Effect of roots on artemisinin and flavonoid production in shoots of Artemisia annua.

Wang, Sibo

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Effect of roots on artemisinin and flavonoid production in shoots of Artemisia annua.

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Artemisinin is a potent antimalarial sesquiterpene lactone produced and stored in the glandular trichomes (GLTs) of Artemisia annua. Although they produce no artemisinin, nor any of the precursor compounds, A. annua roots appear to have a regulatory effect on production of the terpene in leaves. However, more information is needed to define the role of the roots in artemisinin production in the plant. Grafting among three cultivars was used to measure phenotypic responses: SAM, and #15 cultivars both have GLTs, but produce artemisinin at 1.49% and 0.57% DW, respectively; GLS cultivar produces neither GLTs nor artemisinin. Compared to ungrafted plants, all self-grafts, e.g. SAM/SAM (scion/rootstock), increased scion artemisinin probably from grafting stress. SAM/#15 grafts yielded less artemisinin than SAM/SAM, but more than either #15/#15 or ungrafted #15 and SAM suggesting rootstock inhibition of the scion. SAM/SAM also had more artemisinin than #15/SAM, which was also greater than either #15/#15 or ungrafted #15 and SAM. The #15/SAM graft also produced more artemisinin than SAM/#15, and with the other grafting results suggested that SAM roots were stimulating artemisinin production in the #15 scion. There was no appearance of either GLTs or artemisinin when GLS scions were grafted to SAM indicating that GLTs had to be present to receive putative signals from SAM rootstocks. Furthermore, artemisinic acid and arteannuin B were only present in SAM scions and not scions of #15 suggesting a block in one of the side pathways of artemisinin biosynthesis. Other artemisinic metabolites, total flavonoids, and GLTs numbers were also measured. The various phenotypes were analyzed several months after grafting indicating a persistent change and suggesting a possible epigenetic alteration of the scion. This study will provide fundamental information regarding the role that roots play in the production of artemisinin in the shoots of A. annua.

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