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.
Highlights
Malaria is a parasite infection and nearly half of the population in the world is under the risk of malaria, especially in the African region
We identified some transcription factor (TF) in light signaling pathway that can respond to MeJA, which would aid understanding of the potential transcriptional regulation mechanisms of the increase of the artemisinin biosynthesis by jasmonic acid (JA) under the light in A. annua
After analyzing differential expression profile, we found that 284 TFs were down-regulated in the dark treatment (Dark) relative to Light and 96 TFs up-regulated in the Light-MeJA-4h relative to Light (Figure 8)
Summary
Malaria is a parasite infection and nearly half of the population in the world is under the risk of malaria, especially in the African region. An estimated 212 million new cases of malaria and 429,000 deaths worldwide were caused in 2015 alone according to the Malaria World Report 2016 by World Health Organization (WHO). Artemisinin is a sesquiterpene lactone endoperoxide (isolated from a traditional Chinese medicinal plant Artemisia annua) and artemisinin-based combination therapies (ACTs) are recommended as the best treatment of malaria by the WHO (White, 2008). The discoveries concerning artemisinin against malaria were awarded the 2015 Nobel Prize in Physiology or Medicine. It is viable to produce semi-synthetic artemisinin via artemisinic acid (the immediate precursor of artemisinin) in yeast (Ro et al, 2006; Paddon et al, 2013), the A. annua plants remain the natural and main source of artemisinin. To improve the content of artemisinin in plants, it is necessary and urgent to study the transcriptional regulation mechanisms of artemisinin biosynthesis
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