Abstract:

In this study，a full length cDNA encoding linalool synthase was successfully cloned from floral organs of Osmanthus fragrans var. thunbergii with newly designed degenerate primers by reverse transcription (RT)-PCR， Rapid Amplification of cDNA Ends (RACE) technology，and Blastn analysis. The gene was named as OfLis (Osmanthus fragrans var. thunbergiilinalool synthase) and deposited under GenBank accession No. FJ645727. The OfLis full length cDNA was 2 003 bp and contained a complete open reading frame (ORF) of 1 731bp encoding 576 amino acids. Sequence analysis showed that OfLispresented two typical conserved motifs of terpene synthases，i.e DDXXD and (N，D)D(L，I，V)X(S，T)XXXE，which are essential for substrate binding and ionization. There was a N-terminal peptide sequence RR(X)8W which is essential for the enzymatic activity of many monoterpene synthases. The molecular weight and isoeletric point of OfLiswere predicted to be 67.29 ku and 5.26，respectively. Most of the amino acid sequences of OfLiswere hydrophilic regions. At the amino acid sequence level，OfLisexhibited the highest similarity (63.6%) with Lavandula angustifolialinalool synthase，and the lowest similarity (19.0%) with Clarkia concinna linalool synthase gene. RT-PCR analysis revealed that OfLis was specifically expressed in petals，pistils and stamens，but not in sepals and leaves in the whole bloom stage. This study lays a scientific basis for breeding，improvement and regulation and control of flavor profile of fragrant plant varieties.

Key words: Osmanthus fragransvar. thunbergii, monoterpene synthase, linalool synthase, reverse transcription-PCR, Rapid Amplification of cDNA Ends