Regulation of three subtypes of SOD gene in Aleuroglyphus ovatus (Acari:Acaridae) under lead stress

Superoxide dismutase (SOD) is an important enzyme that acts as the first line of protection in the mite antioxidant defense system, involved in eliminating reactive oxygen species (ROS) under harsh environmental conditions. Nevertheless, the SOD gene family was yet to be reported in stored grain pest mite (Aleuroglyphus ovatus). In this study, A. ovatus was used to evaluate the response of SOD gene during lead stress. A. ovatus were separately exposed to different concentration lead (12.5, 25, 50, and 100 mg/kg), which induce the dynamic trend of SOD enzyme activity initially increased and then reduced with an increase in lead concentration, whereas they were still substantially higher than the control group. Moreover, after lead stress, it was found that all of the three SOD genes showed enhanced relative messenger RNA expression at high concentrations and decreased relative expression at low concentrations, which indicated that lead stress induces the expression of AoSODs. The present work implies that AoSODs play an important role in resisting oxidative damage caused by lead stress.

Lead Toxicity-Mediated Growth and Metabolic Alterations at Early Seedling Stages of Maize (Zea mays L.)

To investigate the toxic effects of lead (Pb) on key metabolic activities essential for proper germination and seedling growth of maize seeds, experiments were carried out with different levels of Pb (0 to 120 mg of Pb L-1 as PbCl2) applied through growth medium to two maize hybrids H-3310S and H-6724. The research findings indicated that growth and metabolic activities were adversely affected by increased Pb contamination in growth medium; however, a slow increase in these parameters was recorded with increasing time from 0 to 120 h. Protease activity decreased with an increase in the level of Pb contamination but increased with time; consequently, a reduction in seed proteins and an increase in total free amino acids were observed with time. Similarly, α-amylase activity decreased with an increase in Pb concentration in growth medium while it increased with increasing time from 0 to 120 h; consequently, reducing and non-reducing sugars increased with time but decreased with exposure to lead. The roots of both maize hybrids had higher Pb contents than those of the shoot, which decreased the uptake of nitrogen, phosphorus, and potassium. All these nutrients are essential for optimal plant growth; therefore, the reduction in growth and biomass of maize seedlings could be due to Pb toxicity that altered metabolic processes, as sugar and amino acids are necessary for the synthesis of metabolic compounds, rapid cell division, and proper functioning of enzymes in the growing embryo, but all were dramatically reduced due to suppression of protease and α-amylase by toxicity of Pb. In general, hybrid H-3310S performed better in Pb-contaminated growth medium than H-6724.

Arbuscular mycorrhizal fungi improve growth and tolerance of Platycladus orientalis under lead stress

Platycladus orientalis is a significant woody plant for phytoremediation in heavy metals contaminated soils. The growth and tolerance of host plants under the lead (Pb) stress were enhanced by arbuscular mycorrhizal fungi (AMF). To evaluate the adjustment by AMF on growth and activity of antioxidant system of P. orientalis under Pb stress. The two-factor pot experiment was conducted with three AM fungal treatments (noninoculated, Rhizophagus irregularis, and Funneliformis mosseae) and four Pb levels (0, 500, 1000, and 2000 mg kg-1). AMF increased dry weight, phosphorus uptake, root vitality, and total chlorophyll content of P. orientalis in spite of Pb stress. Compared with nonmycorrhizal treatments, mycorrhizal P. orientalis had lower H2O2 and malondialdehyde (MDA) contents under Pb stress. AMF increased Pb uptake in roots and decreased the Pb translating to the shoots yet under Pb stress. Total glutathione and ascorbate in roots of P. orientalis were decreased by AMF inoculation. Mycorrhizal P. orientalis had higher superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and glutathione S-transferase (GST) activities in shoots and roots than nonmycorrhizal counterparts. Mycorrhizal P. orientalis under Pb stress showed higher expression of PoGST1 and PoGST2 in roots than that in CK treatments. Future studies will explore the function of induced tolerance genes by AMF of P. orientalis under Pb stress.

Seed Priming with Triacontanol Alleviates Lead Stress in Phaseolus vulgaris L. (Common Bean) through Improving Nutritional Orchestration and Morpho-Physiological Characteristics

Worldwide, crop productivity is highly influenced by heavy metal toxicity. Lead (Pb) the is second-most toxic heavy metal that has high persistence in soil. Lead is translocated in plants from rhizosphere soil and enters the food chain, where it poses a significant hazard to the health of humans. In the present investigation, seed priming with triacontanol (Tria) was used to mitigate Pb phytotoxicity in Phaseolus vulgaris L. (common bean). Seeds were primed with different concentrations of Tria (control, 10 µmol L^-1, 20 µmol L^-1, 30 µmol L^-1) solutions. The pot experiment was carried out by sowing Tria-primed seeds in contaminated soil with 400 mg kg^-1 Pb. Lead alone induced a decrease in the rate of germination and a significant reduction in biomass and growth of P. vulgaris as compared to the control. All these negative effects were reversed by Tria-primed seeds. Proliferation of photosynthetic pigments was observed 1.8-fold by Tria under Pb stress. Primed seeds with 20 µmol L^-1 Tria enhanced stomatal conductance (gs), photosynthetic rate (A), transpiration rate (Ei), and uptake of mineral contents (Mg⁺², Zn⁺², Na⁺, and K⁺) and reduced Pb accumulation in seedlings. Tria caused a 1.3-fold increase in osmotic regulator proline synthesis to alleviate Pb stress. Phenolics, soluble protein, and DPPH free radical scavenging activity were enhanced by Tria application, suggesting that exogenous Tria could be employed to improve plant tolerance to Pb stress.

Effects of different concentrations of biochar amendments and Pb toxicity on rhizosphere soil characteristics and bacterial community of red clover (Trifolium pretense L.)

Amending soil with biochar can reduce the toxic effects of heavy metals (HM) on plants and the soil. However, the effects of different concentrations of biochar on the properties and microbial activities in lead (Pb)-contaminated soils are unclear. In this study, two Pb concentrations were set (low, 1000 mg/kg; high, 5000 mg/kg), and five corn straw biochar (CSB) concentrations (0, 2.5, 5, 10 and 15%) were used to determine the response of the growth and rhizosphere of red clover (Trifolium pretense L.) (in terms of soil properties and bacteria) to CSB and Pb application. The results showed that 5% CSB better alleviated the toxicity of Pb on the shoot length of red clover, the biomass increased by 74.55 and 197.76% respectively and reduced the enrichment factor (BCF) and transport factor (TF) of red clover. Pb toxicity reduced soil nutrients, catalase (CAT), acid phosphatase (ACP) and urease activity, while the addition of CSB increased soil pH, soil organic matter (SOM) content and soil enzyme activity. 16S rDNA amplicon sequencing analysis showed that Pb toxicity reduced the diversity of rhizosphere bacteria in red clover and reduced the relative abundance of plant growth-promoting rhizobacteria such as Gemmatimonas, Devosia and Bryobacter. Spearman correlation analysis showed that the addition of alkaline CSB restored the relative abundance of rhizobacteria positively correlated with pH, such as Chitinophaga, Sphingomonas, Devosia and Pseudomonas, and thus restored the rhizosphere soil environment. This study demonstrates that 5% CSB can better alleviate the toxicity of Pb to red clover and soil. We also provide a theoretical basis for the subsequent use of beneficial bacteria to regulate the repair efficiency of red clover.

Triacontanol priming as a smart strategy to attenuate lead toxicity in Brassica oleracea L

The most prevalent heavy metal pollutant in the environment is lead (Pb). Lead potentially contribute 10% of overall heavy metal contamination. Lead uptake by plants has been found to have an impact on their metabolic functions, photosynthetic activity, growth, and productivity. The current experiment was conducted to investigate the impact of triacontanol (Tria) for attenuating Pb stress in Brassica oleracea var. italic (broccoli). Three different Tria concentrations (10, 20 and 30 µmol L^-1) were used to prime broccoli seeds. Growth of broccoli was reduced when exposed to Pb-driven toxicity. Additionally, Pb had a deleterious impact on the protein quantity, stomatal conductance, transpiration and photosynthetic rate. Nevertheless, plants grown from seeds primed with Tria2 (20 µmol L^-1 Tria) exhibited improved morphological characteristics, uptake of mineral content (Mn⁺², Zn⁺², K⁺¹, Na⁺¹) along with biomass production. There was 1.6-fold increase in photosynthetic rate, the phenol (1.3 folds), and DPPH activity (1.2 folds) in seed primed with Tria2. Additionally, plants treated with Tria2 demonstrated enhanced MTI and gas exchange characteristics that improves plant stress tolerance under Pb stress. Seed priming with Tria can be used to increase plant tolerance to Pb stress as evidenced by the improved growth and biochemical characteristics of broccoli seedlings.

Genetic diversity and growth responses of Indonesian tomato (

Tomato (Solanum lycopersicum L.) is cultivated and consumed worldwide, including in Indonesia. It is used in the food, cosmetic, and pharmaceutical industries, due to its high content of carotenoid (lycopene) compounds that have antioxidant and anticancer activities. In Indonesia, although several cultivars of tomato are cultivated, including Opal, Permata, Mutiara, and Rewako, studies on their genetic information are limited. Unpredicted climate change as well as heavy metal contamination, especially Pb pollution, has threatened Indonesian food security. Therefore, our study aimed to analyze the genetic diversity of the four local tomatoes using random amplified polymorphic DNA (RAPD) markers and to determine the growth responses of several local tomato genotypes under Pb stress. In this study, morphological responses to Pb, including plant height and root length were observed. The RAPD analysis showed that Rewako and Permata were distinct, whereas Opal and Mutiara were closely related, possessing 81.8% similarity. Pb stress influenced plant height and root length in the four tomato genotypes, with each genotype exhibiting different morphological responses than others. However, the closely related Mutiara and Opal genotypes demonstrated similar responses to Pb stress to Permata and Rewako. Our study demonstrates that RAPD are sensitive and efficient for elucidating the genomic profile of the tomato genotypes. In addition, our results suggest that genetic variation among tomato genotypes might influence the morphological responses against Pb stress.

Morphological assessment of glutamate zerovalent iron nanoparticles by scanning electron microscopy and its combined effect with indole acetic acid on amelioration of lead toxicity in maize (Zea mays L.)

Food safety is a priority issue for sustainable global development that can be affected by heavy metals, contributing to morbidity and even mortality in crop growth. Heavy metals often accumulate in the soil due to the use of extensive chemical fertilizers and pesticides; therefore, the current experiment was aimed to determine the effect of glutamate zerovalent iron nanoparticles (Glu-ZVFeNPs) and indole acetic acid (IAA) on physiological mechanism of lead (Pb⁺² ) stress tolerance at 4 and 8 ppm in Zea mays variety. Seeds of the selected variety were collected from Cereal Crop Research Institute Persabaq Nowshera and planted in earthen pots in triplicate in the greenhouse of the Botany Department of the University of Peshawar. Nanoparticles were analyzed via scanning electron microscopy and energy dispersive X-ray analysis. Maximum growth responses were recorded from T12 (untreated + NPs + IAA), while minimum were recorded from T5 (8 ppm) indicating from the minimum amplitude of chlorophyll "a" and "b" contents, root length, shoot length, and root/shoot ratio. T5 (8 ppm) enhanced the values of osmolytes and antioxidant enzymes peroxidase and superoxide dismutase which has been ameliorated by the combined application of Glu-ZVFeNPs + IAA, indicating that the plant may resist the toxic effects of heavy metal stress at high concentration. From the present study, we concluded that adverse result of Pb⁺² has been condensed by application of Glu-ZVFeNPs + IAA treatment as compared to the foliar application of IAA and Glu-ZVFeNPs individually.

Functional and Integrative Analysis of the Proteomic Profile of Radish Root under Pb Exposure

Lead (Pb) is one of the most abundant heavy metal (HM) pollutants, which can penetrate the plant through the root and then enter the food chain causing potential health risks for human beings. Radish is an important root vegetable crop worldwide. To investigate the mechanism underlying plant response to Pb stress in radish, the protein profile changes of radish roots respectively upon Pb(NO₃)₂ at 500 mg L^-1(Pb500) and 1000 mg L^-1(Pb1000), were comprehensively analyzed using iTRAQ (Isobaric Tag for Relative and Absolute Quantification). A total of 3898 protein species were successfully detected and 2141 were quantified. Among them, a subset of 721 protein species were differentially accumulated upon at least one Pb treatment, and 135 ones showed significantly abundance changes under both two Pb-stressed conditions. Many critical protein species related to protein translation, processing, and degradation, reactive oxygen species (ROS) scavenging, photosynthesis, and respiration and carbon metabolism were successfully identified. Gene Ontology (GO) and pathway enrichment analysis of the 135 differential abundance protein species (DAPS) revealed that the overrepresented GO terms included "cell wall," "apoplast," "response to metal ion," "vacuole," and "peroxidase activity," and the critical enriched pathways were involved in "citric acid (TCA) cycle and respiratory electron transport," "pyruvate metabolism," "phenylalanine metabolism," "phenylpropanoid biosynthesis," and "carbon metabolism." Furthermore, the integrative analysis of transcriptomic, miRNA, degradome, metabolomics and proteomic data provided a strengthened understanding of radish response to Pb stress at multiple levels. Under Pb stress, many key enzymes (i.e., ATP citrate lyase, Isocitrate dehydrogenase, fumarate hydratase and malate dehydrogenase) involved in the glycolysis and TCA cycle were severely affected, which ultimately cause alteration of some metabolites including glucose, citrate and malate. Meanwhile, a series of other defense responses including ascorbate (ASA)-glutathione (GSH) cycle for ROS scavenging and Pb-defense protein species (glutaredoxin, aldose 1-epimerase malate dehydrogenase and thioredoxin), were triggered to cope with Pb-induced injuries. These results would be helpful for further dissecting molecular mechanism underlying plant response to HM stresses, and facilitate effective management of HM contamination in vegetable crops by genetic manipulation.

Sexual differences in photosynthetic activity, ultrastructure and phytoremediation potential of Populus cathayana exposed to lead and drought

Lead (Pb) and drought frequently coexist in China's forests and seriously affect their biomass, net primary productivity and biodiversity, particularly among dioecious trees with different sex-related reproduction costs. Here, the effects of Pb, deposited into soil (Pbsoil) and leaves (Pb(leaf)), on the traits related directly or indirectly to photosynthetic activity were evaluated in the dioecious tree, Populus cathayana Rehd. In addition, we analysed the potential of P. cathayana males and females for phytoremediation based on the photosynthetic activity, cellular ultrastructure and phytoremediation-related parameters. The Pb level was 2.7 mmol Pb(NO3)2 kg(-1) dry soil in the Pb(soil) treatment and 1.8 mmol Pb(NO3)2 per plant in the Pb(leaf) treatment. In parallel experiments, two watering regimes, 100 and 50% of the field capacity, were applied. The stress duration was 2 months. Dry mass production, net photosynthetic rate increased in both sexes, particularly in females, when exposed to Pb(leaf) alone, Pb(soil) with drought and Pb(leaf) with drought. The study revealed that males exhibit greater plasticity in the photosynthetic capacity than females. Severe damage to cellular ultrastructure was also observed in the leaves of males and females exposed to Pb(leaf), but more strongly in females. However, the Pb(soil) treatment alone did not affect these traits as significantly compared with other treatments. Moreover, drought significantly increased the sensitivity to Pb stress in both sexes, but more so in females. In addition, changes in the photosynthetic capacity and cellular ultrastructure combined with the analysis of tolerance index, translocation factor, bioconcentration factor and Pb concentration showed that males and females could be employed for different purposes in phytoremediation: females are promising candidates for phytoextraction, whereas males are promising candidates for phytostabilization.