Copy number variations of functional genes influence contents of glycyrrhizic acid in Glycyrrhiza uralensis

Glycyrrhiza uralensis is a widely used Chinese herb and glycyrrhizic acid is believed to be its marker compound. Three key enzymes, 3-hydroxy-3-methylglutaryl CoA reductase (HMGR), squalene synthase (SQS) and beta-amyrin synthase (beta-AS), are involved in the glycyrrhizic acid biosynthetic pathway. In this paper, the relationship between copy number variations (CNVs) of HMGR, SQS and beta-AS genes and the content levels of glycyrrhizic acid in G. uralensis were investigated. CNVs of the 62 G. uralensis samples from different origins were determined by real-time PCR and their glycyrrhizic acid contents were analyzed by HPLC. The real-time PCR results showed that the copy numbers of HMGR, SQS1 and beta-AS in the 62 G. uralensis samples were either one copy or two copies. According to the copy number patterns of HMGR, SQS1 and beta-AS, the 62 G. uralensis samples can be divided into six groups. Among the six groups, group B with two copies of HMGR, one copy of SQS1 and beta-AS contained relatively higher contents of glycyrrhizic acid. The accumulation of glycyrrhizic acid was lower in the group C with two copies of beta-AS, one copy of SQS1 and HMGR. The results of this work may provide a basis for enhancing the accumulation of glycyrrhizic acid in cultivars of G. uralensis.