Accumulation of Polyphenols and Associated Gene Expression in Hairy Roots of Salvia viridis Exposed to Methyl Jasmonate

Abstract

Methyl jasmonate (MJA), a signaling molecule in stress pathways, can be used to induce secondary metabolite synthesis in plants. The present study examines its effects on the growth of Salvia viridis hairy roots, and the accumulation of bioactive compounds, and correlates it with the expression of genes involved in the phenylpropanoid pathway. To our knowledge, this study represents the first exploration of elicitation in S. viridis culture and the first comprehensive analysis of MJA’s influence on such a wide array of genes within the polyphenol metabolic pathway in the Salvia genus. Plants were treated with 50 and 100 µM MJA, and samples were collected at intervals of one, three, five, and seven days post-elicitation. HPLC analysis revealed that MJA stimulated the accumulation of all tested compounds, with a 30% increase (38.65 mg/g dry weight) in total polyphenol content (TPC) on day five. Quantitative real-time polymerase chain reaction (RT-PCR) analysis demonstrated a significant increase in the expression of the phenylpropanoid pathway genes—TAT (tyrosine aminotransferase), HPPR (4-hydroxyphenylpyruvate reductase), PAL (phenylalanine ammonia-lyase), C4H (cinnamic acid 4-hydroxylase), 4CL (4-coumarate-CoA ligase), and RAS (rosmarinic acid synthase)—following MJA treatment. For the majority of the genes, this increase was observed after the first day of treatment. Importantly, our present results confirm strong correlations of the analyzed gene expression with polyphenol biosynthesis. These findings support the notion that hairy roots provide a promising biotechnological framework for augmenting polyphenol production. Additionally, the combination of elicitor treatment and transgenic technology emerges as a viable strategy to enhance the biosynthesis of these valuable metabolites.