Synergistic anti-oxidative effects of Pongamia pinnata against nickel mediated by Rhizobium pisi and Ochrobacterium pseudogrignonense

Cataloging the Genetic Response: Unveiling Drought-Responsive Gene Expression in Oil Tea Camellia (Camellia oleifera Abel.) through Transcriptomics

Drought stress is a critical environmental factor that significantly impacts plant growth and productivity. However, the transcriptome analysis of differentially expressed genes in response to drought stress in Camellia oleifera Abel. is still unclear. This study analyzed the transcriptome sequencing data of C. oleifera under drought treatments. A total of 20,674 differentially expressed genes (DEGs) were identified under drought stress, with the number of DEGs increasing with the duration of drought. Specifically, 11,793 and 18,046 DEGs were detected after 8 and 15 days of drought treatment, respectively, including numerous upregulated and downregulated genes. Gene Ontology (GO) enrichment analysis showed that the DEGs were primarily involved in various biological processes. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed that carbon metabolism, glyoxylate and dicarboxylate metabolism, proteasome, glycine, serine, and threonine metabolism were the main affected pathways. Among the DEGs, 376 protein kinases, 42 proteases, 168 transcription factor (TF) genes, and 152 other potential functional genes were identified, which may play significant roles in the drought response of C. oleifera. The expression of relevant functional genes was further validated using quantitative real-time PCR (qRT-PCR). These findings contribute to the comprehension of drought tolerance mechanisms in C. oleifera and bolster the identification of drought-resistant genes for molecular breeding purposes.

Bacterial community drives soil organic carbon transformation in vanadium titanium magnetite tailings through remediation using Pongamia pinnata

With continuous mine exploitation, regional ecosystems have been damaged, resulting in a decline in the carbon sink capacity of mining areas. There is a global shortage of effective soil ecological restoration techniques for mining areas, especially for vanadium (V) and titanium (Ti) magnetite tailings, and the impact of phytoremediation techniques on the soil carbon cycle remains unclear. Therefore, this study aimed to explore the effects of long-term Pongamia pinnata remediation on soil organic carbon transformation of V-Ti magnetite tailing to reveal the bacterial community driving mechanism. In this study, it was found that four soil active organic carbon components (ROC, POC, DOC, and MBC) and three carbon transformation related enzymes (S-CL, S-SC, and S-PPO) in vanadium titanium magnetite tailings significantly (P < 0.05) increased with P. pinnata remediation. The abundance of carbon transformation functional genes such as carbon degradation, carbon fixation, and methane oxidation were also significantly (P < 0.05) enriched. The network nodes, links, and modularity of the microbial community, carbon components, and carbon transformation genes were enhanced, indicating stronger connections among the soil microbes, carbon components, and carbon transformation functional genes. Structural equation model (SEM) analysis revealed that the bacterial communities indirectly affected the soil organic carbon fraction and enzyme activity to regulate the soil total organic carbon after P. pinnata remediation. The soil active organic carbon fraction and free light fraction carbon also directly regulated the soil carbon and nitrogen ratio by directly affecting the soil total organic carbon content. These results provide a theoretical reference for the use of phytoremediation to drive soil carbon transformation for carbon sequestration enhancement through the remediation of degraded ecosystems in mining areas.

Quorum sensing signal autoinducer-2 promotes hydrogen peroxide degradation in water by Gram-positive bacteria

Hydrogen peroxide is widely used to remedy bacterial and parasitic infections, but its excessive use will cause severe damage to aquatic animals. Moreover, there is no safe, efficient and low-cost method to degrade residual hydrogen peroxide in water. Here we developed a hydrogen peroxide removal mechanism by which autoinducer-2 (AI-2), a quorum sensing signal molecule that can promote the hydrogen peroxide degradation by Gram-positive bacteria. Here, we investigated the promotion effect of AI-2 on hydrogen peroxide degradation by Deinococcus sp. Y35 and the response of the antioxidant system. We further sought to understand the key mechanism underlying the promotion effect of AI-2 on hydrogen peroxide degradation is that, AI-2 contributed to the resistance of strain Y35 to oxidative stress induced by hydrogen peroxide, and altered membrane permeability of strain Y35 that allowed more hydrogen peroxide to enter bacterial cells and be degraded. Additionally, AI-2 can also encourage multiple Gram-positive bacteria to degrade hydrogen peroxide. Accordingly, our study serves as a reference for the regulation mechanism of the signal molecule AI-2 and provides the development of new strategies for hydrogen peroxide degradation.

Evaluation of Legume-Rhizobial Symbiotic Interactions Beyond Nitrogen Fixation That Help the Host Survival and Diversification in Hostile Environments

Plants often experience unfavorable conditions during their life cycle that impact their growth and sometimes their survival. A temporary phase of such stress, which can result from heavy metals, drought, salinity, or extremes of temperature or pH, can cause mild to enormous damage to the plant depending on its duration and intensity. Besides environmental stress, plants are the target of many microbial pathogens, causing diseases of varying severity. In plants that harbor mutualistic bacteria, stress can affect the symbiotic interaction and its outcome. To achieve the full potential of a symbiotic relationship between the host and rhizobia, it is important that the host plant maintains good growth characteristics and stay healthy under challenging environmental conditions. The host plant cannot provide good accommodation for the symbiont if it is infested with diseases and prone to other predators. Because the bacterium relies on metabolites for survival and multiplication, it is in its best interests to keep the host plant as stress-free as possible and to keep the supply stable. Although plants have developed many mitigation strategies to cope with stress, the symbiotic bacterium has developed the capability to augment the plant's defense mechanisms against environmental stress. They also provide the host with protection against certain diseases. The protective features of rhizobial-host interaction along with nitrogen fixation appear to have played a significant role in legume diversification. When considering a legume-rhizobial symbiosis, extra benefits to the host are sometimes overlooked in favor of the symbionts' nitrogen fixation efficiency. This review examines all of those additional considerations of a symbiotic interaction that enable the host to withstand a wide range of stresses, enabling plant survival under hostile regimes. In addition, the review focuses on the rhizosphere microbiome, which has emerged as a strong pillar of evolutionary reserve to equip the symbiotic interaction in the interests of both the rhizobia and host. The evaluation would draw the researchers' attention to the symbiotic relationship as being advantageous to the host plant as a whole and the role it plays in the plant's adaptation to unfavorable environmental conditions.

Exogenous application of Bradyrhizobium japonicum AC20 enhances soybean tolerance to atrazine via regulating rhizosphere soil microbial community and amino acid, carbohydrate metabolism related genes expression

Atrazine is used to control broad-leaved weeds in farmland and has negative impacts on soybean growth. Legume-rhizobium symbiosis plays an important role in regulating abiotic stress tolerance of plants, however, the mechanisms of rhizobia regulate the tolerance of soybean to atrazine based on the biochemical responses of the plant-soil system are limited. In this experiment, Glycine max (L.) Merr. Dongnong 252, planted in 20 mg kg^-1 of atrazine-contaminated soil, was inoculated with Bradyrhizobium japonicum AC20, and the plant growth, rhizosphere soil microbial diversity and the expression of the genes related to soybean carbon and nitrogen metabolism were assessed. The results indicated that strain AC20 inoculation alleviated atrazine-induced growth inhibition via increasing the contents of leghemoglobin and total nitrogen in soybean seedlings. The psbA gene expression level of the soybean seedlings that inoculated strain AC20 was 1.4 times than that of no rhizobium inoculating treatments. Moreover, the inoculated AC20 increased the abundance of Acidobacteria and Actinobacteria in soybean rhizosphere. Transcriptome analysis demonstrated that strain AC20 regulated the genes expression of amino acid metabolism and carbohydrate metabolism of soybean seedlings. Correlation analysis between 16S rRNA and transcriptome showed that strain AC20 reduced Planctomycetes abundance so as to down-regulated the expression of genes Glyma. 13G087800, Glyma. 12G005100 and Glyma.12G098900 involved in starch synthesis pathway of soybean leaves. These results provide available information for the rhizobia application to enhance the atrazine tolerate in soybean seedlings.

Exposure to metals and the disruption of sex hormones in 6-19 years old children: An exploration of mixture effects

BACKGROUND

Individual metals have been linked to sex hormones disruption, but the associations of metals mixture are rarely examined among children.

METHODS

A total of 1060 participants of 6-19-year-old who participated in the National Health and Nutrition Examination Survey (2013-2016) were included. Eighteen metals were quantified in the whole blood and urine. Sex hormones were measured in serum, including total testosterone (TT), estradiol (E₂), and sex hormone binding globulin (SHBG). In addition, free androgen index (FAI) and the ratio of TT to E₂ were calculated. Bayesian kernel machine regression and latent class analysis were performed to assess the associations of metals mixture and exposure patterns of metals at varied levels with sex hormones while adjusting for selected covariates. All analyses were conducted by sex-age and sex-puberty groups to explore the potential sex-dimorphic effects.

RESULTS

Exposure to metals mixture was associated with elevated levels of FAI and E₂ among 12-19 years old girls. Moreover, the exposure pattern of metals that was characterized by high levels of blood and urinary cadmium, blood manganese, and urinary cobalt was associated with elevated E₂ and reduced TT/E₂ levels among girls of 12-19 years old. However, the associations of metals mixture with sex hormones were overall nonsignificant among boys. Nevertheless, metals exposure pattern that was characterized by high levels of blood lead, urinary barium, strontium, and lead but comparatively low levels of the other metals was consistently associated with reduced levels of FAI and E₂ but elevated levels of TT/E₂ and SHBG among boys of 12-19 years old.

CONCLUSION

Metals mixture and exposure patterns that were dominated by high levels of certain metals were associated with sex hormones imbalance among 12-19 years old children in a sex-dimorphic pattern, with the identified individual metals that drove the associations of metals mixture varied by sex.