Isolation and functional analysis of a cDNA encoding a myrcene synthase from holm oak (Quercus ilex L.)

An 859-bp cDNA segment of a terpene synthase gene was amplified by PCR from the evergreen sclerophyllous holm. oak (Quercus ilex L.) using heterologou s primers for conserved regions of terpene synthase genes (TPS) in dicotyle donous plants. Based on the sequence of this segment, homologous primers we re designed for amplification by RACE-PCR of a cDNA segment carrying the mo noterpene synthase gene myrS. The gene encodes a protein of 597 amino acids including an N-terminal putative plastid transit peptide. The gene without the segment encoding the transit peptide was cloned by PCR into a bacteria l expression vector. Expression in Escherichia coli yielded an active monot erpene synthase, which converted geranyl diphosphate (GDP) predominantly in to the acyclic monoterpene myrcene and to a very small extent into cyclic m onoterpenes. Sequence comparison with previously cloned monoterpene synthas es revealed that the myrcene synthase from Q. ilex belongs to the TPSb subf amily.