Transcriptome Analysis of Genes Associated with the Artemisinin Biosynthesis by Jasmonic Acid Treatment under the Light in Artemisia annua

Abstract

Artemisinin is a sesquiterpene lactone endoperoxide extracted from a traditional Chinese medicinal plant Artemisia annua. Artemisinin-based combination therapies (ACTs) are recommended as the best treatment of malaria by the World Health Organization (WHO). Both the phytohormone jasmonic acid (JA) and light promote artemisinin biosynthesis in A. annua. Interestingly, we found that the increase of artemisinin biosynthesis by JA was dependent on light. However, the relationship between the two signal pathways mediated by JA and light remains unclear. Here, we collected the A. annua seedlings of 24 h continuous light (Light), 24 h dark treatment (Dark), 4 h MeJA treatment under the continuous light conditions (Light-MeJA-4h) and 4 h MeJA treatment under the dark conditions (Dark-MeJA-4h) and performed the transcriptome sequencing using Illumina HiSeq 4000 System. A total of 266.7 million clean data were produced and assembled into 185,653 unigenes, with an average length of 537 bp. Among them, 59,490 unigenes were annotated and classified based on the public information. Differential expression analyses were performed between Light and Dark, Light and Light-MeJA-4h, Dark and Dark-MeJA-4h, Light-MeJA-4h, and Dark-MeJA-4h, respectively. Furthermore, transcription factor (TF) analysis revealed that 1588 TFs were identified and divided into 55 TF families, with 284 TFs down-regulated in the Dark relative to Light and 96 TFs up-regulated in the Light-MeJA-4h relative to Light. 8 TFs were selected as candidates for regulating the artemisinin biosynthesis and one of them was validated to be involved in artemisinin transcriptional regulation by Dual-Luciferase (Dual-LUC) assay. The transcriptome data shown in our study offered a comprehensive transcriptional expression pattern influenced by the MeJA and light in A. annua seedling, which will serve as a valuable resource for further studies on transcriptional regulation mechanisms underlying artemisinin biosynthesis.

Transcriptome Analyses Revealed the Ultraviolet B Irradiation and Phytohormone Gibberellins Coordinately Promoted the Accumulation of Artemisinin in Artemisia Annua L.

“…Gibberellins are important diterpenoid acid plant hormones that play roles in promoting the biosynthesis of artemisinin [29,49]. In addition, to phytohormones, it has also been found that light has an in uence on the accumulation of artemisinin [39].…”

“…It has been found that the activities of different hormones can be in uenced to varying degrees by light, and thus light and hormones may jointly regulate various processes in plants [21,[26][27][28]. For example, Hao et al [29] demonstrated the co-regulation of artemisinin biosynthetic pathway genes under light and jasmonic acid treatment, with the accumulation of artemisinin in response to jasmonic acid treatment being dependent on light, and identi ed eight transcription factors (TFs) as candidate genes regulating the cross-talk light and jasmonic acid signals in artemisinin biosynthesis. Along similar lines, we wished to determine whether ultraviolet B irradiation and phytohormone gibberellins could coordinately regulate the accumulation of artemisinin in A. annua.…”

Jasmonic acid‐responsive AabHLH1 positively regulates artemisinin biosynthesis in Artemisia annua

“…cDNA was synthesized from 1.0 µg of total RNA using PrimeScript TM RT Master Mix (Takara, Shiga, Japan). The transcript levels of AabHLH1 and artemisinin biosynthetic genes ( AaADS , AaCYP71AV1 , AaDBR2 , and AaALDH1 ) were analyzed by qRT‐PCR as described previously . SYBR Green qPCR Master Mix (Tiangen, Beijing, China) and a Roche Light Cycler 96 Real‐Time PCR System (Roche, Basel, Switzerland) were used for qRT‐PCR according to the manufacturer's instructions.…”

“…Three technical replicates were analyzed. Relative gene expression levels were determined by the 2 −ΔΔCt method and the A. annua Actin gene was used as an internal control . All primer sequences used are listed in Table .…”

“…It was reported that AabHLH1 was strongly induced by abscisic acid (ABA) treatment, and AabHLH1 could bind and activate the promoters of AaADS and AaCYP71AV1 . Through transcriptome analysis, we found that the AabHLH1 expression level was also increased under MeJA treatment . Thus, in this study, we investigated whether JA‐induced artemisinin biosynthesis was regulated by AabHLH1.…”