Transgenerational effects of chromium stress at the phenotypic and molecular level in Arabidopsis thaliana

Transcriptome and metabolome analysis reveal key genes and metabolic pathway responses in Leersia hexandra Swartz under Cr and Ni co-stress

Phytoremediation, an eco-friendly approach for mitigating heavy metal contamination, is reliant on hyperaccumulators. This study focused on Leersia hexandra Swart, a known chromium (Cr) hyperaccumulator with demonstrated tolerance to multiple heavy metals. Our objective was to investigate its response to simultaneous Cr and nickel (Ni) stress over 12 days. Results from physiological experiments demonstrated a significant increase in the activities of antioxidant enzymes (APX, SOD, CAT) and glutathione (GSH) content under Cr and Ni stress, indicating enhanced antioxidant mechanisms. Transcriptome analysis revealed that stress resulted in the differential expression of 27 genes associated with antioxidant activity and metal binding, including APX, SOD, CAT, GSH, metallothionein (MT), and nicotinamide (NA). Among them, twenty differentially expressed genes (DEGs) related to GSH metabolic cycle were identified. Notably, GSTU6, GND1, and PGD were the top three related genes, showing upregulation with fold changes of 4.57, 6.07, and 3.76, respectively, indicating their crucial role in metal tolerance. The expression of selected DEGs was validated by quantitative real-time PCR, confirming the reliability of RNA-Seq data. Metabolomic analysis revealed changes in 1121 metabolites, with amino acids, flavonoids, and carbohydrates being the most affected. Furthermore, glucosinolate biosynthesis and amino acid biosynthesis pathways were represented in the KEGG pathway of differentially expressed metabolites (DEMs). This study provides insights into the tolerance mechanisms of L. hexandra under the co-stress of Cr and Ni, offering a new perspective for enhancing its remediation performance.

Epigenetic changes induced by chronic and acute chromium stress treatments in Arabidopsis thaliana identified by the MSAP-Seq

Chromium (Cr) is an highly toxic metal to plants and causes severe damage to their growth, development, and reproduction. Plant exposure to chronic and acute Cr stress treatments results in significant changes at short time in the gene expression profile and at long time in the genomic DNA methylation profile at a transgenerational level and, consequently, in gene expression. These epigenetic modifications and their implications imposed by the Cr stress are not yet completely known in plants. Herein, were identified the epigenetic changes induced by chronic and acute Cr stress treatments in Arabidopsis thaliana plants using Methylation Sensitive Amplification Polymorphism coupled with next-generation sequencing (MSAP-Seq). First-generation Arabidopsis plants (termed F0 plants) kept under hoagland solution were subjected to Cr stress treatments. For chronic Cr stress, plants were treated through hoagland solution with 2.5 μM Cr during the entire cultivation period until seed harvest. Meanwhile, for acute Cr stress, plants were treated with 5 μM Cr during the first three weeks and returned to unstressful control condition until seed harvest. Seeds from F0 plants were sown and F1 plants were re-submitted to the same Cr stress treatments. The seed germination rate was evaluated from F-2 seeds harvested of F1 plants kept under different Cr stress treatments (0, 10, 20, and 40 μM) compared to the unstressful control condition. These data showed significant changes in the germination rate of F-2 seeds originating from stressed F1 plants compared to F-2 seeds harvested from unstressful control plants. Given this data, F1 plants kept under these chronic and acute Cr stress treatments and unstressful control condition were evaluated for the transgenerational epigenetic modifications using MSAP-Seq. The MSAP-Seq data showed that several genes were modified in their methylation status as a consequence of chronic and acute Cr stress treatment to maintain plant defenses activated. In particular, RNA processing, protein translation, photorespiration, energy production, transmembrane transport, DNA transcription, plant development, and plant resilience were the major biological processes modulated by epigenetic mechanisms identified in F1 plants kept under chronic and acute Cr stress. Therefore, collective data suggested that Arabidopsis plants kept under Cr stress regulate their epigenetic status over generations based on DNA methylation to modulate defense and resilience mechanisms.

Understanding plant stress memory traits can provide a way for sustainable agriculture

Being sessile, plants encounter various biotic and abiotic threats in their life cycle. To minimize the damages caused by such threats, plants have acquired sophisticated response mechanisms. One major such response includes memorizing the encountered stimuli in the form of a metabolite, hormone, protein, or epigenetic marks. All of these individually as well as together, facilitate effective transcriptional and post-transcriptional responses upon encountering the stress episode for a second time during the life cycle and in some instances even in the future generations. This review attempts to highlight the recent advances in the area of plant memory. A detailed understanding of plant memory has the potential to offer solutions for developing climate-resilient crops for sustainable agriculture.

Response characteristics of rhizosphere microbial community and metabolites of Iris tectorum to Cr stress

Chromium (Cr) is a toxic heavy element that interferes with plant metabolite biosynthesis and modifies the plant rhizosphere microenvironment, affecting plant growth. However, the interactions and response mechanisms between plants and rhizosphere bacteria under Cr stress still need to be fully understood. In this study, we used Iris tectorum as a research target and combined physiology, metabolomics, and microbiology to reveal the stress response mechanism of I. tectorum under heavy metal chromium stress. The results showed that Cr stress-induced oxidative stress inhibited plant growth and development and increased malondialdehyde and oxygen free radicals content. Also, it increased ascorbate peroxidase, peroxidase activity, and superoxide dismutase activity, as well as glutathione and soluble sugar content. Microbiome analysis showed that Cr stress changed the rhizosphere bacterial community diversity index by 33.56%. Proteobacteria, Actinobacteriota, and Chloroflexi together accounting for 71.21% of the total sequences. Meanwhile, the abundance of rhizosphere dominant and plant-promoting bacteria increased significantly with increasing time of Cr stress. The improvement of the soil microenvironment and the recruitment of bacteria by I. tectorum root secretions were significantly enhanced. By metabolomic analysis, five vital metabolic pathways were identified, involving 89 differentially expressed metabolites, divided into 15 major categories. In summary, a multi-omics approach was used in this study to reveal the interaction and stress response mechanisms between I. tectorum and rhizosphere bacterial communities under Cr stress, which provided theoretical basis for plant-microbial bioremediation of Cr-contaminated soils in constructed wetlands. This may provide more valuable information for wetland remediation of heavy metal pollution.

Stress Management in Plants: Examining Provisional and Unique Dose-Dependent Responses

The purpose of this review is to critically evaluate the effects of different stress factors on higher plants, with particular attention given to the typical and unique dose-dependent responses that are essential for plant growth and development. Specifically, this review highlights the impact of stress on genome instability, including DNA damage and the molecular, physiological, and biochemical mechanisms that generate these effects. We provide an overview of the current understanding of predictable and unique dose-dependent trends in plant survival when exposed to low or high doses of stress. Understanding both the negative and positive impacts of stress responses, including genome instability, can provide insights into how plants react to different levels of stress, yielding more accurate predictions of their behavior in the natural environment. Applying the acquired knowledge can lead to improved crop productivity and potential development of more resilient plant varieties, ensuring a sustainable food source for the rapidly growing global population.