Expression of β‐glucosidase increases trichome density and artemisinin content in transgenic Artemisia annua plants

Abstract

Artemisinin is highly effective against multidrug-resistant strains of Plasmodium falciparum, the etiological agent of the most severe form of malaria. However, a low level of accumulation of artemisinin in Artemisia annua is a major limitation for its production and delivery to malaria endemic areas of the world. While several strategies to enhance artemisinin have been extensively explored, enhancing storage capacity in trichome has not yet been considered. Therefore, trichome density was increased with the expression of β glucosidase (bgl1) gene in A. annua through Agrobacterium-mediated transformation. Transgene (bgl1) integration and transcript was confirmed by molecular analysis. Trichome density increased up to 20% in leaves and 66% in flowers of BGL1 transgenic plants than Artemisia control plants. High-performance liquid chromatography (HPLC, MS-TOF) data showed that artemisinin content increased up to 1.4% in leaf and 2.56% in flowers (g-1DW), similar to the highest yields achieved so far through metabolic engineering. Artemisinin was enhanced up to 5-fold in BGL1 transgenic flowers. The present study opens the possibility of increasing artemisinin content by manipulating trichomes density, which is a major reservoir of artemisinin. Combining biosynthetic pathway engineering with enhancing trichome density may further increase artemisinin yield in A. annua. Because oral feeding of Artemisia plant cells reduced parasitemia more efficiently than the purified drug, reduced drug resistance and cost of prohibitively expensive purification process, enhanced expression should play a key role in making this valuable drug affordable to treat malaria in a large global population that disproportionally impacts low-socioeconomic areas and underprivileged children.

HOMEODOMAIN PROTEIN 1 is required for jasmonate‐mediated glandular trichome initiation in Artemisia annua

“…S1). Sample treatment followed the method previously reported by Singh et al (2015). Pictures were imaged via extreme-resolution analytical field emission SEM (Jeol, Japan, and Thermo, USA).…”

Integrative Transcriptomic and Metabolic Analyses Provide Insights into the Role of Trichomes in Tea Plant (Camellia Sinensis)

“…Trichomes have been regarded as a perfect system in which to study cell development and secondary metabolite synthesis in the model plants Arabidopsis [10][11][12][13][14][15][16], tomato [17][18][19][20][21][22][23], and Artemisia annua [24][25][26][27][28][29][30], and many genes that are involved in trichome differentiation have been identified, especially various transcription factors (TFs) encoding genes, such as positive regulators of GLABROUS 3 (GL1, GL2, and GL3) and ENHANCER OF GLABROUS 3 (EGL3), TRANSPARENT TESTA 1 (TTG1 and TTG2) and repressors of TRIPTYCHON (TRY), CAPRICE (CPC), ENHANCER OF TRY, CPC 1 (ETC1, ETC2, and ETC3), and TRICHOMELESS 1 (TCL1 and TCL2) [6,12,13,16]. Moreover, an increasing number of studies have indicated that trichomes seem to be an excellent model in which to study the molecular mechanisms of secondary cell wall deposition and fiber synthesis [31,32], which have been well studied in plants.…”

Terpene metabolic engineering via nuclear or chloroplast genomes profoundly and globally impacts off‐target pathways through metabolite signalling

“…One strategy to increase squalene could be to increase sink capacity by sequestering squalene in storage compartments such as lipid droplets (Wang et al, 2015) or additional trichomes (Lange, 2015). Trichome density could be increased via transgenic expression of b-glucosidase (Jin et al, 2011), which improves artemisinin yields in transgenic Artemisia annua (Singh et al, 2015).…”