The Effect of Different Growth Hormones on Gene Expression of Phenylalanine Ammonia Lyase (PAL) in Ocimum basilicum L.

Basil (Ocimum basilicum L.) is a member of a Lamiaceae family with aroma compounds and high essence. Furthermore, the essential oils of basil leaves are composed of phenylpropanoids, which have shown antibacterial and antioxidant properties. Phenylalanine ammonia Lyase is an important enzyme in phenylpropanoid pathway. The literature indicated that plant hormones affect gene expression in plants and increase the production of secondary metabolites. In addition, the hormones stimulate the immune system through transcriptional activation of defense related genes, and in turns, increase induced resistance of plants. In the current study, Real Time PCR was used to evaluate the gene expression and enzymatic activity of phenylalanine ammonia. The plants were treated with three different hormones including gibberellic acid, jasmonic acid, and salicylic acid with 0.1 mM/L concentration. The activities were studied during three different plant growth stages which included seedlings, pre-flowering stage, and flowering stage. The difference between gene expressions levels were analyzed by Duncan method (P≤0.05) using SAS software (version 9.0). During the flowering stage, the results showed an increase in gene expression of phenylalanine ammonia Lyase in plants treated with jasmonic acid. The gene expression of phenylalanine ammonia Lyase was significantly higher (5%) for all treated samples compared to the control samples. The studied hormones increased the gene expression and enzymatic activity of phenylalanine ammonia Lyase.