Molecular cloning and characterization of two cDNAs for Glycyrrhiza glabrasqualene synthase

Two cDNAs (GgSQS1 and GgSQS2) encoding squalene synthase have been isolated from licorice, Glycyrrhiza glabra L., and characterized. The deduced amino acid sequence of GgSQS1 was 88%, 81%, 78%, 45-44%, and 45-41% identical to those of GgSQS2, Nicotiana, Arabidopsis, mammal and yeast squalene synthas es, respectively. Squalene synthase activity was found in the cell-free ext racts of Escherichia coli transformed with the recombinant plasmids for GgS QS1 and GgSQS2, respectively. Genomic Southern blot hybridization indicated that there are three squalene synthase genes in the licorice genome. North ern blot analysis showed that GgSQS2 mRNA is mainly expressed during the ex ponential growth phase of the cultured licorice cells.