Genetic transformation of higher eukaryote mitochondria in vivo is an unresolved and important problem. For efficient expression of foreign genetic material in mitochondria, it is necessary to select regulatory elements that provide a high level of transcription and transcript stability. This work is aimed at studying the effectiveness of regulatory elements of mitochondrial genes flanking exogenous DNA using the phenomenon of natural competence of plant mitochondria. For this purpose, genetic constructs carrying the GFP gene under the control of the promoter regions of the RRN26 or COX1 genes and one of the two 3'-untranslated regions (3'-UTR) of mitochondrial genes were imported into isolated Arabidopsis mitochondria, followed by transcription in organello. It was shown that the level of GFP expression under the control of promoters of the RRN26 or COX1 genes in organello correlates with the level of transcription of these genes observed in vivo. At the same time, the presence of the tRNA^Trp sequence in the 3'-UTR leads to a higher level of the GFP transcript than the presence in this region of the 3'-UTR of the NAD4 gene containing the binding site of the MTSF1 protein. The results we obtained open prospects for creating a system for efficient transformation of the mitochondrial genome.