The Epigenetic Regulation in Plant Specialized Metabolism: DNA Methylation Limits Paclitaxel Biotechnological Production.

Environmental conditions are key factors in the modulation of the epigenetic mechanisms regulating gene expression in plants. Specifically, the maintenance of cell cultures in optimal conditions alters methylation patterns and, consequently, their genetic transcription and metabolism. Paclitaxel production in cell cultures is reduced during its maintenance in conditions, compromising the biotechnological production of this valuable anticancer agent. To understand how DNA methylation influences taxane production, the promoters of three genes (, , and ) involved in taxane biosynthesis have been studied, comparing the methylation patterns between a new line and one of ~14 years old. Our work revealed that while the central promoter of the gene is protected from cytosine methylation accumulation, and promoters accumulate methylation at different levels. The promoter of the old line is the most affected, showing a 200 bp regulatory region where all the cytosines were methylated. This evidence the existence of specific epigenetic regulatory mechanisms affecting the last steps of the pathway, such as the promoter. Interestingly, the promoter, a regulatory sequence of a non-specific taxane biosynthetic gene, was not affected by this mechanism. In addition, the relationship between the detected methylation points and the predicted transcription factor binding sites (TFBS) showed that the action of TFs would be compromised in the old line, giving a further explanation for the production reduction in cell cultures. This knowledge could help in designing novel strategies to enhance the biotechnological production of taxanes over time.