Reproductive Development Modulates Gene Expression and Metabolite Levels with Possible Feedback Inhibition of Artemisinin in Artemisia annua        

Abstract

The relationship between the transition to budding and flowering in Artemisia annua and the production of the antimalarial sesquiterpene, artemisinin (AN), the dynamics of artemisinic metabolite changes, AN-related transcriptional changes, and plant and trichome developmental changes were measured. Maximum production of AN occurs during full flower stage within floral tissues, but that changes in the leafy bracts and nonbolt leaves as the plant shifts from budding to full flower. Expression levels of early pathway genes known to be involved in isopentenyl diphosphate and farnesyl diphosphate biosynthesis leading to AN were not immediately positively correlated with either AN or its precursors. However, we found that the later AN pathway genes, amorpha-4,11-diene synthase (ADS) and the cytochrome P450, CYP71AV1 (CYP), were more highly correlated with AN's immediate precursor, dihydroartemisinic acid, within all leaf tissues tested. In addition, leaf trichome formation throughout the developmental phases of the plant also appears to be more complex than originally thought. Trichome changes correlated closely with the levels of AN but not its precursors. Differences were observed in trichome densities that are dependent both on developmental stage (vegetative, budding, and flowering) and on position (upper and lower leaf tissue). AN levels declined significantly as plants matured, as did ADS and CYP transcripts. Spraying leaves with AN or artemisinic acid inhibited CYP transcription; artemisinic acid also inhibited ADS transcription. These data allow us to present a novel model for the differential control of AN biosynthesis as it relates to developmental stage and trichome maturation and collapse.

Time-course analysis of the artemisinin biosynthesis, and expression of genes coding for artemisinin pathway enzymes, in response to exogenous salicylic and gibberellic acids

“…2 and 3). Several reports have shown that artemisinin has a phytotoxic effect on Artemisia plants and there is a feedback control on artemisinin production (Arsenault et al, 2010a(Arsenault et al, , 2010bZare Mehrjerdi et al, 2013), which could be one of the explanations for the observed down-regulation at 72 and 168 h.…”

An ecological implication of glandular trichome-sequestered artemisinin: as a sink of biotic/abiotic stress-triggered singlet oxygen

“…When AaWRKY1 was transferred into A. annua, artemisinin biosynthesis was found to be greatly enhanced (Ma et al 2009;Han et al 2014). It was also know that the changes of glandular trichomes are closely correlated with artemisinin levels, and the densities of glandular trichomes are dependent on the developmental stages and organ positions (Arsenault et al 2010).…”

“…Another possibility could also come from a difference of artemisinin content in developing leaves. Because it was observed that the maximum artemisinin production occurs by the fully flowering stage within floral tissues, but it can alters in the leafy bracts and non-bolt leaves when the development of plants shifts from budding to fully flowering (Arsenault et al 2010). Where is artemisinin synthesized and sequestered?…”

Sub-Cloning of Genes Encodingcythochrome P450 Monooxygenase (Cyp71avi) Intoexpression Vector in Escherichia Coli

“…CYP71AVI belongs to the cytochrome P450 family. It is a multifunctional sesquiterpene oxidase with a key role in the biosynthesis of sesquiterpene lactone artemisinin which involves the conversion of amorpha-4,11-diene to artemisinic acid [7][8][9][10]. Optimization gene encoding CYP71AVI has been conducted to make its expression more optimum in E. coli.…”