Glandular trichome-specific expression of alcohol dehydrogenase 1 (ADH1) using a promoter-GUS fusion in Artemisia annua L.

Abstract

Artemisinin, isolated from Artemisia annua L., is widely known as a functional anti-malaria drug. Due to the low content of artemisinin in A. annua plants, great efforts have been made to determine the artemisinin biosynthetic pathway by genetic engineering. ADH1, encoding an alcohol dehydrogenase, was cloned from the glandular secretory trichomes (GSTs) in A. annua. The gene expression analysis showed that ADH1 was predominately expressed in buds and young leaves, and the expression of ADH1 was the highest in the youngest leaves. To further investigate the expression pattern of ADH1 in A. annua, a 1070-bp promoter region of ADH1 was cloned. We found 14 putative cis-elements were presented in the ADH1 promoter sequence, indicating that ADH1 is complexly regulated. The ADH1 promoter sequence was fused to the β-glucuronidase reporter gene (GUS) and introduced into A. annua plants. GUS signals were only found in the glandular secretory trichomes of young tissues in transgenic A. annua plants. Besides, the treatment of A. annua seedlings with 100 μM methyl jasmonate (MeJA) and 100 μM abscisic acid (ABA), respectively, increased the ADH1 transcript levels. The dual luciferase (dual-LUC) assay demonstrated that the reported transcription factors, MYC2 and ERF1, activated the expression of ADH1 in vivo. Our study shows that ADH1 gene is exclusively expressed in the glandular secretory trichomes of young tissues of A. annua, it implies that the promoter of ADH1 gene could be used in engineering of A. annua for increasing artemisinin content.