Cloning and analyzing a squalene synthase gene in Pseudostellaria heterophylla

Abstract Triterpene saponins are primary bioactive compounds in the tuberous roots of Pseudostellaria heterophylla , which is one of well-known traditional Chinese medicines. Squalene synthase (SQS) is the key speed-limiting enzyme of saponin biosynthesis pathway. Here, we cloned and analyzed a SQS gene in P. heterophylla . The full length cDNA of SQS was cloned and designated PhSQS (GenBank accession no. KY436585). The open reading frame (ORF) of PhSQS contains 1245 bp and encodes a putative protein of 414 amino acids. In-silico analysis of amino acid sequence of PhSQS showed a conserved isoprenoid family domain and catalytic sites and the three-dimensional (3D) structure of PhSQS was not deviated from that of the SQSs from other species. The phylogenetic relationship of PhSQS was more closely related to that from Beta vulgaris . The semi-quantitative RT-PCR revealed the expression level of PhSQS was significantly higher in root tissue than that of other tissues. Our results suggest that PhSQS is a candidate of functional gene of squalene synthase and may be involved in triterpene saponin biosynthesis.