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1. PCB126 Exposure Revealed Alterations in m6A RNA Modifications in Transcripts Associated With AHR Activation

   https://doi.org/10.1093/toxsci/kfaa158  

   Aluru, Neelakanteswar; Karchner, Sibel I (October 2020, Toxicological Sciences)

   null (Ed.)

   Abstract Chemical modifications of proteins, DNA, and RNA moieties play critical roles in regulating gene expression. Emerging evidence suggests the RNA modifications (epitranscriptomics) have substantive roles in basic biological processes. One of the most common modifications in mRNA and noncoding RNAs is N6-methyladenosine (m6A). In a subset of mRNAs, m6A sites are preferentially enriched near stop codons, in 3′ UTRs, and within exons, suggesting an important role in the regulation of mRNA processing and function including alternative splicing and gene expression. Very little is known about the effect of environmental chemical exposure on m6A modifications. As many of the commonly occurring environmental contaminants alter gene expression profiles and have detrimental effects on physiological processes, it is important to understand the effects of exposure on this important layer of gene regulation. Hence, the objective of this study was to characterize the acute effects of developmental exposure to PCB126, an environmentally relevant dioxin-like PCB, on m6A methylation patterns. We exposed zebrafish embryos to PCB126 for 6 h starting from 72 h post fertilization and profiled m6A RNA using methylated RNA immunoprecipitation followed by sequencing (MeRIP-seq). Our analysis revealed 117 and 217 m6A peaks in the DMSO and PCB126 samples (false discovery rate 5%), respectively. The majority of the peaks were preferentially located around the 3′ UTR and stop codons. Statistical analysis revealed 15 m6A marked transcripts to be differentially methylated by PCB126 exposure. These include transcripts that are known to be activated by AHR agonists (eg, ahrra, tiparp, nfe2l2b) as well as others that are important for normal development (vgf, cebpd, sned1). These results suggest that environmental chemicals such as dioxin-like PCBs could affect developmental gene expression patterns by altering m6A levels. Further studies are necessary to understand the functional consequences of exposure-associated alterations in m6A levels. 

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2. Impact of Polycyclic Aromatic Hydrocarbon Accumulation on Oyster Health

   https://doi.org/10.3389/fphys.2021.734463  

   Gan, Nin; Martin, Leisha; Xu, Wei (September 2021, Frontiers in Physiology)

   In the past decade, the Deepwater Horizon oil spill triggered a spike in investigatory effort on the effects of crude oil chemicals, most notably polycyclic aromatic hydrocarbons (PAHs), on marine organisms and ecosystems. Oysters, susceptible to both waterborne and sediment-bound contaminants due to their filter-feeding and sessile nature, have become of great interest among scientists as both a bioindicator and model organism for research on environmental stressors. It has been shown in many parts of the world that PAHs readily bioaccumulate in the soft tissues of oysters. Subsequent experiments have highlighted the negative effects associated with exposure to PAHs including the upregulation of antioxidant and detoxifying gene transcripts and enzyme activities such as Superoxide dismutase, Cytochrome P450 enzymes, and Glutathione S-transferase, reduction in DNA integrity, increased infection prevalence, and reduced and abnormal larval growth. Much of these effects could be attributed to either oxidative damage, or a reallocation of energy away from critical biological processes such as reproduction and calcification toward health maintenance. Additional abiotic stressors including increased temperature, reduced salinity, and reduced pH may change how the oyster responds to environmental contaminants and may compound the negative effects of PAH exposure. The negative effects of acidification and longer-term salinity changes appear to add onto that of PAH toxicity, while shorter-term salinity changes may induce mechanisms that reduce PAH exposure. Elevated temperatures, on the other hand, cause such large physiological effects on their own that additional PAH exposure either fails to cause any significant effects or that the effects have little discernable pattern. In this review, the oyster is recognized as a model organism for the study of negative anthropogenic impacts on the environment, and the effects of various environmental stressors on the oyster model are compared, while synergistic effects of these stressors to PAH exposure are considered. Lastly, the understudied effects of PAH photo-toxicity on oysters reveals drastic increases to the toxicity of PAHsviaphotooxidation and the formation of quinones. The consequences of the interaction between local and global environmental stressors thus provide a glimpse into the differential response to anthropogenic impacts across regions of the world. 

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3. Contaminants of Emerging Concern on Microplastics Found in the Chrysaora chesapeakei of the Patuxent River, Chesapeake Bay, MD

   https://doi.org/10.3390/microplastics4020032  

   Smith, Carol A; Drichko, Natalie; Lorenzo, Miranda; Pramanik, Saroj (June 2025, Microplastics)

   Previously, we reported that microplastic volatile organic compounds are present within the Chrysaora chesapeakei of Chesapeake Bay, MD. In this study, we report the presence of contaminants of emerging concern (CECs) on the hydrophobic surface of microplastic (MP) particles extracted from the C. chesapeakei, detected by Raman spectroscopy and identified by Wiley’s KnowItAll Software with IR & Raman Spectral Libraries. C. chesapeakei encounters various microplastics and emerging contaminants as it floats through the depths of the Patuxent River water column. This study identifies subsuming CECs found directly on microplastics from within C. chesapeakei in the wild using Raman spectroscopy. Among the extracted microplastics, some of the emerging contaminants found on the different microplastics were pesticides, pharmaceuticals, minerals, food derivatives, wastewater treatment chemicals, hormones, and recreational drugs. Our results represent the first of such findings in C. chesapeakei, obtained directly from the field, and indicate C. chesapeakei’s relationship with microplastics, with this species serving as a vector of emerging contaminants through the marine food web. This paper further illustrates a relationship between different types of plastics that attract dissimilar types of emerging pollutants in the same surrounding environmental conditions, underscoring the urgent need for further research to fully understand and mitigate the risks that MPs coexist with contaminants. 

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4. CONCERTED PLANT GROWTH AND DEFENSE THROUGH TARGETED PHYTOHORMONE CROSSTALK MODIFICATION

   https://doi.org/10.1101/2024.04.08.588615  

   Johnston, Grace A; Berry, Hannah M; Kojima, Mikiko; Sakakibara, Hitoshi; Argueso, Cristiana T (April 2024, bioRxiv)

   ABSTRACT Plant immunity activation often results in suppression of plant growth, particularly in the case of constitutive immune activation. We discovered that signaling of the phytohormone cytokinin (CK), known to regulate plant growth through the control of cell division and shoot apical meristem (SAM) activity, can be suppressed by negative crosstalk with the defense phytohormones jasmonic acid (JA), and most evidently, salicylic acid (SA). We show that changing the negative crosstalk of SA on CK signaling in autoimmunity mutants by targeted increase of endogenous CK levels results in plants resistant to pathogens from diverse lifestyles, and relieves suppression of reproductive growth. Moreover, such changes in crosstalk result in a novel reproductive growth phenotype, suggesting a role for defense phytohormones in the SAM, likely through regulation of nitrogen response and cellular redox status. Our data suggest that targeted phytohormone crosstalk engineering can be used to achieve increased reproductive growth and pathogen resistance. SIGNIFICANCE STATEMENTPlants constantly integrate environmental stimuli with developmental programs to optimize their growth and fitness. Excessive activation of the plant immune system often leads to decreased plant growth, a process known as the growth-defense tradeoff. Here, we adapted phytohormone levels in Arabidopsis reproductive tissues of autoimmunity mutants to change phytohormonal crosstalk and diminish the growth tradeoff, resulting in increased broad resistance to pathogens and decreased growth suppression. Similar approaches to phytohormone crosstalk engineering could be used in different contexts to achieve outcomes of higher plant stress resilience and yield. 

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5. Life Strategies in Placozoa

   https://doi.org/10.1101/2021.11.26.470175  

   Romanova, D.Y.; Mikhail A. Nikitin, M.A.; Sergey V. Shchenkov, S.V.; Moroz, L.L. (November 2021, bioRxiv)

   Placozoans are essential reference species for understanding the origins and evolution of the animal organization. However, little is known about their life strategies in natural habitats. Here, by establishing long-term culturing for four species of Trichoplax and Hoilungia, we extend our knowledge about feeding and reproductive adaptations relevant to their ecology and immune mechanisms. Three modes of population growth depended upon feeding sources, including induction of social behaviors and different reproductive strategies. In addition to fission, representatives of all haplotypes produced ‘swarmers,’ which could be formed from the lower epithelium (with greater cell- type diversity) as a separate asexual reproduction stage. In aging culture, we reported the formation of specialized structures (‘spheres’) from the upper cell layer as a part of the innate immune defense response with the involvement of fiber cells. Finally, we showed that regeneration could be a part of the adaptive reproductive strategies in placozoans and a unique model for regenerative biology in general. 

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