The YABBY Family Transcription Factor AaYABBY5 Directly Targets Cytochrome P450 Monooxygenase (CYP71AV1) and Double-Bond Reductase 2 (DBR2) Involved in Artemisinin Biosynthesis in .

Artemisinin is an effective antimalarial sesquiterpene lactone synthesized in . Various transcription factors have been previously reported that can influence the biosynthesis of artemisinin; however, the effect of YABBY family transcription factors on artemisinin biosynthesis was unknown. In the present study, we cloned and characterized AaYABBY5: a homolog of MsYABBY5 in which is involved in modulating the monoterpenes, as a positive regulator of artemisinin biosynthesis in . AaYABBY5 was found localized to the nucleus, and its expression was found to be induced by exogenous methyl jasmonic acid (MeJA) treatment. In the dual-luciferase reporter assay, it was found that AaYABBY5 significantly increased the activities of promoters of amorpha-4,11-diene synthase (), cytochrome P450 monooxygenase (), double-bond reductase 2 (), and aldehyde dehydrogenase 1 () genes. Yeast one hybrid assay showed that AaYABBY5 directly bonds to the promoters of and genes. Quantitative real-time polymerase chain reaction (qPCR) of overexpression and antisense plants revealed a significant increase in the expression of , , , and in overexpression plants and a significant decrease in the expression of these genes in antisense , respectively. Furthermore, the results of high-performance liquid chromatography (HPLC) showed that the artemisinin and its precursor dihydroartemisinic acid were significantly increased in the overexpression plants while downregulation resulted in a significant decrease in the concentration of artemisinin. Taken together, these results explicitly represent that AaYABBY5 is a positive regulator of artemisinin biosynthesis in .