Isolation, characterization and functional analysis of a novel 3-hydroxy-3-methylglutaryl-coenzyme A synthase gene (GbHMGS2) from Ginkgo biloba

Ginkgo biloba, an industrial plant of high medicinal value, is resistant to pest, disease infections, and environmental stresses. 3-Hydroxy-3-methylglutaryl-coenzyme A synthase (HMGS) is a key mevalonic acid pathway enzyme that plays crucial roles in plant defense mechanism. In the present study, a 1407-bp HMGS gene, GbHMGS2, encoding 468 amino acid residues was cloned from G. biloba. A promoter sequence (1479-bp long) of the gene was screened from G. biloba genome data. The promoter contained the putative light-responsive (Box 4, G-Box, GT1-motif, I-box, and Sp1), cold-responsive (LTR), hormone-responsive (auxin and methyl jasmonate), and defense-related (W-box and MBS) regulatory elements. Putative GbHMGS2 protein shared high similarities to other plant HMGSs containing the conserved motif and all conserved active sites possessed by the plant HMGS protein family. Functional complementation of GbHMGS2 in an hmgs-deficient Saccharomyces cerevisiae strain confirmed the catalytic activity of GbHMGS2 protein. GbHMGS2 was preferentially expressed in the roots of G. biloba among the plant organs. The GbHMGS2 transcription was upregulated in response to cold, dark, methyl jasmonate, salicylic acid, and abscisic acid treatments, in agreement with the regulatory elements predicted in promoter region. The present work on GbHMGS2 could help ensuing research on its function, especially in the signal transduction pathways in G. biloba.