Expression of key genes affecting artemisinin content in five Artemisia species

Bioprospecting of Artemisia genus: from artemisinin to other potentially bioactive compounds

Species from genus Artemisia are widely distributed throughout temperate regions of the northern hemisphere and many cultures have a long-standing traditional use of these plants as herbal remedies, liquors, cosmetics, spices, etc. Nowadays, the discovery of new plant-derived products to be used as food supplements or drugs has been pushed by the exploitation of bioprospection approaches. Often driven by the knowledge derived from the ethnobotanical use of plants, bioprospection explores the existing biodiversity through integration of modern omics techniques with targeted bioactivity assays. In this work we set up a bioprospection plan to investigate the phytochemical diversity and the potential bioactivity of five Artemisia species with recognized ethnobotanical tradition (A. absinthium, A. alba, A. annua, A. verlotiorum and A. vulgaris), growing wild in the natural areas of the Verona province. We characterized the specialized metabolomes of the species (including sesquiterpenoids from the artemisinin biosynthesis pathway) through an LC-MS based untargeted approach and, in order to identify potential bioactive metabolites, we correlated their composition with the in vitro antioxidant activity. We propose as potential bioactive compounds several isomers of caffeoyl and feruloyl quinic acid esters (e.g. dicaffeoylquinic acids, feruloylquinic acids and caffeoylferuloylquinic acids), which strongly characterize the most antioxidant species A. verlotiorum and A. annua. Morevoer, in this study we report for the first time the occurrence of sesquiterpenoids from the artemisinin biosynthesis pathway in the species A. alba.

Identification of the WRKY Gene Family and Characterization of Stress-Responsive Genes in Taraxacum kok-saghyz Rodin

WRKY transcription factors present unusual research value because of their critical roles in plant physiological processes and stress responses. Taraxacum kok-saghyz Rodin (TKS) is a perennial herb of dandelion in the Asteraceae family. However, the research on TKS WRKY TFs is limited. In this study, 72 TKS WRKY TFs were identified and named. Further comparison of the core motifs and the structure of the WRKY motif was analyzed. These TFs were divided into three groups through phylogenetic analysis. Genes in the same group of TkWRKY usually exhibit a similar exon-intron structure and motif composition. In addition, virtually all the TKS WRKY genes contained several cis-elements related to stress response. Expression profiling of the TkWRKY genes was assessed using transcriptome data sets and Real-Time RT-PCR data in tissues during physiological development, under abiotic stress and hormonal treatments. For instance, the TkWRKY18, TkWRKY23, and TkWRKY38 genes were significantly upregulated during cold stress, whereas the TkWRKY21 gene was upregulated under heat-stress conditions. These results could provide a basis for further studies on the function of the TKS WRKY gene family and genetic amelioration of TKS germplasm.

Enhancing artemisinin content in and delivery from Artemisia annua: a review of alternative, classical, and transgenic approaches

This review analyses the most recent scientific research conducted for the purpose of enhancing artemisinin production. It may help to devise better artemisinin enhancement strategies, so that its production becomes cost effective and becomes available to masses. Malaria is a major threat to world population, particularly in South-East Asia and Africa, due to dearth of effective anti-malarial compounds, emergence of quinine resistant malarial strains, and lack of advanced healthcare facilities. Artemisinin, a sesquiterpene lactone obtained from Artemisia annua L., is the most potent drug against malaria and used in the formulation of artemisinin combination therapies (ACTs). Artemisinin is also effective against various types of cancers, many other microbes including viruses, parasites and bacteria. However, this specialty metabolite and its derivatives generally occur in low amounts in the source plant leading to its production scarcity. Considering the importance of this drug, researchers have been working worldwide to develop novel strategies to augment its production both in vivo and in vitro. Due to complex chemical structure, its chemical synthesis is quite expensive, so researchers need to devise synthetic protocols that are economically viable and also work on increasing the in-planta production of artemisinin by using various strategies like use of phytohormones, stress signals, bioinoculants, breeding and transgenic approaches. The focus of this review is to discuss these artemisinin enhancement strategies, understand mechanisms modulating its biosynthesis, and evaluate if roots play any role in artemisinin production. Furthermore, we also have a critical analysis of various assays used for artemisinin measurement. This may help to develop better artemisinin enhancement strategies which lead to decreased price of ACTs and increased profit to farmers.

A hybrid model based on general regression neural network and fruit fly optimization algorithm for forecasting and optimizing paclitaxel biosynthesis in Corylus avellana cell culture

BACKGROUND

Paclitaxel is a well-known chemotherapeutic agent widely applied as a therapy for various types of cancers. In vitro culture of Corylus avellana has been named as a promising and low-cost strategy for paclitaxel production. Fungal elicitors have been reported as an impressive strategy for improving paclitaxel biosynthesis in cell suspension culture (CSC) of C. avellana. The objectives of this research were to forecast and optimize growth and paclitaxel biosynthesis based on four input variables including cell extract (CE) and culture filtrate (CF) concentration levels, elicitor adding day and CSC harvesting time in C. avellana cell culture, as a case study, using general regression neural network-fruit fly optimization algorithm (GRNN-FOA) via data mining approach for the first time.

RESULTS

GRNN-FOA models (0.88-0.97) showed the superior prediction performances as compared to regression models (0.57-0.86). Comparative analysis of multilayer perceptron-genetic algorithm (MLP-GA) and GRNN-FOA showed very slight difference between two models for dry weight (DW), intracellular and extracellular paclitaxel in testing subset, the unseen data. However, MLP-GA was slightly more accurate as compared to GRNN-FOA for total paclitaxel and extracellular paclitaxel portion in testing subset. The slight difference was observed in maximum growth and paclitaxel biosynthesis optimized by FOA and GA. The optimization analysis using FOA on developed GRNN-FOA models showed that optimal CE [4.29% (v/v)] and CF [5.38% (v/v)] concentration levels, elicitor adding day (17) and harvesting time (88 h and 19 min) can lead to highest paclitaxel biosynthesis (372.89 µg l^-1).

CONCLUSIONS

Great accordance between the predicted and observed values of DW, intracellular, extracellular and total yield of paclitaxel, and also extracellular paclitaxel portion support excellent performance of developed GRNN-FOA models. Overall, GRNN-FOA as new mathematical tool may pave the way for forecasting and optimizing secondary metabolite production in plant in vitro culture.

CRISPR-based metabolic editing: Next-generation metabolic engineering in plants

Plants generate many secondary metabolites, so called phyto-metabolites, which can be used as toxins, dyes, drugs, and insecticides in bio-warfare plus bio-terrorism, industry, medicine, and agriculture, respectively. To 2013, the first generation metabolic engineering approaches like miRNA-based manipulation were widely adopted by researchers in biosciences. However, the discovery of the clustered regularly interspaced short palindromic repeat (CRISPR) genome editing system revolutionized metabolic engineering due to its unique features so that scientists could manipulate the biosynthetic pathways of phyto-metabolites through approaches like miRNA-mediated CRISPR-Cas9. According to the increasing importance of the genome editing in plant sciences, we discussed the current findings on CRISPR-based manipulation of phyto-metabolites in plants, especially medicinal ones, and suggested the ideas to phyto-metabolic editing.

Mathematical Modeling of Growth and Paclitaxel Biosynthesis in Corylus avellana Cell Culture Responding to Fungal Elicitors Using Multilayer Perceptron-Genetic Algorithm

Paclitaxel is the top-selling anticancer medicine in the world. In vitro culture of Corylus avellana has been made known as a promising and inexpensive strategy for producing paclitaxel. Fungal elicitors have been named as the most efficient strategy for enhancing the biosynthesis of secondary metabolites in plant cell culture. In this study, endophytic fungal strain HEF₁₇ was isolated from C. avellana and identified as Camarosporomyces flavigenus. C. avellana cell suspension culture (CSC) elicited with cell extract (CE) and culture filtrate (CF) derived from strain HEF₁₇, either individually or combined treatment, in mid and late log phase was processed for modeling and optimizing growth and paclitaxel biosynthesis regarding CE and CF concentration levels, elicitor adding day, and CSC harvesting time using multilayer perceptron-genetic algorithm (MLP-GA). The results displayed higher accuracy of MLP-GA models (0.89-0.95) than regression models (0.56-0.85). The great accordance between the predicted and observed values of output variables (dry weight, intracellular, extracellular and total yield of paclitaxel, and also extracellular paclitaxel portion) for both training and testing subsets supported the excellent performance of developed MLP-GA models. MLP-GA method presented a promising tool for selecting the optimal conditions for maximum paclitaxel biosynthesis. An Excel^® estimator, HCC-paclitaxel, was designed based on MLP-GA model as an easy-to-use tool for predicting paclitaxel biosynthesis in C. avellana CSC responding to fungal elicitors.

Genetic Control of Glandular Trichome Development

Plant glandular trichomes are epidermal secretory structures producing various specialized metabolites. These metabolites are involved in plant adaptation to its environment and many of them have remarkable properties exploited by fragrance, flavor, and pharmaceutical industries. The identification of genes controlling glandular trichome development is of high interest to understand how plants produce specialized metabolites. Our knowledge about this developmental process is still limited, but genes controlling glandular trichome initiation and morphogenesis have recently been identified. In particular, R2R3-MYB and HD-ZIP IV transcription factors appear to play essential roles in glandular trichome initiation in Artemisia annua and tomato. In this review, we focus on the results obtained in these two species and we propose genetic regulation models integrating these data.

Fungal Cell Wall and Methyl-β-Cyclodextrin Synergistically Enhance Paclitaxel Biosynthesis and Secretion in Corylus avellana Cell Suspension Culture

Paclitaxel is the top-selling chemotherapeutic drug used for the treatment of lung, ovarian and breast cancer as well as Kaposi's sarcoma. Cell suspension culture (CSC) of Corylus avellana has been addressed as a promising alternative for producing paclitaxel. In this study, endophytic fungus strain YEF33 was isolated from Taxus baccata and identified as Coniothyrium palmarum. The effects of the elicitors derived from this fungus including cell extract, culture filtrate and cell wall (CW) and also chitin, alone or in combination with Methyl-β-Cyclodextrin (MBCD), on paclitaxel biosynthesis in C. avellana CSC were assayed for the first time. CW of C. palmarum was the most efficient fungal elicitor for paclitaxel biosynthesis in C. avellana CSC. The results revealed that MBCD affected paclitaxel biosynthesis differently depending on fungal elicitor type and vice versa. MBCD, either alone or in combination with fungal elicitors, induced a high secretion of paclitaxel, suggesting the decrement of toxicity and retro-inhibition processes of paclitaxel for cells. The joint effects of C. palmarum CW (2.5% (v/v) on 17th day) and 50 mM MBCD synergistically enhanced paclitaxel biosynthesis (402.4 µg l-1; 5.8-fold), 78.6% of which (316.5 µg l-1) were secreted into culture medium, a level 146% higher than that in control.

Identification and expression analysis of S-alk(en)yl-L-cysteine sulfoxide lyase isoform genes and determination of allicin contents in Allium species

Alliinase is the key enzyme in allicin biosynthesis pathway. In the current study, the identification and sequencing of alliinase genes along with determination of allicin contents were reported for Allium species with a novel report for Iranian endemic species. The presence of different isoforms in the Allium being discovered for the first time. In bulbs tissue, the highest allicin concentration was in Allium sativum, A. umbilicatum, and A. fistolosum (1.185%, 0.367%, and 0.34%, respectively), followed by A. spititatum (0.072%), A. lenkoranicum (0.055%), A. atroviolaseum (0.36%), A. rubellum (0.041%), and A. stamineum (0.007%). The highest allicin content in the leaves and roots were in A. sativum (0.13%), and A. stamineum (0.195%), respectively. The ORFs length ranged from 1416 in A. sativum (iso-alliinase2; ISA2) to 1523 bp in A. sativum (alliinase); the identity with A. sativum (alliinase) varies from 95% to 68% for A. ampeloprasum, and A. sativum (iso-alliinase1, ISA1) respectively. These data suggested that both ISA1 and ISA2 had a high expression in the roots and bulbs compared to A. sativum as the control in all species. Note that ISA1 and ISA2 were not expressed in the leaves. The results showed that isoforms expression patterns among different tissues in Allium species were variable. The presence of various isoforms is a possible explanation for the difference between the species in terms of obtained results, especially the amount of allicin.

The spatio-temporal expression of some genes involved in the biosynthetic pathways of terpenes/phenylpropanoids in yarrow (Achillea millefolium)

Yarrow (Achillea millefolium) is a medicinal plant from the Asteracea which biosynthesize different secondary metabolites especially terpenes and phenylpropanoids. To improve our understanding of the regulatory mechanisms behind the biosynthesis of these compounds we analyzed the expression of some genes associated with the biosynthesis of terpenes and phenylpropanoids in different tissues and in response to trans-cinnamic acid (tCA) as an inhibitor of PAL activity. Isolation and expression analysis of DXR, GPPS, PAL and CHS genes together with linalool synthase (LIS) as monoterpene synthase was conducted in different developmental stages of leaves, flowers and in response to trans-cinnamic acid (tCA). Differential expression of these genes observed in different tissues. tCA up-regulated the biosynthetic genes of monterpenes and down-regulated the biosynthetic genes of phenylpropanoids. Gene expression analysis in intact leaves and leaves without glandular trichomes showed that DXR, LIS, PAL and CHS are highly expressed in glandular trichomes while GPPS expressed ubiquitously. Analysis of essential oils composition showed that sesquiterpenes and monoterpenes are main compounds; in which from 57 identified compounds the highest were germacreneD (% 11.5), guaiol (%10.38), spatulenol (%8.73) and caryophyllene oxide (%7.48).