Changes in Physiological Traits, Gene Expression and Phytochemical Profile of Mentha piperita in Response to Elicitor.

Abstract

Peppermint (Mentha piperita) is a perennial medicinal plant containing active ingredients that can be used for treating liver and prostate cancers, acute respiratory infections, allergies, digestive problems, neuralgia, and migraines. The objective of this research is to investigate the expression of essential genes in the menthol pathway of Mentha piperita, including Pulegone reductase (Pr), Menthofuran synthase (Mfs), and limonene synthase (Ls) using qPCR, physiological analysis and essential oil composition in response to methyl jasmonate (MeJA) (0.5mM) elicitation. Physiological analysis showed that 0.5mM MeJA triggers defensive responsiveness in Mentha piperita by increasing superoxide dismutase (SOD) and Peroxidase (POD) enzymesactivity. The highest transcript levels of Pr and Mfs genes were observed during 8 and 12h after treatment respectively, but following 24h, they were down-regulated. Essential oil analysis indicated that the percentage of constituents in the essential oil was changed using MeJA at 48h and 96h after post-treatment. Effective antimicrobial compounds, α-pinene, β-pinene, linalool and methyl acetate, were induced after 48h. A non-significant positive relationship was detected between menthol content, and expression of the Pr and Mfs genes. Due to the significant change in the expression of Pr and Mfs genes in the menthol pathway, role of Pr gene in directing the pathway to the valuable compound menthol and deviation of the menthol pathway to the menthofuran as an undesirable component of essential oil by Mfs gene, it can be deduced that they are the most critical genes in response to MeJA treatment, which are appropriate candidates for metabolite engineering. In addition, MeJA improved defensive responsiveness and percentage of some constituents with antimicrobial properties in Mentha piperita.