Alleviation of cadmium-induced genotoxicity and cytotoxicity by calcium chloride in faba bean (Vicia faba L. var. minor) roots

Astaxanthin induces plant tolerance against cadmium by reducing cadmium uptake and enhancing carotenoid metabolism for antioxidant defense in wheat (Triticum aestivum L.)

Soil cadmium (Cd) contamination poses a significant threat to global food security and the environment. Astaxanthin (AX), a potent biological antioxidant belonging to the carotenoid group, has been demonstrated to confer tolerance against diverse abiotic stresses in plants. This study investigated the potential of AX in mitigating Cd-induced damage in wheat seedlings. Morpho-physiological, ultrastructural, and biochemical analyses were conducted to evaluate the impact of AX on Cd-exposed wheat seedlings. Illumina-based gene expression profiling was employed to uncover the molecular mechanisms underlying the protective effects of AX. The addition of 100 μM AX alleviated Cd toxicity by enhancing various parameters: growth, photosynthesis, carotenoid content, and total antioxidant capacity (T-AOC), while reducing Cd accumulation, malondialdehyde (MDA), and hydrogen peroxide (H2O2) levels. RNA sequencing analysis revealed differentially expressed genes associated with Cd uptake and carotenoid metabolism, such as zinc/iron permease (ZIP), heavy metal-associated protein (HMA), 3-beta hydroxysteroid dehydrogenase/isomerase (3-beta-HSD), and thiolase. These findings suggest that AX enhances Cd tolerance in wheat seedlings by promoting the expression of detoxification and photosynthesis-related genes. This research offers valuable insights into the potential use of AX to address Cd contamination in agricultural systems, highlighting the significance of antioxidant supplementation in plant stress management.

Physiological and DNA methylation analysis provides epigenetic insights into kenaf cadmium tolerance heterosis

Soil heavy metal pollution is one of the most challenging problems. Kenaf is an important natural fiber crop with strong heterosis and a higher tolerance to heavy metals. However, little is known about the molecular mechanisms of kenaf heavy metal tolerance, especially the mechanism of genomic DNA methylation regulating heterosis. In this study, kenaf cultivars CP085, CP089, and their hybrid F₁ seedlings were subjected to 300 µM cadmium stress and found obvious heterosis of cadmium resistance in morphology and antioxidant enzyme activity of F₁ hybrid seedlings. Through methylation-sensitive amplification polymorphism (MSAP) analysis, we highlighted that the total DNA methylation level under cadmium decreased by 16.9 % in F₁ and increased by 14.0 % and 3.0 % in parents CP085 and CP089, respectively. The hypomethylation rate was highest (21.84 %), but hypermethylation was lowest (17.24 %) in F₁ compared to parent cultivars. In particular, principal coordinates analysis (PCoA) indicates a significant epigenetic differentiation between F₁ and its parents under cadmium. Furthermore, 21 differentially methylated DNA fragments (DMFs) were analyzed. Especially, the expression of NPF2.7, NADP-ME, NAC71, TPP-D, LRR-RLKs, and DHX51 genes were changed due to cadmium stress and related to cytosine methylation regulation. Finally, the knocked-down of the differentially methylated gene NPF2.7 by virus-induced gene silencing (VIGS) resulted in increased sensitivity of kenaf seedlings under cadmium stress. It is speculated that low DNA methylation levels can regulate gene expression that led to the heterosis of cadmium tolerance in kenaf.

Vicia faba seed: a bioindicator of phytotoxicity, genotoxicity, and cytotoxicity of light crude oil

Crude oil contamination is a serious threat to the environment and human health as it can contaminate food chains. Therefore, it is necessary to find efficient tests to monitor soils for crude oil contamination. The present study investigates the efficacy of Vicia faba seeds for monitoring contaminated soils with light crude oil. Vicia faba seeds were planted in 0 (control), 1, 2, and 4 percentages (weight percentage) light crude oil-contaminated soils. The seed germination and root length were measured to evaluate phytotoxicity, while the mitotic index, chromosome aberrations, and micronucleus formation in the root tip cells were examined for cytotoxicity and genotoxicity tests. The results showed that light crude oil had toxic effects on Vicia faba growth characteristics, even at 1% contamination. The phytotoxicity assay showed that crude oil reduced seed germination and root length by 45% and 61.67%, respectively. In contrast, cellular observations indicated an increase in mitotic index, chromosome aberrations, and micronucleus formation up to 3, 3.59, and 5.6 times, respectively, compared to the control. The light crude oil at 4% induced the simultaneous occurrence of nuclear bud, polyploidy, and micronucleus that may be considered as severe clastogenic and aneugenic effects. Accordingly, Vicia faba can be considered a reliable living system for monitoring light crude oil pollution in soils, even at low concentrations.

Heavy metals assessment of ecosystem polluted with wastewaters and taxonomic profiling of multi-resistant bacteria with potential for petroleum hydrocarbon catabolism in nitrogen-limiting medium

The coexistence of heavy metals (HMs) and petroleum hydrocarbons (PHs) exacerbates ecotoxicity and impair the drivers of eco-functionalities that stimulate essential nutrients for the productivity of the impacted environment. Profiling the bacteria that stem the ecological impact via HMs sequestration and PHs catabolism with nitrogen fixation is imperative to bioremediation of the polluted sites. The sediment of site that was consistently contaminated with industrial wastewaters was analysed for ecological toxicants and the bacterial strains that combined HMs resistance with PHs catabolism in a nitrogen-limiting system were isolated from the sediment and characterized. The geochemistry of the samples revealed the co-occurrence of the above-benchmark concentrations of HMs with the derivatives of hydrocarbons. Notwithstanding, nickel and mercury (with 5% each of the total metal concentrations in the polluted site) exhibited probable effect concentrations on the biota and thus hazardous to the ecosystem. Approx. 31% of the bacterial community, comprising unclassified Planococcaceae, unclassified Bradyrhizobiaceae, Rhodococcus, and Bacillus species, resisted 160 µmol Hg²⁺ in the nitrogen-limiting system within 24 h post-inoculation. The bacterial strains adopt volatilization, and sometimes in combination with adsorption/bioaccumulation strategies to sequester Hg²⁺ toxicity while utilizing PHs as sources of carbon and energy. Efficient metabolism of petroleum biomarkers (> 87%) and Hg²⁺ sequestration (≥ 75% of 40 µmol Hg²⁺) displayed by the selected bacterial strains portend the potential applicability of the bacilli for biotechnological restoration of the polluted site.

Manganese-modified biochar promotes Cd accumulation in Sedum alfredii in an intercropping system

Intercropping of crops with hyperaccumulators is a sustainable method to remediate contaminated soil without impeding agro-production. However, the function of engineered biochar in intercropping systems and its possible influence on cadmium (Cd) accumulation in hyperaccumulators remain unknown. A root box experiment on celery and Sedum alfredii with and without root separation was conducted in this study. Pristine and KMnO₄-modified biochar (BC_Mn) were used to investigate the effects of different biochars on plant growth and Cd uptake in an intercropping system, as well as the influence of engineered biochar on Cd accumulation in hyperaccumulators. The results demonstrated that soil pH did not significantly vary with biochar application in the root separation treatment. However, BC_Mn significantly increased soil pH and thus reduced available Cd when the plant roots were not separated. Intercropping (no separation treatment) led to a 34% higher and 24% lower aboveground biomass of celery and S. alfredii, respectively, regardless of biochar addition. Compared with aboveground plant parts, plant roots exhibited more significant responses to biochar. Interestingly, intercropping may favour the phytoextraction of Cd by S. alfredii. In particular, the Cd uptake by S. alfredii roots substantially increased (118-187%), whereas that of celery roots decreased (51-71%) with BC_Mn addition, compared with other treatments. Moreover, after BC_Mn addition the accumulation of Cd in aboveground S. alfredii in the no separation treatment was 136% higher than that in the separation treatment. This was possibly related to the interaction of manganese (Mn) with Cd as well as the roots of S. alfredii. These findings provide new insights into the application of engineered biochar for phytoextraction, which is important for the efficient remediation of Cd-contaminated soils.

Antioxidant and genoprotective effects of osthole against cadmium-induced DNA damage: an in vitro study using comet assay

Background and purpose

Osthole, a plant-derived coumarin, has shown numerous pharmacological effects. However, its genoprotective effects against cadmium-induced DNA damage have not been determined yet. Therefore, this project aimed to assess the effectiveness of osthole against genotoxicity caused by cadmium.

Experimental approach

For this purpose, human umbilical vein endothelial cells (HUVECs) were incubated with various concentrations of osthole (40, 60, 80, and 120 µM) 24 h before cadmium chloride (CdCl₂) treatment (40 µM), and then DNA damage was evaluated by comet assay. Furthermore, DPPH and free thiol group assays were applied to evaluate reactive oxygen species scavenger and antioxidant capacities of osthole.

Findings / Results

In the present study, all concentrations of osthole significantly decreased CdCl₂-induced DNA damage. Furthermore, the antioxidant properties of the osthole were confirmed by DPPH and free thiol assays.

Conclusion and implications

Overall, the findings of this project revealed that osthole could ameliorate cadmium-induced genotoxicity probably by its antioxidant activity.

Effect of different seed priming agents on chromium accumulation, oxidative defense, glyoxalase system and mineral nutrition in canola (Brassica napus L.) cultivars

The present experiment was conducted to appraise the role of different seed priming agents in circumventing the negative impact of chromium (Cr) toxicity on canola plants. Chromium toxicity resulted in significant decline in photosynthetic pigments and growth attributes of two canola cultivars (Puriga and MS-007). Cr toxicity also resulted in higher oxidative stress mirrored as greater accumulation of hydrogen peroxide (H₂O₂) superoxide radical (O₂^•‒), electrolyte leakage (EL) and malondialdehyde (MDA). Further, lipoxygenase enzyme activity that catalyzes the peroxidation of membrane lipids was also enhanced due to Cr toxicity. Canola plants also manifested impaired methylglyoxal (MG) detoxification due to the downregulation of glyoxalase enzymes (GlyI and II) under Cr stress. Seed priming treatments viz. osmo-priming with calcium chloride (CaCl₂) and hormonal priming with salicylic acid (SA) remarkably improved growth and chlorophyll content in both canola cultivars under Cr toxicity as compared to other priming treatments such as hydro-priming, redox priming (H₂O₂) and chemical priming (Se; selenium). Moreover, CaCl₂ and SA seed priming also resulted in lower oxidative stress and improved enzymatic (SOD, POD, CAT, APX, GR, GST) and non-enzymatic (GSH, phenolics, flavonoids, proline) antioxidant system of both cultivars under Cr toxicity. Further, hormonal and osmo-priming strengthened glyoxalase and antioxidant systems, thus improving reactive oxygen species (ROS) and MG detoxification. In this background, the cultivar Puriga is considered Cr tolerant as it exhibited better growth and lesser oxidative stress in both seed priming and non-primed conditions under Cr toxicity than cv. MS-007.

Micronutrient seed priming: new insights in ameliorating heavy metal stress

Plants need to survive with changing environmental conditions, be it different accessibility to water or nutrients, or attack by insects or pathogens. Few of these changes, especially heavy metal stress, can become more stressful and needed strong countermeasures to ensure survival of plants. Priming, a pre-sowing hydration treatment, involves pre-exposure of plants to an eliciting component which enhance the plant's tolerance to later stress events. By considering the role of micronutrients in aiding plants to cope up under adverse conditions, this review addresses various aspects of micronutrient seed priming in attenuating heavy metal stress. Priming using micronutrients is an adaptive strategy that boosts the defensive capacity of the plant by accumulating several active or inactive signaling proteins, which hold considerable importance in signal amplification against the triggered stimulus. Priming induced 'defence memory' persists in both present generation and its progeny. Therefore, it is considered a promising approach by seed technologist for commercial seed lots to enhance the vigour in terms of seed germination potential, productivity and strengthening resistance response against metalloid stress. The present review provides an overview regarding the potency of priming with micronutrient to ameliorate harmful effects of heavy metal stress, possible mechanism how attenuation is accomplished, role of priming in enhancing crop productivity and inducing defence memory against the metalloid stress stimulus.

Heavy metal (loid)s phytotoxicity in crops and its mitigation through seed priming technology

Unexpected bioaccumulation and biomagnification of heavy metal(loid)s (HMs) in the environment have become a predicament for all living organisms, including plants. The presence of these HMs in the plant system raised the level of reactive oxygen species (ROS) and remodeled several vital cellular biomolecules. These lead to several morphological, physiological, metabolic, and molecular aberrations in plants ranging from chlorosis of leaves to the lipid peroxidation of membranes, and degradation of proteins and nucleic acid including the modulation of the enzymatic system, which ultimately affects the plant growth and productivity. Plants are equipped with several mechanisms to counteract the HMs toxicity. Among them, seed priming (SP) technology has been widely tested with the use of several inorganic chemicals, plant growth regulators (PGRs), gasotransmitters, nanoparticles, living organisms, and plant leaf extracts. The use of these compounds has the potential to alleviate the HMs toxicity through the strengthening of the antioxidant defense system, generation of low molecular weight metallothionein's (MTs), and phytochelatins (PCs), and improving seedling vigor during early growth stages. This review presents an account of the sources, uptake and transport, and phytotoxic effects of HMs with special attention to different mechanism/s, occurring to mitigate the HMs toxicity in plants employing SP technology.Novelty statement: To the best of our knowledge, this review has delineated the consequences of HMs on the crucial plant processes, which ultimately affect plant growth and development. This review also compiled the up to dated information on phytotoxicity of HMs through the use of SP technology, this review discussed how different types of SP approaches help in diminishing the concentration HMs in plant systems. Also, we depicted mechanisms, represent how HMs transport and their actions on cellular levels, and emphasized, how diverse SP technology effectiveness in the mitigation of plants' phytotoxicity in unique ways.

Integrated ionomic and transcriptomic dissection reveals the core transporter genes responsive to varying cadmium abundances in allotetraploid rapeseed

BACKGROUND

Oilseed rape (B. napus L.) has great potential for phytoremediation of cadmium (Cd)-polluted soils due to its large plant biomass production and strong metal accumulation. Soil properties and the presence of other soluble compounds or ions, cause a heterogeneous distribution of Cd.

RESULTS

The aim of our study was to reveal the differential responses of B. napus to different Cd abundances. Herein, we found that high Cd (50 μM) severely inhibited the growth of B. napus, which was not repressed by low Cd (0.50 μM) under hydroponic culture system. ICP-MS assays showed that the Cd2+ concentrations in both shoots and roots under 50 μM Cd were over 10 times higher than those under 0.50 μM Cd. Under low Cd, the concentrations of only shoot Ca2+/Mn2+ and root Mn2+ were obviously changed (both reduced); under high Cd, the concentrations of most cations assayed were significantly altered in both shoots and roots except root Ca2+ and Mg2+. High-throughput transcriptomic profiling revealed a total of 18,021 and 1408 differentially expressed genes under high Cd and low Cd conditions, respectively. The biological categories related to the biosynthesis of plant cell wall components and response to external stimulus were over-accumulated under low Cd, whereas the terms involving photosynthesis, nitrogen transport and response, and cellular metal ion homeostasis were highly enriched under high Cd. Differential expression of the transporters responsible for Cd uptake (NRAMPs), transport (IRTs and ZIPs), sequestration (HMAs, ABCs, and CAXs), and detoxification (MTPs, PCR, MTs, and PCSs), and some other essential nutrient transporters were investigated, and gene co-expression network analysis revealed the core members of these Cd transporters. Some Cd transporter genes, especially NRAMPs and IRTs, showed opposite responsive patterns between high Cd and low Cd conditions.

CONCLUSIONS

Our findings would enrich our understanding of the interaction between essential nutrients and Cd, and might also provide suitable gene resources and important implications for the genetic improvement of plant Cd accumulation and resistance through molecular engineering of these core genes under varying Cd abundances in soils.

Calcium and ethylene glycol tetraacetic acid mitigate toxicity and alteration of gene expression associated with cadmium stress in chickpea (Cicer arietinum L.) shoots

In the aim to estimate the protective role of calcium (Ca) and ethylene glycol tetraacetic acid (EGTA) against cadmium (Cd)-induced damage, chickpea (Cicer arietinum L.) seeds were exposed to 200 μM Cd stress for 6 days or 3 days then subjected to co-treatment of the metal with either 100 mM CaCl₂ or 100 μM EGTA for 3 additional days. The addition of Ca and EGTA improved seedling growth. This protecting effect was correlated to the alleviation of the metal-induced oxidative stress, exemplified by the reduction of hydrogen peroxide (H₂O₂) contents. Besides, Ca and EGTA stimulated thioredoxin (Trx) and thioredoxin reductase (NTR) activities (2.75- and 1.75-fold increase when compared to Cd-stressed, respectively) protecting, thereby, protein -SH groups from the Cd-mediated oxidation, and modulated ferredoxin (Fdx) activity to a control level. Moreover, Ca and EGTA reinstated the glutathione redox steady state, mainly via preserving a high level of glutathione reduced form (GSH). This effect coincided with the maintaining of the Cd-stimulated glutathione reductase (GR) activity and the decline of glutathione peroxidase (GPX, 43% lower than Cd-stressed shoots) activity. Ca and EGTA counteracted the inhibitory effect of Cd on the activity and gene expression of Cu/Zn-superoxide dismutase (Cu/Zn-SOD) isoenzyme and modulated the activities of catalase (CAT) and ascorbate peroxidase (APX). Overall, our results provided evidence that Ca and EGTA supplement could be a promising approach in the remediation of Cd-contaminated environment.

Interactive Effects of Lanthanum and Calcium on Cadmium Accumulation in Wheat with Special Reference to TaNramp5 Expression Regulated by Calmodulin

Lanthanum (La), calcium (Ca), and cadmium (Cd) have similar physical and chemical properties because of their similar ionic radius. Although the interactions between La, Ca, and Cd have been frequently reported in plants, few studies have investigated the interactive effects of La and Ca on the growth and Cd accumulation in plants. Therefore, we investigated the interactive effects of La and Ca on the growth and Cd accumulation in wheat under Cd exposure by a hydroponic experiment. The results indicated that wheat growth was significantly affected by La-Cd and La-Ca interactions. The accumulation of Cd in wheat was significantly affected by La-Ca and La-Cd interactions and La-Ca-Cd interplay. Correlation analysis indicated that Ca deficiency stimulated La to promote wheat growth and mitigate Cd toxicity. Simultaneously, a low Ca supply stimulated La to decrease Cd accumulation in wheat and induce TaNramp5 expression. In addition, Cd accumulation in wheat was significantly affected by the W7-La interaction and W7-La-Ca interplay. All of the results suggested that La, Ca, and Cd probably share the same binding sites in calmodulin (TaCaM) and La could affect Cd accumulation in wheat by interacting with TaCaM and then downregulating the expression of TaNramp5.

Fava bean intercropping with Sedum alfredii inoculated with endophytes enhances phytoremediation of cadmium and lead co-contaminated field

Phytoremediation coupled with agro-production is considered a sustainable strategy for remediation of trace element contaminated fields without interrupting crop production. In this study hyperaccumulator Sedum alfredii was intercropped with a leguminous plant fava bean (Vicia fava) in cadmium (Cd) and lead (Pb) co-contaminated field to evaluate the effects of intercropping on growth performance and accumulations of trace elements in plants with plant growth promoting endophyte (PGPE) consortium application. The results showed, compared with monoculture, intercropping coupled with inoculation application promoted biomass as well as Cd and Pb concentrations in individual parts of both plants, thus increasing the removal efficiencies of trace elements (4.49-folds for Cd and 5.41-folds for Pb). Meanwhile, this superposition biofortification measure maintained normal yield and nutrient content, and limited the concentration of Cd and Pb within the permissible limit (<0.2 mg kg^-1 FW) in fava bean during the grain production. These results demonstrated a feasible technical system for phytoremediation coupled with agro-production in slightly or moderately Cd and Pb co-contaminated field, and also provided useful information for further investigation of interaction mechanisms between intercropping and PGPEs inoculation.

Comparative Transcriptome Analysis Provides Insights into the Seed Germination in Cotton in Response to Chilling Stress

Gossypium hirsutum L., is a widely cultivated cotton species around the world, but its production is seriously threatened by its susceptibility to chilling stress. Low temperature affects its germination, and the underlying molecular mechanisms are rarely known, particularly from a transcriptional perspective. In this study, transcriptomic profiles were analyzed and compared between two cotton varieties, the cold-tolerant variety KN27-3 and susceptible variety XLZ38. A total of 7535 differentially expressed genes (DEGs) were identified. Among them, the transcripts involved in energy metabolism were significantly enriched during germination based on analysis of Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, such as glycolysis/gluconeogenesis, tricarboxylic acid cycle (TCA cycle), and glyoxylate cycle (GAC). Results from further GO enrichment analysis show the earlier appearance of DNA integration, meristem growth, cotyledon morphogenesis, and other biological processes in KN27-3 compared with XLZ38 under chilling conditions. The synthesis of asparagine, GDP-mannose, and trehalose and the catabolic process of raffinose were activated. DEGs encoding antioxidants (spermidine) and antioxidase (CAT1, GPX4, DHAR2, and APX1) were much more up-regulated in embryos of KN27-3. The content of auxin (IAA), cis-zeatin riboside (cZR), and trans-zeatin riboside (tZR) in KN27-3 are higher than that in XLZ38 at five stages (from 12 h to 54 h). GA3 was expressed at a higher level in KN27-3 from 18 h to 54 h post imbibition compared to that in XLZ38. And abscisic acid (ABA) content of KN27-3 is lower than that in XLZ38 at five stages. Results from hormone content measurements and the related gene expression analysis indicated that IAA, CTK, and GA3 may promote germination of the cold-tolerant variety, while ABA inhibits it. These results expand the understanding of cottonseed germination and physiological regulations under chilling conditions by multiple pathways.

Plant growth regulators improve growth, photosynthesis, mineral nutrient and antioxidant system under cadmium stress in menthol mint (Mentha arvensis L.)

Menthol mint (Mentha arvensis L.) cultivation is significantly affected by the heavy metals like cadmium (Cd) which also imposes severe health hazards. Two menthol mint cultivars namely Kosi and Kushal were evaluated under Cd stress conditions. Impact of plant growth regulators (PGRs) like salicylic acid (SA), gibberellic acid (GA₃) and triacontanol (Tria) on Cd stress tolerance was assessed. Reduced growth, photosynthetic parameters, mineral nutrient concentration, and increased oxidative stress biomarkers like electrolyte leakage, malondialdehyde, and hydrogen peroxide contents were observed under Cd stress. Differential upregulation of proline content and antioxidant activities under Cd stress was observed in both the cultivars. Interestingly, low electrolyte leakage, lipid peroxidation, hydrogen peroxide and Cd concentration in leaves were observed in Kushal compared to Kosi. Among all the PGRs tested, SA proved to be the best in improving Cd-stress tolerance in both the cultivars but Kushal responded better than Kosi.