(621l) An Improved Kinetic Model of Mint Essential Oil Biosynthesis That Accounts for Transport and the Early Monoterpene Metabolic Steps

We have previously reported a tested kinetic model for essential oil biosynthesis in peppermint [Rios-Estepa et al., 2008, Rios-Estepa et al., 2010]. The mathematical model used, as input variables, the diverse profiles of gene expression, enzyme concentration/activity, levels of metabolites and the number of secretory cells involved in oil biosynthesis, and the kinetic properties as parameters. A second generation model described changes in essential oil profiles under various environmental conditions and in different transgenic lines. It was also included variables accounting for variations in the number of glandular trichomes (specialized essential oil-producing structures on leaf surfaces), the amount of essential oil stored per trichome, the distribution of glandular trichomes at different stages of leaf development, and modulation of gene expression patterns in transgenic lines with modified essential oil composition. The refined model was used to identify the key factors controlling monoterpenoid essential oil biosynthesis under adverse environmental conditions. It also was used for investigating determinants of essential oil biosynthesis in transgenic peppermint lines with modulated essential oil profiles. A computational perturbation analysis, which was implemented to identify the variables that exerted prominent control over the outputs of the model, indicated that the essential oil composition should be highly dependent on certain biosynthetic enzyme concentrations [(+)-pulegone reductase and (+)-menthofuran synthase], whereas oil yield should be particularly sensitive to the density and/or distribution of leaf glandular trichomes, the specialized anatomical structures responsible for the synthesis and storage of essential oils.

Here we present an improved modeling approach to account for transport in the secretory cell wall, the endoplasmatic reticulum and the mitochondria where some of most important metabolic catalysts are present. Also, the enhanced model did consider the early metabolic steps in monoterpene biosynthesis.

The implications of these model modifications for wild type and transgenic approaches aimed at improving essential oil yield and composition are discussed. [Rios-Estepa et al., 2008. PNAS Feb 26;105(8):2818-23; Rios-Estepa et al., 2010. April 152: 2105-2119]