AaCycTL Regulates Cuticle and Trichome Development in Arabidopsis and Artemisia annua L.

Artemisinin is an important drug for resistance against malaria. Artemisinin is derived from the glandular trichome of leaves, stems, or buds of the Chinese traditional herb Artemisia annua. Increasing the trichome density may enhance the artemisinin content of A. annua. It has been proven that cyclins are involved in the development of trichomes in tomato, Arabidopsis, and tobacco, but it is unclear whether the cyclins in A. annua influence trichome development. In this study, we showed that AaCycTL may regulate trichome development and affect the content of artemisinin. We cloned AaCycTL and found that it has the same expression files as the artemisinin biosynthesis pathway gene. We overexpressed AaCycTL in Arabidopsis, and the results indicated that AaCycTL changed the wax coverage on the surface of Arabidopsis leaves. The trichome density decreased as well. Using yeast two-hybrid and BiFC assays, we show that AaCycTL can interact with AaTAR1. Moreover, we overexpressed AaCycTL in A. annua and found that the expression of AaCycTL was increased to 82–195%. Changes in wax coverage on the surface of transgenic A. annua leaves or stems were found as well. We identified the expression of the artemisinin biosynthesis pathway genes ADS, CYP71AV1, and ALDH1 has decreased to 88–98%, 76–97%, and 82–97% in the AaCycTL-overexpressing A. annua lines, respectively. Furthermore, we found reduced the content of artemisinin. In agreement, overexpression of AaCycTL in A. annua or Arabidopsis may alter waxy loading, change the initiation of trichomes and downregulate trichome density. Altogether, AaCycTL mediates trichome development in A. annua and thus may serve to regulate trichome density and be used for artemisinin biosynthesis.

An R2R3-MYB Transcription Factor Positively Regulates the Glandular Secretory Trichome Initiation in Artemisia annua L.

Artemisia annua L. is known for its specific product “artemisinin” which is an active ingredient for curing malaria. Artemisinin is secreted and accumulated in the glandular secretory trichomes (GSTs) on A. annua leaves. Earlier studies have shown that increasing GST density is effective in increasing artemisinin content. However, the mechanism of GST initiation is not fully understood. To this end, we isolated and characterized an R2R3-MYB gene, AaMYB17, which is expressed specifically in the GSTs of shoot tips. Overexpression of AaMYB17 in A. annua increased GST density and enhanced the artemisinin content, whereas RNA interference of AaMYB17 resulted in the reduction of GST density and artemisinin content. Additionally, neither overexpression lines nor RNAi lines showed an abnormal phenotype in plant growth and the morphology of GSTs. Our study demonstrates that AaMYB17 is a positive regulator of GSTs’ initiation, without influencing the trichome morphology.

In silico identification of cis-Regulatory elements and their functional annotations from assembled ESTs of Artemisia annua L. involved in abiotic stress signaling

Salt stress is a common side-effect in plants impacted on plant growth, metabolism and productivity. A. annua L. is one of the well-known antimalarial plants, biosynthesized artemisinin in its leaf, now introduced in all-over the world. In this article, we have analyzed the A. annua L. ESTs under salt stress and predicted cis-regulatory elements, roles in abiotic stress signaling. Further, the predicted abiotic stress responsive factors were analyzed in order to their function annotations as compare to the genome of Arabidopsis thaliana. 11 EST-contigs assembled from 127 were 29 signals elements were identified by CAP3 program. In order to evaluate accuracy of the identified factors, gene ontology functions were performed. GOBP analysis enriched the genes (85.71%) as the response to abiotic signaling. The co-expression analysis was revealed by gene investigators and String 10.0, these factors-oriented genes had at least 0.40 correlations and 0.7 mutual connection. In projected PPI network, the recognized factors belong to plant hormone signaling and diterpene pathways. These factors (ABF1, APX CCC1, CPK6, JAZ1, MYC2) introduced as candidate genes responsive factors could be overexpressed in A. annua L. plants either alone or in a shuttle may led the good metabolism and higher artemisinin content.

In vitro reduction of Plasmodium falciparum gametocytes by Artemisia spp. tea infusions

In this study, we showed in vitro evidence that supports the efficacy of A. annua and A. afra tea infusions used in a 2015 clinical trial not only for clearing asexual Plasmodium falciparum parasites, but also for eliminating sexual gametocytes. P. falciparum NF54 was grown in vitro, synchronized, and induced to form gametocytes using N-acetylglucosamine. Cultures during asexual, early, and late stage gametogenesis were treated with artemisinin, methylene blue, and Artemisia annua and A. afra tea infusions (5g DW/L) using cultivars that contained 0-283 μM artemisinin. Asexual parasitemia and gametocytemia were analyzed microscopically. Gametocyte morphology was also scored. Markers of early (PfGEXP5) and late stage (Pfs25) gametocyte gene expression were also measured using RT-qPCR. Both A. annua and A. afra tea infusions reduced gametocytemia in vitro, and the effect was mainly artemisinin dependent. Expression levels of both marker genes were reduced with the effect mainly attributed to artemisinin content of the our tested Artemisia cultivars. Tea infusions of both species also inhibited asexual parasitemia and although mainly artemisinin dependent, there was a weak antiparasitic effect from artemisinin-deficient A. afra. These results showed that A. annua and to a lesser extent, A. afra, inhibited parasitemia and gametogenesis in vitro, and results are consistent with earlier observed clinical results.