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This study investigated the efficacy of incorporating nitric oxide (NO; 10 μM) and ascorbic acid (Asc; 10 μM) into the culture medium to confer cadmium (Cd; 5 μM) tolerance in thyme (Zataria multiflora). The phytotoxicity of Cd resulted in a decrease in shoot biomass, which NO or Asc mitigated. Adding Asc and NO to the culture medium was associated with substantial DNA hypomethylation. The NO + Cd and Asc + Cd treatments were accompanied by an increase in the unmethylation percentages, about 3-fold higher than the control. The hemi-methylation percentages in the Asc-supplemented seedlings also displayed an upward trend. The transcriptional upregulation in the γ-terpinene synthase (TPS) gene resulted from the applied elicitors, especially NO. In response to the NO and Asc treatments, the transcription of two cytochrome P450 monooxygenase genes (CYP71D178 and CYP71D180) went up. Incorporating Asc or NO into the culture medium enhanced the concentrations of proline, carvacrol, and thymol metabolites. Employing NO or Asc mitigated the 43% decrease in protein content due to the Cd cytotoxicity. The NO and Asc applications improved the activity of the phenylalanine ammonia-lyase (PAL) enzyme. NO and Asc utilization increased the accumulation of flavonoids. NO and Asc also up-regulated the activities of two enzymatic antioxidants (catalase and peroxidase). Collectively, this study provided novel insight into how Asc or NO confers Cd tolerance by epigenetically remodeling DNA methylation, transcriptionally up-regulating terpenoid and phenylpropanoid metabolism, increasing proline concentration, and improving antioxidants. [Display omitted] • Epigenetic DNA hypomethylation contributes to mitigating Cd cytotoxicity. • Nitric oxide (NO) and ascorbate (Asc) transcriptionally improved terpenoid metabolism. • NO and Asc transcriptionally upregulated CYP71D178 and CYP71D180 genes. • NO and Asc conferred Cd tolerance by stimulating terpenoid and phenylpropanoid metabolism. • NO and Asc alleviated Cd risks by increasing proline osmo-protectant and reinforcing antioxidants. [ABSTRACT FROM AUTHOR]

The cytotoxicity assessment of nanomaterials has become a global concern for diverse disciplines, including agriculture. This study explored the physiological and molecular responses of pepper seedlings to the foliar application of copper nanoparticles (CuNPs; 50, 100, and 200 mg L−1) compared to the bulk control. The CuNPs treatment at 50 mg L−1 increased the shoot biomass by 20%, whereas the treatments at concentrations above 100 mg L−1 adversely influenced biomass (25%), chlorophyll content (21%), and starch concentration (23%). Moreover, the CuNPs treatments at the toxic doses increased H 2 O 2 concentration (60%) and lipid peroxidation levels (27%), implying oxidative stress and potentially impaired membrane integrity. However, the phytotoxicity risk associated with the CuNPs application was lower than the bulk control. The CuNPs treatments upregulated the activities of catalase (2-folds), peroxidase (85%), and polyphenol oxidase (70%). The toxic doses of CuNPs increased the protease activity by 16%. The Cu supplementation influenced the transcription of microRNA159 (miR159) and Mevalonate kinase (MVK) genes in concentration and material type-dependent manners. Toxic concentrations of CuNP transcriptionally upregulated miR159 by approximately 2-folds. The expression of the MVK gene displayed a downregulation trend (5-folds) in response to the bulk Cu, while the CuNPs treatments slightly downregulated this gene. With increasing the concentration of CuNPs, the accumulations of protein and non-protein thiols displayed an increasing trend by approximately 45%. The CuNPs-treated plants contained a higher concentration of proline (59%) and phenols (34%). This study underlines the potential cytotoxicity risk associated with the application of CuNPs as a fertilizer or pesticide in agriculture-related industries. [Display omitted] • Representing potential benefits and phytotoxicity of copper nanoparticle (CuNP). • Toxic concentrations of CuNP transcriptionally upregulated miR159. • CuNP down-regulated transcription of MVK gene involved in terpenoid metabolism. • Providing evidence on the correlation between developmental transition and miR159. • The phytotoxicity risk of CuNP was lower than the bulk counterpart. [ABSTRACT FROM AUTHOR]

This study aimed to explore whether supplementation of the culture medium with selenium nanoparticles (nSe) can influence growth, biochemistry, expression of transcription factors, and epigenetic DNA methylation in Capsicum annuum. The seeds were grown in hormone-free MS culture medium supplemented with nSe (0, 0.5, 1, 10, and 30 mgL−1) or corresponding doses of bulk type selenate (BSe). Incorporation of nSe into the medium caused variations in morphology and growth in a manner dependent on the dose and Se type. The low doses of nSe displayed growth-promoting effects, whereas nSe at 10 and 30 mgL−1 were associated with severe toxicity and abnormality in leaf and root development. MSAP analysis confirmed the substantial variation in cytosine DNA methylation in response to the toxic dose of nSe exhibiting epigenetic modification. The nSe toxicity was associated with DNA hyper-methylations. The nSe treatments transcriptionally upregulated the bZIP1 transcription factor by an average of 3.5 folds. With a similar trend, the upregulation (mean = 9.8 folds) in the expression of the WRKY1 transcription factor resulted from the nSe application. The nSe0.5 or nSe1 treatments resulted in a significant induction (mean = 48%) in nitrate reductase activity. A high dose of nSe led to an increase in proline concentration. The nSe treatments were also associated with modifications in activities of peroxidase and catalase enzymes. Besides, the nSe utilization increased the activity of phenylalanine ammonia-lyase enzyme (mean = 76%) and concentrations of soluble phenols (mean = 51%). The toxic dose of nSe also caused abnormalities in the structure of the stem apical meristem. The nSe toxicity was also associated with inhibition in the differentiation of xylem tissues. These findings provide novel insights into the nSe-associated molecular variations in conferring the modified growth, anatomy, and metabolism. Image 1 • Potential benefits/phytotoxicity of selenium nanoparticle (nSe) as a supplement. • Providing evidence on nSe-associated epigenetic changes. • nSe transcriptionally up-regulated bZIP1 and WRKY1 transcription factors. • nSe influenced growth, anatomy, and metabolism. • The nSe toxicity was associated with DNA hyper-methylations. Summary: This is the first report on the nSe-associated changes in toxicity, epigenetic DNA hyper-methylation, transcriptional regulation of transcription factors, biochemistry, and anatomy. [ABSTRACT FROM AUTHOR]