Effect of lead on expression of genes in synthesis of Menthol in peppermint (Mentha piperita L.)

Mentha piperita L. is one the most important species of the Lamiaceae that presence of menthol in its essential oil has intensify the importance of the plant. In this experiment, effect of four levels of soil lead consist of ۰ to ۶۰۰ ppm was evaluated for the first time on gens expression involved in the menthol production and changes in the composition (GC-MS analysis) of essential oil in peppermint (Mentha piperita L.). According to the GC-MS results, Essential oil level increased as the rising of Pb level. Moreover, the main compounds detected at four Pb levels, which were menthol, menthone, menthofuran, pulegone, cineole and methyl acetate. The result showed that if the Pb stress increases, the level of expressions menthofuran synthase (MFS) will decline in plant; whereas, the gene expression of both menthol reductase (MR) and pulegone reductase (PR) were increased, which is confirmed the GC-MS results. Therefore, the stress acted as an elicitor to decrease the expression of menthofuran synthase gene and increase the menthol reductase gene expression; hence, menthol level enhances in the plant. So, peppermint can be cultivated in lead-contaminated soils to enhance menthol, hence increase the quality of its essential oil