Molecular insights into AabZIP1-mediated regulation on artemisinin biosynthesis and drought tolerance in Artemisia annua

Artemisia annua is the main natural source of artemisinin production. In A. annua, extended drought stress severely reduces its biomass and artemisinin production while short-term water-withholding or abscisic acid (ABA) treatment can increase artemisinin biosynthesis. ABA-responsive transcription factor AabZIP1 and JA signaling AaMYC2 have been shown in separate studies to promote artemisinin production by targeting several artemisinin biosynthesis genes. Here, we found AabZIP1 promote the expression of multiple artemisinin biosynthesis genes including AaDBR2 and AaALDH1, which AabZIP1 does not directly activate. Subsequently, it was found that AabZIP1 up-regulates AaMYC2 expression through direct binding to its promoter, and that AaMYC2 binds to the promoter of AaALDH1 to activate its transcription. In addition, AabZIP1 directly transactivates wax biosynthesis genes AaCER1 and AaCYP86A1. The biosynthesis of artemisinin and cuticular wax and the tolerance of drought stress were significantly increased by AabZIP1 overexpression, whereas they were significantly decreased in RNAi-AabZIP1 plants. Collectively, we have uncovered the AabZIP1-AaMYC2 transcriptional module as a point of cross-talk between ABA and JA signaling in artemisinin biosynthesis, which may have general implications. We have also identified AabZIP1 as a promising candidate gene for the development of A. annua plants with high artemisinin content and drought tolerance in metabolic engineering breeding.

Transcriptome Analysis of Artemisinin Biosynthetic Genes / 广州中医药大学学报

Objective To investigate the expression patterns of artemisinin biosynthetic genes in Artemisia annua L.during the development stage and in different tissues,and to explore the mechanism of spatial and temporal modulators for artmisinin production.Methods The transcriptional profiles of artemisinin biosynthetic genes in the capital and cooperative pathways were quantitatively assayed by real time fluorescence quantitative-polymerase chain reaction(RTFQ-PCR) in different tissues of roots,stems,leaves and flowers,and in leaf-flourishing,pre-floral,and post-floral periods.Results The expression levels of the tested genes were extremely low in June,raised in July,and reached their peak values in August(before flowering),but dropped gradually in September(after blooming).In August,the transcription levels of the tested genes increased by 3 to 15 times compared to the lowestlevels.In particular,ADS and CYP71AV1 mRNA levels had the great elevation,which were 12 and 15 times as much as those in June.During the flowering period,the artemisinin biosynthetic genes mRNA expression was detectable in roots,stems,leaves and flowers,and the expression levels had no obvious difference except that ADS mRNA level in leaves was 2 times higher than that in other tissues(P