Gene expression and activity of phenyl alanine amonialyase 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 regulationof phenylpropanoid production in plants. It catalyzes the first step of the phenylpropanoid pathway in whichL-phenylalanine is deaminated to trans-cinnamic acid. This step is significant for metabolic engineering andhyper-expression of the major phenylpropanoid, methyl chavicol. We followed gene expression andactivity of PAL in Ocimum basilicum L. at different stages of growth including seedling, beginning andmiddle 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 andphenylpropanoid compounds were identified by gas chromatography/mass spectrometry (GC/MS). PALactivity was assayed using spectrophotometer. The results indicated that the level of gene expression andactivity of PAL enzyme are altered during the plant development, where the highest expression and activity(0.851 μmol cinnamic acid/mg/min) was achieved at budding stage. In this experiment, changes ofmethylchvicol content were correlated to the transcription and activity of PAL enzyme.