AaPDR3, a PDR Transporter 3, Is Involved in Sesquiterpene β-Caryophyllene Transport in Artemisia annua

Abstract

Artemisinin, a sesquiterpenoid endoperoxide, isolated from the plant <i>Artemisia annua</i> L., is widely used in the treatment of malaria. Another sesquiterpenoid, β-caryophyllene having antibiotic, antioxidant, anticarcinogenic and local anesthetic activities, is also presented in <i>A. annua</i>. The role played by sesquiterpene transporters in trichomes and accumulation of these metabolites is poorly understood in <i>A. annua</i> and in trichomes of other plant species. We identified <i>AaPDR3</i>, encoding a pleiotropic drug resistance (PDR) transporter located to the plasma membrane from <i>A. annua</i>. Expression of <i>AaPDR3</i> is tissue-specifically and developmentally regulated in <i>A. annua</i>. GUS activity is primarily restricted to T-shaped trichomes of old leaves and roots of transgenic <i>A. annua</i> plants expressing <i>proAaPDR3</i>: <i>GUS</i>. The level of β-caryophyllene was decreased in transgenic <i>A. annua</i> plants expressing <i>AaPDR3</i>-RNAi while transgenic <i>A. annua</i> plants expressing increased levels of <i>AaPDR3</i> accumulated higher levels of β-caryophyllene. When AaPDR3 was expressed in transformed yeast, yeasts expressing <i>AaPDR3</i> accumulated more β-caryophyllene, rather than germacrene D and β-farnesene, compared to the non-expressing control.