The Effect of Magnetic Iron Oxide Nanoparticles and Ferric Chloride on the Expression of Some Rosmarinic Acid Biosynthetic Genes in Melissa Officinalis L.

Rosmarinic acid (RA), an anticancer, antiallergic, and antimicrobial agent, is a secondary metabolite in many plants of the family Lamiaceae including M. officinalis L. The application of nanoparticles (NPs) as a novel elicitor for the biosynthesis of bioactive compounds shown that the NPs could affect the secondary metabolites in plants by eliciting the expression of biosynthetic pathway genes. The present paper aimed to assess the effect of Magnetic Iron Oxide Nanoparticles (MIONPs) in comparison with their dissolved counterpart.

Foliar application of different concentrations: including 5, 10, 25, and 50 mg/L Fe of ferric chloride and MIONPs on the plant leaves was performed. The relative mRNA levels of TAT, RAS, and HPPR were evaluated with quantitative real-time PCR (qRT-PCR) and compared between treated and untreated samples.

This study showed the positive effects of ferric chloride and MIONPs on the expression of genes involved in the biosynthesis pathway of RA. The highest expression level of TAT, HPPR, and RAS genes was observed in plants treated with MIONPs at the concentration of 25 mg/L and the expression of genes decreased as the concentration increased to 50 mg/L. However, the genes expression was still higher compared to the control plant.

The results showed that the exposure of plants to ferric chloride and magnetic iron oxide nanoparticles led to an increase in the expression of the genes under study compared to control samples. However, the application of nano-scale iron particles had more effect than ferric chloride on the expression levels. An increase in the expression of genes involved in the biosynthesis pathway of RA through treatment with MIONPs provides an opportunity for induction of synthesis and accumulation of RA. Therefore, we hope to be able to enhance the production of RA in M. officinalis L. by using these NPs.