Cloning and Characterization of the Gene Encoding 3-hydroxy-3-Methylglutaryl-coenzyme A (HMG-CoA) Reductase from Fritillaria Cirrhosa D. Don

The enzyme 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR; EC1.1.1.34) catalyzes the first committed step of isoprenoids biosynthesis in Mevalonate (MVA) pathway. Here we report for the first time the cloning and characterization of a full-length cDNA encoding HMGR from Fritillaria cirrhosa (FcHMGR), a bulbous medicinal plant. The full-length cDNA of FcHMGR was 2072 base pair (bp), containing a 1680-bp open reading frame. Bioinformatical analyses revealed that FcHMGR had HMG CoA-binding domains and two NADPH binding domains, which are required for HMGR activity. Quantitative real-time PCR (qRT-PCR) analysis revealed that FcHMGR expressed high in mature bulbs. A truncated version of FcHMGR protein lacking the N-terminal 249-bp GC rich area was expressed in Escherichia coli. The crude cell lysate containing the recombinant protein showed a better HMGR activity than the control and the relative enzyme activity was calculated to be 1.62 U/mg. The cloning, characterization and functional analysis of FcHMGR gene allowed us to further understand the role of FcHMGR involved in steroidal alkaloid biosynthetic pathway in F. cirrhosa at the molecular level.