Carboxylic Acid-Functionalized Multi-Walled Carbon Nanotubes (COOH-MWCNTs) Elicit Concordant Variations in DNA Cytosine Methylation, Gene Expression, Growth, Morphogenesis, Metabolism, and Callogenesis in Salvia nemorosa; An In Vitro Biological Assessment

The recent decade has witnessed remarkable breakthroughs in the use of nano-scaled substances in the field of the cell, tissue, and organ culture of plants. This study investigated how Salvia nemorosa responds to the supplementation of a culture medium with different concentrations of carboxylic acid-functionalized multi-walled carbon nanotubes (COOH-MWCNTs; 0, 40, 80, and 120 mgl −1 ). The application of COOH-MWCNTs influenced plant growth, morphogenesis, and organogenesis. COOH-MWCNTs, especially at 80 mgl −1 , reinforced the shoot and root development. The nano-supplements increased biomass accumulations by 2.3-fold. MWCNTs at 120 mgl −1 contributed to the modification in DNA methylation. Moreover, COOH-MWCNTs contributed to the slight increase in the concentrations of photosynthetic pigments. The COOH-MWCNTs-supplemented seedlings contained higher total protein contents than the control. The activities of peroxidase and catalase enzymes displayed an upward trend (about 2-fold) in response to the COOH-MWCNTs. Likewise, COOH-MWCNTs significantly stimulated the activity of the phenylalanine ammonia-lyase enzyme. The COOH-MWCNTs application enhanced the concentrations of phenylpropanoid derivatives and alkaloids. The nano-scaled material also up-regulated the expression of the tyrosine aminotransferase ( TAT ) gene. Moreover, the COOH-MWCNTs improved callogenesis performance and callus biomass. The biological assessments support the hypothesis that COOH-MWCNTs can be considered as a highly potent elicitor of plant morphogenesis, organogenesis, cell differentiation, callogenesis, metabolism, transcriptome, and DNA methylome. Graphical Abstract