Molecular identification and functional characterization of a stilbene synthase gene in Rheum officinale

Stilbene synthase (STS), is a pivotal gene involved in the biosynthesis and regulation of stilbenes compounds, playing a crucial role in plant growth, development and stress adaptation. Meantime, stilbene compounds hold promising prospects of the wide-ranging clinical applications. Rheum officinale contains abundant stilbene compounds, yet the precise regulatory genes governing their biosynthesis remain elusive. In this study, the ORF of RoSTS gene was amplified, yielding a length of 1,140 bp and encoding a protein consisting of 379 amino acids with a relative molecular mass of 41 640.25 Da. The RoSTS protein contained the conserved residues (Cys 164, His 303, and Asn 336), and was closely related to STS of R. palmatum and R. tataricum. Moreover, qRT-PCR analysis revealed that RoSTS had the highest expression in the roots and rhizomes of 2-year-old plants, with significantly up-regulation under MeJA and SA treatments. Subcellular localization analysis showed that RoSTS protein was localized in the nucleus and cell membrane. Furthermore, RoSTS was cloned into pGEX6p-1, expressed in Escherichia coli BL21(DE3), And the purified recombinant protein could catalyze the synthesis of resveratrol from specific substrates in vitro. Overexpression of RoSTS could significantly increase the content of resveratrol in hairy roots of R. officinale, and qRT-PCR analysis showed that the relative expression of RoSTS in transgenic hairy roots was also significantly higher than that of WT. These results indicated that RoSTS might be involved in the stilbenes biosynthesis in R. officinale. Our work may contribute to understanding the mechanism of resveratrol biosynthesis in R. officinale.