(759c) Towards the Elucidation of the Limonin Biosynthetic Pathway, a Triterpene Derived Natural Product in Citrus sinensis

Triterpene derived plant natural products have essential properties in plant immunity and wide uses in the food, health and biotechnology sectors. The bioactivities of these molecules are attributed to the vast range of enzymatic tailoring on the triterpene scaffold including oxygenations, glycosylations, and acylations. These tailoring reactions modify triterpenes into complex molecules that are outside our chemical synthesis capabilities. Thus, the discovery and characterization of enzymes involved in triterpenoid biosynthesis is necessary to uncover novel chemistries and for metabolic engineering efforts towards the production of intricate triterpene derivatives.

One important group of triterpene derivatives are the limonoids. Limonoids display potent insect-deterrent properties including anti-feedant, growth disruptive, and reproduction inhibitive activities. Limonoids exhibit high degrees of oxygenation and complex intermolecular rearrangements resulting from an estimate of a dozen unknown genes. Herein, we aim to elucidate the biosynthetic pathway of limonin, a prototypical limonoid found in Citrus sinensis (sweet or Valencia orange). We selected gene candidates via a homology and transcriptome analysis, and we developed a platform for rapid pathway discovery combining transient expression in the host Nicotiana benthamiana with liquid chromatography mass spectrometry (LC-MS) metabolomics. The utilization of this platform allows for fast screening of gene candidates potentially involved in the limonin biosynthetic pathway.