Salt stress-induced changes in soil metabolites promote cadmium transport into wheat tissues

System-wide analysis of groundnut's salinity resilience: Integrating plant-cell interactions with environmental stress dynamics through cutting-edge transcriptomics

Salinity stress is a major concern in regions where irrigation relies on saline water. This study aimed to investigate the relative water content (RWC), electrolytic leakage (EL), total chlorophyll content, free amino acid content, and total soluble sugar content were analyzed in different groundnut species subjected to various salinity treatments. The results showed that salinity stress significantly reduced the RWC in groundnut leaves, with A. duranensis (wild type) exhibiting higher RWC values compared to the Arachis hypogaea species. RNA sequencing was performed to identify differentially expressed genes (DEGs) during salt stress. A total of 9079 DEGs were identified, with 1372 genes upregulated and 2509 genes downregulated. Genes belonging to transcription factor families, such as WRKY, MYB, bHLH, E2F, and Auxin efflux carrier proteins, were induced under salt stress in the tolerant genotype. Conversely, genes encoding NADH dehydrogenase, glutathione S-transferase, protein kinases, UDP-glycosyltransferase, and peroxidase were downregulated. Gene ontology and pathway analyses revealed several enriched categories and metabolic pathways associated with salt stress response, including catalytic activity, response to salt stress, ATP-dependent activity, and oxidative phosphorylation. The findings of this study provide insights into the physiological and molecular responses of groundnut to salinity stress. A. duranensis exhibited better salinity tolerance than Arachis hypogaea, as indicated by higher RWC values, lower electrolytic leakage, and differential gene expression patterns. These results contribute to our understanding of the mechanisms underlying salt stress tolerance in groundnut and may guide future efforts to develop salinity-tolerant groundnut species, ultimately improving crop yield in saline-affected regions.

Translational toxicology of metal(loid) species: linking their bioinorganic chemistry in the bloodstream to organ damage onset

The quantification of arsenic, mercury, cadmium and lead in the human bloodstream is routinely used today to assess exposure to these toxic metal(loid)s, but the interpretation of the obtained data in terms of their cumulative health relevance remains problematic. Seemingly unrelated to this, epidemiological studies strongly suggest that the simultaneous chronic exposure to these environmental pollutants is associated with the etiology of autism, type 2 diabetes, irritable bowel disease and other diseases. This from a public health point of view undesirable situation urgently requires research initiatives to establish functional connections between human exposure to multiple toxic metal(loid) species and adverse health effects. One way to establish causal exposure-response relationships is a molecular toxicology approach, which requires one to unravel the biomolecular mechanisms that unfold after individual toxic metal(loid)s enter the bloodstream/organ nexus as these interactions ultimately determine which metabolites impinge on target organs and thus provide mechanistic links to diseases of unknown etiology. In an attempt to underscore the importance of the toxicological chemistry of metal(loid)s in the bloodstream, this review summarizes recent progress into relevant bioinorganic processes that are implicated in the etiology of adverse organ-based health effects and possibly diseases. A better understanding of these bioinorganic processes will not only help to improve the regulatory framework to better protect humans from the adverse effects of toxic metal(loid) species, but also represents an important starting point for the development of treatments to ameliorate pollution-induced adverse health effects on human populations, including pregnant women, the fetus and children.

Cellular Cd2+ fluxes in roots confirm increased Cd availability to rice (Oryza sativa L.) induced by soil acidifications

Soil acidifications become one of the main causes restricting the sustainable development of agriculture and causing issues of agricultural product safety. In order to explore the effect of different acidification on soil cadmium (Cd) availability, soil pot culture and hydroponic (soil potting solution extraction) were applied, and non-invasive micro-test technique (NMT) was combined. Here three different soil acidification processes were simulated, including direct acidification by adding sulfuric acid (AP1), acid rain acidification (AP2) by adding artificial simulated acid rain and excessive fertilization acidification by adding (NH4)2SO4 (AP3). The results showed that for direct acidification (AP1), DTPA-Cd concentration in field soils in Liaoning (S1) and Zhejiang (S2) increased by 0.167 - 0.217 mg/kg and 0.181 - 0.346 mg/kg, respectively, compared with control group. When soil pH decreased by 0.45 units in S1, the Cd content of rice stems, leaves and roots increased by 0.48 to 6.04 mg/kg and 2.58 to 12.84 mg/kg, respectively, When the pH value of soil S1 and S2 decreased by 0.20 units, the average velocity of Cd2+ at 200 µm increased by 10.03 - 33.11 pmol/cm2/sec and 21.33 -52.86 pmol/cm2/sec, respectively, and followed the order of AP3 > AP2 > AP1. In summary, different acidification measures would improve the effectiveness of Cd, under the same pH reduction condition, fertilization acidification increased Cd availability most significantly.

Caffeic Acid O-Methyltransferase Gene Family in Mango (Mangifera indica L.) with Transcriptional Analysis under Biotic and Abiotic Stresses and the Role of MiCOMT1 in Salt Tolerance

Caffeic acid O-methyltransferase (COMT) participates in various physiological activities in plants, such as positive responses to abiotic stresses and the signal transduction of phytohormones. In this study, 18 COMT genes were identified in the chromosome-level reference genome of mango, named MiCOMTs. A phylogenetic tree containing nine groups (I-IX) was constructed based on the amino acid sequences of the 71 COMT proteins from seven species. The phylogenetic tree indicated that the members of the MiCOMTs could be divided into four groups. Quantitative real-time PCR showed that all MiCOMT genes have particularly high expression levels during flowering. The expression levels of MiCOMTs were different under abiotic and biotic stresses, including salt and stimulated drought stresses, ABA and SA treatment, as well as Xanthomonas campestris pv. mangiferaeindicae and Colletotrichum gloeosporioides infection, respectively. Among them, the expression level of MiCOMT1 was significantly up-regulated at 6-72 h after salt and stimulated drought stresses. The results of gene function analysis via the transient overexpression of the MiCOMT1 gene in Nicotiana benthamiana showed that the MiCOMT1 gene can promote the accumulation of ABA and MeJA, and improve the salt tolerance of mango. These results are beneficial to future researchers aiming to understand the biological functions and molecular mechanisms of MiCOMT genes.

Discrimination of toxigenic and non-toxigenic Aspergillus flavus in wheat based on nanocomposite colorimetric sensor array

A novel method was developed for the early detection of wheat infected with Aspergillus flavus (A. flavus) using a nanocomposite colorimetric sensors array (CSA). LC-MS analysis revealed the presence of Aflatoxin B1 (AFB1) and Aflatoxin B2 (AFB2) on day seven, demonstrating mycotoxin variabilities in infected wheat. HS-SPME-GC-MS analysis detected 2-methylbutyral, a gas exclusively associated with toxigenic A. flavus. The CSA was modified using three nanoparticles of MOF and successfully used to detect the wheat infected with A. flavus. Discrimination of different types of infected wheat samples was achieved using the RGB difference map and Principal Component Analysis (PCA) model. Additionally, the Linear Discriminant Analysis (LDA) model accurately predicted the presence of toxigenic A. flavus at various stages of infection. These findings highlight the promising capabilities of nanocomposite CSA for early-stage detection of A. flavus infection in wheat.

Protective effects of polymer amendment on specific metabolites in soil and cotton leaves under cadmium contamination

Polymer materials have great potential for soil heavy metal contamination remediation, but the metabolic mechanism by which polymer amendments regulate the responses of soil-plant systems to cadmium (Cd) stress is still unclear. To clarify the metabolic mechanism by which a self-developed soluble polymer amendment (PA) remediates Cd contamination in cotton fields, the common and differential metabolites in soil and cotton leaves were analyzed during the critical period of cotton growth (flowering and bolling stage) in a field experiment. The results showed that Cd stress increased Cd concentration in the soil-cotton system, and reduced enzyme activity in soil and cotton leaves. Besides, Cd stress also reduced the abundance of α-linolenic acid in soil and the abundance of 2-Oxoarginine and S-Adenosylmethionine in cotton leaves. These ultimately led to reductions in weight, boll number, yield, and fiber elongation. However, the application of PA to the Cd-contaminated soil significantly reduced the soil exchangeable Cd (Ex-Cd) concentration by 41.43%, and increased the boll number, yield, and fiber strength by 14.17%, 21.04%, and 19.89%, respectively compared with the Cd treatment. The results of metabolomic analysis showed that PA application mainly affected the Nicotinate and nicotinamide metabolism pathway, Lysine degradation pathway, and Arginine and proline metabolism pathway in cotton leaves and soil. Besides, in these metabolic pathways, succinic acid semialdehyde of cotton leaves, saccharopine of soil, and S-Adenosylmethionine of soil and cotton had the most significant response to PA application. Therefore, the application of PA to Cd-contaminated soil can increase soil and cotton leaf enzyme activity and cotton yield (boll number and seed cotton yield) and quality (fiber strength), and maintain soil-plant material balance by regulating the distribution of Cd ions and key metabolites in the soil-cotton system. This study will deepen our understanding of the metabolic mechanism of PA remediating Cd-contaminated cotton fields, and provide a technical reference for the remediation of heavy metal contamination in drip-irrigated cotton fields in arid areas.

Effect of iron nanoparticles and conventional sources of Fe on growth, physiology and nutrient accumulation in wheat plants grown on normal and salt-affected soils

Salt stress is becoming a serious problem for the global environment and agricultural sector. Different sources of iron (Fe) can provide an eco-friendly solution to remediate salt-affected soils. The Fe nanoparticles (FeNPs) and conventional sources of Fe (iron-ethylene diamine tetra acetic acid; Fe-EDTA; and iron sulfate; FeSO₄) were used to evaluate their effects on wheat crop grown in normal and salt-affected soils. Application of FeNPs (25 mg/kg) on normal soil increased the dry weights of wheat roots, shoots, and grains by 46%, 59%, and 77%, respectively. In salt-affected soil, FeNPs increased the dry weights of wheat roots, shoots, and grains by 65%, 78%, and 61%, respectively. The application of FeSO₄ and Fe-EDTA increased the growth parameters of wheat in both normal and salt-affected soils compared to the respective controls. The photosynthetic parameters, including chlorophyll a (50%), chlorophyll b (67%), carotenoids (62%), and total chlorophyll contents (50%), were increased with the application of FeNPs under salt stress. The FeNPs increased plant-essential nutrients like iron, zinc, calcium, magnesium, and potassium in both normal and salt-affected soils. The experiment revealed that the application of Fe plays a significant role in enhancing the growth of wheat on alkaline normal and salt-affected soils. Maximum growth response was recorded with FeNPs than other Fe sources. The future must be focused on long term field experiments to economize the application of FeNPs on a large scale for commercialization.

Variance of soil bacterial community and metabolic profile in the rhizosphere vs. non-rhizosphere of native plant Rumex acetosa L. from a Sb/As co-contaminated area in China

Heavy metals (HMs) contamination poses a serious threat to soil health. However, the rhizosphere effect of native pioneer plants on the soil ecosystem remains unclear. Herein, how the rhizosphere (Rumex acetosa L.) influenced the process of HMs threatening soil micro-ecology was investigated by coupling various fractions of HMs, soil microorganisms and soil metabolism. The rhizosphere effect alleviated the HMs' stress by absorbing and reducing HMs' direct bioavailability, and the accumulation of ammonium nitrogen increased in the rhizosphere soil. Meanwhile, severe HMs contamination covered the rhizosphere effect on the richness, diversity, structure and predicted function pathways of soil bacterial community, but the relative abundance of Gemmatimonadota decreased and Verrucomicrobiota increased. The content of total HMs and physicochemical properties played a more important role than rhizosphere effect in shaping soil bacterial community. Furthermore, As was observed to have a more significant impact compared to Sb. Moreover, plant roots improved the stability of bacterial co-occurrence network, and significantly changed the critical genera. The process influenced bacterial life activity and nutrient cycling in soil, and the conclusion was further supported by the significant difference in metabolic profiles. This study illustrated that in Sb/As co-contaminated area, rhizosphere effect significantly changed soil HMs content and fraction, soil properties, and microbial community and metabolic profiles.

Green manure increases peanut production by shaping the rhizosphere bacterial community and regulating soil metabolites under continuous peanut production systems

BACKGROUND

Green manure (GM) is a crop commonly grown during fallow periods, which has been applied in agriculture as a strategy to regulate nutrient cycling, improve organic matter, and enhance soil microbial biodiversity, but to date, few studies have examined the effects of GM treatments on rhizosphere soil bacterial community and soil metabolites from continuous cropping peanut field.

RESULTS

In this study, we found that the abundances of several functionally significant bacterial groups containing Actinobacteria, Acidobacteria, and genus Sphingomonas, which are associated with nitrogen cycling, were dramatically increased in GM-applied soils. Consistent with the bacterial community results, metabolomics analysis revealed a strong perturbation of nitrogen- or carbon-related metabolisms in GM-applied soils. The substantially up-regulated beneficial metabolites including sucrose, adenine, lysophosphatidylcholine (LPC), malic acid, and betaines in GM-applied soils may contribute to overcome continuous cropping obstacle. In contrast to peanut continuous cropping, planting winter wheat and oilseed rape in winter fallow period under continuous spring peanut production systems evidently improved the soil quality, concomitantly with raised peanut pod yield by 32.93% and 25.20%, in the 2020 season, respectively.

CONCLUSIONS

GMs application is an effective strategy to overcome continuous cropping obstacle under continuous peanut production systems by improving nutrient cycling, soil metabolites, and rhizobacterial properties.

Targeted and non-targeted analysis for the investigation of pesticides influence on wheat cultivated under field conditions

A comprehensive approach was applied to evaluate the effects of pesticides on the metabolism of wheat (Triticum aestivum L). The application of commercially available pesticide formulations under field cultivation conditions provided a source of metabolic data unlimited by model conditions, representing a novel approach to study the effects of pesticides on edible plants. Gas and liquid chromatography coupled to tandem mass spectrometry were employed for targeted and non-targeted analysis of wheat roots and shoots sampled six times during the six-week experiment. The applied pesticides: prothioconazole, tebuconazole, fluoxastrobin, diflufenican, florasulam, and penoxulam were found at concentrations ranging 0.0070-25.20 mg/kg and 0.0020-2.2 mg/kg in the wheat roots and shoots, respectively. The following pesticide metabolites were identified in shoots: prothioconazole-desthio (prothioconazole metabolite), 5-(4-chlorophenyl)-2,2-dimethyl-3-(1,2,4-triazol-1-ylmethyl)pentane-1,3-diol (tebuconazole metabolite), and N-(5,8-dimethoxy[1,2,4]triazolo[1,5-c]pyrimidin-2-yl)-2,4-dihydroxy-6-(trifluoromethyl)benzene sulphonamide (penoxulam metabolite). The metabolic fingerprints and profiles changed during the experiment, reflecting the cumulative response of wheat to both its growth environment and pesticides, as well as their metabolites. Approximately 15 days after the herbicide treatment no further changes in the plant metabolic profiles were observed, despite the presence of pesticide and their metabolites in both roots and shoots. This is the first study to combine the determination of pesticides and their metabolites plant tissues with the evaluation of plant metabolic responses under field conditions. This exhaustive approach contributes to broadening the knowledge of pesticide effects on edible plants, relevant to food safety.