Sixi Zhu

Elevated atmospheric carbon dioxide (ECO₂) is a key climatic factor influencing the resilience of plant–microbial symbiotic systems against heavy metal contamination. Robinia pseudoacacia–rhizobia symbiosis shows great potential for cadmium (Cd) remediation. However, the mechanism by which ECO₂ regulates Cd phytostabilization in symbiosis remains unclear. This study conducted a 90-day experiment in growth chambers to investigate the effects of ECO₂ on the growth, Cd accumulation and chemical forms, as well as nutrient uptake and antioxidant system in Robinia pseudoacacia–rhizobia symbiosis. Results indicated that ECO₂ significantly increased plant biomass and photosynthetic efficiency while significantly raising Cd content in roots (34.5%, p < 0.001) and decreasing it in shoots (31.4%, p < 0.001). This resulted in a significant reduction in Cd translocation factor (TF). Meanwhile, ECO₂ markedly increased Cd accumulation in roots (81.2%, p < 0.001) and reduced the bioavailability of Cd in the symbiosis. Moreover, ECO₂ promoted the content of nutrients and stimulated the antioxidant system. The random forest model indicated that root weight, Cd and Mn contents are the core factors for ECO₂-driven Cd phytostabilization. This study demonstrates that ECO₂ enhanced Cd phytostabilization by optimizing the resistance of symbiosis to Cd, offering a novel perspective for predicting plant–microbe joint restoration of heavy metal pollution under global climate change scenarios.

As emerging pollutants, nanoplastics (NPs) are profoundly threatening aquatic ecosystems. However, the systematic response mechanisms of aquatic floating macrophytes to NP stress and the mitigation strategies of nanoselenium (Se) remain poorly understood. This study used P. stratiotes, a dominant species in freshwater ecological restoration, as the research object. By intervening in NP stress via foliar application of Se, the study systematically deciphered the plant’s response and mitigation mechanisms to NPs pollution through integrating physiological and biochemical analyses, ultrastructural observation of cells, and transcriptomic and metabolomic multi-omics techniques. The results showed that NP stress significantly reduced photosynthetic pigment concentration and inhibited photosystem function in Pistia stratiotes L., disrupted energy metabolism homeostasis, and simultaneously induced an outburst of reactive oxygen species (ROS). It activated non-enzymatic antioxidant substances such as flavonoids and glutathione (GSH), as well as enzymatic defense systems including catalase (CAT) and peroxidase (POD), promoting the reprogramming of the plant’s metabolic strategy from growth priority to defense dominance. At the transcriptomic level, NP stress significantly altered the gene expression profile, with core pathways enriched in photosynthesis antenna proteins and phenylpropanoid biosynthesis. Metabolomic analysis revealed significant differences in metabolites, with markedly upregulated contents of defense-related metabolites such as lipids and terpenoids. The intervention of NPs-Se effectively restored photosynthetic pigment contents and enzyme activities, alleviated cell membrane damage by repairing the photosynthetic apparatus, optimizing ribosome-mediated protein synthesis pathways, and strengthening the antioxidant defense network. Meanwhile, it regulated the expression of specific genes and the accumulation of core differential metabolites, reconstructed the balance between energy supply and defense investment, enabling the plant to achieve more efficient adaptive regulation. Multi-omics correlation analysis further confirmed that the responses of P. stratiotes to NPs and NPs-Se exhibited characteristics of coordinated regulation, highlighting the modular regulatory patterns of nano-stress responses. In conclusion, Se can effectively alleviate the stress damage of nanoplastics to P. stratiotes through multi-dimensional regulation, providing a key experimental basis and theoretical support for the ecological restoration of NP-polluted water bodies and ecological risk assessment.

The uptake and accumulation of nanoplastics by plants have emerged as a major research focus. Exogenous selenium nanoparticles (SeNPs) are widely used to mitigate the toxicity of abiotic stresses, such as nanoplastics (NPs) and polyethylene (PE—NPs) nanoplastics, and represent a feasible strategy to enhance plant performance. However, the molecular mechanisms by which SeNPs alleviate the phytotoxicity of microplastics and nanoplastics remain poorly defined. To address this gap, we used Pistia stratiotes L. (P. stratiotes) as a model and silicon dioxide nanoparticles (SiO2NPs) as a comparator, integrating physiological assays, ultrastructural observations, and proteomic analyses. We found that NP stress caused ultrastructural damage in root tips, exacerbated oxidative stress, and intensified membrane lipid peroxidation. SeNPs treatment significantly mitigated NP-induced oxidative injury and metabolic suppression. Compared to the NPs group, SeNPs increased T-AOC by 38.2% while reducing MDA and ·OH by 33.3% and 89.6%, respectively. Antioxidant enzymes were also elevated, with CAT and POD rising by 47.1% and 39.2%. SeNPs further enhanced the photosynthetic capacity and osmotic adjustment, reflected by increases in chlorophyll a, chlorophyll b, and soluble sugar by 49.7%, 43.8%, and 27.0%, respectively. In contrast, proline decreased by 17.4%, indicating stress alleviation rather than an osmotic compensation response. Overall, SeNPs outperformed SiO2NPs. These results indicate that SeNPs broadly strengthen anti-oxidative defenses and metabolic regulation in P. stratiotes, effectively alleviating NP-induced oxidative damage. Proteomics further showed that SeNPs specifically activated the MAPK signaling cascade, phenylpropanoid biosynthesis, and energy metabolic pathways, enhancing cell-wall lignification to improve the mechanical barrier and limiting NPs translocation via a phytochelatin-mediated vacuolar sequestration mechanism. SiO2NPs produced similar but weaker alleviative effects. Collectively, these findings elucidate the molecular basis by which SeNPs mitigate NPs’ phytotoxicity and provide a theoretical foundation and practical outlook for using nanomaterials to enhance phytoremediation in aquatic systems.

Cadmium (Cd) toxicity destroys plant cells and affects plant growth and development. Due to its unique metallic properties, selenium (Se) has been shown to be effective in antioxidants, cellular immunity, and heavy metal detoxification. When Se and Cd are present together in plants, they antagonize. However, the mechanism of action of the two in the rice cell wall remains to be clarified. In this study, we analyzed the mechanism of Cd detoxification by rice (Oryza sativa L.) cellular polysaccharides mediated by Se, using the cell wall as an entry point. Proteomic and transcriptomic analyses revealed that “Glycosyl hydrolases family 17”, “O-methyltransferase”, and “Polygalacturonase” protein pathways were significantly expressed in the cell wall. The most abundant enzymes involved in polysaccharide biosynthesis were found, including bglB, otsB, HK, PFP, ADH1, and ALDH, which resulted in the synthetic pathway of polysaccharide formation in the rice cell wall. Finally, the essential genes/proteins, such as protein Os03g0170500, were identified. The study showed that Se inhibits Cd uptake and transport when Se (1 mg/kg) is low relative to Cd (3 mg/kg), has little inhibitory effect, and even promotes Cd (3 mg/kg) uptake when Se (5 mg/kg) is relatively high.

Chromium (Cr) can interfere with plant gene expression, change the content of metabolites and affect plant growth. However, the molecular response mechanism of wetland plants at different time sequences under Cr stress has yet to be fully understood. In this study, Canna indica was exposed to 100 mg/kg Cr-contaminated soil for 0, 7, 14, and 21 days and analyzed using untargeted metabolomics (LC–MS) and transcriptomics. The results showed that Cr stress increased the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX) and peroxidase (POD), the contents of glutathione (GSH), malondialdehyde (MDA), and oxygen free radical (ROS), and inhibited the biosynthesis of photosynthetic pigments, thus leading to changes in plant growth and biomass. Metabonomics analysis showed that Cr stress mainly affected 12 metabolic pathways, involving 38 differentially expressed metabolites, including amino acids, phenylpropane, and flavonoids. By transcriptome analysis, a total of 16,247 differentially expressed genes (DEGs, 7710 up-regulated genes, and 8537 down-regulated genes) were identified, among which, at the early stage of stress (Cr contaminate seven days), C. indica responds to Cr toxicity mainly through galactose, starch and sucrose metabolism. With the extension of stress time, plant hormone signal transduction and MAPK signaling pathway in C. indica in the Cr14 (Cr contaminate 14 days) treatment group were significantly affected. Finally, in the late stage of stress (Cr21), C. indica co-defuses Cr toxicity by activating its Glutathione metabolism and Phenylpropanoid biosynthesis. In conclusion, this study revealed the molecular response mechanism of C. indica to Cr stress at different times through multi-omics methods.

Intercropping systems can improve soil fertility and health, however, soil microbial communities and functional genes related to carbon, nitrogen and phosphorus cycling under the intercropping system of mesquite and perilla have not been studied. Therefore, in the present study, different planting densities and varieties of Perilla frutescens (L.) Britt and kiwifruit were used for intercropping, and changes in soil microbial communities and carbon, nitrogen, and phosphorus cycling genes in kiwifruit inter-roots under inter-cropping conditions were investigated by macro-genome sequencing technology. The results showed that intercropping with Perill caused a decrease in most soil nutrients, soil enzyme activities, and had a significant impact on the microbial (bacteria and fungi) diversity. Inter-cropping increased the relative abundance of the dominant bacterial phylum “Proteobacteria” and “Actinobacteria” by 47 and 57%, respectively, but decreased the relative abundance of the dominant fungal phylum “Chordata” and “Streptophyta” by 11 and 20%, respectively, in the inter-root soil of kiwifruit, and had a significant impact on the microbial (bacteria and fungi) diversity. In addition, inter-cropping could greatly increase the inter-root soil carbon sequestration (PccA, korA/B/C/D, fhs, and rbcl/s), carbon degradation (abfD), organic nitrogen mineralization (GDH2), denitrification (napA/B, nirB, norB), organic phosphorus mineralization (phop, phn), and inorganic phosphorus solubilization (gcd, ppk) gene abundance. The gene co-occurrence network indicated that soil korB, nirB, and gnd key functional genes for carbon, nitrogen, and phosphorus cycling in kiwifruit inter-root soils and their expression was up-regulated in the inter-cropping group. Structural equation (SEM) further showed that soil total nitrogen, organic matter, total carbon and acid phosphatase had significant effects on microbial diversity (p < 0.05) and soil carbon cycling gene korB and phosphorus cycling gene purH (p < 0.001), while korB and purH had positive effects on kiwifruit quality. In conclusion, intercropping perilla in kiwifruit orchards changed the structure of bacterial and fungal communities in the inter-root soil of kiwifruit, but I believe that intercropping perilla stimulates carbon degradation, leading to carbon emission and serious loss of soil nutrients, and that prolonged intercropping may adversely affect the quality of kiwifruit, and thus its limitations should be noted in future studies.

Background: Cadmium (Cd) pollution has declined crop yields and quality. Selenium (Se) is a beneficial mineral element that protects plants from oxidative damage, thereby improving crop tolerance to heavy metals. The molecular mechanism of Se-induced Cd tolerance in rice (Oryza sativa) is not yet understood. This study aimed to elucidate the beneficial mechanism of Se (1 mg/kg) in alleviating Cd toxicity in rice seedlings. Results: Exogenous selenium addition significantly improved the toxic effect of cadmium stress on rice seedlings, increasing plant height and fresh weight by 20.53% and 34.48%, respectively, and increasing chlorophyll and carotenoid content by 16.68% and 15.26%, respectively. Moreover, the MDA, ·OH, and protein carbonyl levels induced by cadmium stress were reduced by 47.65%, 67.57%, and 56.43%, respectively. Cell wall metabolism, energy cycling, and enzymatic and non-enzymatic antioxidant systems in rice seedlings were significantly enhanced. Transcriptome analysis showed that the expressions of key functional genes psbQ, psbO, psaG, psaD, atpG, and PetH were significantly up-regulated under low-concentration Se treatment, which enhanced the energy metabolism process of photosystem I and photosystem II in rice seedlings. At the same time, the up-regulation of LHCA, LHCB family, and C4H1, PRX, and atp6 functional genes improved the ability of photon capture and heavy metal ion binding in plants. Combined with proteome analysis, the expression of functional proteins OsGSTF1, OsGSTU11, OsG6PDH4, OsDHAB1, CP29, and CabE was significantly up-regulated under Se, which enhanced photosynthesis and anti-oxidative stress mechanism in rice seedlings. At the same time, it regulates the plant hormone signal transduction pathway. It up-regulates the expression response process of IAA, ABA, and JAZ to activate the synergistic effect between each cell rapidly and jointly maintain the homeostasis balance. Conclusion: Our results revealed the regulation process of Se-mediated critical metabolic pathways, functional genes, and proteins in rice under cadmium stress. They provided insights into the expression rules and dynamic response process of the Se-mediated plant resistance mechanism. This study provided the theoretical basis and technical support for crop safety in cropland ecosystems and cadmium-contaminated areas.