Cloning and Expression Analysis of Key Enzyme Gene Involved in Iridoid Glycoside Synthesis in

Cornus iridoid glycosides (CIGs), including loganin and morroniside, are the main active components of . As one of the key enzymes in the biosynthesis of CIGs, geranyl pyrophosphate synthase (GPPS) catalyzes the formation of geranyl pyrophosphate, which is the direct precursor of CIGs. In this study, the geranyl pyrophosphate synthase (CoGPPS) sequence was cloned from and analyzed. The cDNA sequence of the gene was 915 bp (GenBank No. OR725699). Phylogenetic analysis showed that CoGPPS was closely related to the GPPS sequence of and , but relatively distantly related to and . Results from the quantitative real-time PCR showed the spatiotemporal expression pattern of ; that is, was specifically expressed in the fruits. Subcellular localization assay proved that CoGPPS was specifically found in chloroplasts. Loganin and morroniside contents in the tissues were detected by high-performance liquid chromatography, and both compounds were found to be at higher levels in the fruits than in leaves. Thus, this study laid the foundation for further studies on the synthetic pathway of CIGs.