(316b) Kinetic Modeling of the Phenylpropanoid Pathway in Petunia Hybrida

Plant volatiles consist of a mixture of secondary metabolites mainly constituted by terpenoids, phenylpropanoids/benzenoids, fatty acid derivatives, and amino acid derivatives. Volatile scent compounds produced by flowering plants ensure reproductive and evolutionary success, by attracting pollinators and seed disseminators. Although production of volatile scent compounds by plants is widespread in nature, the knowledge about their synthesis and genetic regulation is poorly understood. The volatile ester methyl benzoate is one of the most abundant scent compounds in Petunia and is derived from the phenylpropanoid pathway. There is focus on increasing scent production in flowers by metabolic engineering due to its broad impact on perfume and horticulture industry. Metabolic engineering of flowers to enhance the scent production can be done in an efficient and targeted manner, if there is mechanistic information about the kinetics and regulation of the pathways involved in scent production. Thus it is imperative to develop mechanistic models that can simulate the metabolism and further should be able to predict the results of environmental or genetic changes on the network.

We developed a kinetic model for the phenylpropanoid pathway in Petunia with transient concentration and isotopic labeling data of Petunia, fed with 5-2H-labelled phenylalanine. We estimated the in vivo kinetic parameters of the reactions using network decoupling and least square optimization. Furthermore, the model was successful in predicting changes in metabolism in a BBPT mutant of Petunia. Moreover, the modeling also gave interesting insights into regulation of the pathway. For example, the presence of feedback inhibition on the first committed step of the phenylpropanoid pathway, regulated by the enzyme PAL (phenylalanine ammonia lyase) was found.