Changes of DNA methylation of Isoetes sinensis under Pb and Cd stress

The role of microbial partners in heavy metal metabolism in plants: a review

Heavy metal pollution threatens plant growth and development as well as ecological stability. Here, we synthesize current research on the interplay between plants and their microbial symbionts under heavy metal stress, highlighting the mechanisms employed by microbes to enhance plant tolerance and resilience. Several key strategies such as bioavailability alteration, chelation, detoxification, induced systemic tolerance, horizontal gene transfer, and methylation and demethylation, are examined, alongside the genetic and molecular basis governing these plant-microbe interactions. However, the complexity of plant-microbe interactions, coupled with our limited understanding of the associated mechanisms, presents challenges in their practical application. Thus, this review underscores the necessity of a more detailed understanding of how plants and microbes interact and the importance of using a combined approach from different scientific fields to maximize the benefits of these microbial processes. By advancing our knowledge of plant-microbe synergies in the metabolism of heavy metals, we can develop more effective bioremediation strategies to combat the contamination of soil by heavy metals.

The role of epigenetic and epitranscriptomic modifications in plants exposed to non-essential metals

Contamination of the soil with non-essential metals and metalloids is a serious problem in many regions of the world. These non-essential metals and metalloids are toxic to all organisms impacting crop yields and human health. Crop plants exposed to high concentrations of these metals leads to perturbed mineral homeostasis, decreased photosynthesis efficiency, inhibited cell division, oxidative stress, genotoxic effects and subsequently hampered growth. Plants can activate epigenetic and epitranscriptomic mechanisms to maintain cellular and organism homeostasis. Epigenetic modifications include changes in the patterns of cytosine and adenine DNA base modifications, changes in cellular non-coding RNAs, and remodeling histone variants and covalent histone tail modifications. Some of these epigenetic changes have been shown to be long-lasting and may therefore contribute to stress memory and modulated stress tolerance in the progeny. In the emerging field of epitranscriptomics, defined as chemical, covalent modifications of ribonucleotides in cellular transcripts, epitranscriptomic modifications are postulated as more rapid modulators of gene expression. Although significant progress has been made in understanding the plant's epigenetic changes in response to biotic and abiotic stresses, a comprehensive review of the plant's epigenetic responses to metals is lacking. While the role of epitranscriptomics during plant developmental processes and stress responses are emerging, epitranscriptomic modifications in response to metals has not been reviewed. This article describes the impact of non-essential metals and metalloids (Cd, Pb, Hg, Al and As) on global and site-specific DNA methylation, histone tail modifications and epitranscriptomic modifications in plants.

Cadmium toxicity in medicinal plants: An overview of the tolerance strategies, biotechnological and omics approaches to alleviate metal stress

Medicinal plants, an important source of herbal medicine, are gaining more demand with the growing human needs in recent times. However, these medicinal plants have been recognized as one of the possible sources of heavy metal toxicity in humans as these medicinal plants are exposed to cadmium-rich soil and water because of extensive industrial and agricultural operations. Cadmium (Cd) is an extremely hazardous metal that has a deleterious impact on plant development and productivity. These plants uptake Cd by symplastic, apoplastic, or via specialized transporters such as HMA, MTPs, NRAMP, ZIP, and ZRT-IRT-like proteins. Cd exerts its effect by producing reactive oxygen species (ROS) and interfere with a range of metabolic and physiological pathways. Studies have shown that it has detrimental effects on various plant growth stages like germination, vegetative and reproductive stages by analyzing the anatomical, morphological and biochemical changes (changes in photosynthetic machinery and membrane permeability). Also, plants respond to Cd toxicity by using various enzymatic and non-enzymatic antioxidant systems. Furthermore, the ROS generated due to the heavy metal stress alters the genes that are actively involved in signal transduction. Thus, the biosynthetic pathway of the important secondary metabolite is altered thereby affecting the synthesis of secondary metabolites either by enhancing or suppressing the metabolite production. The present review discusses the abundance of Cd and its incorporation, accumulation and translocation by plants, phytotoxic implications, and morphological, physiological, biochemical and molecular responses of medicinal plants to Cd toxicity. It explains the Cd detoxification mechanisms exhibited by the medicinal plants and further discusses the omics and biotechnological strategies such as genetic engineering and gene editing CRISPR- Cas 9 approach to ameliorate the Cd stress.

Theories and Molecular Basis of Vascular Aging: A Review of the Literature from VascAgeNet Group on Pathophysiological Mechanisms of Vascular Aging

Vascular aging, characterized by structural and functional alterations of the vascular wall, is a hallmark of aging and is tightly related to the development of cardiovascular mortality and age-associated vascular pathologies. Over the last years, extensive and ongoing research has highlighted several sophisticated molecular mechanisms that are involved in the pathophysiology of vascular aging. A more thorough understanding of these mechanisms could help to provide a new insight into the complex biology of this non-reversible vascular process and direct future interventions to improve longevity. In this review, we discuss the role of the most important molecular pathways involved in vascular ageing including oxidative stress, vascular inflammation, extracellular matrix metalloproteinases activity, epigenetic regulation, telomere shortening, senescence and autophagy.

Crosstalk of DNA Methylation Triggered by Pathogen in Poplars With Different Resistances

DNA methylation plays crucial roles in responses to environmental stimuli. Modification of DNA methylation during development and abiotic stress responses has been confirmed in increasing numbers of plants, mainly annual plants. However, the epigenetic regulation mechanism underlying the immune response to pathogens remains largely unknown in plants, especially trees. To investigate whether DNA methylation is involved in the response to infection process or is related to the resistance differences among poplars, we performed comprehensive whole-genome bisulfite sequencing of the infected stem of the susceptible type Populus × euramerican ‘74/76’ and resistant type Populus tomentosa ‘henan’ upon Lonsdalea populi infection. The results revealed that DNA methylation changed dynamically in poplars during the infection process with a remarkable decrease seen in the DNA methylation ratio. Intriguingly, the resistant P. tomentosa ‘henan’ had a much lower basal DNA methylation ratio than the susceptible P. × euramerican ‘74/76’. Compared to mock-inoculation, both poplar types underwent post-inoculation CHH hypomethylation; however, significant decreases in mC and mCHH proportions were found in resistant poplar. In addition, most differentially CHH-hypomethylated regions were distributed in repeat and promoter regions. Based on comparison of DNA methylation modification with the expression profiles of genes, DNA methylation occurred in resistance genes, pathogenesis-related genes, and phytohormone genes in poplars during pathogen infection. Additionally, transcript levels of genes encoding methylation-related enzymes changed during pathogen infection. Interestingly, small-regulator miRNAs were subject to DNA methylation in poplars experiencing pathogen infection. This investigation highlights the critical role of DNA methylation in the poplar immune response to pathogen infection and provides new insights into epigenetic regulation in perennial plants in response to biotic stress.

DNA methylation and histone modifications induced by abiotic stressors in plants

BACKGROUND

A review of research shows that methylation in plants is more complex and sophisticated than in microorganisms and animals. Overall, studies on the effects of abiotic stress on epigenetic modifications in plants are still scarce and limited to few species. Epigenetic regulation of plant responses to environmental stresses has not been elucidated. This study summarizes key effects of abiotic stressors on DNA methylation and histone modifications in plants.

DISCUSSION

Plant DNA methylation and histone modifications in responses to abiotic stressors varied and depended on the type and level of stress, plant tissues, age, and species. A critical analysis of the literature available revealed that 44% of the epigenetic modifications induced by abiotic stressors in plants involved DNA hypomethylation, 40% DNA hypermethylation, and 16% histone modification. The epigenetic changes in plants might be underestimated since most authors used methods such as methylation-sensitive amplification polymorphism (MSAP), High performance liquid chromatography (HPLC), and immunolabeling that are less sensitive compared to bisulfite sequencing and single-base resolution methylome analyses. More over, mechanisms underlying epigenetic changes in plants have not yet been determined since most reports showed only the level or/and distribution of DNA methylation and histone modifications.

CONCLUSIONS

Various epigenetic mechanisms are involved in response to abiotic stressors, and several of them are still unknown. Integrated analysis of the changes in the genome by omic approaches should help to identify novel components underlying mechanisms involved in DNA methylation and histone modifications associated with plant response to environmental stressors.

Health repercussions of environmental exposure to lead: Methylation perspective

Lead (Pb) exposure has been a major public health concern for a long time now due to its permanent adverse effects on the human body. The process of lead toxicity has still not been fully understood, but recent advances in Omics technology have enabled researchers to evaluate lead-mediated alterations at the epigenome-wide level. DNA methylation is one of the widely studied and well-understood epigenetic modifications. Pb has demonstrated its ability to induce not just acute deleterious health consequences but also alters the epi-genome such that the disease manifestation happens much later in life as supported by Barkers Hypothesis of the developmental origin of health and diseases. Furthermore, these alterations are passed on to the next generation. Based on previous in-vivo, in-vitro, and human studies, this review provides an insight into the role of Pb in the development of several human disorders.

Effects of thermal stress-induced lead (Pb) toxicity on apoptotic cell death, inflammatory response, oxidative defense, and DNA methylation in zebrafish (Danio rerio) embryos

Lead (Pb) is a toxic environmental pollutant that is frequently present in effluents from urban, mining, and industrial sources. The combinatorial effects of heavy metal exposure and temperature in aquatic organisms have received considerable attention as heat stress occurs simultaneously in conjunction with several contaminants in a natural environment. In this study, we examined the potential effects of Pb exposure in conditions of thermal stress (34 °C) in zebrafish (Danio rerio) embryos. Thermal stress at 34 °C induced a dramatic decrease in the survival rate, although exposure to Pb at 26 °C decreased the survival rate of the embryos. Malformations, such as the curved body shape, were increased in response to exposure to a combination of Pb and heat stress. The combination of Pb and heat stress also caused a decrease in the heart rate. Moreover, Pb and high-temperature exposure induced the upregulation of SOD, CAT, TNF-α, IL-1β, p53, and BAX transcripts, and downregulation of Dnmt1 and Dnmt3b transcripts. Thermal stress enhanced transcriptional responses of eight indicator genes following Pb toxicity. The induction of cell death in response to combined exposures was also confirmed in the body of zebrafish by fluorescence intensity image analysis. These data indicated that thermal stress enhanced the poisonous effects of Pb exposure on antioxidant defense, inflammation, and apoptotic mechanisms. Transcriptional inhibition of DNA methylation-related genes might serve as a crucial factor contributing to the possibility of epigenetic adaptation by altering combined stress. We suggest that a careful evaluation of the potential effects of climate change (especially temperature) should be considered when investigating the toxic levels of metal pollution, such as Pb, in an aquatic environment.

Mass Spectrometry for Investigating the Effects of Toxic Metals on Nucleic Acid Modifications

The extensive use of toxic metals in industry and agriculture leads to their wide distribution in the environment, which raises critical concerns over their toxic effects on human health. Many toxic metals are reported to be mildly mutagenic or non-mutagenic, indicating that genetic-based mechanisms may not be primarily responsible for toxic metal-induced carcinogenesis. Increasing evidence has demonstrated that exposure to toxic metals can alter epigenetic modifications, which may lead to the dysregulation of gene expression and disease susceptibility. It is now becoming clear that a full understanding of the effects of toxic metals on cellular toxicity and carcinogenesis will need to consider both genetic- and epigenetic-based mechanisms. Uncovering the effects of toxic metals on epigenetic modifications in nucleic acids relies on the detection and quantification of these modifications. Mass spectrometry (MS)-based methods for deciphering epigenetic modifications have substantially advanced over the past decade, and they are now becoming widely used and essential tools for evaluating the effects of toxic metals on nucleic acid modifications. This Review provides an overview of MS-based methods for analysis of nucleic acid modifications. In addition, we also review recent advances in understanding the effects of exposure to toxic metals on nucleic acid modifications.