Regulation of gene expression in <i>Nicotiana tabacum</i> seedlings by the MKASAA peptide through DNA methylation via the RdDM pathway

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<abstract> <p>DNA methylation is involved in the protection of the genome, the regulation of gene expression, splicing, and is associated with a serious reprogramming of plant development. Using fluorescence microscopy, it was shown that the MKASAA peptide penetrates through the root system of <italic>Nicotiana tabacum</italic> tobacco, mainly into the cap, meristem, and elongation zones. In the cell, the peptide is localized mainly on the nuclei. In tobacco seedlings grown in the presence of the peptide at a concentration of 10<sup>–7</sup> M, an increase in the expression of DNA methyltransferases, especially DRM2, which methylates previously unmethylated DNA sites, is observed. In the presence of the peptide in the roots and leaves of tobacco, the level of global DNA methylation increases. An increase in DNA methylation occurs via the RdDM pathway. Presumably, the peptide binds to siRNAs, forming giant particles that remodulate chromatin and facilitate the entry of DNA methyltransferases. An increase in the level of DNA methylation is accompanied by silencing of the genes of the <italic>GRF</italic>, <italic>KNOX</italic>, and <italic>EXP</italic> families. Suppression of gene expression of these families is accompanied by significant morphological changes in tobacco seedlings. Thus, the short exogenous MKASAA peptide is involved in global morphological and genetic changes in tobacco seedlings.</p> </abstract>