Elicitation of Phenylpropanoids and Expression Analysis of PAL Gene in Suspension Cell Culture of Ocimum tenuiflorum L.

Abstract

The accumulation of total phenylpropanoids and the real time expression of PAL genes in Ocimum tenuiflorum suspension cell cultures were investigated. A comprehensive analysis of the effects of various abiotic elicitors like jasmonic acid (JA), methyl jasmonate (MeJA), salicylic acid (SA) and precursor feeder L-phenylalanine (L-phe) was done in O. tenuiflorum suspension cell cultures during elicitation. Ultra performance liquid chromatography based metabolite profiling revealed differential accumulation of three pharmaceutically important phenylpropanoids: caffeic acid, vanillin and ferulic acid. This accumulation corroborated well with real time expression of PAL genes. Biomass analysis during elicitation showed L-phe and JA moderately and MeJA and SA marginally affected the cell growth. Single and repetitive feeding with L-phe induced 22.5 fold accumulations in caffeic acid, ferulic acid and vanillin on day 16 with PAL expression increasing by 9.8–12 fold. SA (1.5 mM) induced 61 fold increase in caffeic acid accumulation with PAL expressions raised by 4.5 fold. MeJA at 25 µM promoted ferulic acid production up to 62 fold having PAL expression raised by seven fold on day 16 of elicitor treatment. Enhanced accumulation of total phenylpropanoids and elevated expression of PAL gene were observed during the course of treatment with elicitors and precursor feeder. This stipulates that PAL may modulate the biosynthesis of phenylpropanoids especially vanillin, caffeic acid and ferulic acid. The present study is of particular significance for using suspension cell culture systems of O. tenuiflorum, a less explored plant, for biotechnological production of pharmaceutically important plant secondary metabolites.