Probing the function of protein farnesyltransferase in Tripterygium wilfordii.

KEY MESSAGE: We found two subunits FTase/GGTaseI-α and FTase-β formed a heterodimer to transfer a farnesyl group from FPP to protein N-dansyl-GCVLS, confirming they are responsible for protein farnesylation in planta. Tripterygium wilfordii is a medicinal plant with a broad spectrum of anti-inflammatory, immunosuppressive and anti-cancer activities. Recently, a number of studies have focused on investigating the biosynthetic pathways of its bioactive compounds, whereas little attention has been paid to the enzymes which play important roles in regulating diverse developmental processes of T. wilfordii. In this study, we report for the first time the identification and characterization of two subunits of farnesyltransferase (FTase), farnesyltransferase/geranylgeranyltransferase I-α (TwFTase/GGTase I-α) and farnesyltransferase-β (TwFTase-β), in this important medicinal plant. Cell-free in vivo assays, yeast two-hybrid (Y2H) and pull-down assays showed that the two subunits interact with each other to form a heterodimer to perform the role of specifically transferring a farnesyl group from FPP to the CAAX-box protein N-dansyl-GCVLS. Furthermore, we discovered that the two subunits had the same cytoplasmic localization pattern and displayed the same tissue expression pattern. These results indicated that we identified a functional TwFTase enzyme which contains two functionally complementary subunits TwFTase/GGTase I-α and TwFTase-β, which provides us promising genetic targets to construct transgenic plants or screen for more adaptable T. wilfordii mutants, which are able to survive in changing environments.