Genetics and metabolic responses of Artemisia annua L to the lake of phosphorus under the sparingly soluble phosphorus fertilizer: evidence from transcriptomics analysis.

The medicinal herb Artemisia annua L. is prized for its capacity to generate artemisinin, which is used to cure malaria. Potentially influencing the biomass and secondary metabolite synthesis of A. annua is plant nutrition, particularly phosphorus (P). However, most soil P exist as insoluble inorganic and organic phosphates, which results to low P availability limiting plant growth and development. Although plants have developed several adaptation strategies to low P levels, genetics and metabolic responses to P status remain largely unknown. In a controlled greenhouse experiment, the sparingly soluble P form, hydroxyapatite (Ca5OH(PO4)3/CaP) was used to simulate calcareous soils with low P availability. In contrast, the soluble P form KH2PO4/KP was used as a control. A. annua's morphological traits, growth, and artemisinin concentration were determined, and RNA sequencing was used to identify the differentially expressed genes (DEGs) under two different P forms. Total biomass, plant height, leaf number, and stem diameter, as well as leaf area, decreased by 64.83%, 27.49%, 30.47%, 38.70%, and 54.64% in CaP compared to KP; however, LC-MS tests showed an outstanding 37.97% rise in artemisinin content per unit biomass in CaP contrary to KP. Transcriptome analysis showed 2015 DEGs (1084 up-regulated and 931 down-regulated) between two P forms, including 39 transcription factor (TF) families. Further analysis showed that DEGs were mainly enriched in carbohydrate metabolism, secondary metabolites biosynthesis, enzyme catalytic activity, signal transduction, and so on, such as tricarboxylic acid (TCA) cycle, glycolysis, starch and sucrose metabolism, flavonoid biosynthesis, P metabolism, and plant hormone signal transduction. Meanwhile, several artemisinin biosynthesis genes were up-regulated, including DXS, GPPS, GGPS, MVD, and ALDH, potentially increasing artemisinin accumulation. Furthermore, 21 TF families, including WRKY, MYB, bHLH, and ERF, were up-regulated in reaction to CaP, confirming their importance in P absorption, internal P cycling, and artemisinin biosynthesis regulation. Our results will enable us to comprehend how low P availability impacts the parallel transcriptional control of plant development, growth, and artemisinin production in A. annua. This study could lay the groundwork for future research into the molecular mechanisms underlying A. annua's low P adaptation.

Graphene enhances artemisinin production in the traditional medicinal plant Artemisia annua via dynamic physiological processes and miRNA regulation.

We investigated the effects of graphene on the model herb Artemisia annua, which is renowned for producing artemisinin, a widely used pharmacological compound. Seedling growth and biomass were promoted when A. annua was cultivated with low concentrations of graphene, an effect which was attributed to a 1.4-fold increase in nitrogen uptake, a 15%-22% increase in chlorophyll fluorescence, and greater abundance of carbon cycling-related bacteria. Exposure to 10 or 20 mg/L graphene resulted in a âˆ¼60% increase in H2O2, and graphene could act as a catalyst accelerator, leading to a 9-fold increase in catalase (CAT) activity in vitro and thereby maintaining reactive oxygen species (ROS) homeostasis. Importantly, graphene exposure led to an 80% increase in the density of glandular secreting trichomes (GSTs), in which artemisinin is biosynthesized and stored. This contributed to a 5% increase in artemisinin content in mature leaves. Interestingly, expression of miR828 was reduced by both graphene and H2O2 treatments, resulting in induction of its target gene AaMYB17, a positive regulator of GST initiation. Subsequent molecular and genetic assays showed that graphene-induced H2O2 inhibits micro-RNA (miRNA) biogenesis through Dicers and regulates the miR828-AaMYB17 module, thus affecting GST density. Our results suggest that graphene may contribute to yield improvement in A. annua via dynamic physiological processes together with miRNA regulation, and it may thus represent a new cultivation strategy for increasing yield capacity through nanobiotechnology.

Bio Prospecting of Endophytes and PGPRs in Artemisinin Production for the Socio-economic Advancement.

The growing demand for Artemisia annua plants in healthcare, food, and pharmaceutical industries has led to increased cultivation efforts to extract a vital compound, Artemisinin. The efficacy of Artemisinin as a potent drug against malaria disease is well established but its limited natural abundance. However, the common practice of using chemical fertilizers for maximum yield has adverse effects on plant growth, development, and the quality of phytochemicals. To address these issues, the review discusses the alternative approach of harnessing beneficial rhizosphere microbiota, particularly plant growth-promoting rhizobacteria (PGPR). Microbes hold substantial biotechnological potential for augmenting medicinal plant production, offering an environmentally friendly and cost-effective means to enhance medicinal plant production. This review article aims to identify a suitable endophytic population capable of enabling Artemisia sp. to thrive amidst abiotic stress while simultaneously enhancing Artemisinin production, thereby broadening its availability to a larger population. Furthermore, by subjecting endophytes to diverse combinations of harsh conditions, this review sheds light on the modulation of essential artemisinin biosynthesis pathway genes, both up regulated and down regulated. The collective findings suggest that through the in vitro engineering of endophytic communities and their in vivo application to Artemisia plants cultivated in tribal population fields, artemisinin production can be significantly augmented. The overall aim of this review to explore the potential of harnessing microbial communities, their functions, and services to enhance the cultivation of medicinal plants. It outlines a promising path toward bolstering artemisinin production, which holds immense promise in the fight against malaria.

Chromatin architecture of two different strains of Artemisia annua reveals the alterations in interaction and gene expression.

MAIN CONCLUSION: The hierarchical architecture of chromatins affects the gene expression level of glandular secreting trichomes and the artemisinin biosynthetic pathway-related genes, consequently bringing on huge differences in the content of artemisinin and its derivatives of A. annua. The plant of traditional Chinese medicine "Qinghao" is called Artemisia annua L. in Chinese Pharmacopoeia. High content and the total amount of artemisinin is the main goal of A. annua breeding, nevertheless, the change of chromatin organization during the artemisinin synthesis process has not been discovered yet. This study intended to find the roles of chromatin structure in the production of artemisinin through bioinformatics and experimental validation. Chromosome conformation capture analysis was used to scrutinize the interactions among chromosomes and categorize various scales of chromatin during artemisinin synthesis in A. annua. To confirm the effect of the changes in chromatin structure, Hi-C and RNA-sequencing were performed on two different strains to find the correlation between chromatin structure and gene expression levels on artemisinin synthesis progress and regulation. Our results revealed that the frequency of intra-chromosomal interactions was higher in the inter-chromosomal interactions between the root and leaves on a high artemisinin production strain (HAP) compared to a low artemisinin production strain (LAP). We found that compartmental transition was connected with interactions among different chromatins. Interestingly, glandular secreting trichomes (GSTs) and the artemisinin biosynthetic pathway (ABP) related genes were enriched in the areas which have the compartmental transition, reflecting the regulation of artemisinin synthesis. Topologically associated domain boundaries were associated with various distributions of genes and expression levels. Genes associated with ABP and GST in the adjacent loop were highly expressed, suggesting that epigenetic regulation plays an important role during artemisinin synthesis and glandular secreting trichomes production process. Chromatin structure could show an important status in the mechanisms of artemisinin synthesis process in A. annua.

Developing population identification tool based on polymorphism of rDNA for traditional Chinese medicine: Artemisia annua L.

BACKGROUND: Artemisia annua, a well-known traditional Chinese medicine, is the main source for production of artemisinin, an anti-malaria drug. A. annua is distributed globally, with great diversity of morphological characteristics and artemisinin contents. Diverse traits among A. annua populations impeded the stable production of artemisinin, which needs an efficient tool to identify strains and assess population genetic homogeneity. PURPOSE: In this study, ribosomal DNA (rDNA), were characterized for A. annua for strains identification and population genetic homogeneity assessment. METHODS: The ribosomal RNA (rRNA) genes were identified using cmscan and assembled using rDNA unit of LQ-9 as a reference. rDNA among Asteraceae species were compared performing with 45S rDNA. The rDNA copy number was calculated based on sequencing depth. The polymorphisms of rDNA sequences were identified with bam-readcount, and confirmed by Sanger sequencing and restriction enzyme experiment. The ITS2 amplicon sequencing was used to verify the stability of ITS2 haplotype analysis. RESULTS: Different from other Asteraceae species, 45S and 5S linked-type rDNA was only found in Artemisia genus. Rich polymorphisms of copy number and sequence of rDNA were identified in A. annua population. The haplotype composition of internal transcribed spacer 2 (ITS2) region which had moderate sequence polymorphism and relative short size was significantly different among A. annua strains. A population discrimination method was developed based on ITS2 haplotype analysis with high-throughput sequencing. CONCLUSION: This study provides comprehensive characteristics of rDNA and suggests that ITS2 haplotype analysis is ideal tool for A. annua strain identification and population genetic homogeneity assessment.

RNA sequencing in Artemisia annua L explored the genetic and metabolic responses to hardly soluble aluminum phosphate treatment.

Artemisia annua L. is a medicinal plant valued for its ability to produce artemisinin, a molecule used to treat malaria. Plant nutrients, especially phosphorus (P), can potentially influence plant biomass and secondary metabolite production. Our work aimed to explore the genetic and metabolic response of A. annua to hardly soluble aluminum phosphate (AlPO4, AlP), using soluble monopotassium phosphate (KH2PO4, KP) as a control. Liquid chromatography-mass spectrometry (LC-MS) was used to analyze artemisinin. RNA sequencing, gene ontology (GO), and the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were applied to analyze the differentially expressed genes (DEGs) under poor P conditions. Results showed a significant reduction in plant growth parameters, such as plant height, stem diameter, number of leaves, leaf areas, and total biomass of A. annua. Conversely, LC-MS analysis revealed a significant increase in artemisinin concentration under the AlP compared to the KP. Transcriptome analysis revealed 762 differentially expressed genes (DEGs) between the AlP and the KP. GH3, SAUR, CRE1, and PYL, all involved in plant hormone signal transduction, showed differential expression. Furthermore, despite the downregulation of HMGR in the artemisinin biosynthesis pathway, the majority of genes (ACAT, FPS, CYP71AV1, and ALDH1) were upregulated, resulting in increased artemisinin accumulation in the AlP. In addition, 12 transcription factors, including GATA and MYB, were upregulated in response to AlP, confirming their importance in regulating artemisinin biosynthesis. Overall, our findings could contribute to a better understanding the parallel transcriptional regulation of plant hormone transduction and artemisinin biosynthesis in A. annua L. in response to hardly soluble phosphorus fertilizer.

Genome-wide identification and characterisation of bHLH transcription factors in Artemisia annua.

BACKGROUND: A. annua (also named Artemisia annua, sweet wormwood) is the main source of the anti-malarial drug artemisinin, which is synthesised and stored in its trichomes. Members of the basic Helix-Loop-Helix (bHLH) family of transcription factors (TFs) have been implicated in artemisinin biosynthesis in A. annua and in trichome development in other plant species. RESULTS: Here, we have systematically identified and characterised 226 putative bHLH TFs in A. annua. All of the proteins contain a HLH domain, 213 of which also contain the basic motif that mediates DNA binding of HLH dimers. Of these, 22 also contained a Myc domain that permits dimerisation with other families of TFs; only two proteins lacking the basic motif contained a Myc domain. Highly conserved GO annotations reflected the transcriptional regulatory role of the identified TFs, and suggested conserved roles in biological processes such as iron homeostasis, and guard cell and endosperm development. Expression analysis revealed that three genes (AabHLH80, AabHLH96, and AaMyc-bHLH3) exhibited spatiotemporal expression patterns similar to genes encoding key enzymes in artemisinin synthesis. CONCLUSIONS: This comprehensive analysis of bHLH TFs provides a new resource to direct further analysis into key molecular mechanisms underlying and regulating artemisinin biosynthesis and trichome development, as well as other biological processes, in the key medicinal plant A. annua.

Jasmonate- and abscisic acid-activated AaGSW1-AaTCP15/AaORA transcriptional cascade promotes artemisinin biosynthesis in Artemisia annua.

Artemisinin, a sesquiterpene lactone widely used in malaria treatment, was discovered in the medicinal plant Artemisia annua. The biosynthesis of artemisinin is efficiently regulated by jasmonate (JA) and abscisic acid (ABA) via regulatory factors. However, the mechanisms linking JA and ABA signalling with artemisinin biosynthesis through an associated regulatory network of downstream transcription factors (TFs) remain enigmatic. Here we report AaTCP15, a JA and ABA dual-responsive teosinte branched1/cycloidea/proliferating (TCP) TF, which is essential for JA and ABA-induced artemisinin biosynthesis by directly binding to and activating the promoters of DBR2 and ALDH1, two genes encoding enzymes for artemisinin biosynthesis. Furthermore, AaORA, another positive regulator of artemisinin biosynthesis responds to JA and ABA, interacts with and enhances the transactivation activity of AaTCP15 and simultaneously activates AaTCP15 transcripts. Hence, they form an AaORA-AaTCP15 module to synergistically activate DBR2, a crucial gene for artemisinin biosynthesis. More importantly, AaTCP15 expression is activated by the multiple reported JA and ABA-responsive TFs that promote artemisinin biosynthesis. Among them, AaGSW1 acts at the nexus of JA and ABA signalling to activate the artemisinin biosynthetic pathway and directly binds to and activates the AaTCP15 promoter apart from the AaORA promoter, which further facilitates formation of the AaGSW1-AaTCP15/AaORA regulatory module to integrate JA and ABA-mediated artemisinin biosynthesis. Our results establish a multilayer regulatory network of the AaGSW1-AaTCP15/AaORA module to regulate artemisinin biosynthesis through JA and ABA signalling, and provide an interesting avenue for future research exploring the special transcriptional regulation module of TCP genes associated with specialized metabolites in plants.

Overexpression of blue light receptor AaCRY1 improves artemisinin content in Artemisia annua L. .

Artemisinin, an effective antimalarial compound, is isolated from the medicinal plant Artemisia annua L. However, because of the low content of artemisinin in A. annua, the demand of artemisinin exceeds supply. Previous studies show that the artemisinin biosynthesis is promoted by light in A. annua. Cryptochrome1 (CRY1) is involved in many processes in the light response. In this study, AaCRY1 was cloned from A. annua. Overexpressing AaCRY1 in Arabidopsis thaliana cry1 mutant resulted in blue-light-dependent short hypocotyl phenotype and short coleoptile under blue light. Yeast two-hybrid and subcellular colocalization showed that AaCRY1 interacted with AtCOP1 (ubiquitin E3 ligase CONSTITUTIVE PHOTOMORPHOGENIC1). Overexpression of AaCRY1 in transgenic A. annua increased the artemisinin content. When AaCRY1 was overexpressed in A. annua driven by the CYP71AV1 (cytochrome P450 dependent amorpha-4,11-diene 12-hydroxylase) promoter, the artemisinin content was 1.6 times higher than that of the control. Furthermore, we expressed the C terminal of AaCRY1(CCT) involved a GUS-CCT fusion protein in A. annua. The results showed that the artemisinin content was increased to 1.7- to 2.4-fold in GUS-CCT transgenic A. annua plants. These results demonstrate that overexpression of GUS-CCT is an effective strategy to increase artemisinin production in A. annua.

The ameliorative effects of exogenous inoculation of Piriformospora indica on molecular, biochemical and physiological parameters of Artemisia annua L. under arsenic stress condition.

Aim of the current study was to investigate the effect of exogenously inoculated root endophytic fungus, Piriformospora indica, on molecular, biochemical, morphological and physiological parameters of Artemisia annua L. treated with different concentrations (0, 50, 100 and 150 µmol/L) of arsenic (As) stress. As was significantly accumulated in the roots than shoots of P. indica-inoculated plants. As accumulation and immobilization in the roots is directly associated with the successful fungal colonization that restricts most of As as compared to the aerial parts. A total of 4.1, 11.2 and 25.6 mg/kg dry weight of As was accumulated in the roots of inoculated plants supplemented with 50, 100 and 150 µmol/L of As, respectively as shown by atomic absorption spectroscopy. P. indica showed significant tolerance in vitro to As toxicity even at high concentration. Furthermore, flavonoids, artemisinin and overall biomass were significantly increased in inoculated-stressed plants. Superoxide dismutase and peroxidase activities were increased 1.6 and 1.2 fold, respectively under 150 µmol/L stress in P. indica-colonized plants. Similar trend was followed by ascorbate peroxidase, catalase and glutathione reductase. Like that, phenolic acid and phenolic compounds showed a significant increase in colonized plants as compared to their respective control/un-colonize stressed plants. The real-time PCR revealed that transcriptional levels of artemisinin biosynthesis genes, isoprenoids, terpenes, flavonoids biosynthetic pathway genes and signal molecules were prominently enhanced in inoculated stressed plants than un-inoculated stressed plants.

AaCOI1, Encoding a CORONATINE INSENSITIVE 1-Like Protein of Artemisia annua L., Is Involved in Development, Defense, and Anthocyanin Synthesis.

Artemisia annua is an important medicinal plant producing the majority of the antimalarial compound artemisinin. Jasmonates are potent inducers of artemisinin accumulation in Artemisisa annua plants. As the receptor of jasmonates, the F-box protein COI1 is critical to the JA signaling required for plant development, defense, and metabolic homeostasis. AaCOI1 from Artemisia annua, homologous to Arabidopsis AtCOI1, encodes a F-box protein located in the nuclei. Expressional profiles of the AaCOI1 in the root, stem, leaves, and inflorescence was investigated. The mRNA abundance of AaCOI1 was the highest in inflorescence, followed by in the leaves. Upon mechanical wounding or MeJA treatment, expression of AaCOI1 was upregulated after 6 h. When ectopically expressed, driven by the native promoter from Arabidopsis thaliana, AaCOI1 could partially complement the JA sensitivity and defense responses, but fully complemented the fertility, and the JA-induced anthocyanin accumulation in a coi1-16 loss-of-function mutant. Our study identifies the paralog of AtCOI1 in Artemisia annua, and revealed its implications in development, hormone signaling, defense, and metabolism. The results provide insight into JA perception in Artemisia annua, and pave the way for novel molecular breeding strategies in the canonical herbs to manipulate the anabolism of pharmaceutic compounds on the phytohormonal level.

[Breeding of new Artemisia annua variety "Kehao No.1"].

As a natural plant source of artemisinin,a first-line drug against malaria,Artemisia annua directly affects the extraction process of artemisinin and the source of artemisinin. At present,traditional breeding methods combined with tissue culture are often used to breed high-yield artemisinin-containing new varieties of A. annua. However,the breeding method has the disadvantages of low efficiency and continuous selection. In this study,heavy ion beam irradiation technology was used to observe the specific germplasm resources of A. annua,and the morphological characteristics,agronomic traits and artemisinin content were used as indicators to observe the selection materials and materials. The cultivated new varieties were compared with trials and regional trials. In addition,the new variety of A. annua was identified by SRAP molecular marker technology. The results showed that the new variety of A. annua, " Kehao No.1",had an average yield of 235. 0 kg of dry leaf per mu,which was more than 20% higher than that of the control. Especially,the average artemisinin content was 2. 0%,which was 45% higher than that of the control,and the " Kehao No.1" has high anti-white powder disease,high-yield and high-quality new varieties. Therefore,mutagenic breeding of heavy ion beam irradiation can significantly improve the yield and artemisinin content of the " Kehao No. 1" and it has a good promotion value.

Breeding of new Artemisia annua variety "Kehao No.1" / 中国中药杂志

As a natural plant source of artemisinin,a first-line drug against malaria,Artemisia annua directly affects the extraction process of artemisinin and the source of artemisinin. At present,traditional breeding methods combined with tissue culture are often used to breed high-yield artemisinin-containing new varieties of A. annua. However,the breeding method has the disadvantages of low efficiency and continuous selection. In this study,heavy ion beam irradiation technology was used to observe the specific germplasm resources of A. annua,and the morphological characteristics,agronomic traits and artemisinin content were used as indicators to observe the selection materials and materials. The cultivated new varieties were compared with trials and regional trials. In addition,the new variety of A. annua was identified by SRAP molecular marker technology. The results showed that the new variety of A. annua, " Kehao No.1",had an average yield of 235. 0 kg of dry leaf per mu,which was more than 20% higher than that of the control. Especially,the average artemisinin content was 2. 0%,which was 45% higher than that of the control,and the " Kehao No.1" has high anti-white powder disease,high-yield and high-quality new varieties. Therefore,mutagenic breeding of heavy ion beam irradiation can significantly improve the yield and artemisinin content of the " Kehao No. 1" and it has a good promotion value.

[Statues and research strategy of molecular breeding in Artemisia annua].

Malaria is one of the three most deadly diseases in the world. Artemisinin is the first line and effective drug for treating malaria, and only can be extracted from Artemisia annua. Therefore, it is of great significance to cultivate new varieties of A. annua with high artemisinin content. Based on the germplasm bank and the whole genome, transcriptome and genetic map, the authors can explore high-quality genes, stress-resistant genes and genetic markers which have been used for rapid breeding of superior varieties of A. annua. So these methods of molecular breeding will become the main breeding direction of A. annua in the future. The breeding times of new varieties of A. annua can be shortened with molecular breeding technology. Based on the genetic background and the current situation of molecular breeding of A. annua, the strategy and technical route of molecular breeding were discussed and worked out in this paper, which provided a guidance and scientific reference for molecular breeding of A. annua in the future.

[Prokaryotic expression， purification and crystallization of CYP71AV1, key enzyme in artemisinin biosynthesis].

Malaria is a worldwide epidemic that extensively endangers health of human beings. Before artemisinin was developed to treat with malaria, about 400 million person-time of malaria infections and at least 1 million deaths from malaria were reported in the world every year. Thus malaria has been listed as one of the world's three major death diseases by the WHO. The discovery of artemisinin by Chinese scientists created a novel therapy approach to treat with malaria effectively. Amorpha-4,11-diene oxidase is a plant cytochrome P450 enzymes, i.e. CYP71AV1, which catalyzes each of the three oxidation steps from amorpha-4,11-diene to form artemisinic acid, the intermediate of artemisinin. CYP71AV1 is the key enzyme in artemisinin biosynthesis. By constructing the prokaryotic expression vector pCWOri(+)-CYP71AV1, functional expression and purification of complementary CYP71AV1 were performed. The enzyme activity was monitored by CO differential spectrum assay and the heme-based activity analysis. The preliminary crystallization condition was obtained by crystallization screening. These studies provide basis for resolving the crystal structure of CYP71AV1 and for producing artemisinin in large scale through biosynthetic biology approach, and will provide references for over expression, purification and crystallization of other plant P450 enzymes.

Expression of key genes affecting artemisinin content in five Artemisia species.

Artemisinin, an effective anti-malarial drug is synthesized in the specialized 10-celled biseriate glandular trichomes of some Artemisia species. In order to have an insight into artemisinin biosynthesis in species other than A. annua, five species with different artemisinin contents were investigated for the expression of key genes that influence artemisinin content. The least relative expression of the examined terpene synthase genes accompanied with very low glandular trichome density (4 No. mm-2) and absence of artemisinin content in A. khorassanica (S2) underscored the vast metabolic capacity of glandular trichomes. A. deserti (S4) with artemisinin content of 5.13 mg g-1 DW had a very high expression of Aa-ALDH1 and Aa-CYP71AV1 and low expression of Aa-DBR2. It is possible to develop plants with high artemisinin synthesis ability by downregulating Aa-ORA in S4, which may result in the reduction of Aa-ALDH1 and Aa-CYP71AV1 genes expression and effectively change the metabolic flux to favor more of artemisinin production than artemisinic acid. Based on the results, the Aa-ABCG6 transporter may be involved in trichome development. S4 had high transcript levels and larger glandular trichomes (3.46 fold) than A. annua found in Iran (S1), which may be due to the presence of more 2C-DNA (3.48 fold) in S4 than S1.

[Molecular cloning and characterization of CMK from Artemisia annua].

Artemisinin is a preferred medicine in the treatment of malaria. In this study, AaCMK, a key gene involved in the upstream pathway of artemisinin biosynthesis, was cloned and characterized from Artemisia annua for the first time. The full-length cDNA of AaCMK was 1 462 bp and contained an ORF of 1 197 bp that encoded a 399-anomo-acid polypeptide. Tissue expression pattern analysis showed that AaCMK was expressed in leaves, flowers, roots and stems, but with higher expression level in glandular secretory trichomes. In addition, the expression of AaCMK was markedly increased after MeJA treatment. Subcellular localization showed that the protein encoded by AaCMK was localized in chloroplast. Overexpression of AaCMK in Arabidopsis increased the contents of chlorophyll a, chlorophyll b and carotenoids. These results suggest that AaCMK plays an important role in the biosynthesis of terpenoids in A. annua and this research provids a candidate gene that could be used for engineering the artemisinin biosynthesis.

The roles of AaMIXTA1 in regulating the initiation of glandular trichomes and cuticle biosynthesis in Artemisia annua.

The glandular secretory trichomes (GSTs) on Artemisia annua leaves have the capacity to secrete and store artemisinin, a compound which is the most effective treatment for uncomplicated malaria. An effective strategy to improve artemisinin content is therefore to increase the density of GSTs in A. annua. However, the formation mechanism of GSTs remains poorly understood. To explore the mechanisms of GST initiation in A. annua, we screened myeloblastosis (MYB) transcription factor genes from a GST transcriptome database and identified a MIXTA transcription factor, AaMIXTA1, which is expressed predominantly in the basal cells of GST in A. annua. Overexpression and repression of AaMIXTA1 resulted in an increase and decrease, respectively, in the number of GSTs as well as the artemisinin content in transgenic plants. Transcriptome analysis and cuticular lipid profiling showed that AaMIXTA1 is likely to be responsible for activating cuticle biosynthesis. In addition, dual-luciferase reporter assays further demonstrated that AaMIXTA1 could directly activate the expression of genes related to cuticle biosynthesis. Taken together, AaMIXTA1 regulated cuticle biosynthesis and prompted GST initiation without any abnormal impact on the morphological structure of the GSTs and so provides a new way to improve artemisinin content in this important medicinal plant.

Complete Chloroplast Genome Sequence and Phylogenetic Analysis of the Medicinal Plant Artemisia annua.

The complete chloroplast genome of Artemisia annua (Asteraceae), the primary source of artemisinin, was sequenced and analyzed. The A. annua cp genome is 150,995 bp, and harbors a pair of inverted repeat regions (IRa and IRb), of 24,850 bp each that separate large (LSC, 82,988 bp) and small (SSC, 18,267 bp) single-copy regions. Our annotation revealed that the A. annua cp genome contains 113 genes and 18 duplicated genes. The gene order in the SSC region of A. annua is inverted; this fact is consistent with the sequences of chloroplast genomes from three other Artemisia species. Fifteen (15) forward and seventeen (17) inverted repeats were detected in the genome. The existence of rich SSR loci in the genome suggests opportunities for future population genetics work on this anti-malarial medicinal plant. In A. annua cpDNA, the rps19 gene was found in the LSC region rather than the IR region, and the rps19 pseudogene was absent in the IR region. Sequence divergence analysis of five Asteraceae species indicated that the most highly divergent regions were found in the intergenic spacers, and that the differences between A. annua and A. fukudo were very slight. A phylogenetic analysis revealed a sister relationship between A. annua and A. fukudo. This study identified the unique characteristics of the A. annua cp genome. These results offer valuable information for future research on Artemisia species identification and for the selective breeding of A. annua with high pharmaceutical efficacy.