MOLECULAR CLONING, BIOINFORMATION ANALYSIS AND EXPRESSION OF THE STRICTOSIDINE SYNTHASE IN Dendrobium officinale

Abstract

The enzyme strictosidine synthase (STR, EC: 4.3.3.2) plays a key role in the biosynthetic pathway of terpenoid indole alkaloid (TIA). It catalyzes the condensation of the tryptamine and secologanin to form 3α(S)-strictosidine, which is the common precursor of all TIAs. In this paper, a STR gene designated as DoSTR (GenBank: KX068707) was first cloned and characterized from Dendrobium officinale with rapid amplified cDNA ends method (RACE). DoSTR has a length of 1380bp with 1179bp open reading frame encoding 392 amino acids. BlastP analyses showed that its amino acid sequence was classified into Str_synth superfamily. qRT-PCR showed that DoSTR was expressed in all tissues tested, with a significantly higher level in flower and the lowest in stem. Four different treatments with MeJA, SA, ABA and AgNO3, respectively, could induce the DoSTR expression to a different extent. And the effect of MeJA was the most obvious and transcript level of DoSTR induced by MeJA was 20.7 times greater than that of control at 48 hours after treatment. Furthermore, it was found that DoSTR was localized in vacuole through transient expression in tobacco. The characterization and expression of DoSTR can help in further studying the role of DoSTR in the biosynthesis of TIAs in D. officinale. This study may throw light on the alkaloid biosynthesis pathway of D. officinale.