Polymer amendment regulates cadmium migration in cadmium contaminated cotton field: Insights from genetic adaptation and phenotypic plasticity

Ecotoxicity of Cadmium along the Soil-Cotton Plant-Cotton Bollworm System: Biotransfer, Trophic Accumulation, Plant Growth, Induction of Insect Detoxification Enzymes, and Immunocompetence

Cadmium (Cd) is a hazardous element that may jeopardize environmental safety and human health through biotransfer and trophic accumulation. Here, we tested Cd toxicity on cotton plants, cotton bollworms, and their responses. Results demonstrated that Cd accumulated in plant roots, aerial parts, insect larvae, pupae, and frass in a dose-dependent pattern. The ∼9.35 mg kg-1 of Cd in plant aerial parts, ∼3.68 in larvae, ∼6.43 in pupae, and high transfer coefficient (∼5.59) indicate significant mobility. The ∼19.61 mg kg-1 of Cd in larvae frass suggests an effective detoxification strategy, while BAFcotton (∼1.14) and BAFworm (∼0.54) indicated low bioaccumulation. Cadmium exposure resulted in compromised plant growth and yield as well as alterations in photosynthetic pigment contents, antioxidant enzyme activities, and certain life history traits of cotton bollworms. Furthermore, carboxylesterase activity and encapsulation rates of insect larvae decreased with increasing Cd concentrations, whereas acetylcholinesterase, phenol oxidase, glutathione S-transferase, and multifunctional oxidase exhibited hormesis responses.

Melatonin alleviates cadmium toxicity by regulating root endophytic bacteria community structure and metabolite composition in apple

The level of cadmium (Cd) accumulation in orchard soils is increasing, and excess Cd will cause serious damage to plants. Melatonin is a potent natural antioxidant and has a potential role in alleviating Cd stress. This study aimed to investigate the effects of exogenous melatonin on a root endophyte bacteria community and metabolite composition under Cd stress. The results showed that melatonin significantly scavenged the reactive oxygen species and restored the photosynthetic system (manifested by the improved photosynthetic parameters, total chlorophyll content and the chlorophyll fluorescence parameters (Fv/Fm)), increased the activity of antioxidant enzymes (the activities of catalase, superoxide dismutase, peroxidase and ascorbate oxidase) and reduced the concentration of Cd in the roots and leaves of apple plants. High-throughput sequencing showed that melatonin increased the endophytic bacterial community richness significantly and changed the community structure under Cd stress. The abundance of some potentially beneficial endophytic bacteria (Ohtaekwangia, Streptomyces, Tabrizicola and Azovibrio) increased significantly, indicating that the plants may absorb potentially beneficial microorganisms to resist Cd stress. The metabolomics results showed that melatonin significantly changed the composition of root metabolites, and the relative abundance of some metabolites decreased, suggesting that melatonin may resist Cd stress by depleting root metabolites. In addition, co-occurrence network analysis indicated that some potentially beneficial endophytes may be influenced by specific metabolites. These results provide a theoretical basis for studying the effects of melatonin on the endophytic bacterial community and metabolic composition in apple plants.

Removal of nitrate nitrogen by Pseudomonas JI-2 under strong alkaline conditions: Performance and mechanism

The nitrate nitrogen removal characteristics of Pseudomonas JI-2 under strong alkaline conditions and the composition and functional groups of extracellular polymeric substance were analyzed. Furthermore, nontargeted metabonomics and bioinformatics technology were used to investigate the alkaline tolerance mechanism. JI-2 removed 11.05 mg N/(L·h) of nitrate with the initial pH, carbon to nitrogen ratio and temperature were 11.0, 8 and 25 °C respectively. Even when the pH was maintained at 11.0, JI-2 could still effectively remove nitrate. JI-2 contains a large number of Na+/H+ antiporters, such as Mrp, Mnh (mnhACDEFG) and Pha (phaACDEFG), which can stabilize the intracellular acid-base environment, and SlpA can enable quick adaptation to alkaline conditions. Moreover, JI-2 responds to the strong alkaline environment by secreting more polysaccharides, acidic functional groups and compatible solutes and regulating key metabolic processes such as pantothenate and CoA biosynthesis and carbapenem biosynthesis. Therefore, JI-2 can survive in strong alkaline environments and remove nitrate efficiently.

Joint toxicity mechanisms of perfluorooctanoic acid and sulfadiazine on submerged macrophytes and periphytic biofilms

Hazardous chemicals, such as perfluoroalkyl substances (PFASs) and antibiotics, coexist in aquatic environments and pose a severe threat to aquatic organisms. However, research into the toxicity of these pollutants on submerged macrophytes and their periphyton is still limited. To assess their combined toxicity, Vallisneria natans (V. natans) was exposed to perfluorooctanoic acid (PFOA) and sulfadiazine (SD) at environmental concentrations. Photosynthetic parameters such as chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids were lower in the SD exposure group, indicating that SD had a significant effect on the photosynthesis of aquatic plants. Single and combined exposures effectively induced antioxidant responses, with increases in superoxide dismutase, peroxidase activities, and ribulose-1,5-bisphosphate carboxylase concentrations, as well as malondialdehyde content. Accordingly, antagonistic toxicity was assessed between PFOA and SD. Furthermore, metabolomics revealed that V. natans improved stress tolerance through changes in enoic acid, palmitic acid, and palmitoleoyloxymyristic acid related to the fatty acid metabolism pathway responding to the coexisting pollutants. Additionally, PFOA and SD in combination induced more effects on the microbial community of biofilm. The alternation of α- and β-D-glucopyranose polysaccharides and the increased content of autoinducer peptides and N-acylated homoserine lactones indicated that PFOA and SD changed the structure and function of biofilm. These investigations provide a broader perspective and comprehensive analysis of the responses of aquatic plants and periphyton biofilms to PFAS and antibiotics in the environment.

Abscisic acid (ABA) alleviates cadmium toxicity by enhancing the adsorption of cadmium to root cell walls and inducing antioxidant defense system of Cosmos bipinnatus

Cadmium (Cd) pollution is a global problem affecting soil ecology and plant growth. Abscisic acid (ABA) acts as a growth and stress hormone, regulates cell wall synthesis, and plays an important role in plant responses to stress. There are few studies on the mechanisms behind abscisic acid alleviation of cadmium stress in Cosmos bipinnatus, especially in regards to regulation of the root cell wall. This study examined the effects of different concentrations of abscisic acid at different concentrations of cadmium stress. Through adding 5 μmol/L and 30 μmol/L cadmium, followed by spraying 10 μmol/L and 40 μmol/L ABA in a hydroponic experiment, it was found that under two concentrations of cadmium stress, low concentration of ABA improved root cell wall polysaccharide, Cd, and uronic acid content. Especially in pectin, after the application of low concentration ABA, the cadmium concentration was significantly increased by 1.5 times and 1.2 times compared with the Cd concentration under Cd5 and Cd30 treatment alone, respectively. Fourier-Transform Infrared spectroscopy (FTIR) demonstrated that cell wall functional groups such as -OH and -COOH were increased with exposure to ABA. Additionally, the exogenous ABA also increased expression of three kinds of antioxidant enzymes and plant antioxidants. The results of this study suggest that ABA could reduce Cd stress by increasing Cd accumulation, promoting Cd adsorption on the root cell wall, and activating protective mechanisms. This result could help promote application of C. bipinnatus for phytostabilization of cadmium-contaminated soil.

Cotton straw biochar and compound Bacillus biofertilizer reduce Cd stress on cotton root growth by regulating root exudates and antioxidant enzymes system

INTRODUCTION

Cotton straw biochar (biochar) and compound Bacillus biofertilizer (biofertilizer) have attracted wide attentions in the remediation of heavy metal-contaminated soils in recent years. However, few studies have explored the metabolomics of lateral roots of Cd-stressed cotton to determine the mechanism of biochar and biofertilizer alleviating Cd stress.

METHODS

In this pot experiment, biochar and biofertilizer were applied to the soils with different Cd contamination levels (1, 2, and 4 mg kg^-1). Then, the responses of cotton root morphology, vitality, Cd content, and antioxidant enzyme activities were analyzed, and the mechanism of biochar and biofertilizer alleviating Cd stress was determined by metabolomic analysis.

RESULTS

The results showed that exogenous Cd addition decreased the SOD and POD activities in cotton taproot and lateral root. Besides, with the increase of soil Cd content, the maximum Cd content in taproot (0.0250 mg kg^-1) and lateral root (0.0288 mg kg^-1) increased by 89.11% and 33.95%, respectively compared with those in the control (p< 0.05). After the application of biochar and biofertilizer, the SOD and POD activities in cotton taproot and lateral root increased. The Cd content of cotton taproot in biochar and biofertilizer treatments decreased by 16.36% and 19.73%, respectively, and that of lateral root decreased by 13.99% and 16.68%, respectively. The metabolomic analysis results showed that the application of biochar and biofertilizer could improve the resistance of cotton root to Cd stress through regulating the pathways of ABC transporters and phenylalanine metabolism.

DISCUSSION

Therefore, the application of biochar and biofertilizer could improve cotton resistance to Cd stress by increasing antioxidant enzyme activities, regulating root metabolites (phenols and amino acids), and reducing Cd content, thus promoting cotton root growth.

Insights into growth-promoting effect of nanomaterials: Using transcriptomics and metabolomics to reveal the molecular mechanisms of MWCNTs in enhancing hyperaccumulator under heavy metal(loid)s stress

Carbon nanotubes present potential applications in soil remediation, particularly in phytoremediation. Yet, how multi-walled carbon nanotubes (MWCNTs) induced hyperaccumulator growth at molecular level remains unclear. Here, physio-biochemical, transcriptomic, and metabolomic analyses were performed to determine the effect of MWCNTs on Solanum nigrum L. (S. nigrum) growth under cadmium and arsenic stresses. 500 mg/kg MWCNTs application significantly promoted S. nigrum growth, especially for root tissues. Specially, MWCNTs application yields 1.38-fold, 1.56-fold, and 1.37-fold enhancement in the shoot length, root length, and fresh biomass, respectively. Furthermore, MWCNTs significantly strengthened P and Fe absorption in roots, as well as the activities of antioxidative enzymes. Importantly, the transcriptomic analysis indicated that S. nigrum gene expression was sensitive to MWCNTs, and MWCNTs upregulated advantageous biological processes under heavy metal(loid)s stress. Besides, MWCNTs reprogramed metabolism that related to defense system, leading to accumulation of 4-hydroxyphenylpyruvic acid (amino acid), 4-hydroxycinnamic acid (xenobiotic), and (S)-abscisic acid (lipid). In addition, key common pathways of differentially expressed metabolites and genes, including "tyrosine metabolism" and "isoquinoline alkaloid biosynthesis" were selected via integrating transcriptome and metabolome analyses. Combined omics technologies, our findings provide molecular mechanisms of MWCNTs in promoting S. nigrum growth, and highlight potential application of MWCNTs in soil remediation.