Effects of phenology on the activity and gene expression of phenolic acid -biosynthetic enzymes in Salvia leriifolia Benth.

Salvia leriifolia Benth. is one of the native Iranian medicinal plants which has been received attention in recent years due to its numerous therapeutic properties. The pharmaceutical properties of this species have been attributed to the presence of phenolic compounds, especially phenolic acids. The present study investigated the effect of plant age (phenology) on the gene expression and activity of phenolic acid-biosynthetic enzymes. Plant seeds were collected from Torbat-e-Heydariyeh (Khorasan Razavi province, Iran) and planted under greenhouse conditions. Leaves were sampled at 8-, 16- and 24-leaf stages of the growth period. Total contents of phenols, flavonoids, and phenolic acids were measured using spectrophotometry, and the phenolic acid profile was determined by high-performance liquid chromatography (HPLC). The activities of phenylalanine ammonia-lyase (PAL) and tyrosine aminotransferase (TAT) were measured by spectrophotometry, and the activity of rosmarinic acid synthase (RAS) was evaluated by HPLC. The relative expression of the corresponding genes was quantified by RT-PCR. The results showed that the content of all phenolic compounds and the activities of TAT and RAS enzymes/genes increased significantly (p < /em>≤0.05) with increasing plant age. At the 24-leaf stage, the total content of phenols, flavonoids, and phenolic acids were 3.47-, 2.80-, and 7.78-fold of those measured at the 8-leaf stage, respectively. The concentration of rosmarinic acid and caffeic acid (0.69 and 0.36 mg/g DW at the 8-leaf stage, respectively) increased by 3.41- and 4.05-fold during the vegetative growth, respectively. Lithospermic acid and salvianolic acids had a smaller share of total phenolic acids (0.01-0.06 mg/g DW at the 8-leaf stage), and their contents increased 2- to 10-fold with increasing plant age. Also, a strong positive correlation was observed between plant age and phenolic acid accumulation and between plant age and the activity and gene expression of TAT and RAS. TAT enzyme might play the main role in the biosynthesis of rosmarinic acid compared to PAL.