WNT-inhibitory factor 1-mediated glycolysis protects photoreceptor cells in diabetic retinopathy.

BACKGROUND: In diabetic retinopathy (DR), hypoxia-inducible factor (HIF-1α) induces oxidative stress by upregulating glycolysis. This process leads to neurodegeneration, particularly photoreceptor cell damage, which further contributes to retinal microvascular deterioration. Further, the regulation of Wnt-inhibitory factor 1 (WIF1), a secreted Wnt signaling antagonist, has not been fully characterized in neurodegenerative eye diseases. We aimed to explore the impact of WIF1 on photoreceptor function within the context of DR. METHOD: Twelve-week-old C57BL/KsJ-db/db mice were intravitreally injected with WIF1 overexpression lentivirus. After 4 weeks, optical coherence tomography (OCT), transmission electron microscopy (TEM), H&E staining, and electroretinography (ERG) were used to assess the retinal tissue and function. The potential mechanism of action of WIF1 in photoreceptor cells was explored using single-cell RNA sequencing. Under high-glucose conditions, 661 W cells were used as an in vitro DR model. WIF1-mediated signaling pathway components were assessed using quantitative real-time PCR, immunostaining, and western blotting. RESULT: Typical diabetic manifestations were observed in db/db mice. Notably, the expression of WIF1 was decreased at the mRNA and protein levels. These pathological manifestations and visual function improved after WIF1 overexpression in db/db mice. TEM demonstrated that WIF1 restored damaged mitochondria, the Golgi apparatus, and photoreceptor outer segments. Moreover, ERG indicated the recovery of a-wave potential amplitude. Single-cell RNA sequencing and in vitro experiments suggested that WIF1 overexpression prevented the expression of glycolytic enzymes and lactate production by inhibiting the canonical Wnt signaling pathway, HIF-1α, and Glut1, thereby reducing retinal and cellular reactive oxygen species levels and maintaining 661 W cell viability. CONCLUSIONS: WIF1 exerts an inhibitory effect on the Wnt/ß-catenin-HIF-1α-Glut1 glycolytic pathway, thereby alleviating oxidative stress levels and mitigating pathological structural characteristics in retinal photoreceptor cells. This mechanism helps preserve the function of photoreceptor cells in DR and indicates that WIF1 holds promise as a potential therapeutic candidate for DR and other neurodegenerative ocular disorders.

AaMYB108 is the core factor integrating light and jasmonic acid signaling to regulate artemisinin biosynthesis in Artemisia annua.

Artemisinin, a sesquiterpene compound synthesized and stored in the glandular trichome of Artemisia annua leaves, has been used to treat malaria. Previous studies have shown that both light and jasmonic acid (JA) can promote the biosynthesis of artemisinin, and the promotion of artemisinin by JA is dependent on light. However, the specific molecular mechanism remains unclear. Here, we report a MYB transcription factor, AaMYB108, identified from transcriptome analysis of light and JA treatment, as a positive regulator of artemisinin biosynthesis in A. annua. AaMYB108 promotes artemisinin biosynthesis by interacting with a previously characterized positive regulator of artemisinin, AaGSW1. Then, we found that AaMYB108 interacted with AaCOP1 and AaJAZ8, respectively. The function of AaMYB108 was influenced by AaCOP1 and AaJAZ8. Through the treatment of AaMYB108 transgenic plants with light and JA, it was found that the promotion of artemisinin by light and JA depends on the presence of AaMYB108. Taken together, our results reveal the molecular mechanism of JA regulating artemisinin biosynthesis depending on light in A. annua. This study provides new insights into the integration of light and phytohormone signaling to regulate terpene biosynthesis in plants.

Multicellular immune dynamics implicate PIM1 as a potential therapeutic target for uveitis.

Uveitis is a severe autoimmune disease, and a common cause of blindness; however, its individual cellular dynamics and pathogenic mechanism remain poorly understood. Herein, by performing single-cell RNA sequencing (scRNA-seq) on experimental autoimmune uveitis (EAU), we identify disease-associated alterations in cell composition and transcriptional regulation as the disease progressed, as well as a disease-related molecule, PIM1. Inhibiting PIM1 reduces the Th17 cell proportion and increases the Treg cell proportion, likely due to regulation of PIM1 to the protein kinase B (AKT)/Forkhead box O1 (FOXO1) pathway. Moreover, inhibiting PIM1 reduces Th17 cell pathogenicity and reduces plasma cell differentiation. Importantly, the upregulation of PIM1 in CD4+ T cells and plasma cells is conserved in a human uveitis, Vogt-Koyanagi-Harada disease (VKH), and inhibition of PIM1 reduces CD4+ T and B cell expansion. Collectively, a dynamic immune cellular atlas during uveitis is developed and implicate that PIM1 may be a potential therapeutic target for VKH.

Systemic glucocorticoid-free therapy with adalimumab plus immunosuppressants versus conventional therapy in treatment-naïve Vogt-Koyanagi-Harada disease patients.

Background: High dose systemic glucocorticoid is the main therapy of treatment-naïve Vogt-Koyanagi-Harada (VKH) disease. However, series side effects induced by high dose systemic glucocorticoid frequently occur, which makes alternative therapy necessary for certain patients. This study sought to compare the efficacy and safety of systemic glucocorticoid-free (SGF) therapy with conventional therapy (CT) as an initial treatment for VKH patients. Methods: VKH patients who had not been systemically treated were enrolled. Patients were allocated into 2 therapeutic groups depending on their treatments. In CT group, patients received systemic glucocorticoid plus immunosuppressants (IS), and in SGF group, patients received adalimumab (ADA) plus IS. Patients received approximately 12 months treatment and visit monthly. The outcome parameters included the changes of best-corrected visual acuity (BCVA), intraocular inflammation (including anterior chamber cell grade and vitritis grade) and central macular thickness (CMT) (the change values define as the final-visit values subtracted from baseline counterparts). Other outcomes included the relapses times of ocular inflammation, adverse events (AEs), changes of optic nerve inflammation (ONI) and intraocular/extraocular manifestations. Results: A total of 30 patients (60 eyes) were included. with 19 patients (38 eyes) in CT group and 11 patients (22 eyes) in SGF group. After approximately 1 year of treatment, the improvements of BCVA were slight better in the SGF group (0.57±0.23) than in the CT group (0.40±0.26), (P=0.014). In both groups, the ocular inflammatory improvements in both groups were similar, with an improvement of AC cell grade of -1.5 (-2, -0.5) in CT group versus -1 (-2, -1) in SGF group (P=0.367); improvement of vitritis grade was 0 (-1.25, 0) in CT group and -1 (-1, -1) in SGF group (P=0.050). The improvement in CMT was similar in both groups, with -523.47±412.09 µm in CT group and -362.73±375.73 µm in SGF group (P=0.572). The mean number of relapses was 1 (0, 2) in the CT group and 0 (0, 2) in the SGF group (P=0.372). No severe AEs were observed in this study. Conclusions: SGF therapy is effective, safe, and well-tolerated in treatment-naïve VKH patients. SGF therapy seems to be a feasible option in patients with existing systemic diseases intolerant to glucocorticoid.

Single-cell RNA sequencing depicts the local cell landscape in thyroid-associated ophthalmopathy.

There is a specific reactivity and characteristic remodeling of the periocular tissue in thyroid-associated ophthalmopathy (TAO). However, local cell changes responsible for these pathological processes have not been sufficiently identified. Here, single-cell RNA sequencing is performed to characterize the transcriptional changes of cellular components in the orbital connective tissue in individuals with TAO. Our study shows that lipofibroblasts with RASD1 expression are highly involved in inflammation and adipogenesis during TAO. ACKR1+ endothelial cells and adipose tissue macrophages may engage in TAO pathogenesis. We find CD8+CD57+ cytotoxic T lymphocytes with the terminal differentiation phenotype to be another source of interferon-γ, a molecule actively engaging in TAO pathogenesis. Cell-cell communication analysis reveals increased activity of CXCL8/ACKR1 and TNFSF4/TNFRSF4 interactions in TAO. This study provides a comprehensive local cell landscape of TAO and may be valuable for future therapy investigation.

Insights gained from Single-Cell analysis of immune cells on Cyclosporine A treatment in autoimmune uveitis.

Cyclosporine A (CsA) is a widely known immunosuppressive agent that is clinically important in autoimmune diseases owing to its selective suppression of T lymphocytes. Although it has long been recognized to inhibit T cell responses by blocking calcineurin, the potential targets and specific downstream mechanisms remain elusive. Herein, we built a comprehensive single-cell transcriptomic landscape of immune cells in the blank, untreated experimental autoimmune uveitis (EAU), and CsA-treated EAU mice. CsA reversed EAU-associated changes in cell type composition, genomic expression, cell trajectory, and cell-cell communication. We found that CsA reverses the proportion change of disease-related immune cells; regulates several crucial pathogenic factors (eg. IL1r1, CD48, and Bhlhe40) in T helper 17 cells (Th17), the transcription factor Bhlhe40 was also rescued in T helper 1 cells (Th1); and may differentiate Tregs into a state of enhanced immunosuppression. In addition, we revealed the rescued impact of CsA on all immune cell types, especially on plasma B cells differentiation and immunoglobulin secretion. Furthermore, comparisons with glucocorticoids showed that CsA might have a more premium rescue effect involved in attenuating the pathogenicity of autoreactive T cells. Our work provides a comprehensive single-cell transcriptional atlas of immune cells under CsA therapy, providing advanced insights into the mechanisms underlying CsA and a reference for developing new therapeutic strategies for autoimmune diseases.

Basic Helix-Loop-Helix Transcription Factors AabHLH2 and AabHLH3 Function Antagonistically With AaMYC2 and Are Negative Regulators in Artemisinin Biosynthesis.

Plants have evolved sophisticated systems for regulating the biosynthesis of specialized phytochemicals. Artemisinin, which is a sesquiterpene lactone widely used in anti-malaria treatment, is produced by the Artemisia annua L. plant. However, the artemisinin content in A. annua is low and difficult to meet market demands. Studies have shown that artemisinin biosynthesis in A. annua has complex temporal and spatial specificity and is under tightly transcriptional regulation. However, the mechanism of transcriptional regulation of artemisinin biosynthesis remains unclear. In this study, we identified two MYC-type bHLH transcription factors (AabHLH2 and AabHLH3) as novel regulators of artemisinin biosynthesis. These bHLH TFs act as transcription repressors and function redundantly to negatively regulate artemisinin biosynthesis. Furthermore, AabHLH2 and AabHLH3 are nuclear proteins that bind to DNA elements with similar specificity to that of AaMYC2, but lack the conserved activation domain, suggesting that repression is achieved by competition for the same cis-regulatory elements. Together, our findings reveal a novel artemisinin biosynthesis regulatory network, provide new insight into how specialized metabolites are modulated in plants, and propose a model in which different bHLH TFs coordinated in regulating artemisinin production in the plant. Finally, this study provides some useful target genes for metabolic engineering of artemisinin production via CRISPR/Cas9 gene editing.

Aging weakens Th17 cell pathogenicity and ameliorates experimental autoimmune uveitis in mice.

Aging-induced changes in the immune system are associated with a higher incidence of infection and vaccination failure. Lymph nodes, which filter the lymph to identify and fight infections, play a central role in this process. However, careful characterization of the impact of aging on lymph nodes and associated autoimmune diseases is lacking. We combined single-cell RNA sequencing (scRNA-seq) with flow cytometry to delineate the immune cell atlas of cervical draining lymph nodes (CDLNs) of both young and old mice with or without experimental autoimmune uveitis (EAU). We found extensive and complicated changes in the cellular constituents of CDLNs during aging. When confronted with autoimmune challenges, old mice developed milder EAU compared to young mice. Within this EAU process, we highlighted that the pathogenicity of T helper 17 cells (Th17) was dampened, as shown by reduced GM-CSF secretion in old mice. The mitigated secretion of GM-CSF contributed to alleviation of IL-23 secretion by antigen-presenting cells (APCs) and may, in turn, weaken APCs' effects on facilitating the pathogenicity of Th17 cells. Meanwhile, our study further unveiled that aging downregulated GM-CSF secretion through reducing both the transcript and protein levels of IL-23R in Th17 cells from CDLNs. Overall, aging altered immune cell responses, especially through toning down Th17 cells, counteracting EAU challenge in old mice.

Therapeutic Effect of IL-38 on Experimental Autoimmune Uveitis: Reprogrammed Immune Cell Landscape and Reduced Th17 Cell Pathogenicity.

Purpose: The purpose of this study was to elucidate the effects of interleukin (IL)-38 on experimental autoimmune uveitis (EAU) and its underlying mechanisms. Methods: Mice with EAU were treated with IL-38, and the retinas and cervical draining lymph nodes (CDLNs) were analyzed by flow cytometry. Single-cell RNA sequencing (scRNA-seq) was conducted to analyze the immune cell profiles of CDLNs from normal, EAU, and IL-38-treated mice. Results: Administration of IL-38 attenuated EAU symptoms and reduced the proportion of T helper 17 (Th17) and T helper 1 (Th1) cells in the retinas and CDLNs. In scRNA-seq analysis, IL-38 downregulated the IL-17 signaling pathway and reduced the expression of Th17 cell pathogenicity-related genes (Csf2 and Il23r), findings which were also confirmed by flow cytometry. In vitro, IL-38 reduced the granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulation function of IL-23 and inhibited IL-23R expression in Th17 cells. Moreover, when co-cultured with Th17 cells, IL-38 prevented IL-23 production in antigen-presenting cells (APCs). Conclusions: Our data demonstrate the therapeutic effect of IL-38 on EAU, and suggest that the effect of IL-38 may be caused by dampening of the GM-CSF/IL-23R/IL-23 feedback loop between Th17 cells and APCs.

Effects of poor sleep on the immune cell landscape as assessed by single-cell analysis.

Poor sleep has become an important public health issue. With loss of sleep durations, poor sleep has been linked to the increased risks for diseases. Here we employed mass cytometry and single-cell RNA sequencing to obtain a comprehensive human immune cells landscape in the context of poor sleep, which was analyzed in the context of subset composition, gene signatures, enriched pathways, transcriptional regulatory networks, and intercellular interactions. Participants subjected to staying up had increased T and plasma cell frequency, along with upregulated autoimmune-related markers and pathways in CD4+ T and B cells. Additionally, staying up reduced the differentiation and immune activity of cytotoxic cells, indicative of a predisposition to infection and tumor development. Finally, staying up influenced myeloid subsets distribution and induced inflammation development and cellular senescence. These findings could potentially give high-dimensional and advanced insights for understanding the cellular and molecular mechanisms of pathologic conditions related to poor sleep.

A high-efficiency Agrobacterium-mediated transient expression system in the leaves of Artemisia annua L.

BACKGROUND: The Agrobacterium-mediated transient transformation, which proved effective in diverse plant species, has been widely applied for high-throughput gene function studies due to its simplicity, rapidity, and high efficiency. Despite the efforts have made on Artemisia annua transient expression, achieving high-throughput gene functional characterization basing on a fast and easy-manipulated transient transformation system in A. annua remains challenging. RESULTS: The first pair of true leaves of A. annua is an ideal candidate for Agrobacterium injection. EHA105 was the optimal strain that can be used for the development of the transient expression system. The supplementation of Triton X-100 at a concentration of 0.005% greatly improved the transient expression frequency. According to the histochemical ß-Glucuronidase (GUS) staining assay, high transient expression level of the reporter gene (GUS) maintained at least a week. Dual-luciferase (Dual-LUC) transient assays showed that the activity of cauliflower mosaic virus 35S (CaMV35S) promoter and its derivates varied between A. annua and tobacco. In A. annua, the CaMV35S promoter had comparable activity with double CaMV35S promoter, while in tobacco, CaMV35S exhibited approximately 50% activity of double CaMV35S promoter. Otherwise, despite the CaMV35S promoter and double CaMV35S promoter from GoldenBraid Kit 2.0 displayed high activity strength in tobacco, they demonstrated a very low activity in transiently expressed A. annua. The activity of UBQ10 promoter and endogenous UBQb promoter was investigated as well. Additionally, using our transient expression system, the transactivation of AaGSW1 and AaORA on AaCYP71AV1 promoter was confirmed. Dual-LUC assays demonstrated that AaHD8 activated the expression of two glandular secreting trichomes-specific lipid transfer protein genes AaLTP1 and AaLTP2, indicating that AaLTP1 and AaLTP2 might serve as downstream components of AaHD8-involved glandular trichome initiation and cuticle formation, as well as artemisinin secretion in A. annua. CONCLUSIONS: A simple, rapid, good-reproducibility, high-efficiency and low-cost transient transformation system in A. annua was developed. Our method offered a new way for gene functional characterization studies such as gene subcellular localization, promoter activity and transcription activation assays in A. annua, avoiding the aberrant phenotypes resulting from gene expression in a heterologous system.

AaWRKY17, a positive regulator of artemisinin biosynthesis, is involved in resistance to Pseudomonas syringae in Artemisia annua.

Artemisia annua, a traditional Chinese medicinal plant, remains the only plant source for artemisinin production, yet few genes have been identified to be involved in both the response to biotic stresses, such as pathogens, and artemisinin biosynthesis. Here, we isolated and identified the WRKY transcription factor (TF) AaWRKY17, which could significantly increase the artemisinin content and resistance to Pseudomonas syringae in A. annua. Yeast one-hybrid (Y1H), dual-luciferase (dual-LUC), and electrophoretic mobility shift assay (EMSA) results showed that AaWRKY17 directly bound to the W-box motifs in the promoter region of the artemisinin biosynthetic pathway gene amorpha-4,11-diene synthase (ADS) and promoted its expression. Real-time quantitative PCR (RT-qPCR) analysis revealed that the transcript levels of two defense marker genes, Pathogenesis-Related 5 (PR5) and NDR1/HIN1-LIKE 10 (NHL10), were greatly increased in AaWRKY17-overexpressing transgenic A. annua plants. Additionally, overexpression of AaWRKY17 in A. annua resulted in decreased susceptibility to P. syringae. These results indicated that AaWRKY17 acted as a positive regulator in response to P. syringae infection. Together, our findings demonstrated that the novel WRKY transcription factor AaWRKY17 could potentially be used in transgenic breeding to improve the content of artemisinin and pathogen tolerance in A. annua.

Prednisone Reprograms the Transcriptional Immune Cell Landscape in CNS Autoimmune Disease.

Glucocorticoids (GCs) are widely used immunosuppressive drugs for autoimmune diseases, although considerable gaps exist between current knowledge of the mechanisms of GCs and their conclusive immune-regulatory effects. Here we generated a single-cell transcriptional immune cell atlas based on prednisone-treated or untreated experimental autoimmune uveitis (EAU) mice. Immune cells were globally activated in EAU, and prednisone partially reversed this effect in terms of cell composition, gene expression, transcription factor regulation, and cell-cell communication. Prednisone exerted considerable rescue effects on T and B cells and increased the proportion of neutrophils. Besides commonly regulated transcriptional factors (Fosb, Jun, Jund), several genes were only regulated in certain cell types (e.g. Cxcr4 and Bhlhe40 in T cells), suggesting cell-type-dependent immunosuppressive properties of GC. These findings provide new insights into the mechanisms behind the properties and cell-specific effects of GCs and can potentially benefit immunoregulatory therapy development.

Effects of sex and aging on the immune cell landscape as assessed by single-cell transcriptomic analysis.

Sex and aging influence the human immune system, resulting in disparate responses to infection, autoimmunity, and cancer. However, the impact of sex and aging on the immune system is not yet fully elucidated. Using small conditional RNA sequencing, we found that females had a lower percentage of natural killer (NK) cells and a higher percentage of plasma cells in peripheral blood compared with males. Bioinformatics revealed that young females exhibited an overrepresentation of pathways that relate to T and B cell activation. Moreover, cell-cell communication analysis revealed evidence of increased activity of the BAFF/APRIL systems in females. Notably, aging increased the percentage of monocytes and reduced the percentage of naïve T cells in the blood and the number of differentially expressed genes between the sexes. Aged males expressed higher levels of inflammatory genes. Collectively, the results suggest that females have more plasma cells in the circulation and a stronger BAFF/APRIL system, which is consistent with a stronger adaptive immune response. In contrast, males have a higher percentage of NK cells in blood and a higher expression of certain proinflammatory genes. Overall, this work expands our knowledge of sex differences in the immune system in humans.

The Efficacy of Adalimumab as an Initial Treatment in Patients with Behçet's Retinal Vasculitis.

Background: No study has evaluated the effectiveness of Adalimumab (ADA) as first-line in treatment-naïve patients with retinal vasculitis due to Behçet's Uveitis (BU). Objective: To compare the efficacy of ADA plus conventional therapy and conventional therapy alone as initial treatments in naïve BU patients characterized by retinal vasculitis. Methods: Medical records of BU patients characterized by retinal vasculitis treated with conventional therapy (CT, refers to glucocorticoid and immunosuppressive agents) alone or ADA plus conventional therapy with at least 6 months of follow-up between February 2015 and June 2020 were analyzed. Only patients who were first diagnosed with BU without previous systemic treatment were reviewed. The retinal vasculitis score based on fluorescein angiography (FA), best-corrected visual acuity, glucocorticoid-sparing effect, the number of relapses and ocular complications were evaluated. Results: A total of 45 patients (87 eyes) were included. Twenty-four patients (55.33%) in the CT group were treated with conventional therapy and 21 patients (46.67%) in the ADA group were treated with ADA plus conventional therapy. The inflammatory parameters improved in both groups. FA scores showed significantly greater improvement in ADA group than CT group (p < 0.001). The median number of relapses was significantly lower, and the duration of remission was longer in ADA group than CT group (p < 0.001). At the last visit, a significantly better BCVA improvement (p = 0.024), better inflammation control (anterior chamber inflammation p = 0.017 and vitritis p < 0.001) and lower daily glucocorticoid dosage (p = 0.005) were identified in patients received ADA therapy. In CT group, 1 patient suffered hepatitis B and tuberculosis, 1 had growth retardation, 1 patient had with osteoporosis, then followed by other mild AEs (mostly respiratory upper tract infections); while in ADA group, 1 patient experienced a mild pneumonia (n = 1) while milder AEs were represented mostly by respiratory upper tract infections followed by gastrointestinal discomfort. Conclusion: ADA plus conventional therapy achieved superiority over conventional therapy as initial treatment in naïve BU patients with retinal vasculitis.

Single-Cell Analysis Reveals the Heterogeneity of Monocyte-Derived and Peripheral Type-2 Conventional Dendritic Cells.

Dendritic cells (DCs) are critical for pathogen recognition and Ag processing/presentation. Human monocyte-derived DCs (moDCs) have been extensively used in experimental studies and DC-based immunotherapy approaches. However, the extent of human moDC and peripheral DCs heterogeneity and their interrelationship remain elusive. In this study, we performed single-cell RNA sequencing of human moDCs and blood DCs. We identified seven subtypes within moDCs: five corresponded to type 2 conventional DCs (cDC2s), and the other two were CLEC10A+CD127+ cells with no resemblance to any peripheral DC subpopulations characterized to date. Moreover, we defined five similar subtypes in human cDC2s, revealed the potential differentiation trajectory among them, and unveiled the transcriptomic differences between moDCs and cDC2s. We further studied the transcriptomic changes of each moDC subtype during maturation, demonstrating SLAMF7 and IL15RA as maturation markers and CLEC10A and SIGLEC10 as markers for immature DCs. These findings will enable more accurate functional/developmental analyses of human cDC2s and moDCs.

AaWRKY9 contributes to light- and jasmonate-mediated to regulate the biosynthesis of artemisinin in Artemisia annua.

Artemisinin, isolated from Artemisia annua, is recommended as the preferred drug to fight malaria. Previous research showed that jasmonate (JA)-mediated promotion of artemisinin accumulation depended on light. However, the mechanism underlying the interaction of light and JA in regulating artemisinin accumulation is still unknown. We identified a WRKY transcription factor, AaWRKY9, using transcriptome analysis. The glandular trichome-specific AaWRKY9 positively regulates artemisinin biosynthesis by directly binding to the promoters of AaDBR2 and AaGSW1. The key regulator in the light pathway AaHY5 activates the expression of AaWRKY9 by binding to its promoter. In addition, AaWRKY9 interacts with AaJAZ9, a repressor in the JA signalling pathway. AaJAZ9 represses the transcriptional activation activity of AaWRKY9 in the absence of methyl jasmonate. Notably, in the presence of methyl jasmonate, the transcriptional activation activity of AaWRKY9 is increased. Taken together, our results reveal a novel molecular mechanism underlying AaWRKY9 contributes to light-mediated and jasmonate-mediated to regulate the biosynthesis of artemisinin in A. annua. Our study provides new insights into integrating the two signalling pathways to regulate terpene biosynthesis in plants.

AaMYB15, an R2R3-MYB TF in Artemisia annua, acts as a negative regulator of artemisinin biosynthesis.

Artemisinin is a secondary metabolite extracted from Artemisia annua. As an effective antimalarial component certified by WHO, artemisinin has extensive economical values. Numerous studies about transcription factors positively regulating artemisinin biosynthesis have been published while negative regulators are rarely reported. In the present study, we identified AaMYB15 as the first R2R3-MYB that negatively regulates artemisinin biosynthesis in A. annua. Experimental evidences showed that AaMYB15 is a transcription factor within nucleus and predominantly expressed in glandular secretory trichomes (GSTs) in A. annua where artemisinin is synthesized and accumulated. The expression of AaMYB15 was induced by dark and JA treatment. Overexpression of AaMYB15 led to a significant decline in the expression levels of key enzyme genes ADS, CYP, DBR2, and ALDH1 and a significant decrease in the artemisinin contents of transgenic A. annua. AaMYB15 directly bound to the promoter of AaORA, a reported positive regulator of artemisinin biosynthesis in JA signaling pathway, to repress its transcriptional activity, thus downregulating the expression levels of downstream key enzyme genes and negatively regulating the artemisinin biosynthesis. Our study provides candidate gene for improvement of A. annua germplasm and new insights into the artemisinin biosynthesis regulation network mediated by light and JA.

An HD-ZIP-MYB complex regulates glandular secretory trichome initiation in Artemisia annua.

Plant glandular secretory trichomes (GSTs) produce various specialized metabolites. Increasing GST density represents a strategy to enhance the yield of these chemicals; however, the gene regulatory network that controls GST initiation remains unclear. In a previous study of Artemisia annua L., we found that a HD-ZIP IV transcription factor, AaHD1, promotes GST initiation by directly regulating AaGSW2. Here, we identified two AaHD1-interacting transcription factors, namely AaMIXTA-like 2 (AaMYB16) and AaMYB5. Through the generation and characterization of transgenic plants, we found that AaMYB16 is a positive regulator of GST initiation, whereas AaMYB5 has the opposite effect. Notably, neither of them regulates GST formation independently. Rather, they act competitively, by interacting and modulating AaHD1 promoter binding activity. Additionally, the phytohormone jasmonic acid (JA) was shown to be associated with the AaHD1-AaMYB16/AaMYB5 regulatory network through transcriptional regulation via a JASMONATE-ZIM DOMAIN (JAZ) protein repressor. These results bring new insights into the mechanism of GST initiation through regulatory complexes, which appear to have similar functions in a range of vascular plant taxa.

Transcriptomic analysis reveals the parallel transcriptional regulation of UV-B-induced artemisinin and flavonoid accumulation in Artemisia annua L.

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 responses of A. annua L. leaves to UV-B radiation were analyzed using the Illumina transcriptome sequencing. A total of 10705 differentially expressed genes (DEGs) including 533 transcription factors (TFs), were identified. Based on the expression trends of the differentially expressed TFs as well as artemisinin and flavonoid biosynthesis genes, we speculated that TFs belonging to 6 clusters were most likely to be involved in the regulation of artemisinin and/or flavonoid biosynthesis. The regulatory relationship between TFs 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 an R2R3 MYB TF, AaMYB4 which potentially 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. Overall, our findings would provide an insight into the elucidation of the parallel transcriptional regulation of artemisinin and flavonoid biosynthesis in A. annua L. under UV-B radiation.