendment displayed a stronger negative correlation between PTE and antioxidants, suggesting effective bioremediation. Overall, compost amendments offer promise for mitigating PTE in metropolitan floodplains.

Unboxing PGPR-mediated management of abiotic stress and environmental cleanup: what lies inside?

Abiotic stresses including heavy metal toxicity, drought, salt and temperature extremes disrupt the plant growth and development and lowers crop output. Presence of environmental pollutants further causes plants suffering and restrict their ability to thrive. Overuse of chemical fertilizers to reduce the negative impact of these stresses is deteriorating the environment and induces various secondary stresses to plants. Therefore, an environmentally friendly strategy like utilizing plant growth-promoting rhizobacteria (PGPR) is a promising way to lessen the negative effects of stressors and to boost plant growth in stressful conditions. These are naturally occurring inhabitants of various environments, an essential component of the natural ecosystem and have remarkable abilities to promote plant growth. Furthermore, multifarious role of PGPR has recently been widely exploited to restore natural soil against a range of contaminants and to mitigate abiotic stress. For instance, PGPR may mitigate metal phytotoxicity by boosting metal translocation inside the plant and changing the metal bioavailability in the soil. PGPR have been also reported to mitigate other abiotic stress and to degrade environmental contaminants remarkably. Nevertheless, despite the substantial quantity of information that has been produced in the meantime, there has not been much advancement in either the knowledge of the processes behind the alleged positive benefits or in effective yield improvements by PGPR inoculation. This review focuses on addressing the progress accomplished in understanding various mechanisms behind the protective benefits of PGPR against a variety of abiotic stressors and in environmental cleanups and identifying the cause of the restricted applicability in real-world.

Single and combined phytoextraction of lead and cadmium on submerged plants Potamogeton pusillus L.: removal, bioaccumulation pattern, and phytotoxicity

Under the present investigation, the submerged plant Potamogeton pusillus has been tested for the removal of lead (Pb) and cadmium (Cd). P. pusillus removal efficiency and accumulation capacity were examined in separated Pb and Cd solutions, at 0.5, 1.0, and 2 mg L-1, and in solutions where both metals were present at the same concentration (0.5, 1.0, and 2 mg L-1), under laboratory conditions for 3, 7, and 10 days. Also, we examined the removal efficiency and accumulation capacity when a set of plants were exposed to 0.5 mg L-1 of Pb (or Cd) and increasing concentrations (0.5, 1, and 2 mg L-1) of Cd (or Pb) for 10 days. The effect of Cd and Pb was assessed by measuring changes in the chlorophylls, carotenoids, and malondialdehyde contents. Results showed that P. pusillus could accumulate Cd and Pb from individual solutions. Roots and leaves accumulated the highest amount of Cd and Pb followed by the stems. Some phytotoxic effects were observed, especially at individual Cd exposures, but these effects were not observed in the two-metal system. The removal and accumulation of Pb by P. pusillus were significantly enhanced in the presence of Cd under certain conditions, presenting a good alternative for the removal of these metals from polluted aquifers. To the extent of our knowledge, this is the first report on both enhanced phytoextraction of Pb in the presence of Cd and bioaccumulation of these heavy metals by P. pusillus.

Transcriptomic and physiological analyses of Trichoderma citrinoviride HT-1 assisted phytoremediation of Cd contaminated water by Phragmites australis

Plant growth promoting microbe assisted phytoremediation is considered a more effective approach to rehabilitation than the single use of plants, but underlying mechanism is still unclear. In this study, we combined transcriptomic and physiological methods to explore the mechanism of plant growth promoting microbe Trichoderma citrinoviride HT-1 assisted phytoremediation of Cd contaminated water by Phragmites australis. The results show that the strain HT-1 significantly promoted P. australis growth, increased the photosynthetic rate, enhanced antioxidant enzyme activities. The chlorophyll content and the activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) were increased by 83.78%, 23.17%, 47.60%, 97.14% and 12.23% on average, and decreased the content of malondialdehyde (MDA) by 31.10%. At the same time, strain HT-1 improved the absorption and transport of Cd in P. australis, and the removal rate of Cd was increased by 7.56% on average. Transcriptome analysis showed that strain HT-1 induced significant up-regulated the expression of genes related to oxidative phosphorylation and ribosome pathways, and these upregulated genes promoted P. australis remediation efficiency and resistance to Cd stress. Our results provide a mechanistic understanding of plant growth promoting microbe assisted phytoremediation under Cd stress.

Higher cadmium and zinc accumulation in parsley (Petroselinum crispum) roots activates its antioxidants defense system

Parsley (Petroselinum crispum) is herb with many biological and medicinal benefits for humans. However, growth on zinc (Zn) and cadmium (Cd) contaminated sites might get severely affected due to over accumulation of heavy metals (HM) in different plant tissues. Antioxidants play a crucial role in minimizing the negative effects of HM. The present study investigates the effects of Zn and Cd stress on P. crispum morphological parameters, enzymatic/non-enzymatic antioxidant profiling and metal accumulation in shoot/root. Plants were exposed to different concentrations of Zn (50, 100, 150 and 200 µM) and Cd (10, 20, 40 and 80 µM) along with control (no stress), in soil-less Hoagland's solution. The results showed that Zn and Cd substantially decrease the growth parameters with increased contents of malondialdehyde (MDA), hydrogen peroxide (H2O2), and electrolyte leakage (EL). Non-enzymatic antioxidant activities, like total phenolic contents (TPC) and ferric reducing antioxidant power (FRAP), were induced high in leaves only upon Cd stress and contrarily decreased upon Zn stress. Total flavonoid contents (TFC) were decreased under Zn and Cd stress. Enzymatic antioxidant activities like superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) were also strongly induced upon Cd stress. At the same time, SOD and guaiacol peroxidase (GPX) activity was induced significantly upon Zn stress. Cd uptake and accumulation was notably high in roots as compared to shoots, which suggests P. crispum have a reduced ability to translocate Cd towards aboveground parts (leaves). Additionally, strong induction of antioxidants by P. crispum under Cd stress might indicate the capacity to effectively re-modulate its physiological response. However, further investigations regarding other HMs and experiments at the molecular level are still needed.

Effects of Cd treatment on morphology, chlorophyll content and antioxidant enzyme activity of Elymus nutans Griseb., a native plant in Qinghai-Tibet Plateau

Cd pollution is a global environmental problem. However, the response mechanism of the alpine plant Pelagia under Cd stress remains unclear. Therefore, in this study, a native plant(Elymus nutans Griseb.) of the Qinghai-Tibet Plateau was used as the material to quantify plant height, leaf number, length of leaf, crown width, root number, biomass, Dry weight malondialdehyde (MDA), free proline, superoxide dismutase (SOD), ascorbate enzyme (APX), catalase (CAT) and chlorophyll contents under different Cd concentrations. The results showed that the growth of Elymus nutans Griseb. was a phenomenon of "low concentration promotes growth, high concentration inhibited growth" under Cd treatment. It meant that 10 mg·L^-1 Cd promoted the growth of leaf number, plant height, crown width and tiller number, while 40 mg·L^-1 Cd inhibited the growth of root number and biomass of Elymus nutans Griseb. compare with the control. The MDA content, free proline content, SOD activity, APX activity and CAT activity of Elymus nutans Griseb. was increased with the increase of Cd treatment concentration to resist the oxidative damage caused by Cd to the body. At the same time, the accumulation of chlorophyll A, chlorophyll B and chlorophyll AB was decreased with the increase of Cd stress concentration. In addition, the carotenoid content did not change much between the control group and the treatment group, indicating that Cd treatment had little effect on it. The results could provide a reference for the mechanism of heavy metal resistance and the selection and improvement of Cd -resistant varieties of Elymus nutans Griseb.

Adaptation of Betula pendula Roth., Pinus sylvestris L., and Larix decidua Mill. to environmental stress caused by tailings waste highly contaminated by trace elements

The seedlings of some tree species can successfully develop in areas polluted by heavy metals. Research on such species is important in order to explore the possibility of introducing tree species for the permanent biological stabilization and reclamation of post-flotation tailings, especially after the final recycling of trace metals, but where concentrations remain much higher than in natural soils. To better understand the adaptation and reaction of Betula pendula Roth., Pinus sylvestris L., and Larix decidua Mill. seedlings to heavy metals pollution caused by tailings waste highly contaminated by trace elements: 1) the relationships between the concentration of heavy metals in the soil substrate, the efficiency of heavy metal ions accumulation in plant organs, and the biometric parameters of the seedlings; and 2) the threshold content of heavy metals in the roots above which the plant physiological response is triggered was determined. We assume that there are certain limit concentrations of heavy metals in the soil and fine roots, which depend on the tree species and beyond which the plant responds strongly to stressThe obtained results showed that Betula is a suitable species for the phytostabilization of post-flotation tailings due to its rapid growth rate and production of root biomass. The accumulation of metals in Betula roots was found to be much greater than in Pinus and Larix. Despite the high concentrations of heavy metals in the prepared substrates, there was only a slight transfer of these elements to the aboveground parts of the plant. At high soil concentrations, the heavy metals adversely affected the cellular and physiological processes of plants. In plants growing in such conditions, the activity of the antioxidant system depended both on the species and organ of the plant, as well as on the type and metal concentration.

Assessment of heavy metals bioaccumulation in Silver Birch (Betula pendula Roth) from an AMD active, abandoned gold mine waste

Acid mine drainage (AMD) is generally outlined as one of the largest environmental concerns, characterized by very low pH value of mine waste, heavy metals and high sulphate content. This extremely hostile environment reduces plant ability to develop and grow. Present study focuses on a silver birch (Betula pendula Roth), a pioneer species that grows on an extremely hostile gold mine waste, to investigate the bioaccumulation of rare metals (thallium (Tl) and indium (In)), as well as nine other more common heavy metals (bismuth (Bi), cadmium (Cd), cobalt (Co), copper (Cu), lead (Pb), manganese (Mn), nickel (Ni), silver (Ag) and zinc (Zn)), and to asses phytoextraction and phytostabilization potential of silver birch. Additionally, parameters determining AMD process and overall contamination (pH, electrical conductivity (EC), sulphates (SO42-), arsenic (As), iron (Fe), oxidation-reduction potential (ORP), turbidity, dissolved oxygen (DO), total dissolved solids (TDS), acidity, hardness, X-ray diffraction (XRD) and radioactivity) were determined in mine waste and drainage water samples. To assess the heavy metals bioaccumulation and mine waste status, statistical geochemical indices were determined: bioaccumulation factor (BCF), pollution load index (PLI), geochemical abundance index (GAI) and exposure index (EI). The results show that silver birch bioaccumulates the essential elements Cu, Ni, Mn and Zn, and the nonessential elements Tl (average BCF = 24.99), In (average BC = 23.01) and Pb (average BCF = 0.84). Investigated mine waste was enriched by Bi, Ag and Cd according to positive values of GAI index. Present research provides a novel insight into bioaccumulation of nonessential heavy metals in silver birches who grow on the extremely hostile mine waste, and they exhibit significant phytoremediation potential.

Metal tolerance and Cd phytoremoval ability in Pisum sativum grown in spiked nutrient solution

In the presented study, the effects of cadmium (Cd) stress and silicon (Si) supplementation on the pea plant (Pisum sativum L.) were investigated. The tendency to accumulate cadmium in the relevant morphological parts of the plant (roots and shoots respectively)-bioaccumulation, the transfer of this element in the plant (translocation) and the physiological parameters of the plant through indicators of oxidative stress were determined. Model studies were carried out at pH values 6.0 and 5.0 plant growth conditions in the hydroponic cultivation. It was shown that Cd accumulates mostly in plant roots at both pH levels. However, the Cd content is higher in the plants grown at lower pH. The Cd translocation factor was below 1.0, which indicates that the pea is an excluder plant. The contamination of the plant growth environment with Cd causes the increased antioxidant stress by the growing parameters of the total phenolic content (TPC), polyphenol oxidase activity (PPO), the malondialdehyde (MDA) and lipid peroxidation (LP). The results obtained showed that the supplementation with Si reduces these parameters, thus lowering the oxidative stress of the plant. Moreover, supplementation with Si leads to a lower content of Cd in the roots and reduces bioaccumulation of Cd in shoots and roots of pea plants.

Geranium robertianum L. tolerates various soil types burdened with heavy metals

Many heavy metals (HMs) are essential micronutrients for the growth and development of plants. However, human activities such as mining, smelting, waste disposal, and industrial processes have led to toxic levels of HMs in soil. Fortunately, many plant species have developed incredible adaptive mechanisms to survive and thrive in such harsh environments. As a widespread and ruderal species, Geranium robertianum L. inhabits versatile soil types, both polluted and unpolluted. Considering the ubiquity of G. robertianum, the study aimed to determine whether geographically distant populations can tolerate HMs. We collected soil and plant samples from serpentine, an anthropogenic heavy metal contaminated, and a non-metalliferous site to study the physiological state of G. robertianum. HMs in soil and plants were determined using flame atomic absorption spectrometry. Spectrophotometric methods were used to measure the total content of chlorophylls a and b, total phenolics, phenolic acids, flavonoids, and proline. Principal component analysis (PCA) was used to investigate the potential correlation between HMs concentrations gathered from various soil types and plant samples and biochemical data acquired for plant material. A statistically significant difference was observed for all localities regarding secondary metabolite parameters. A positive correlation between Ni and Zn in soil and Ni and Zn in plant matter was observed (p<0.0005) indicating higher absorption. Regardless of high concentrations of heavy metals in investigated soils, G. robertianum displayed resilience and was capable of thriving. These results may be ascribed to several protective mechanisms that allow G. robertianum to express normal growth and development and act as a pioneer species.

Modifications in Ultrastructural Characteristics and Redox Status of Plants under Environmental Stress: A Review

The rate of global environmental change is unprecedented, with climate change causing an increase in the oscillation and intensification of various abiotic stress factors that have negative impacts on crop production. This issue has become an alarming global concern, especially for countries already facing the threat of food insecurity. Abiotic stressors, such as drought, salinity, extreme temperatures, and metal (nanoparticle) toxicities, are recognized as major constraints in agriculture, and are closely associated with the crop yield penalty and losses in food supply. In order to combat abiotic stress, it is important to understand how plant organs adapt to changing conditions, as this can help produce more stress-resistant or stress-tolerant plants. The investigation of plant tissue ultrastructure and subcellular components can provide valuable insights into plant responses to abiotic stress-related stimuli. In particular, the columella cells (statocytes) of the root cap exhibit a unique architecture that is easily recognizable under a transmission electron microscope, making them a useful experimental model for ultrastructural observations. In combination with the assessment of plant oxidative/antioxidative status, both approaches can shed more light on the cellular and molecular mechanisms involved in plant adaptation to environmental cues. This review summarizes life-threatening factors of the changing environment that lead to stress-related damage to plants, with an emphasis on their subcellular components. Additionally, selected plant responses to such conditions in the context of their ability to adapt and survive in a challenging environment are also described.

Glomus mosseae improved the adaptability of alfalfa (Medicago sativa L.) to the coexistence of cadmium-polluted soils and elevated air temperature

The coexistence of heavy metal-polluted soils and global warming poses serious threats to plants. Many studies indicate that arbuscular mycorrhizal fungi (AMF) can enhance the resistance of plants to adverse environments such as heavy metals and high temperature. However, few studies are carried out to explore the regulation of AMF on the adaptability of plants to the coexistence of heavy metals and elevated temperature (ET). Here, we investigated the regulation of Glomus mosseae on the adaptability of alfalfa (Medicago sativa L.) to the coexistence of cadmium (Cd)-polluted soils and ET. G. mosseae significantly enhanced total chlorophyll and carbon (C) content in the shoots by 15.6% and 3.0%, respectively, and Cd, nitrogen (N), and phosphorus (P) uptake by the roots by 63.3%, 28.9%, and 85.2%, respectively, under Cd + ET. G. mosseae significantly increased ascorbate peroxidase activity, peroxidase (POD) gene expression, and soluble proteins content in the shoots by 13.4%, 130.3%, and 33.8%, respectively, and significantly decreased ascorbic acid (AsA), phytochelatins (PCs), and malondialdehyde (MDA) contents by 7.4%, 23.2%, and 6.5%, respectively, under ET + Cd. Additionally, G. mosseae colonization led to significant increases in POD (13.0%) and catalase (46.5%) activities, Cu/Zn-superoxide dismutase gene expression (33.5%), and MDA (6.6%), glutathione (22.2%), AsA (10.3%), cysteine (101.0%), PCs (13.8%), soluble sugars (17.5%), and proteins (43.4%) contents in the roots and carotenoids (23.2%) under ET + Cd. Cadmium, C, N, G. mosseae colonization rate, and chlorophyll significantly influenced shoots defenses and Cd, C, N, P, G. mosseae colonization rate, and sulfur significantly affected root defenses. In conclusion, G. mosseae obviously improved the defense capacity of alfalfa under ET + Cd. The results could improve our understanding of the regulation of AMF on the adaptability of plants to the coexistence of heavy metals and global warming and phytoremediation of heavy metal-polluted sites under global warming scenarios.

SgNramp1, a plasma membrane-localized transporter, involves in manganese uptake in Stylosanthes guianensis

Transporters belonging to the natural resistance-associated macrophage protein (Nramp) family play important roles in metal uptake and homeostasis. Although Nramp members have been functionally characterized in plants, the role of Nramp in the important tropical forage legume Stylosanthes guianensis (stylo) is largely unknown. This study aimed to determine the responses of Nramp genes to metal stresses and investigate its metal transport activity in stylo. Five SgNramp genes were identified from stylo. Expression analysis showed that SgNramp genes exhibited tissue preferential expressions and diverse responses to metal stresses, especially for manganese (Mn), suggesting the involvement of SgNramps in the response of stylo to metal stresses. Of the five SgNramps, SgNramp1 displayed the highest expression in stylo roots. A close correlation between SgNramp1 expression and root Mn concentration was observed among nine stylo cultivars under Mn limited condition. The higher expression of SgNramp1 was correlated with a high Mn uptake in stylo. Subsequent subcellular localization analysis showed that SgNramp1 was localized to the plasma membrane. Furthermore, heterologous expression of SgNramp1 complemented the phenotype of the Mn uptake-defective yeast (Saccharomyces cerevisiae) mutant Δsmf1. Mn concentration in the yeast cells expressing SgNramp1 was higher than that of the empty vector control, suggesting the transport activity of SgNramp1 for Mn in yeast. Taken together, this study reveals that SgNramp1 is a plasma membrane-localized transporter responsible for Mn uptake in stylo.

Increasing Sugar Content in Source for Biofuel Production Using Agrochemical and Genetic Approaches at the Stages of BioMass Preharvesting and Harvesting

In order to optimize biofuel (including bioethanol) production processes, various problems need to be solved, such as increasing the sugar content of raw materials/biomass to gain a higher yield of the product. This task can be solved in several ways, with their own advantages and disadvantages, and an integrated approach, such as using a combination of ripening agents and phytohormones or application of a superabsorbent polymer with at least one sugar-enhancing agent, can be applied as well. Here, we reviewed several methods, including pre- and postharvest factors (light, temperature, partial replacement of potassium with magnesium, etc.), genetic modifications (traditional breeding, phytohormones, etc.), chemical ripening methods (Ethephon, Moddus, etc.), and some alternative methods (DMSO treatment, ionic liquids, etc.). The aim of this review was to provide a comprehensive, up-to-date summary of methods of increasing the carbohydrate level in plants/biomass for bioethanol production.

Addition of silicon to boron foliar spray in cotton plants modulates the antioxidative system attenuating boron deficiency and toxicity

BACKGROUND

Boron (B) nutritional disorders, either deficiency or toxicity, may lead to an increase in reactive oxygen species production, causing damage to cells. Oxidative damage in leaves can be attenuated by supplying silicon (Si). The aim of this study was to assess the effect of increasing foliar B accumulation on cotton plants to determine whether adding Si to the spray solution promotes gains to correct deficiency and toxicity of this micronutrient by decreasing oxidative stress via synthetizing proline and glycine-betaine, thereby raising dry matter production.

RESULTS

B deficiency or toxicity increased H₂O₂ and MDA leaf concentration in cotton plants. H₂O₂ and MDA leaf concentration declined, with quadratic adjustment, as a function of increased leaf B accumulation. Proline and glycine-betaine leaf concentration increased under B-deficiency and B-toxicity. In addition, production of these nonenzymatic antioxidant compounds was greater in plants under toxicity, in relation to deficient plants. Adding Si to the B spray solution reduced H₂O₂ and MDA concentration in the plants under nutrient deficiency or toxicity. Si reduced H₂O₂, primarily in B-deficient plants. Si also increased proline and glycine-betaine concentration, mainly in plants under B toxicity. Dry matter production of B-deficient cotton plants increased up to an application of 1.2 g L^- 1 of B. The critical B level in the spray solution for deficiency and toxicity was observed at a concentration of 0.5 and 1.9 g L^- 1 of B, respectively, in the presence of Si, and 0.4 and 1.9 g L^- 1 of B without it. In addition, the presence of Si in the B solution raised dry matter production in all B concentrations evaluated in this study.

CONCLUSION

Our findings demonstrated that adding Si to a B solution is important in the foliar spraying of cotton plants because it increases proline and glycine-betaine production and reduces H₂O₂ and MDA concentration, in addition to mitigating the oxidative stress in cotton plants under B deficiency or toxicity.

The endophyte Stenotrophomonas maltophilia EPS modulates endogenous antioxidant defense in safflower (Carthamus tinctorius L.) under cadmium stress

Cadmium (Cd) pollution in agricultural soils induces oxidative stress in plants that in turn is the foremost limiting factor for agricultural productivity. In past few decades, plant-metal-microbe interaction is of great interest as an emerging environmentally friendly technology that can be exploited to alleviate metal stress in plants. Considering these, in the present study an endophytic bacterium strain EPS has been isolated from the roots of common bean. The present strain was identified as Stenotrophomonas maltophilia based on 16S rRNA gene sequence. The strain showed Cd tolerance and Cd-adsorption potentials. The inoculation of strain EPS in safflower seeds significantly enhanced the antioxidant defense of plants under Cd-stress conditions through increasing the levels of antioxidant molecules like phenolics, flavonoids and carotenoids as well as improving the activities of the antioxidative enzymes including guaiacol peroxidase (POX), ascorbate peroxidase (APX) and superoxide dismutase (SOD). The output of this study is that strain EPS inoculation mitigates Cd-induced oxidative stress and consequently it may be beneficial, especially in Cd-contaminated crop fields.

Gene-coexpression network analysis identifies specific modules and hub genes related to cold stress in rice

Background

When plants are subjected to cold stress, they undergo a series of molecular and physiological changes to protect themselves from injury. Indica cultivars can usually withstand only mild cold stress in a relatively short period. Hormone-mediated defence response plays an important role in cold stress. Weighted gene co-expression network analysis (WGCNA) is a very useful tool for studying the correlation between genes, identifying modules with high phenotype correlation, and identifying Hub genes in different modules. Many studies have elucidated the molecular mechanisms of cold tolerance in different plants, but little information about the recovery process after cold stress is available.

Results

To understand the molecular mechanism of cold tolerance in rice, we performed comprehensive transcriptome analyses during cold treatment and recovery stage in two cultivars of near-isogenic lines (9311 and DC907). Twelve transcriptomes in two rice cultivars were determined. A total of 2509 new genes were predicted by fragment splicing and assembly, and 7506 differentially expressed genes were identified by pairwise comparison. A total of 26 modules were obtained by expression-network analysis, 12 of which were highly correlated with cold stress or recovery treatment. We further identified candidate Hub genes associated with specific modules and analysed their regulatory relationships based on coexpression data. Results showed that various plant-hormone regulatory genes acted together to protect plants from physiological damage under short-term low-temperature stress. We speculated that this may be common in rice. Under long-term cold stress, rice improved the tolerance to low-temperature stress by promoting autophagy, sugar synthesis, and metabolism.

Conclusion

Through WGCNA analysis at the transcriptome level, we provided a potential regulatory mechanism for the cold stress and recovery of rice cultivars and identified candidate central genes. Our findings provided an important reference for the future cultivation of rice strains with good tolerance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08438-3.

Detoxification of Copper and Chromium via Dark Hydrogen Fermentation of Potato Waste by Clostridium butyricum Strain 92

The accumulation of various types of waste containing both organic and inorganic metal-containing compounds is extremely hazardous for living organisms. The possibility of polymer degradation, biohydrogen synthesis, and metal detoxification via the dark fermentation of model potato waste was investigated. For this purpose, the strict anaerobic strain was isolated and identified as Clostridium butyricum. The high efficiency of dark hydrogen fermentation of potatoes with yield of hydrogen in 85.8 ± 15.3 L kg−1 VSpotato was observed. The copperand chromium salts solutions were added to the culture fluid to obtain the concentrations of 50, 100, and 200 mg L−1 Cu(II) and Cr(VI) in the active phase of growth (19 h of cultivation). Metals at a concentration of 200 mg L−1 inhibited the fermentation process the most. The hydrogen yield decreased in 7.2 and 3.6 times to 11.9 ± 2.1 and 23.8 ± 5.6 L kg−1 VSpotato in the presence of 200 mg L−1 Cu(II) and Cr(VI), respectively. The efficiencies of the chromium bioremoval in all variants of the experiment were 100%, and those of copper bioremoval were about 90%. A pure culture of strict anaerobes Clostridium butyricum strain 92 was used for the first time for the detoxification of metals. The presented results confirmed the possibility of this promising strain application for industrial H2 production and the bioremediation of contaminated sites.

Evaluation of Cadmium Bioaccumulation-Related Physiological Effects in Salvinia biloba: An Insight towards Its Use as Pollutant Bioindicator in Water Reservoirs

Free-living macrophytes play an important role in the health of aquatic ecosystems. Therefore, the use of aquatic plants as metal biomonitors may be a suitable tool for the management of freshwater reservoirs. Hence, in this study, we assessed the effects of cadmium (Cd) in Salvinia biloba specimens collected from the Middle Paraná River during a 10-day experiment employing artificially contaminated water (100 μM Cd). S. biloba demonstrated a great ability for Cd bioaccumulation in both the root-like modified fronds (named "roots") and the aerial leaf-like fronds (named "leaves") of the plants. Additionally, Cd toxicity was determined by the quantification of photosynthetic pigments (chlorophylls a and b, and carotenoids), flavonoids, and soluble carbohydrate contents in S. biloba over time (1, 3, 5, 7, and 10 days). In general, deterioration was more pronounced in leaves than in roots, suggesting a greater implication of the former in long-term Cd sequestration in S. biloba. Deleterious effects in the appraised parameters were well correlated with the total amount of Cd accumulated in the leaves, and with the qualitative changes observed in the plants' phenotype during the 10-day metal exposure assay. The flavonoids and carotenoids in leaves were highly affected by low Cd levels followed by root carbohydrates. In contrast, chlorophylls and root flavonoids were the least impacted physiological parameters. Therefore, our results demonstrate that S. biloba displays dissimilar organ-linked physiological responses to counteract Cd phytotoxicity and that these responses are also time-dependent. Though further research is needed, our work suggests that easy-handled physiological data obtained from autochthonous free-floating S. biloba specimens may be used as a valuable tool for metal-polluted water biomonitoring.

Biochemical and Metabolic Plant Responses toward Polycyclic Aromatic Hydrocarbons and Heavy Metals Present in Atmospheric Pollution

Heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) are toxic components of atmospheric particles. These pollutants induce a wide variety of responses in plants, leading to tolerance or toxicity. Their effects on plants depend on many different environmental conditions, not only the type and concentration of contaminant, temperature or soil pH, but also on the physiological or genetic status of the plant. The main detoxification process in plants is the accumulation of the contaminant in vacuoles or cell walls. PAHs are normally transformed by enzymatic plant machinery prior to conjugation and immobilization; heavy metals are frequently chelated by some molecules, with glutathione, phytochelatins and metallothioneins being the main players in heavy metal detoxification. Besides these detoxification mechanisms, the presence of contaminants leads to the production of the reactive oxygen species (ROS) and the dynamic of ROS production and detoxification renders different outcomes in different scenarios, from cellular death to the induction of stress resistances. ROS responses have been extensively studied; the complexity of the ROS response and the subsequent cascade of effects on phytohormones and metabolic changes, which depend on local concentrations in different organelles and on the lifetime of each ROS species, allow the plant to modulate its responses to different environmental clues. Basic knowledge of plant responses toward pollutants is key to improving phytoremediation technologies.

Identification and characterization of Nramp transporter AoNramp1 in Aspergillus oryzae

The Nramp (natural resistance-associated macrophage protein) family of genes has been identified and characterized widely in many species. However, the Nramp genes and their characterizations have not been reported for Aspergillus oryzae. Here, only one Nramp gene AoNramp1 in A. oryzae genome was identified. Phylogenetic analysis revealed that AoNramp1 is not clustered with Nramps from yeast genus. Expression analysis showed that the transcript level of AoNramp1 was strongly induced under both Zn/Mn-replete and -deplete conditions. The GUS-staining assay indicated that the expression of AoNramp1 was strongly induced by Zn/Mn. Moreover, the AoNramp1 deletion and overexpression strains were constructed by the CRISPR/Cas9 system and A. oryzae amyB promoter, respectively. Phenotypic analysis showed that overexpression and deletion of AoNramp1 caused growth defects under Zn/Mn-deplete and -replete conditions, including mycelium growth and conidia formation. Together, these findings provide valuable information for further study on the biological roles of AoNramp1 in A. oryzae.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02998-z.

Robinsonecio gerberifolius as a sentinel organism for atmospheric pollution by heavy metals in several sites of Mexico city and its metropolitan area

Evaluate the effect of heavy metals (HM) on sentinel organisms such as vascular plants represent a model to estimate toxic hazard due to environmental pollution. In the present study, the plant Robinsonecio gerberifolius was used to evaluate the toxic effects of the HM contained in the leaves of plants that were exposed to 4 different sites in Mexico city and its metropolitan area, during the rainy and dry seasons in the period 2017-2019. The comet assay to evaluate genotoxicity revealed an increase with respect to control (p < 0.05), in 2nd and 8th week of exposure, in all 4 study sites and in both seasons, more significant in the rainy period. An increase in the induction of oxidative stress was also observed in the exposed leaves from the 4 study sites when compared with the control; in some cases, the increases were significant (p < 0.05). In general, α- and ß-carotenoids were increased at 8th week of exposure, in all plants exposed in both seasons, while miR398 increased in plants exposed in 2 study sites (p < 0.05). Finally, toxic HM like aluminum, vanadium, and cadmium, increased significantly in the rainy season, while lead increased in the dry season. We conclude that R. gerberifolius can be considered a sentinel plant for evaluating the presence and general toxic effects caused by the presence of toxic HM that have been documented in the atmosphere of Mexico City and its metropolitan area.

Antioxidant status of the organisms of young bulls in the conditions of lead-cadmium load and effect of correcting factors

Prolonged ingress of heavy metals into the organisms of animals, even in low concentrations, causes a number of toxic impacts, affecting various organs and systems. The objective of this study was to research parameters of enzymatic and non-enzymatic links of the system of antioxidant protection of the organism of young cattle in the condition of lead-cadmium load and the effect of Metisevit Plus feed additive. Studies were conducted on the basis of the Private Agricultural Company “Ukraina”, located in Dubrovytsia district of Rivne Oblast, using 12 six-month old bulls of Ukrainian Black Pied Dairy breed divided into two groups, each consisting of 6 animals. Bulls of the control group received the standard diet. The bulls of the experimental group were fed with Metisevit Plus feed additive in the dose of 0.5 g/kg of feed. The contents of lead and cadmium in feed at the enterprise were determined to be high. According to the conducted studies, it was determined that in conditions of cadmium and lead load, there is a decrease in activity of glutathione link of the system of antioxidant protection of the organism of bulls. Feeding the bulls of the experimental group with Metisevit Plus feed additive for 30 days led to increase in the levels of non-enzymatic and enzymatic activities of the glutathione system. Significant increase in the level of reduced glutathione was recorded on days 30 and 40 of the experiment. Consumption of Metisevit Plus by the animals of the experimental group promoted increase in the activity of catalase and superoxide dismutase starting on the 20th day of the experiment. On days 30 and 40 of the experiment, the activity of the studied enzymes ranged within the physiological values. Therefore, the studies conducted on the bulls indicate that in the conditions of cadmium and lead load the feed additive Metisevit Plus fed to the bulls activated the system of antioxidant protection by increasing the levels of enzymatic and non-enzymatic links. When feeding bulls of the experimental group with Metisevit Plus feed additive, we determined significant decreases in diene conjugates and TBA-active products in their blood starting already on the 10th day of the experiment. On days 20 and 30 of the experiment, the level of diene conjugates in the blood of animals of the experimental group decreased by 14.5% and 24.0%. Efficiency of the feed additive may be explained by the effect of its constituents on the main pathogenic links of the pathological process caused by cadmium and lead. As indicated in the studies, liquidation of the syndrome of endogenous intoxication restores the functional condition of cellular membranes of the liver, protein-synthesizing function of the liver, increases the antioxidant status of the organisms of bulls. The studies we conducted confirm the expedience of using feed additive Metisevit Plus to prevent lead-cadmium toxicosis.

Oxidative Stress-Induced Alteration of Plant Central Metabolism

Oxidative stress is an integral component of various stress conditions in plants, and this fact largely determines the substantial overlap in physiological and molecular responses to biotic and abiotic environmental challenges. In this review, we discuss the alterations in central metabolism occurring in plants experiencing oxidative stress. To focus on the changes in metabolite profile associated with oxidative stress per se, we primarily analyzed the information generated in the studies based on the exogenous application of agents, inducing oxidative stress, and the analysis of mutants displaying altered oxidative stress response. Despite of the significant variation in oxidative stress responses among different plant species and tissues, the dynamic and transient character of stress-induced changes in metabolites, and the strong dependence of metabolic responses on the intensity of stress, specific characteristic changes in sugars, sugar derivatives, tricarboxylic acid cycle metabolites, and amino acids, associated with adaptation to oxidative stress have been detected. The presented analysis of the available data demonstrates the oxidative stress-induced redistribution of metabolic fluxes targeted at the enhancement of plant stress tolerance through the prevention of ROS accumulation, maintenance of the biosynthesis of indispensable metabolites, and production of protective compounds. This analysis provides a theoretical basis for the selection/generation of plants with improved tolerance to oxidative stress and the development of metabolic markers applicable in research and routine agricultural practice.

Dose-Dependent Physiological and Transcriptomic Responses of Lettuce (Lactuca sativa L.) to Copper Oxide Nanoparticles-Insights into the Phytotoxicity Mechanisms

Understanding the complex mechanisms involved in plant response to nanoparticles (NPs) is indispensable in assessing the environmental impact of nano-pollutants. Plant leaves can directly intercept or absorb NPs deposited on their surface; however, the toxicity mechanisms of NPs to plant leaves are unclear. In this study, lettuce leaves were exposed to copper oxide nanoparticles (CuO-NPs, 0, 100, and 1000 mg/L) for 15 days, then physiological tests and transcriptomic analyses were conducted to evaluate the negative impacts of CuO-NPs. Both physiological and transcriptomic results demonstrated that CuO-NPs adversely affected plant growth, photosynthesis, and enhanced reactive oxygen species (ROS) accumulation and antioxidant system activity. The comparative transcriptome analysis showed that 2270 and 4264 genes were differentially expressed upon exposure to 100 and 1000 mg/L CuO-NPs. Gene expression analysis suggested the ATP-binding cassette (ABC) transporter family, heavy metal-associated isoprenylated plant proteins (HIPPs), endocytosis, and other metal ion binding proteins or channels play significant roles in CuO-NP accumulation by plant leaves. Furthermore, the variation in antioxidant enzyme transcript levels (POD1, MDAR4, APX2, FSDs), flavonoid content, cell wall structure and components, and hormone (auxin) could be essential in regulating CuO-NPs-induced stress. These findings could help understand the toxicity mechanisms of metal NPs on crops, especially NPs resulting from foliar exposure.

Metal and Metalloid Toxicity in Plants: An Overview on Molecular Aspects

Worldwide, the effects of metal and metalloid toxicity are increasing, mainly due to anthropogenic causes. Soil contamination ranks among the most important factors, since it affects crop yield, and the metals/metalloids can enter the food chain and undergo biomagnification, having concomitant effects on human health and alterations to the environment. Plants have developed complex mechanisms to overcome these biotic and abiotic stresses during evolution. Metals and metalloids exert several effects on plants generated by elements such as Zn, Cu, Al, Pb, Cd, and As, among others. The main strategies involve hyperaccumulation, tolerance, exclusion, and chelation with organic molecules. Recent studies in the omics era have increased knowledge on the plant genome and transcriptome plasticity to defend against these stimuli. The aim of the present review is to summarize relevant findings on the mechanisms by which plants take up, accumulate, transport, tolerate, and respond to this metal/metalloid stress. We also address some of the potential applications of biotechnology to improve plant tolerance or increase accumulation.

Biochemical metabolism of young plants of Ucuúba (Virola surinamensis) in the presence of cadmium

Virola surinamensis is a forest species widely distributed in the estuaries of the Amazon. These ecosystems are susceptible to contamination by Cadmium (Cd), indicating that the plant has strategies for tolerating this metal. The aim of this study was to assess the nitrogen and carbon metabolism of young plants of Ucuúba (Virola surinamensis) in the presence of cadmium with the perspective of the phytoremediation of contaminated environments. The used experimental design was a completely randomized design with five Cd concentrations (0, 15, 30, 45, and 60 mg L^- 1), for 60 days. In general, Cd did not affect nitrate concentration in the root but had a positive effect on leaves. The reduction of nitrate reductase (NR) in plants exposed to Cd was followed by a decrease in ammonia, total soluble amino acids (TSA), and total soluble proteins (TSP). Cd promoted an increase in the concentration of total soluble carbohydrates (TSC), proline, sucrose, and reducing sugars in the plants. The increase in TSC, sucrose and proline, suggests a metabolic regulatory mechanism of V. surinamensis against Cd stress.

Downstream Signalling from Molecular Hydrogen

Molecular hydrogen (H2) is now considered part of the suite of small molecules that can control cellular activity. As such, H2 has been suggested to be used in the therapy of diseases in humans and in plant science to enhance the growth and productivity of plants. Treatments of plants may involve the creation of hydrogen-rich water (HRW), which can then be applied to the foliage or roots systems of the plants. However, the molecular action of H2 remains elusive. It has been suggested that the presence of H2 may act as an antioxidant or on the antioxidant capacity of cells, perhaps through the scavenging of hydroxyl radicals. H2 may act through influencing heme oxygenase activity or through the interaction with reactive nitrogen species. However, controversy exists around all the mechanisms suggested. Here, the downstream mechanisms in which H2 may be involved are critically reviewed, with a particular emphasis on the H2 mitigation of stress responses. Hopefully, this review will provide insight that may inform future research in this area.

The Morphological and Functional Organization of Cattails Typha laxmannii Lepech. and Typha australis Schum. and Thonn. under Soil Pollution by Potentially Toxic Elements

The aim of this study is to investigate the adaptation of two species of cattail Typha australis Schum. and Thonn. and Typha laxmannii Lepech. based on analysis of the morphological and anatomical features of their vegetative and generative organs to soil pollution with potentially toxic elements (PTE) in the riparian zones of the sea edge of the Don River delta (Southern Russia). Both species of the cattail are able to accumulate high concentrations of Ni, Zn, Cd, Pb and can be used for phytoremediation of polluted territories. The pattern of PTE accumulation in hydrophytes has changed on polluted soils of coastal areas from roots/rhizomes > inflorescences > stems to roots/rhizomes > stems ≥ inflorescences. The comparative morphological and anatomical analysis showed a statistically significant effect of the environmental stress factor by the type of proliferation in T. australis, and species T. laxmannii was visually in a depressed, deformed state with mass manifestations of hypogenesis. These deformations should be considered, on one hand, as adaptive, but on the other, as pathological changes in the structure of the spikes of the cattails. Light-optical and electron microscopic studies have shown that the degree and nature of ultrastructural changes in cattails at the same level of soil pollution are different and most expressed in the assimilation tissue of leaves. However, these changes were destructive for T. australis, but for T. laxmannii, these indicated a high level of adaptation to the prolonged technogenic impact of PTE.

The Fungicide Tetramethylthiuram Disulfide Negatively Affects Plant Cell Walls, Infection Thread Walls, and Symbiosomes in Pea (Pisum sativum L.) Symbiotic Nodules

In Russia, tetramethylthiuram disulfide (TMTD) is a fungicide widely used in the cultivation of legumes, including the pea (Pisum sativum). Application of TMTD can negatively affect nodulation; nevertheless, its effect on the histological and ultrastructural organization of nodules has not previously been investigated. In this study, the effect of TMTD at three concentrations (0.4, 4, and 8 g/kg) on nodule development in three pea genotypes (laboratory lines Sprint-2 and SGE, and cultivar 'Finale') was examined. In SGE, TMTD at 0.4 g/kg reduced the nodule number and shoot and root fresh weights. Treatment with TMTD at 8 g/kg changed the nodule color from pink to green, indicative of nodule senescence. Light and transmission electron microscopy analyses revealed negative effects of TMTD on nodule structure in each genotype. 'Finale' was the most sensitive cultivar to TMTD and Sprint-2 was the most tolerant. The negative effects of TMTD on nodules included the appearance of a senescence zone, starch accumulation, swelling of cell walls accompanied by a loss of electron density, thickening of the infection thread walls, symbiosome fusion, and bacteroid degradation. These results demonstrate how TMTD adversely affects nodules in the pea and will be useful for developing strategies to optimize fungicide use on legume crops.

Effects of lead, cadmium and zinc on protein changes in Silene vulgaris shoots cultured in vitro

In the present research, Silene vulgaris as a representative species growing on both unpolluted and heavy metal (HM) polluted terrains were used to identify ecotype-specific responses to metallic stress. Growth, cell ultrastructure and element accumulations were compared between non-metallicolous (NM), calamine (CAL) and serpentine (SER) specimens untreated with HMs and treated with Pb, Cd and Zn ions under in vitro conditions. Moreover, proteins' modifications related to their level, carbonylation and degradations via vacuolar proteases were verified and linked with potential mechanisms to cope with ions toxicity. Our experiment revealed diversified strategy of HM uptake in NM and both metallicolous ecotypes, in which antagonistic relationship of Zn and Pb/Cd ions provided survival benefits for the whole organism. Despite this similarity, growth rate and metabolic pathways induced in CAL and SER shoots varied significantly. Exposition to HMs in CAL culture led to drop in protein level by approximately 16% compared to the control. This parameter nearly correlated with the enhanced activity of proteases at pH 5.2 as well as possible glutamate changes to proline and reduced glutathione, resulting in intensified growth and first signs of cell senescence. In turn, SER shoots were characterized by growth retardation (to 53% of the control), although protein level and carbonylation were not modified, while a deeper insight into protein network showed its remodeling towards production of polyamines and 2-oxoglutarate delivered to the Krebs cycle. Contrary, an uncontrolled HM influx in NM shoots contributed to morpho-structural disorders accompanied by an increase activity of proteases involved in the degradation of oxidized proteins, what pointed to metal-induced autophagy. Taken together, S. vulgaris ecotypes respond to stress by triggering various mechanisms engaged their survival and/or death under HM treatment.

Hydrogenases and the Role of Molecular Hydrogen in Plants

Molecular hydrogen (H2) has been suggested to be a beneficial treatment for a range of species, from humans to plants. Hydrogenases catalyze the reversible oxidation of H2, and are found in many organisms, including plants. One of the cellular effects of H2 is the selective removal of reactive oxygen species (ROS) and reactive nitrogen species (RNS), specifically hydroxyl radicals and peroxynitrite. Therefore, the function of hydrogenases and the action of H2 needs to be reviewed in the context of the signalling roles of a range of redox active compounds. Enzymes can be controlled by the covalent modification of thiol groups, and although motifs targeted by nitric oxide (NO) can be predicted in hydrogenases sequences it is likely that the metal prosthetic groups are the target of inhibition. Here, a selection of hydrogenases, and the possibility of their control by molecules involved in redox signalling are investigated using a bioinformatics approach. Methods of treating plants with H2 along with the role of H2 in plants is also briefly reviewed. It is clear that studies report significant effects of H2 on plants, improving growth and stress responses, and therefore future work needs to focus on the molecular mechanisms involved.

Edible Plant Oil: Global Status, Health Issues, and Perspectives

Edible plant oil (EPO) is an indispensable nutritional resource for human health. Various cultivars of oil-bearing plants are grown worldwide, and the chemical compositions of different plant oils are diverse. The extremely complex components in oils lead to diverse standards for evaluating the quality and safety of different EPOs. The environment poses great challenges to the EPO safety and quality during the entire industrial chain, including plant cultivation, harvesting, oil processing, and storage. Environmental risk factors include heavy metal or pesticide residue pollution, insect or harmful microbial infestation, and rancidity. Here, the diverse components in oil and various oil-producing processes are discussed, including plant species, oil yield, and composition complexity, environmental factors that degrade oil quality. Additionally, we propose a whole-industrial-chain monitoring system instead of current single-link-monitoring approach by monitoring and tracking the quality and safety of EPOs during the entire process of plant cultivation, raw materials harvest, oil process, and EPOs storage. This will provide guidance for monitoring the quality and safety of EPOs, which were challenged by the deteriorating environment.

Differential effects of Zn concentrations on Cr(VI) uptake by two Salvinia species: involvement of thiol compounds

Floating ferns of the genus Salvinia have great potential for phytoremediation of heavy metals. To date, the effect of essential metals on the accumulation and transport of toxic metals by aquatic ferns has not been suitably established. The aim of this study was to compare the ability of floating leaves of Salvinia minima and Salvinia rotundifolia species to accumulate Cr from Cr(VI solutions containing very low (0.02 mg L^-1) and low (5 mg L^-1) Zn concentrations. After 7-day metal-exposure period, results showed that Zn increased Cr accumulation in S. minima leaves whereas in S. rotundifolia decreased significantly. Contrarily Zn accumulation did not show great differences between species. This fact may indicate that Zn interfere Cr(VI) uptake by S. rotundifolia. Bioconcentration factor (BCF) and translocation factor (TF) were affected differently by Zn in both Salvinia species. Membrane stability index (MSI) of both Salvinia species was decreased significantly by 5 mg L^-1 Zn concentration. Zn ions also increased hydrogen peroxide accumulation in fronds of Salvinia species. Total thiols (TT), non-protein thiols (NPT) and protein-bound thiols (PBT) were differentially affected by Cr(VI) and Zn ions. This study provides evidences on the involvement of different mechanisms against Cr(VI)/Zn toxicity in S. minima and S rotundifolia species.

Toxicity, Physiological, and Ultrastructural Effects of Arsenic and Cadmium on the Extremophilic Microalga Chlamydomonas acidophila

The cytotoxicity of cadmium (Cd), arsenate (As(V)), and arsenite (As(III)) on a strain of Chlamydomonas acidophila, isolated from the Rio Tinto, an acidic environment containing high metal(l)oid concentrations, was analyzed. We used a broad array of methods to produce complementary information: cell viability and reactive oxygen species (ROS) generation measures, ultrastructural observations, transmission electron microscopy energy dispersive x-ray microanalysis (TEM-XEDS), and gene expression. This acidophilic microorganism was affected differently by the tested metal/metalloid: It showed high resistance to arsenic while Cd was the most toxic heavy metal, showing an LC₅₀ = 1.94 µM. Arsenite was almost four-fold more toxic (LC₅₀= 10.91 mM) than arsenate (LC₅₀ = 41.63 mM). Assessment of ROS generation indicated that both arsenic oxidation states generate superoxide anions. Ultrastructural analysis of exposed cells revealed that stigma, chloroplast, nucleus, and mitochondria were the main toxicity targets. Intense vacuolization and accumulation of energy reserves (starch deposits and lipid droplets) were observed after treatments. Electron-dense intracellular nanoparticle-like formation appeared in two cellular locations: inside cytoplasmic vacuoles and entrapped into the capsule, around each cell. The chemical nature (Cd or As) of these intracellular deposits was confirmed by TEM-XEDS. Additionally, they also contained an unexpected high content in phosphorous, which might support an essential role of poly-phosphates in metal resistance.

You Want it Sweeter: How Glycosylation Affects Plant Response to Oxidative Stress

Oxidative stress is a cellular threat which puts at risk the productivity of most of crops valorized by humankind in terms of food, feed, biomaterial, or bioenergy. It is therefore of crucial importance to understand the mechanisms by which plants mitigate the deleterious effects of oxidizing agents. Glycosylation of antioxidant molecules and phytohormones modifies their chemical properties as well as their cellular and histological repartition. This review emphasizes the mechanisms and the outcomes of this conjugation reaction on plant ability to face growing conditions favoring oxidative stress, in mirror with the activity of deglycosylating enzymes. Pioneer evidence bridging flavonoid, glycosylation, and redox homeostasis paved the way for numerous functional analyses of UDP-glycosyltransferases (UGTs), such as the identification of their substrates and their role to circumvent oxidative stress resulting from various environmental challenges. (De)glycosylation appears as a simple chemical reaction regulating the biosynthesis and/or the activity of a myriad of specialized metabolites partaking in response to pathogen and abiotic stresses. This outcome underlies the possibility to valorize UGTs potential to upgrade plant adaptation and fitness in a rising context of sub-optimal growing conditions subsequent to climate change.

Epigenetic Control of Plant Response to Heavy Metal Stress: A New View on Aluminum Tolerance

High concentrations of heavy metal (HM) ions impact agronomic staple crop production in acid soils (pH ≤ 5) due to their cytotoxic, genotoxic, and mutagenic effects. Among cytotoxic ions, the trivalent aluminum cation (Al³⁺) formed by solubilization of aluminum (Al) into acid soils, is one of the most abundant and toxic elements under acidic conditions. In recent years, several studies have elucidated the different signal transduction pathways involved in HM responses, identifying complementary genetic mechanisms conferring tolerance to plants. Although epigenetics has become more relevant in abiotic stress studies, epigenetic mechanisms underlying plant responses to HM stress remain poorly understood. This review describes the main epigenetic mechanisms related to crop responses during stress conditions, specifically, the molecular evidence showing how epigenetics is at the core of plant adaptation responses to HM ions. We highlight the epigenetic mechanisms that induce Al tolerance. Likewise, we analyze the pivotal relationship between epigenetic and genetic factors associated with HM tolerance. Finally, using rice as a study case, we performed a general analysis over previously whole-genome bisulfite-seq published data. Specific genes related to Al tolerance, measured in contrasting tolerant and susceptible rice varieties, exhibited differences in DNA methylation frequency. The differential methylation patterns could be associated with epigenetic regulation of rice responses to Al stress, highlighting the major role of epigenetics over specific abiotic stress responses.

The Roles of Environmental Factors in Regulation of Oxidative Stress in Plant

Exposure to a variety of environmental factors such as salinity, drought, metal toxicity, extreme temperature, air pollutants, ultraviolet-B (UV-B) radiation, pesticides, and pathogen infection leads to subject oxidative stress in plants, which in turn affects multiple biological processes via reactive oxygen species (ROS) generation. ROS include hydroxyl radicals, singlet oxygen, and hydrogen peroxide in the plant cells and activates signaling pathways leading to some changes of physiological, biochemical, and molecular mechanisms in cellular metabolism. Excessive ROS, however, cause oxidative stress, a state of imbalance between the production of ROS and the neutralization of free radicals by antioxidants, resulting in damage of cellular components including lipids, nucleic acids, metabolites, and proteins, which finally leads to the death of cells in plants. Thus, maintaining a physiological level of ROS is crucial for aerobic organisms, which relies on the combined operation of enzymatic and nonenzymatic antioxidants. In order to improve plants' tolerance towards the harsh environment, it is vital to reinforce the comprehension of oxidative stress and antioxidant systems. In this review, recent findings on the metabolism of ROS as well as the antioxidative defense machinery are briefly updated. The latest findings on differential regulation of antioxidants at multiple levels under adverse environment are also discussed here.

Variations in the antioxidant and free radical scavenging under induced heavy metal stress expressed as proline content in chickpea

This study pertains to the effects of heavy metal salts viz., copper (Cu), manganese (Mn), lead (Pb) and zinc (Zn) on the chickpea accession ICC-4812. The salts were given as treatments to the chickpea seeds at various ascending levels of doses till proving toxic. The treatment of 24 h soaked and swollen seeds were then extended to 7 days duration from the date of treatment. Atomic absorption spectrophotometric analysis of bioassay tissue Cicer, showed maximum uptake of 9.41 mg/g and minimum of 1.65 mg/g tissue dry weight for Pb and Zn respectively. The study reveals that enhanced antioxidant responses are associated with substantial proline accumulation indicating induced stress. Ferric reducing antioxidant power assay measuring antioxidant activity was highest in the chickpea seedling treated with Zn, whereas, free radical scavenging activity was highest in the treatments with Mn. The total phenolic and flavonoid contents ranged between 0.24-0.97 and 0.27-1.00 mg/g of dry matter content respectively. Higher Pb and Zn doses seem to elicit higher proline levels therefore, suggesting an extreme condition of induced abiotic stress. Dose dependent protein oxidation coupled with DNA degradation was observed in all treatments, depicting genotoxicity. Unweighted pair-group method arithmetic average analysis presented similarity coefficients between the treatments.

Copper excess detoxification is mediated by a coordinated and complementary induction of glutathione, phytochelatins and metallothioneins in the green seaweed Ulva compressa

In order to analyze the involvement of intracellular thiol-chelators in the accumulation and detoxification of copper, the marine alga Ulva compressa was cultivated with increasing concentrations of copper such as 2.5, 5, 7.5 and 10 μM for up to 12 d, and the amount of intracellular copper, glutathione (GSH), phytochelatins (PCs) and transcripts encoding three metallothioneins (MTs) were determined. Over this exposure period and concentration range there was a linear correlation between intracellular copper and the copper concentration in the culture medium. Increases in GSH concentrations occurred mainly between days 1 and 3 and at lower concentrations of copper (2.5 and 5 μM). The level of PCs, and particularly PC2, increased from day 1 of exposure mainly at higher concentrations of copper (7.5 and 10 μM). The levels of transcripts encoding MT7 increased at day 3, whereas those of MT3 and MT6 increased between days 9-12, mainly at higher concentrations of copper. Thus in U. compressa, the initial responses to increasing intracellular copper concentrations are increases in GSH and PCs that are followed by higher levels of MTs expression, suggesting that thiol-containing peptides and proteins may participate in copper accumulation and detoxification responding in a coordinated and complementary manner. In addition, the alga was cultivated with 10 μM copper for 5 d and transferred to synthetic seawater with no copper and cultivated for 3 d. The release of copper from cells to culture medium was observed and accompanied by a similar nanomolar amount of GSH; no PCs or small proteins were detected. These results could suggest that a component of the detoxification mechanism also involves the release of copper and GSH to the extracellular medium.