P-117 Analysis of Expressed Sequence Tags from Glycyrrhiza uralensis Shed a Light on Genes Related to Glycyrrhizin Biosynthesis

Glycyrrhiza uralensis is one of the most popular medicinal plants in the world, and is widely used in medicine as well for the flavoring of foods and tobacco. Because of limited genomic and transcriptomic data, the biosynthetic processes of glycyrrhizin, the major bioactive compound in G. uralensis, are currently unclear [1]. Identification of the candidate genes involved in the glycyrrhizin biosynthetic pathway will contribute significantly to the understanding of the biosynthetic and medicinal chemistry of this compound. We used the latest 454-FLX Titanium platform to produce a substantial expressed sequence tags (EST) dataset from the vegetative organs of G. uralensis. A total of 59,219 ESTs with an average read length of 409 bp were generated. These reads were assembled into 7,763 contigs and 13,370 singletons. A total of 16,850 unique gene elements were annotated using BLAST searches (e-value ≤ 1e-5) against the SwissProt, KEGG, TAIR, Nr and Nt databases. With respect to genes related to glycyrrhizin metabolism, genes encoding 16 enzyme types were found for the 18 total steps of the glycyrrhizin skeleton synthesis pathway. To discover novel genes encoding cytochromes P450 and glycosyltransferases that are related to glycyrrhizin metabolism, our ESTs were combined with the ESTs in GenBank; after re-assembly, a total of 135 and 220 unigenes were homologous to cytochromes P450 and glycosyltransferases, respectively. The cytochrome P450 candidate genes were classified into 32 CYP families, while the glycosyltransferase candidate genes were classified into 34 families by GO analysis. Our study provides a high-quality EST database for G. uralensis using 454 FLX the Titanium sequencing technology. Novel candidate genes related to the secondary metabolite pathway of glycyrrhizin, including novel genes encoding cytochromes P450 and glycosyltransferases, are discussed.

Acknowledgements: This study was supported by the National Natural Science Foundation of China (30772735). We thank Prof. Jun Wang (School of Biological Science, Ningxia University, China) for his kind help with the G. uralensis sampling in the Ningxia province.

Reference: [1] Seki H, Ohyama K, et al. (2008) Proceedings of the National Academy of Sciences of the United States of America 105: 14204-14209.