AaABI5 transcription factor mediates light and abscisic acid signaling to promote anti-malarial drug artemisinin biosynthesis in Artemisia annua

Comparative transcriptome analysis reveals abscisic acid-induced bHLH transcription factors involved in saikosaponin biosynthesis in Bupleurum chinense DC

Bupleurum chinense DC. a medicinal plant valued for saikosaponins (SSs) with antipyretic and hepatoprotective properties, faces constrained SS biosynthesis mediated by abscisic acid (ABA) during growth. Basic helix-loop-helix (bHLH) transcription factors (TFs) are hypothesized to participate in ABA signaling cascades, but their mechanistic role in SS regulation remains undefined. In this study, 20 differentially expressed BcbHLH genes were identified by transcriptomic profiling of ABA-induced hairy roots, with four MYC-family candidates (BcbHLH1-BcbHLH4) demonstrating ABA-responsive regulatory potential. ABA exposure (100 or 200 μmol/L, 24-72 h) induced dose-dependent SS reduction, while correlation analyses revealed coordinated expression between BcbHLH1-BcHMGR (r = 0.62) and BcbHLH4-BcBAS (r = 0.78), pinpointing these TFs as critical nodes in SS pathway modulation. Tissue-specific profiling showed predominant BcbHLH expression in stems and young leaves, with nuclear localization confirming their transcriptional regulatory organelles. BcbHLH3/4 exhibited transcriptional activation activity in the MYC_N domain, while molecular docking predicted 11th Arginine in the HLH domain as essential for G-box DNA binding. Collectively, our findings suggest that BcbHLH1-BcbHLH4 may serve as potential switches for fine-tuning ABA responsiveness in SS biosynthesis. Strategic manipulation of BcbHLH activity through genetic engineering approaches such as CRISPR-based editing or overexpression could alleviate ABA-mediated biosynthetic repression. Furthermore, precision engineering of the critical functional domain in BcbHLH could enhance promoter-binding activity to target genes and improve SS biosynthesis efficiency. These findings provide a reference framework for harnessing transcriptional regulators to optimize SS production in Bupleurum chinense DC.

Unlocking the potential of Artemisia annua for artemisinin production: current insights and emerging strategies

Malaria is a deadly disease, and the best effective treatments depend on artemisinin, a sesquiterpene lactone compound isolated from the plant Artemisia annua. However, artemisinin is produced in very small amount within the plant which is insufficient to meet the global demand. Although researchers have investigated synthetic and semi-synthetic approaches, they still face significant challenges, such as high costs and low efficiency, making A. annua the most viable source. Biotechnological advances in breeding and genetic engineering have developed new A. annua varieties with higher artemisinin content, and some varieties have achieved up to 3.2% of plant dry weight. Furthermore, researchers have identified the key genes and transcription factors that can be modified to boost production further. Environmental factors, such as light and specific plant hormones, play a crucial role in regulating this pathway. Also, tissue culture, hairy root systems, and natural elicitors have shown promising results, but need further refinement. Interestingly, the use of whole plants (such as dried leaf powder) instead of purified artemisinin alone has been found to improve drug absorption in the body, improve its effectiveness, and help combat artemisinin resistance. Beyond treating malaria, A. annua also demonstrates other therapeutic potential in treating other diseases, including cancer and viral infections. These findings highlight that A. annua is not just a source of artemisinin; it is a valuable medicinal plant that deserves continued research focus, primarily through approaches that improve artemisinin production directly in the plant.

Abscisic acid enhances SmAPK1-mediated phosphorylation of SmbZIP4 to positively regulate tanshinone biosynthesis in Salvia miltiorrhiza

Tanshinones, isolated from Salvia miltiorrhiza, is efficient to treat cardiovascular and cerebrovascular diseases. Abscisic acid (ABA) treatment is found to promote tanshinone biosynthesis; however, the underlying mechanism has not been fully elucidated. A protein kinase namely SmAPK1 was identified as an important positive regulator of ABA-induced tanshinone accumulation in S. miltiorrhiza. Using SmAPK1 as bait, a basic region leucine zipper (bZIP) family transcription factor SmbZIP4 was screened from the cDNA library. Functional identification reveals that SmbZIP4 negatively regulates tanshinone biosynthesis in hairy roots and transgenic plants through directly targeting SmGGPPS and SmCYP76AK1. SmAPK1 phosphorylates the Ser97 and Thr99 site of SmbZIP4, leading to its degradation via the 26S proteasome pathway, which is promoted by ABA-induced enhancement of SmAPK1 kinase activity. Degradation of SmbZIP4 upregulates the expression levels of SmGGPPS and SmCYP76AK1, resulting in increased tanshinone content. Taken together, our results reveal new molecular mechanism by which SmAPK1-SmbZIP4 module plays a crucial role in ABA-induced tanshinone accumulation. This study sheds new insights in the biosynthesis of bioactive compounds in medicinal plants.

Molecular regulation of the key specialized metabolism pathways in medicinal plants

The basis of modern pharmacology is the human ability to exploit the production of specialized metabolites from medical plants, for example, terpenoids, alkaloids, and phenolic acids. However, in most cases, the availability of these valuable compounds is limited by cellular or organelle barriers or spatio-temporal accumulation patterns within different plant tissues. Transcription factors (TFs) regulate biosynthesis of these specialized metabolites by tightly controlling the expression of biosynthetic genes. Cutting-edge technologies and/or combining multiple strategies and approaches have been applied to elucidate the role of TFs. In this review, we focus on recent progress in the transcription regulation mechanism of representative high-value products and describe the transcriptional regulatory network, and future perspectives are discussed, which will help develop high-yield plant resources.

Advanced metabolic engineering strategies for increasing artemisinin yield in Artemisia annua L

Artemisinin, also known as 'Qinghaosu', is a chemically sesquiterpene lactone containing an endoperoxide bridge. Due to the high activity to kill Plasmodium parasites, artemisinin and its derivatives have continuously served as the foundation for antimalarial therapies. Natural artemisinin is unique to the traditional Chinese medicinal plant Artemisia annua L., and its content in this plant is low. This has motivated the synthesis of this bioactive compound using yeast, tobacco, and Physcomitrium patens systems. However, the artemisinin production in these heterologous hosts is low and cannot fulfil its increasing clinical demand. Therefore, A. annua plants remain the major source of this bioactive component. Recently, the transcriptional regulatory networks related to artemisinin biosynthesis and glandular trichome formation have been extensively studied in A. annua. Various strategies including (i) enhancing the metabolic flux in artemisinin biosynthetic pathway; (ii) blocking competition branch pathways; (iii) using transcription factors (TFs); (iv) increasing peltate glandular secretory trichome (GST) density; (v) applying exogenous factors; and (vi) phytohormones have been used to improve artemisinin yields. Here we summarize recent scientific advances and achievements in artemisinin metabolic engineering, and discuss prospects in the development of high-artemisinin yielding A. annua varieties. This review provides new insights into revealing the transcriptional regulatory networks of other high-value plant-derived natural compounds (e.g., taxol, vinblastine, and camptothecin), as well as glandular trichome formation. It is also helpful for the researchers who intend to promote natural compounds production in other plants species.