Gene expression and activity of phenyl alanine amonia-lyase and essential oil composition of Ocimum basilicum L. at different growth stages

Phenylalanine amonia-lyase (PAL) is one of the most important enzymes that plays a key role in regulation of phenylpropanoid production in plants. It catalyzes the first step of the phenylpropanoid pathway in which L-phenylalanine is deaminated to trans-cinnamic acid. This step is significant for metabolic engineering and hyper-expression of the major phenylpropanoid, methyl chavicol. We followed gene expression and activity of PAL in Ocimum basilicum L. at different stages of growth including seedling, beginning and middle of growth phase, budding stage and flowering, and their correlation with final concentration of phenylpropanoid compounds. The level of gene expression was monitored by semi quantitative RT-PCR and phenylpropanoid compounds were identified by gas chromatography/mass spectrometry (GC/MS). PAL activity was assayed using spectrophotometer. The results indicated that the level of gene expression and activity of PAL enzyme are altered during the plant development, where the highest expression and activity (0.851 mmol cinnamic acid/mg/min) was achieved at budding stage. In this experiment, changes of methylchvicol content were correlated to the transcription and activity of PAL enzyme.