Activation of polyketide synthase gene promoter in Cannabis sativa by heterologous transcription factors derived from Humulus lupulus

Cannabis sativa, an annual herbaceous plant, produce wide variety of secondary metabolites among which delta-9-tetrahydrocannabinol (THC) is the most important one. The dissection of biosynthetic pathway(s) of this compound and its regulation by transcription factors (TFs) is an important prerequisite for efficient biotechnological manipulation of its secondary metabolome. A polyketide synthase (PKS) of C. sativa catalyzes the first step of cannabinoid biosynthesis, leading to the biosynthesis of olivetolic acid. Cloning and analysis of PKS promoter based on online PLACE, PlantCARE, and Genomatix Matinspector professional databases, indicated that PKS promoter consisted of cis-elements such as TATA-box, CAAT-box, W-box, Myb-box, E-box, and P-box. Plant expression vector PKS::GUS was constructed in such a way that the ATG of the PKS gene was in the frame with the β-glucuronidase (GUS) coding region. Using a combinatorial transient GUS expression system in Nicotiana benthamania leaves, it was shown that heterologous TFs such as HlWRKY1, HlMYB3, HlWDR1 and HlbZIP1 from Humulus lupulus significantly activated PKS promoter. Moreover, Tombusvirus p19 core protein, which is known for silencing suppressor functions, acted in our combinatorial transient expression system as an enhancer of PKS promoter activity along with hop TFs. Our analyses suggested the involvement of the hop derived TFs (HlWRKY1, HlMYB3, HlWDR1 and HlbZIP1A) and p19 in the activation of PKS gene promoter, which could be used for the genetic manipulation of C. sativa to enhance the cannabinoid production.