GLANDULAR TRICHOME‐SPECIFIC WRKY 1 promotes artemisinin biosynthesis in Artemisia annua

Abstract

Artemisinin is a type of sesquiterpene lactone well known as an antimalarial drug, and is specifically produced in glandular trichomes of Artemisia annua. However, the regulatory network for the artemisinin biosynthetic pathway remains poorly understood. Exploration of trichome-specific transcription factors would facilitate the elucidation of regulatory mechanism of artemisinin biosynthesis. The WRKY transcription factor GLANDULAR TRICHOME-SPECIFIC WRKY 1 (AaGSW1) was cloned and analysed in A. annua. AaGSW1 exhibited similar expression patterns to the trichome-specific genes of the artemisinin biosynthetic pathway and AP2/ERF transcription factor AaORA. A β-glucuronidase (GUS) staining assay further demonstrated that AaGSW1 is a glandular trichome-specific transcription factor. AaGSW1 positively regulates CYP71AV1 and AaORA expression by directly binding to the W-box motifs in their promoters. Overexpression of AaGSW1 in A. annua significantly improves artemisinin and dihydroartemisinic acid contents; moreover, AaGSW1 can be directly regulated by AaMYC2 and AabZIP1, which are positive regulators of jasmonate (JA)- and abscisic acid (ABA)-mediated artemisinin biosynthetic pathways, respectively. These results demonstrate that AaGSW1 is a glandular trichome-specific WRKY transcription factor and a positive regulator in the artemisinin biosynthetic pathway. Moreover, we propose that two trifurcate feed-forward pathways involving AaGSW1, CYP71AV1 and AaMYC2/AabZIP1 function in the JA/ABA response in A. annua.

TRANSPARENT TESTA GLABRA1 (TTG1) regulates leaf trichome density in tea Camellia sinensis

“…Trichomes can synthesize, store and sometimes secrete large amounts and various types of specialized metabolites, such as terpenes, phenylpropanoid derivatives and flavonoids (van Der Hoeven et al 2000, Gang et al 2001, Valkama et al 2003. Secondary metabolites have become popular not only because of their significance in the protection of plants against environmental stressors but also because they have great commercial value as food additives or pharmaceuticals (Schilmiller et al 2008, Glas et al 2012, Chen et al 2017, Huchelmann et al 2017, Yan et al 2017, Sun et al 2019a. For example, Cistus salvifolius trichomes synthesize and store polyphenols that affect both radiation absorbance and plant desiccation, which evolved for adaptation to high light stress and poor soil conditions along Mediterranean coasts (Tattini et al 2007).…”

Transcription factor SmWRKY1 positively promote the biosynthesis of tanshinones inSalvia miltiorrhiza

“…A jasmonate- and salicin-inducible WRKY transcription factor from Withania somnifera named as WsWRKY1 could bind to W-box sequences in promoters of squalene synthase and squalene epoxidase genes in W. somnifera genes regarding triterpenoid biosynthesis such as phytosterol and withanolides (Singh et al, 2017). The WRKY transcription factor GLANDULAR TRICHOME-SPECIFIC WRKY l ( AaGSWl ) positively regulated the expression of AaCYP7lAVl and AaORA by conjunction to the W-box motifs in their promoters (Chen et al, 2017). However, lack of research on the function of WRKY TFs in S. miltiorrhiza especially in the regulation of tanshinone biosynthesis were reported.…”

“…Subsequently, much attention has been paid to identify and analyze WRKY genes from different model and crop plants, for instance Arabidopsis (Eulgem et al, 2000; Kalde et al, 2003; Wang et al, 2011), soybean ( Glycine max ) (Yin et al, 2013), tobacco (Yoda et al, 2002), rice ( Oryza sativa ) (Wu et al, 2005) and so on. Meanwhile, WRKY has been isolated from some traditional herbal plants including Artemisia annua, Coptis japonica and Catharanthus roseus (Jiang et al, 2015; Chen et al, 2017; Kato et al, 2007; Suttipanta et al, 2011). The significant feature of WRKY transcription factor is their WRKY domain which is approximately 60-amino acid long with the highly conserved amino acid sequence WRKYGQK located at the N-terminal and a non-typical zinc-finger-like motif C2HC (C–X 7 –C–X 23 –H–X 1 –C) or C2H2(C–X 4–5 –C–X 22–23 –H–X 1 –H) at the C-terminus (Xu et al, 2004; Lu et al, 2015).…”

“…C. roseus WRKY1 (CrWRKY1) bound to the W-box elements of the tryptophan decarboxylase (TDC) promoter involved in terpenoid indole alkaloid (TIA) biosynthetic pathway and accumulated up to 3-fold higher levels of serpentine compared with control hairy roots (Suttipanta et al, 2011). The WRKY transcription factor GLANDULAR TRICHOME-SPECIFIC WRKY 1 ( AaGSW1 ) positively regulated the expression of AaCYP71AV1 and AaORA by conjunction to the W-box motifs in their promoters (Chen et al, 2017). Glycine max WRKY27 responsive to various abiotic stresses interacted with GmMYB174, and then cooperatively inhibited GmNAC29 expression, facilitating stress-tolerance of drought and cold in soybean (Wang et al, 2015).…”

A novel HD‐ZIP IV/MIXTA complex promotes glandular trichome initiation and cuticle development in Artemisia annua

“…The analyses were promoted using the yeast EGY48a strain as described previously and empty vectors were used as negative controls. The SD/‐Thr/‐Ura medium without and with X‐gal were used in the assay (Chen et al ., ).…”