GSE159604
Transcriptome analysis of Artemisia annua L. seedlings under UV-B radiation
Purpose: UV-B radiation is a pivotal photomorphogenic signal and positively regulates plant growth and metabolite biosynthesis. In order to elucidate the transcriptional regulation mechanism underlying UV-B-induced artemisinin and flavonoid biosynthesis in Artemisia annua, the transcriptional response of A. annua leaves to UV-B radiation was analyzed using the Illumina transcriptome sequencing. Methods: For UV-B treatment, six-week-old A. annua seedlings growing under normal growth condition were supplemented with extra narrowband UV-B lamps (Philips TL20W/01RS; 1.5 µmol·m-2·s-1)(Yin et al. 2016). The most recently expanded leaf for each A. annua seedling was collected at 0, 2, 4 and 6 hours after exposure to UV-B radiation. Results: A total of 10706 differentially expressed genes including 533 transcription factors, were identified. Based on the expression trends of the differentially expressed factors as well as artemisinin and flavonoid biosynthesis genes, we speculated that transcription factors belonging to 6 clusters were most likely to be involved in the regulation of artemisinin and/or flavonoid biosynthesis. The regulatory relationship between transcription factors and artemisinin/flavonoid biosynthetic genes was further studied. Dual-LUC assays results showed that AaMYB6 is a positive regulator of AaLDOX, which belongs to flavonoid biosynthesis pathway. In addition, we identified a R2R3MYB transcription factor, AaMYB4 which positively mediated both artemisinin and flavonoid biosynthesis pathways by activating the expression of AaADS and AaDBR2 in artemisinin biosynthesis pathway and AaUFGT in flavonoid biosynthesis pathway. Conclusions: our findings provide fundamental knowledge for the further analysis of the parallel transcriptional regulation of artemisinin and flavonoid biosynthesis in A. annua L. under UV-B radiation. Overall design: Six-week-old A. annua seedlings growing under normal growth condition were supplemented with extra narrowband UV-B lamps (Philips TL20W/01RS; 1.5 µmol·m-2·s-1). The most recently expanded leaf for each A. annua seedling was collected at 0, 2, 4 and 6 hours after exposure to UV-B radiation.